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Table of Content
20 December 2022, Volume 41 Issue 12
    Invited review
    Analysis of development path of modern coal chemical industry
    YAN Guochun, WEN Liang, ZHANG Hua
    2022, 41(12):  6201-6212.  doi:10.16085/j.issn.1000-6613.2022-1852
    Abstract ( 167 )   HTML ( 19)   PDF (1857KB) ( 207 )  
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    The development of modern coal chemical industry is of great significance for ensuring national energy security, supporting the development of national economy and expanding the channels of raw materials for petrochemical industry. The paper briefly introduces the achievements and problems in the development of modern coal chemical industry. The competitiveness of modern coal chemical industry are systematically analyzed from the aspects of raw material characteristics, process technology and product characteristics, cost competitiveness, project layout and scale, water consumption, energy consumption, and waste discharge. Compared with the oil refining and petrochemical industry, modern coal chemical industry currently is still in demonstration, which produced overlapped products with higher water consumption, higher energy consumption and higher carbon emissions. However, products in line with the composition and structure of coal and chemical reaction characteristics are believed to be competitive and potential, such as special fuel, high carbon with low hydrogen content chemicals and high carbon with high oxygen content chemicals. Under the goals of carbon peak and carbon neutrality, modern coal chemical industry should accelerate the transformation and upgrading from the high carbon emissions industry of replacing petrochemical products to the green and low-carbon industry based on the characteristics of coal. It should pay attention to build a high-end and differentiated product system, adhere to clean and low-carbon production, couple with clean and low-carbon energy, petrochemical industry and other industries, and build a competitive integrated base with coal, oil, chemicals, new materials and new energy, which contributes to promote the high-quality and sustainable development of modern coal chemical industry.

    Research progress on the shaping technology of solid amine adsorbents for CO2 capture by adsorption method
    LEI Ting, YU Shunan, ZHOU Chang’an, SONG Lei, MA Kui, LI Zipeng, YUE Hairong
    2022, 41(12):  6213-6225.  doi:10.16085/j.issn.1000-6613.2021-2238
    Abstract ( 140 )   HTML ( 21)   PDF (2219KB) ( 132 )  
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    Adsorption method for CO2 capture is an important approach to achieve CO2 separation and removal from industrial process or atmosphere, and the development of high-performance adsorbents is the key for CO2 capture technology. In recent years, solid amine adsorbents (SAAs) have attracted much attention due to their excellent CO2 capture ability, high selectivity and low energy consumption. However, the shaped SAAs for industrial applications still face key problems, such as low mechanical strength, poor stability and serious amine loss, which hinder the large-scale applications in industry. In this paper, the key issues in the preparation of shaped SAAs are first analyzed. Emphatically, the research progress of shaping technologies at home and abroad is presented in recent years. The development direction of integral industrial CO2 adsorbents is also prospected. Based on the adsorption reaction mechanism and the characteristics of industrial flue gas, the innovation of the shaping technology for industrial SAAs preparation, improvement of the CO2 adsorption capacity, amine efficiency, mechanical and cyclic stability, and development of processes and related devices with low energy consumption are the future research directions of SAAs adsorption method for CO2 capture technology.

    Chemical processes and equipment
    On-line monitoring and process control of membrane-assisted seeding for ammonium persulfate cooling crystallization
    SHAO Guanying, HE Gaohong, JIANG Xiaobin
    2022, 41(12):  6226-6234.  doi:10.16085/j.issn.1000-6613.2022-0427
    Abstract ( 48 )   HTML ( 4)   PDF (2752KB) ( 31 )  
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    Cooling crystallization is a classical solution crystallization process, which is often used to separate substances whose solubility varies greatly with temperature and prepare high quality crystal products. Direct cooling leads to uncontrollable nucleation rate and poor crystal quality. Industrial crystallization processes are often controlled by adding crystal seeds within the metastable zone to induce nucleation. The process of seeds preparation is complex. And a successful seeding process depends on a lot of factors, such as the size distribution, amount, time point and experience of operators, which decreases the batch repeatability of product quality. In this work, a polytetrafluoroethylene (PTFE) hollow fiber membrane module was used to provide heat exchange interface for the crystallization solution and the cooling liquid, and the temperature of the crystallization solution decreased to form a relatively uniform supercooling gradient near the membrane surfaces. Heterogeneous nucleation occurred at a low supersaturation, realizing a new type of membrane-assisted seeding for ammonium persulfate cooling crystallization. The seeds generated in the membrane module were circulated into the batch crystallizer and continue to grow, decoupling the nucleation and growth process. The images captured by the on-line crystallization monitoring system confirmed that seed crystals with good morphology and narrow size distribution can be obtained by controlling two operating parameters, namely the membrane-involved temperature and the duration. Compared to the direct cooling crystallization, at a similar cooling rate, the crystal products prepared by membrane-assisted seeding processes had larger mean crystal sizes, narrower distributions and smoother surfaces. Thus, membrane-assisted cooling crystallization exhibits good nucleation control capability, and is expected to realize automatic preparation and addition of seeds, which opens up a new direction for the industrial cooling crystallization process design of high value-added crystal products.

    Performance of flat plate heat pipes with variable pore capillary wicks
    LU Ningxiang, LI Jinwang, YANG Maofei
    2022, 41(12):  6235-6244.  doi:10.16085/j.issn.1000-6613.2022-0444
    Abstract ( 53 )   HTML ( 0)   PDF (3375KB) ( 42 )  
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    The capillary wick is a core component of the heat pipe. A single uniform pore capillary wick is often difficult to take into account the needs of high-performance heat pipe for capillary pumping and permeability at the same time. Variable pore capillary wick can set the required capillary pumping and permeability respectively according to the needs. In this paper, fiber felt was used as the main material to prepare variable pore capillary wicks with different pore distribution, and built a flat plate heat pipe test-bed with variable pore capillary wick. Through experiments, the effects of pore distribution and other parameters of capillary wick on the starting performance and heat transfer performance of heat pipe were studied. The results showed that the heat pipe with variable pore composite capillary wick had shorter startup time and better heat transfer performance than that with uniform pore capillary wick. When other conditions were the same and the inclination angle was 45°, the heating power of the flat plate heat pipe with reduced pore diameter capillary wick in the reflux direction was about 2W higher than that of the flat plate heat pipe with uniform capillary wick and 3—4W higher than that of the gravity heat pipe.

    Rule of heat and mass transfer during the pyrolysis process of pine sawdust particles
    XUE Xiaohui, YUAN Mengli, SONG Yuncai, FENG Jie
    2022, 41(12):  6245-6254.  doi:10.16085/j.issn.1000-6613.2022-0337
    Abstract ( 55 )   HTML ( 1)   PDF (1645KB) ( 50 )  
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    To explore the mechanism of heat and mass transfer during the pyrolysis process of organic solid waste particles in a fixed-bed reactor, the pyrolysis of organic solid waste, pine sawdust chosen as raw materials, was simulated and analyzed at the particle scale. The secondary cracking reaction of tar, the mass and momentum transfer of volatile in the pores of particles were considered. Additionally, the flow phenomenon of volatile in the particles was simulated by Darcy’s law. The effects of endothermic reaction and convective heat transfer on particle temperature during particle pyrolysis were also considered. Based on the model of two-step reaction kinetic, the effects of different particle sizes and pyrolysis temperature on the pyrolysis of organic solid waste particles were discussed. The results showed that the endothermic reaction and the convective heat transfer of volatile hindered heat transfer to particle center and prolonged the time for the particles to reach the average temperature. During pine sawdust particles pyrolysis, there was a significant temperature gradient inside the particles. The rate-control step for the pyrolysis of the particles surface was the chemical reaction kinetics while that inside the particles was heat transfer. Additionally, the results showed that the lower pyrolysis temperature was and the larger the particle size was, the more significant the heat transfer resistance was inside the particle. The time required for complete pyrolysis of pine wood chips particles would rise with the increase of particle size, but when particle size was above 10mm, the increment of time required for complete pyrolysis of pine sawdust was greater than that of particles below 10mm.

    One-step continuous synthesis of anisole in microreactor
    WANG Deqiang, SUN Chao, WANG Kai, LUO Guangsheng
    2022, 41(12):  6255-6260.  doi:10.16085/j.issn.1000-6613.2022-0227
    Abstract ( 67 )   HTML ( 4)   PDF (975KB) ( 47 )  
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    As an important chemical intermediate, anisole is mainly made by batch process using dimethyl sulfate and sodium phenol as raw materials in industry. However, neither the utilization rate of raw materials nor the production efficiency of anisole is satisfactory. Meanwhile, there are potential risks of dimethyl sulfate leakage during the production. In this paper, a microreactor system based on a microdispersion mixer and a static mixer was proposed, which employed phenol, sodium hydroxide, and dimethyl sulfate as the reactants, to implement the coupling of the formation of sodium phenate and the phenol methylation reaction and to realize the continuation and process intensification of the reaction process. The key influence factors such as feeding flow rate, molar ratio of phenol/dimethyl sulfate and concentration of sodium hydroxide were investigated, which demonstrated a transfer-controlled reaction mechanism within microreactor. Based on the mass transfer enhancement of micromixer and static mixer elements, up to 98.5% anisole yield was obtained in a reaction time less than 2min, and the consumption of dimethyl sulfate was reduced by 10% compared with the traditional reaction process, which provided the fundamental research for the upgrading of industrial production process.

    Energy processes and technology
    Analysis of present status and future technical route on large-scale hydrogen liquefaction plant
    ZHANG Zhenyang, MIAO Cong, WANG Feng, LAN Yuqi, AN Gang, YANG Shenyin
    2022, 41(12):  6261-6274.  doi:10.16085/j.issn.1000-6613.2022-0279
    Abstract ( 69 )   HTML ( 3)   PDF (1187KB) ( 59 )  
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    Hydrogen, as a zero carbon energy, is an effective strategic way to achieve China’s carbon peaking and carbon neutrality goals. The commercial application of hydrogen is about to increase sharply with the incorporation of hydrogen energy into China’s energy system. Hydrogen utilization has always been restricted by the lacking of high energy density storage and transportation technology due to the physical characteristics of hydrogen. Large-scale hydrogen liquefaction technology is a valid way to deal with the high-efficiency storage, transportation and utilization during the hydrogen application on account for the high storage density of liquid hydrogen. A statistical analysis of the currently known large-scale hydrogen liquefaction plants in the world on the capacity scale and operation status is achieved in this paper. Industrial hydrogen liquefaction plants in main producing countries are introduced. Three basic hydrogen liquefaction cycles are compared and the characteristics of the actual industrial plants are summarized. The principle and energy efficiency of the currently proposed large-scale conceptual hydrogen liquefaction systems are analyzed. The future design methods and development directions are suggested, so as to provide effective support for the development of high-efficiency and large-scale storage and transportation technologies of hydrogen energy and accelerate the wide commercial application of hydrogen energy.

    ISO/IEC, American, Japanese and Chinese hydrogen technical standardization system: comparison and suggestions
    SHI Wenbo, TSAI Chunming, LI Dewei, ONO Kei, ZHANG Jianbo
    2022, 41(12):  6275-6284.  doi:10.16085/j.issn.1000-6613.2022-1154
    Abstract ( 48 )   HTML ( 4)   PDF (3304KB) ( 40 )  
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    Technical standards are the cornerstone of industrial upgrading and international trade. A comprehensive overview and comparison of the development and current status of hydrogen technical standardization is essential to regulate and promote technological progress and global trade. In this work, the development and current status of hydrogen technical standardization of ISO/IEC, America, Japan and China were reviewed. It introduced hydrogen technical standardization organizations, compared detailly the ratio, structure and specific content of ISO/IEC international standards and national/industry standards of America, Japan and China, classified them into 8 technical categories of hydrogen technical standard system and revealed their distribution as well as features. Compared with America and Japan, Chinese hydrogen technical standardization system had the defects of fewer number of industry standards, weak dominance of hydrogen energy industrial associations in standardization process and insufficient technical coverage of some technical categories. Based on the comparisons, 2 practical suggestions were proposed for the development of Chinese technical standardization system, including authoring industrial associations the right of formulate hydrogen technical industry standard and optimizing the distribution of Chinese hydrogen technical standards.

    Research process of hydrate-based hydrogen storage
    LI Haoyang, ZHANG Wei, LI Xiaosen, XU Chungang
    2022, 41(12):  6285-6294.  doi:10.16085/j.issn.1000-6613.2022-0321
    Abstract ( 75 )   HTML ( 6)   PDF (718KB) ( 70 )  
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    Hydrogen as clean energy attracts more and more attention, and the demand for hydrogen energy utilization technology is increasingly urgent. Hydrogen storage and transportation are widely recognized as the key challenge within hydrogen technologies. Hydrates allow safe, long-term storage of hydrogen under relatively mild temperature and pressure conditions, providing an option for hydrogen storage. Hydrogen storage in hydrates has great potential for industrial application due to its safety and environmental protection characteristics, and the two key issues in its current industrial application are hydrogen storage density and hydrogen storage rate. This paper illustrated the research history of hydrogen hydrates, summarized the phase equilibrium data of several common hydrogen hydrates, then concluded the hydrogen storage densities of different hydrogen hydrates, and finally, generalized the effects of physical strengthening and chemical strengthening on hydration. Through the evaluation and summary of the hydrogen storage of hydrates in recent years, the current problems and future research directions of hydrogen storage in hydrates were put forward to provide references for the industrial application of hydrate gas storage and the research of hydrogen hydrate.

    Analysis on hydrogen energy economy and low cost of hydrogen source in typical cities of China
    TENG Xinyu, ZHANG Guohua, HU Chenshu, ZHU Cheng, YU Dan, LIU Di, LIU Sha
    2022, 41(12):  6295-6301.  doi:10.16085/j.issn.1000-6613.2022-0393
    Abstract ( 51 )   HTML ( 4)   PDF (540KB) ( 31 )  
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    Hydrogen economy is the focus of hydrogen and fuel cell vehicle industry development. A simple and effective calculation model for hydrogen cost of hydrogen refueling station(HRS) was built and can be used for the economic calculation of HRS under actual operation. Through the actual research, the hydrogen cost of HRS in Zhangjiakou, Zhengzhou, Yancheng and Foshan was obtained using the calculation model, respectively. These calculated results reflected that the hydrogen energy economy of HRS varies greatly due to different practical conditions such as hydrogen source, storage and transportation distance, and market scale of application. In order to promoted hydrogen economy and explored the feasibility of hydrogen cost less than 40CNY/kg, one station in Zhangjiakou was taken as an example where hydrogen comes from electrolysis of water by wind power generation, the composition of hydrogen cost was analyzed in detail, which concluded that the development of low-cost hydrogen source was very significant to reduce the hydrogen cost. In addition, according to the development status of hydrogen industry and its application prospect in the field of transportation, some suggestions were put forward from the aspects of reducing hydrogen production cost, hydrogen storage and transportation cost, depreciation of fixed assets and operating cost of HRS for improving hydrogen economy.

    Performance of thermal regenerative batteries with organic solvents
    LI Dong, SHI Yu, ZHANG Liang, LI Jun, FU Qian, ZHU Xun, LIAO Qiang
    2022, 41(12):  6302-6309.  doi:10.16085/j.issn.1000-6613.2022-0274
    Abstract ( 45 )   HTML ( 3)   PDF (993KB) ( 32 )  
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    Electrochemistry based thermal regenerative batteries (TRBs) can effectively convert low-grade waste heat into electric energy. However, there are still some limitations such as low open circuit voltage (<450mV), low energy density (<1260Wh/m3) and low thermal efficiency (<1.0%) for aqueous TRBs. Thus, the TRB system with organic solvent and acetonitrile as ligand was constructed by using copper complex to break through the limitation of low open circuit voltage of aqueous TRB. The effects of different organic solvents (propylene carbonate, ethylene glycol and ethylene carbonate), flow rate, acetonitrile content and operating temperature on the TRBs performance are investigated. The results showed that the open circuit voltage of the TRB system with acetonitrile as ligand was around 1.0V and the highest power density of 82W/m2 with an energy density of 3672Wh/m3 and a thermal efficiency of 2.6% was obtained in the TRB using propylene carbonate solvent electrolyte at 27℃. The maximum power density firstly increased with flow rate and afterwards kept approximately unchanged. The acetonitrile content had a significant effect on the open circuit voltage and the maximum power density of the battery, and the peak value was obtained at acetonitrile volume fraction of 75%. In addition, due to the enhancement of chemical reaction and the decrease of electrolyte viscosity, the maximum power density linearly increased with the increase of operating temperature in a certain range.

    Industrial catalysis
    Research progress on titanium dioxide based catalysts for catalytic oxidation of formaldehyde
    CUI Weiyi, DING Guomin, TAN Naidi
    2022, 41(12):  6310-6318.  doi:10.16085/j.issn.1000-6613.2022-0681
    Abstract ( 56 )   HTML ( 9)   PDF (3304KB) ( 53 )  
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    Formaldehyde (HCHO) is a primary indoor air pollutant with high carcinogenicity and mutagenicity. Catalytic oxidation is an ideal and effective method for indoor HCHO removal. Titanium dioxide as a carrier to support noble metal catalyst has showed excellent catalytic performance in the catalytic oxidation of formaldehyde. This review introduces recent progress of titanium dioxide based catalysts for catalytic oxidation of HCHO, summarizes the adsorption mechanisms of titanium dioxide, and analyzes the effects of titanium dioxide crystal structure, surface morphology and microstructure, surface active oxygen species and reducibility on the catalytic oxidation performance of HCHO with the focus on the relationship between the chemical and structural properties of catalysts and HCHO oxidation activity. Finally, the future research directions of titanium dioxide based catalysts in HCHO catalytic oxidation are given, namely, to further enhance the catalytic activity by reasonably designing various defects and crystal surface exposure of TiO2, to improve the dispersion of precious metals and atomic utilization efficiency, and to speed up the designing and practical application of monolithic catalyst while maintaining the high activity and stability of the catalyst.

    Recent progress in nickel-based catalysts for ammonia decomposition to hydrogen
    GUAN Jingying, ZHANG Huanhuan, SU Zikai, SHI Daxin, WU Qin, CHEN Kangcheng, ZHANG Yaoyuan, LI Hansheng
    2022, 41(12):  6319-6337.  doi:10.16085/j.issn.1000-6613.2022-0442
    Abstract ( 60 )   HTML ( 4)   PDF (2312KB) ( 43 )  
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    As a promising portable hydrogen production method, ammonia decomposition is clean and efficient, and easy for industrialization. Nickel is the best and most widely used non-precious metal catalysts for ammonia decomposition, but there are still unsolved problems such as low activity at low temperature and easy sintering. In this paper, the reaction mechanism, kinetics and thermodynamics of ammonia decomposition reaction are summarized, and the research status of nickel-based catalysts for ammonia decomposition at home and abroad in recent years is reviewed. It has been found that the adjustment of nickel particle size, the addition of second metals (Fe, Co, Mo, etc.), carriers (Al2O3, SiO2, molecular sieves, etc.), and additives (alkaline earth metals, rare earth metals, etc.) and designing the core-shell structure could be applied to control the dispersion and sintering resistance of nickel metal. Finally, the improvement measures and future development directions of nickel-based catalysts are proposed to provide a basis for the further design of low-temperature and high-activity nickel-based catalysts.

    Effect of carrier surface hydroxyl group on performance of Cu/SiO2 catalyst for DMO hydrogenation
    YUN Hongfei, ZHAO Yu, LI Guixian
    2022, 41(12):  6338-6349.  doi:10.16085/j.issn.1000-6613.2022-0285
    Abstract ( 52 )   HTML ( 2)   PDF (2579KB) ( 38 )  
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    Cu/SiO2 catalyst was prepared by ammonia evaporation method using nano-silica vapor as carrier and the contents and types of hydroxyl groups on the carrier surface were changed by step heating roasting. The structure, acidity and alkalinity of the Cu/SiO2 catalysts were characterized by BET, FTIR, DRIFT, XRD, TEM, H2-TPR, NH3/CO2-TPD, XPS and AES. Hydrogenation of dimethyl oxalate to ethylene glycol over the Cu/SiO2 was carried out in a continuous flow fixed-bed reactor to evaluate the catalytic activity at low temperature (448K) and low pressure (1.5MPa). The results showed that calcination of SiO2 at high temperature could significantly change the structure of the Cu/SiO2 catalyst and reduce its acidity and alkalinity, and greatly reduce the selectivity of alcohols or ethers in the hydrogenation of dimethyl oxalate. The selectivity of ethylene glycol over the Cu/SiO2-4 catalyst prepared by calcination of silica at 873K increased from 92% over the Cu/SiO2 prepared under low temperature roasted silica to more than 97% under the optimum reaction conditions. However, the calcination of silica lowered the performance of Cu/SiO2 catalyst, which should be improved by increasing the ratio of hydrogen to ester to obtain the best reaction result.

    Rod La x Ce1-x O y supported Ru catalyst for hydrogen production by ammonia decomposition
    ZHANG Shan, LIU Huazhang
    2022, 41(12):  6350-6357.  doi:10.16085/j.issn.1000-6613.2022-0392
    Abstract ( 54 )   HTML ( 3)   PDF (1513KB) ( 41 )  
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    The hydrogen by ammonia decomposition does not contain CO x, SO x, NO x and other harmful substances, which is advantageous to other carbon-containing hydrogen production methods. In this paper, a series of rod-like supports were prepared by a template-free hydrothermal method, and Ru/La x Ce1-x O y catalysts were prepared by a deposition precipitation method. The effects of preparation method and catalyst composition on the decomposition performance were investigated and the catalysts were characterized by SEM, XRD, BET, H2-TPR and CO2-TPD. The results showed that the ammonia decomposition rate of Ru/La0.4Ce0.6O1.8 catalyst with 40% La2O3 doping was 98% at normal pressure, 7800h-1 and 450℃. The high activity was attributed to the electro donating to metal Ru by the partially reduced CeO2-x and the strong basicity of the Ru/La0.4Ce0.6O1.8 catalyst surface. At the same time, the influence of K2O was investigated, and the optimal catalyst was Ru-2%K/La0.4Ce0.6O1.8, which gave an ammonia conversion of 93% at 400℃, 7800h-1, allowing it to be used as a promising new type high-efficiency ammonia decomposition catalyst in industry.

    FCC heavy cycle oil selective hydrogenation-catalytic cracking to produce more high value products
    FANG Dong, HE Yi, CUI Xiaochen
    2022, 41(12):  6358-6363.  doi:10.16085/j.issn.1000-6613.2022-0343
    Abstract ( 49 )   HTML ( 1)   PDF (1440KB) ( 36 )  
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    With the excess domestic diesel output and low gasoline demand, reducing the diesel-to-gasoline ratio and increasing the production of chemical products have become the preferred transformation route for refineries. In this work, based on the molecular structure, HCO was selectively hydrogenated to convert PAHs to crackable components, which were then cracked in an FCC unit. According to market demand, flexible adjustment between light oil and chemical feeds could be made. After selective hydrogenation of HCO, FCC conversion rate is up to 60.14%(mass ratio), and the yield of gasoline and diesel increased 19.16%(mass ratio) and 6.50%(mass ratio) from HCO, respectively. The total aromatics in gasoline is 56.8%(mass ratio), of which triphenyl is 21.3%(mass ratio), about 37% of the total aromatics. Moreover, the yields of heavy oil and coke decrease significantly.

    Secondary growth mechanism of nano-ZSM-5 in solution of high SiO2/Al2O3 ratio and its performance of methanol to aromatics
    HUI Yan, FU Tingjun, MA Qian, LI Zhong
    2022, 41(12):  6364-6376.  doi:10.16085/j.issn.1000-6613.2022-0363
    Abstract ( 42 )   HTML ( 1)   PDF (5458KB) ( 23 )  
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    Low selectivity is the main issue in methanol to aromatics (MTA) reaction catalyzed by ZSM-5. Rational design and control of the acid properties of ZSM-5 catalysts is an effective strategy to promote highly selective generation of aromatic hydrocarbons. In this study, nano ZSM-5 with SiO2/Al2O3 ratio of 50 was placed in ZSM-5 synthesis system with different SiO2/Al2O3 ratios (50, 110, 220, 440 and 660) for secondary growth to prepare a series of samples to optimize the surface acidities and improve the selectivity of light aromatics. The morphology, texture properties and acid properties of the ZSM-5 zeolites were characterized by using X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray fluorescence (XRF), pyridine adsorption Fourier-transform infrared (Py-IR) and temperature-programmed desorption of ammonia (NH3-TPD), and the crystal growth mechanism was studied accordingly. During the crystal growth, the parent powder was partially dissolved and small crystals were formed firstly, surrounding the surface of the parent ZSM-5. The crystals grown over N50 to form nanosized single-crystal coated ZSM-5. The particle size distribution of the sample was not uniform after secondary growth in the feed solution with low SiO2/Al2O3 ratio. But on the whole, with the increase of SiO2/Al2O3 ratio, the crystal particles tended to be uniform and zeolites with rough protrusions structure. The secondary growth significantly changed the acid properties of the zeolite surface and aromatization properties. The total acid amount increased to 194.9μmol/g, after secondary growing in the feed solution with a higher SiO2/Al2O3 ratio (220), which was significantly higher than that of the parent powder (169.7μmol/g). It is worth noting that the proportion of strong acid on the catalyst surface also increased significantly from 37% of the parent powder to 53%, and B/L ratio also increased from 0.56 to 3.19. The acidity modulation not only facilitated the conversion of methanol to aromatics, but also strengthened the dealkylation conversion of aromatics and BTX selectivity increased accordingly. Thus, the selectivities of aromatics and BTX were increased from 16.1% and 8.2% to 23.8% and 13.5%, respectively.

    Preparation of Pt/C catalyst by continuous pipeline microwave technology and its oxygen reduction performance
    FENG Zhanxiong, WANG Yun, MA Qiang, ZHANG Chuang, WANG Cheng
    2022, 41(12):  6377-6384.  doi:10.16085/j.issn.1000-6613.2022-0305
    Abstract ( 46 )   HTML ( 2)   PDF (5194KB) ( 38 )  
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    Traditional preparation of Fuel cell catalyst is uncontrollable and takes long reaction time, and the produced catalyst has poor consistency and durability. In this work, a rapid, simple and consistent continuous pipeline microwave method for catalyst preparation was developed. Traditional ethylene glycol reduction of chloroplatinic acid was used to prepare catalyst with 50%(mass) platinum capacity using carbon black treated at 1400℃ as carbon carrier. The half-wave potential of Pt/C-1400 catalyst is more than 0.9V. After 20000 cyclic voltammetry decay tests of carbon carrier in the high potential range of 1.0—1.5V for the reference reversible hydrogen electrode, the retention rate of the electrochemically active surface area and the mass specific activity of Pt/C-1400 catalyst are up to 79% and 85%, respectively, showing its significant corrosion resistance and excellent durability. This work provides an effective and feasible way for the production of high durability catalyst.

    Materials science and technology
    Research progress of membrane electrode assembly of proton exchange membrane water electrolysis for hydrogen production
    WAN Nianfang
    2022, 41(12):  6385-6394.  doi:10.16085/j.issn.1000-6613.2022-0383
    Abstract ( 69 )   HTML ( 5)   PDF (1209KB) ( 48 )  
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    Hydrogen production from proton exchange membrane water electrolysis (PEMWE) has the advantages of its adaptability to intermittence and fluctuation of renewable energy such as wind and solar energy, high energy conversion efficiency, start-up quickly, small volume, etc., It has attracted great attention as a technology for green hydrogen production. Membrane electrode assembly (MEA), a key parts of hydrogen production from water electrolysis, is of significant importance to the performance, efficiency and lifetime of water electrolysis. Furthermore, its cost contribution to the overall system increases significantly with the increase of production capacity. It is critical to develop MEA with high performance, low cost and high durability for the large scale production of low cost green hydrogen. In this paper,the research progress and achievements of some key materials and components for MEA of PEMWE, including proton exchange membrane, catalyst layer, porous transport layer etc., as well as manufacturing technology of MEA are reviewed. Some progress on how to improve performance of hydrogen generation from water electrolysis, how to reduce the cost of MEA, etc., are systematically analyzed from the aspect of MEA design and development. Finally, some future research directions are proposed.

    Research status and application in H2/CH4 separation of MOFs-based membrane
    GAO Yifei, YI Qun, QI Kai, GAO Lili, LI Xuelian
    2022, 41(12):  6395-6407.  doi:10.16085/j.issn.1000-6613.2022-0404
    Abstract ( 47 )   HTML ( 3)   PDF (3155KB) ( 44 )  
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    The production of hydrogen, its separation and storage for use is an important component of the green energy economy of the world. It is a promising separation technology to purify hydrogen from industrial by-products by membrane separation, which is not only easy to operate, but also significantly reduces the energy consumption of separation. Metal-organic frameworks (MOFs) materials possess crystal phase, ordered well-defined porous structure and large surface area, which are considered as an ideal membrane material for gas separation. Based on the literature, the recent progresses in conventional MOFs-based membrane preparation techniques of hydrothermal/solvothermal method, interfacial synthesis method, secondary growth method and casting method are reviewed, including the synthesis mechanism and application. Moreover, the design principle and application of MOFs membrane for H2/CH4 separation are also reviewed. Aiming at the problems of the flexibility, pore size, grain boundary structure and stability in order to realize the regulation of MOFs membrane’s performance, the improvement of preparation method and the post-modification strategy for MOFs membrane are introduced. By analyzing and comparing the key technologies, it is pointed that the challenges of MOFs membrane is difficult for large-scale production and the separation performance is insufficient. The effort to promote application of the MOFs membrane in the future is to develop large-scale and low-cost preparation methods and to improve MOFs membrane’s separation performance.

    Research progress of metal-organic framework-based phase-change materials for thermal energy storage
    ZHANG Xinyu, ZHAO Zhenxia
    2022, 41(12):  6408-6418.  doi:10.16085/j.issn.1000-6613.2022-0402
    Abstract ( 42 )   HTML ( 1)   PDF (2819KB) ( 43 )  
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    Solid-liquid phase-change materials (PCMs) are abundant in variety and have relatively high latent heat, thus making them important working media for latent heat storage systems. Combining solid-liquid PCMs with porous supporting materials is an effective way to improve their application performance and service life. Metal-organic frameworks (MOFs) is a new kind of porous material, which has advantages of large specific surface area, high porosity, adjustable pore size and surface properties, thereby making them promising supporting materials for solid-liquid PCMs. This paper thoroughly reviewed the MOF-based composite PCMs. Specifically, the composite PCMs directly employing the MOFs as the supporting materials, the composite PCMs employing the MOFs derived porous carbon materials as the matrices, and the composite PCMs employing the hybrid materials prepared by in-situ growing MOFs on thermally conductive matrices as the carriers, are introduced respectively. The strong capillary force generated by the microporous structure of MOFs had a strong fixation effect on the solid-liquid PCMs. Synthesizing the MOFs with large pore sizes or modifying the MOFs to adjust its interactions with the PCMs are useful to increase the loadings of the PCMs and thus the latent heat of the obtained composite PCMs. Carbonizing the MOFs at high temperatures to obtain MOFs derived porous carbon materials could enlarge the pores of the MOFs, and the accompanying nitrogen and phosphorus doping could enhance the hydrogen bonding between the supporting materials and PCMs, all of which helped to acquire the composite PCMs with high loadings and latent heat. The in-situ growing MOFs on thermally conductive matrices to build a continuous heat transfer network could effectively enhance the thermal conductivity of the obtained composite PCMs. The thermal conductivity of the composite PCMs could be further increased by employing the hybrid materials prepared by carbonizing the in-situ growing MOFs thermally conductive matrices as the carriers. In the end, it is pointed out that the types of MOFs and phase-change materials used in MOF-based composite phase-change materials, the influence of the interaction between MOFs and phase-change materials on the heat storage performance, and the stability of MOFs after compounded with phase-change materials needed further exploration in the future. Besides, developing multifunctional materials by combining the catalytic and detection functions of MOFs with the heat storage and temperature control functions of phase-change materials was also one of the future development directions.

    Application and research progress of carbonization consolidation of high temperature coal tar pitch binder in formed carbon material
    YANG Yongbin, DONG Yinrui, ZHONG Qiang, LI Qian, WANG Lin, JIANG Tao
    2022, 41(12):  6419-6429.  doi:10.16085/j.issn.1000-6613.2022-0284
    Abstract ( 44 )   HTML ( 0)   PDF (2154KB) ( 27 )  
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    High temperature coal tar pitch (HTCTP) has excellent wettability and cohesiveness, and can be used as binder. HTCTP binder can produce good consolidation with carbonaceous granular materials, so it has been widely used and studied in the preparation of different types of formed carbon material. The mechanical strength and physicochemical properties of formed carbon material are determined by the bonding performance and carbonization consolidation effect of HTCTP in high temperature process. In this paper, the general technological process and relative research progress of carbonization materials prepared with HTCTP as binder are reviewed, and the common mechanism and individual characteristics of carbonization consolidation of HTCTP in different application fields are combed. The factors affecting the performance of HTCTP and the mechanism of carbonation consolidation are also summarized. By analyzing the role and transformation process of different components of coal pitch in carbonization consolidation process, the related mechanism between the carbonization consolidation of HTCTP and the mechanical strength of formed carbon material and the key factors influencing the carbonization consolidation strength are revealed. The measures to strengthen the carbonization consolidation of HTCTP were proposed to enhance the application effect of carbonization consolidation in the preparation of formed carbon material.

    Research progress on modification strategy of graphite carbon nitride based on dimensional regulation
    ZHOU Jie, SUN Yue, BAO Yan, LIU Zejue, ZHANG Shasha, ZHU Beibei, WANG Lu, GUAN Guofeng
    2022, 41(12):  6430-6442.  doi:10.16085/j.issn.1000-6613.2022-0365
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    As a non-metallic semiconductor material, graphite phase carbon nitride (g-C3N4) shows good application prospects in the fields of energy and environmental catalysis due to its unique physical and chemical properties and excellent photocatalytic performance.However, the disadvantages of bulk phase g-C3N4, such as low degree of polymerization, small specific surface area and few active sites, restrict its further application. The synthesis of bulk g-C3N4 into various low-dimensional structure is one of the effective strategies to overcome the above defects. Based on the above modification strategies, this article systematically introduces the main synthesis methods of low-dimensional g-C3N4 with zero dimensional, one-dimensional, two-dimensional and three-dimensional nanostructures in recent years, analyzes the effects of different dimensions on the energy band structure, generation and transfer efficiency of photogenerated electrons and holes, light absorption capacity and photocatalytic performance of g-C3N4, and summarizes the specific applications of materials with different dimensions in the fields of energy and environmental catalysis. At the same time, it is pointed out that the current research work generally had some problems, such as lack of in-depth reaction mechanism, and lack of large-scale synthesis and industrial application. Looking forward to the future while strengthening the theoretical in-depth research, it is necessary to further expand the development of key technologies of g-C3N4 in the field of industrial treatment of wastewater and waste gas and that of carbon conversion in order to provide direction and guidance for the follow-up research work.

    Research progress on artificial intervention and characterization of physicochemical properties of microplastics aging
    CHEN Guodong, LIU Haicheng, MENG Wushuang, YOU Yu, ZHANG Hao, CAO Mengru
    2022, 41(12):  6443-6453.  doi:10.16085/j.issn.1000-6613.2022-0300
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    Microplastics could undergo natural aging process in the environment. Due to the problems of slow aging and complex process, natural aging is not conducive to the research on long-term fate and risk assessment of microplastics in the environment. Therefore, the researchers used artificial intervention techniques to accelerate the aging process of microplastics in the experiment, but the method types and parameter conditions used to accelerate aging are different. This paper summarizes the artificial intervention techniques used in the existing microplastics aging research, and pointed out their characteristics and applicability. Among these aging methods, the optical radiation and advanced oxidation processes are widely used because of simple operation and obvious aging effect. Then, the changes in physicochemical properties of microplastics caused by aging process are described from the aspects of micro-morphology, specific surface area and surface functional groups, and introduced the application of corresponding characterization techniques. Finally, for the future research work of microplastics aging, some suggestions are proposed to provide support for aging technology development and relevant standards formulation, such as emphasizing the in situ environmental aging research of microplastics, considering various aging ways or environmental factors, investigating the release of additives or oxidation by-products, and formulating the standard / protocol of microplastics aging.

    Effect of hydrochloric acid pretreatment on the electrochemical properties of enteromorpha-based activated carbon
    WANG Yilin, LI Shijie
    2022, 41(12):  6454-6460.  doi:10.16085/j.issn.1000-6613.2022-0435
    Abstract ( 38 )   HTML ( 0)   PDF (1225KB) ( 20 )  
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    Activated carbons prepared by conventional processes have sufficient micropores but lack medium and large pore contents, resulting in low levels of electrochemical performance when used as electrode materials for supercapacitors. To solve this problem, hydrochloric acid was used to pretreat the enteromorpha raw material before charring. The acid treatment removed most of the impurity metals from the raw material, in which calcium alginate reacted chemically with hydrochloric acid to form eggshell initial pores and acid-soluble alkali metal ions reacted with hydrochloric acid to form irregular initial pores, significantly increasing the mesoporous content of the activated carbon. The experimental results showed that the specific surface area of activated carbon increased significantly after hydrochloric acid pretreatment from 2273m2/g to 3166m2/g and the pore volume increased from 2.10cm3/g to 3.82cm3/g. The mesoporosity increased significantly, improving the connectivity of the pore structure and promoting the diffusion of electrolyte ions within the material. When the current density was 0.1A/g, the specific capacitance of the acid-washed activated carbon was as high as 359F/g, an increase of 23% over the 293F/g specific capacitance of the as-built activated carbon, and the capacitor equivalent series resistance was very small, showing excellent electrochemical performance.

    Preparation and performance of anode material modifiers based on coal series heavy aromatic hydrocarbons
    CHEN Xue, LIU Shulin, HE Fengxiang, LYU Han, WU Quanyu, WANG Hao, QU Bin
    2022, 41(12):  6461-6468.  doi:10.16085/j.issn.1000-6613.2022-0352
    Abstract ( 43 )   HTML ( 1)   PDF (2146KB) ( 26 )  
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    The modification agents for the current commercial anode material are mainly made of refined bitumen of coal and petroleum, while the quality is remarkably different and the cost is always high. To address these problems it was proposed to use low-cost coal-based heavy aromatic hydrocarbons as the precursor to prepare the modification agent through purification and polymerization processes. The modification was firstly ground and coated on the needle coke, and then the anode was obtained by a subsequent granulation process with a pyrolysis process. The rheological properties and thermogravimetric properties of the modifier were analyzed by rotational rheometer and thermogravimetric analyzer. The apparent morphology, pore structure, layer spacing, crystallinity and electrochemical properties of the modified samples were characterized by scanning electron microscope, gas adsorption apparatus, X-ray diffractometer, laser Raman spectrometer and a battery test system. The electrochemical test showed that the reversible capacity of the modified negative electrode increased from 333.02mAh/g before modification to 356.34mAh/g and 359.67mAh/g, and the initial coulombic efficiency increases by 1.72% and 1.31%. The retention rate of 98.87% over 100 cycles at 30mA/g can be obtained. The reversible capacity increased from 95.27mAh/g before modification to 147.52mAh/g and 187.30mAh/g at 300mA/g. The results indicated that the anode material prepared by adding modifier exhibited excellent specific capacity, rate performance and cycle stability. Simultaneously, the cost was low and the industrialization of preparation process was feasible.

    Preparation of g-C3N4/MIL-125(Ti) magnetic composites for Rhodamine B removal
    CHEN Zhangxu, LI Yanhui, REN Hongyun, ZHANG Lidan, ZHENG Bingyun
    2022, 41(12):  6469-6476.  doi:10.16085/j.issn.1000-6613.2022-0302
    Abstract ( 43 )   HTML ( 2)   PDF (1984KB) ( 30 )  
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    To solve the problems of energy shortage and environmental pollution, semiconductor photocatalysis materials were used for organic pollutants removal in this paper. A series of visible light responsive MIL-125(Ti) composites with different mass ratios were synthesized by solvothermal method with using MIL-125(Ti) as photocatalyst carrier, g-C3N4 as organic semiconductor and Fe3O4@SiO2 as magnetic carrier. The obtained composites were thoroughly characterized by Fourier transform infrared spectrometer, X-ray diffractometer, field emission scanning electron microscope and thermal gravimetric analyzer. The performance of the composite material for Rhodamine B removal was further investigated by L16(45) orthogonal array. The results showed that the optimum processing conditions for Rhodamine B removal were as follows: the photocatalysis time of 4.0h, the mass ratio of g-C3N4 to MIL-125(Ti) of 1∶20, the catalyst dosage of 0.01g and the Rhodamine B solution concentration of 10.0mg/L. The removal rate of Rhodamine B reached 96.57% under the optimal condition. After 4 cycles of experiments, the removal rate can still reach 86.52%. The preparation process of g-C3N4/MIL-125(Ti) magnetic composites and the mechanism on organic dyes removal can be used as a reference for the treatment of organic dye wastewater.

    Preparation and performance of floating carbon nitride photocatalyst CNx@mEP
    CHEN Yu, WANG Jiajia, TANG Lin
    2022, 41(12):  6477-6488.  doi:10.16085/j.issn.1000-6613.2022-0414
    Abstract ( 33 )   HTML ( 2)   PDF (5191KB) ( 19 )  
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    A floating carbon nitride photocatalyst, CNx@mEP, was prepared by the “impregnation-calcination” method using expanded perlite as the carrier, which can be easily recycled and reused. The CNx@mEP was analyzed by Scanning electric microscopic (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Automatic specific surface and aperture analyzer (BET), Fourier transform infrared spectroscopy (FTIR) and UV-vis absorption spectroscopy (UV-vis). The photocatalytic performance of the catalysts was investigated by dye degradation experiments and harmful algae removal experiments. The best photocatalytic performance of the CN2@mEP material was obtained when the mass ratio of dicyandiamide used to the expanded perlite carrier was 2∶1. At a dosage of 4g/L, 67.2% of Rhodamine B, 86.8% of Congo red, 31.2% of Methyl orange dye and 35% of Microcystis aeruginosa were degraded under visible light irradiation for 4h. The floating carbon nitride photocatalyst maintained a relatively stable removal efficiency after 3 reuse cycles.

    Preparation of acid-modified pig manure biochar and its adsorption performance on Direct Red 23
    JIANG Ruqing, YU Guangwei, WANG Yu, LI Changjiang, XING Zhenjiao
    2022, 41(12):  6489-6499.  doi:10.16085/j.issn.1000-6613.2022-0445
    Abstract ( 41 )   HTML ( 2)   PDF (2077KB) ( 29 )  
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    Direct Red 23 (DR23) solution was used to simulate dye wastewater, and the adsorption characteristics and mechanism of pig manure biochar before and after acid modification were compared. The influence of pH, initial concentration, adsorption time, adsorption temperature and the amount of adsorbent on the adsorption effect were investigated by static adsorption experiments, and the adsorption kinetics and adsorption isotherms were determined. It is found that compared with unmodified biochar (PMB), acid-modified biochar (PMBacid) exhibits better decolorization performance with porous structure and rich surface functional groups. The maximum adsorption removal rate of DR23 is 96.10%, the maximum saturated adsorption capacity is 111.51mg/g, and the removal rate of DR23 by PMBacid can still reach 88.31% after three cycles of regeneration. In addition, pH value has little influence on the adsorption performance of PMBacid. The adsorption of DR23 by PMBacid is a complex process controlled by reaction rate and diffusion, which fits the pseudo-second-order kinetic model and Langmuir isothermal adsorption model. The adsorption mechanism of biochar for DR23 depends on the physicochemical properties of the adsorbent, and its pore structure and functional groups participate in the adsorption process of biochar for DR23 through different mechanisms.

    Asymmetric Janus membranes based on hydrophilic modification of dopamine for efficient oil/water separation
    SHAN Linna, YANG Zhensheng, YAN Guofei, LI Chunli, LI Hao, WANG Zhiying
    2022, 41(12):  6500-6510.  doi:10.16085/j.issn.1000-6613.2022-0268
    Abstract ( 43 )   HTML ( 2)   PDF (5292KB) ( 32 )  
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    Current special wetting materials used for treating oily wastewater are usually divided into the oil-removing type or the water-removing type, which are limited to separating single emulsion. In this paper, Janus membranes with asymmetric wettability were fabricated by alternating soaking process and non-woven peeling upon dopamine-modified PVDF membranes. By facilely adjusting the number of alternating soaking and peeling the nonwoven fabric, superhydrophilic/underwater superoleophobic surface and superhydrophobic/superoleophobic bottom surface could be respectively obtained, where the discrepancy in water contact angle between these two surfaces water contact angle was up to 150°. Based on the asymmetric wettability of Janus membranes, high permeate flux of 367L/(m2·h) and 1729L/(m2·h) were achieved for surfactant-stabilized oil-in-water (O/W) and water-in-oil (W/O) emulsions by simply switching the transmembrane direction, where the COD in the permeate of oil-in-water fulfilled the petrochemical discharge standard and the water content in the permeate of water-in-oil was less than 80mg/L, achieving efficient separation of O/W and W/O emulsions. Moreover, Janus membranes exhibited ideal antifouling property and reusability during BSA solution separation process.

    Biochemical and pharmaceutical engineering
    Dynamic regulation strategies and regulation network construction of metabolic pathways in microbial cell factories
    XU Jianping, WANG Ying, LI Chun, ZHOU Xiaohong
    2022, 41(12):  6511-6521.  doi:10.16085/j.issn.1000-6613.2022-0418
    Abstract ( 37 )   HTML ( 0)   PDF (2103KB) ( 33 )  
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    The production of target products in microbial cell factories will face problems such as nutrient consumption, metabolite accumulation, heterologous pathway pressure and genetic instability, leading to metabolic imbalances. Therefore, it is necessary to redesign the metabolic pathway of cells, so that the metabolic pathway can automatically adjust metabolic flux according to the changes of fermentation conditions and other environmental conditions to achieve efficient production. In this review, the classification, regulatory mechanism and application of dynamic regulatory elements are introduced firstly, and the proteinous transcription factor regulatory elements and RNA ribose switch regulatory elements which interact with inducers or inducing factors are mainly described. Then the design and modification strategies of dynamic regulatory elements based on transcription factors and promoter sequences are introduced. Subsequently, strategies for construction of dynamic regulatory network in metabolic pathway using inducible regulatory elements are summarized. The regulation of gene expression has shifted from single-input signal regulation to multi-input signal logic gate regulation, and a more accurate dynamic regulatory network can be constructed through multiple input signal logic gate and closed-loop metabolite feedback loop. The construction of dynamic regulatory network will be significant for construction of most effective microbial cell factories.

    ZIF-8-glutaraldehyde-immobilized cells to produce α-ketoglutaric acid
    DAI Jingxin, SONG Wei, CHEN Xiulai, LIU Liming, WU Jing
    2022, 41(12):  6522-6530.  doi:10.16085/j.issn.1000-6613.2022-0385
    Abstract ( 44 )   HTML ( 1)   PDF (2688KB) ( 27 )  
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    In order to improve the catalytic stability of recombinant Escherichia coli (E.coli) containing L-glutamate oxidase (LGOX), a combined immobilization technique of zeolite imidazole framework (ZIF-8) coating and glutaraldehyde (GA) cross-linking was used in this study. The process parameters of immobilized cells were determined and the stability of α-ketoglutarate (α-KG) produced by immobilized cells was studied. The specific activity and activity recovery of immobilized cells (E.coli@ZIF-8-GA) were reached 33.4U/g and 95.83%, respectively, when 2-methylimidazole, zinc acetate and glutaraldehyde were added at 240mmol/L, 80mmol/L, and 50mmol/L, respectively. The results showed that the yield of α-KG could still reached 70.03g/L after reusing immobilized cells for 10 batches, which meant the stability of free cells in the reaction was enhanced. Compared with free cells, the tolerance to temperature and pH of immobilized cells was significantly improved, which laid a solid foundation for the application of immobilized catalyst to producing α-KG.

    Balanced optimization of the 1,2,4-butanetriol synthesis pathway in recombinant Escherichia coli
    GUO Chao, FENG Ao, LU Xinyao, ZONG Hong, ZHUGE Bin
    2022, 41(12):  6531-6539.  doi:10.16085/j.issn.1000-6613.2022-0459
    Abstract ( 32 )   HTML ( 0)   PDF (1590KB) ( 25 )  
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    1,2,4-Butantriol (BT) is a non-natural chemical product, which is the precursor of 1,2,4-butantriol trinitrate of military materials. In recombinant E. coli, BT was synthesized from xylose by dehydrogenation, dehydration, decarboxylation and reduction. However, the unbalanced reactions of the pathways lead to the accumulation of intermediate metabolites, which limits bacterial growth and product synthesis. In this study, CRISPR/Cas9 was used to knock out genes yjhG and yqhD to construct a backgroundless expression host bacteria, and then different promoter combinations were used to regulate the expression of genes xdh, yjhG and yqhD in the BT synthesis pathway. It was found that expression of the alcohol dehydrogenase gene yqhD with P inv resulted in BT yield of 14.4g/L and the combination of dehydrogenase gene xdh expressed by P tac and dehydrase gene yjhG expressed by P rrnH P1 made BT yield reach 15.6g/L, which was 5.9% and 14.7% higher than that of the control strain KXW3009, respectively. This study facilitated the synthesis of BT through the regulation of upstream and downstream gene expression of intermediate metabolites, which provides a reference for subsequent studies.

    MOF-immobilized lipase-catalyzed epoxidation of limonene in a single-phase system
    MENG Zihao, LI Qingyun, LIU Youyan, LIN Dongliang, TANG Aixing
    2022, 41(12):  6540-6548.  doi:10.16085/j.issn.1000-6613.2022-0468
    Abstract ( 35 )   HTML ( 0)   PDF (2193KB) ( 27 )  
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    Chemoenzymatic epoxidation of olefins is a green and environmental friendly alternative process. However, as an oxidant, hydrogen peroxide leads to the inactivation of lipase and the interphase mass transfer of the reaction system, which needs to be solved urgently. In this work, a stable MOF-immobilized lipase catalyst CALB@Uio-66-NH2 was successfully synthesized by covalent cross-linking, the structure and crystal form were characterized by scanning electron microscope (SEM) and X-ray diffractometer (XRD). In order to solve the problem of two-phase mass transfer resistance caused by hydrogen peroxide, the effects of polar solvents and ester acyl donors on the reaction were studied. Tert-butanol was finally determined as the solvent and ethyl acetate as the acyl donor. A single-phase reaction system suitable for the chemoenzymatic epoxidation of limonene was constructed to replace the traditional “organic-water” two-phase reaction system. Then, the catalyst addition, hydrogen peroxide concentration and acyl donor concentration were optimized to obtain the optimal reaction efficiency. When the concentration of limonene was 0.1mol/L, the optimized catalyst addition was 20%, and the optimum concentration of hydrogen peroxide and ethyl acetate was 0.5mol/L and 3mol/L, respectively, the yield of 1,2-epoxide was 85.1%, under this condition, CALB@Uio-66-NH2 can still maintain 90.9% relative activity after 6 times of reuse.

    Fine chemicals
    Polyacrylamide porous microspheres prepared by multiple Pickering emulsions method and its application
    XU Ruixue, CHENG Fengru, MA Jing, DENG Yufeng, ZHAO Jianbo
    2022, 41(12):  6549-6556.  doi:10.16085/j.issn.1000-6613.2022-1510
    Abstract ( 46 )   HTML ( 0)   PDF (3255KB) ( 25 )  
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    O/W/O double emulsion was prepared by using hydrophilic fumed silica N20 and hydrophobic fumed silica H30 to compounded surfactants, and polyacrylamide (PAM) porous microspheres were prepared by using this as a template, polymerizing the mesophase and volatilizing the inner phase, while their adsorption properties to methylene blue were tested. The results showed that the water oil ratio had a great influence on the formation of double emulsion, and when the water oil ratio (O1/W)/O2 was (1/2)/2, a stable double emulsion can be obtained. Scanning electron microscope (SEM) photos showed that PAM porous microspheres were basically spherical, but the particle size was uneven, the surface of the sphere was rough, and the interior was hollow. The results of Laser Particle Sizer (DLS) showed that the average particle size of PAM microspheres was 356nm, the polydispersity coefficient (PDI) was 0.718, BET surface area was 54.695m2/g, and the particle size distribution was wide. At the adsorption temperature of 35℃, the adsorption rate of methylene blue can reach 98.89% in 5s, which was better than the traditional PAM adsorbent in adsorption rate and adsorption quantity. This study provided a new method for the treatment of dye wastewater.

    Resources and environmental engineering
    A review of superhydrophobic three-dimensional porous materials for oil/water separation of emulsions
    LIANG Ge, HUANG Xiangfeng, LIU Wanqi, XIONG Yongjiao, PENG Kaiming
    2022, 41(12):  6557-6572.  doi:10.16085/j.issn.1000-6613.2022-0430
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    Superhydrophobic three-dimensional(3D) porous materials can effectively adsorb and recover oil slick based on special wettability and capillary action, which have recently been applied in oil/water separation of emulsions. In this paper, the preparation methods of superhydrophobic 3D porous materials are summarized, and the oil/water separation efficiency of emulsion and the action mechanism of oil droplets in the material are analyzed. In terms of preparation methods, porous materials represent by sponge mainly obtained super-hydrophobicity by modifying with low surface energy substances and constructing rough structures. High adsorption capacities (31—131g/g) of oil are achieved as a result. As for the oil/water separation of emulsions, superhydrophobic 3D porous materials are mostly applied to oil-in-water model emulsions with low concentration of oil and surfactants, and containing micron-scale droplets, while the actual emulsions are rarely treated. The application methods included immersion and filtration based on adsorption and adsorption coupled with rejection, respectively. It is found that the key factors affecting the oil/water separation efficiency are pore size, hydrophobicity and surface electrical property of the materials. Furthermore, the process of adsorption of oil droplets by hydrophobic porous materials remain at a theoretical speculation level. The main view is that the materials efficiently trapped and adsorbed oil droplets by a synergy between the cage-like porous structure and hydrophobic surface. Then, the oil droplets coalesced to form oil layer and finally be removed. Although the superhydrophobic 3D porous materials made some progress in the oil/water separation of emulsions, it is still necessary to promote its applicability to actual waste emulsions, and design and develop continuous separation equipment to realize engineering application. The migration and transformation of oil droplets in porous materials and the key steps should be analyzed and identified by in-situ observation, numerical simulation and mechanical analysis to reveal the mechanism involved in depth.

    Progress of oily sludge extraction by supercritical CO2
    JIA Wenlong, SONG Shuoshuo, LI Changjun, WU Xia, YANG Fan, ZHANG Yuanrui
    2022, 41(12):  6573-6585.  doi:10.16085/j.issn.1000-6613.2022-0314
    Abstract ( 44 )   HTML ( 0)   PDF (2370KB) ( 42 )  
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    Oily sludge is a complex multiphase stable emulsified colloid system, which contains a large amount of organic matter and flocs. It mainly comes from the process of oil and gas development and transportation. The volumetric content of oil in the sludge is generally 10%—30%. Extraction and recovery of the oil in the sludge can realize the harmless treatment of the sludge and produce considerable economic benefits. Supercritical carbon dioxide (supercritical CO2, scCO2) can dissolve small molecules of organic matter. And its diffusion coefficient is much larger than that of liquid, approaching that of gas. And it has good flow permeability. This technology has great application prospects for extracting oil-based components in oily sludge. In this paper, the principle and industrial application of scCO2 extraction were reviewed. Combined with experiment and theory, following three aspects of the research could be focused: ①According to the characteristics of complex composition and high content of polar components of oily sludge, combined with the multiphase equilibrium experiment of scCO2 and oily sludge, the multiphase equilibrium model of scCO2 extraction was established to clarify the multiphase equilibrium characteristics and influencing factors of scCO2 extraction of oily sludge. ② Based on the microscopic effects of scCO2 extraction of oil base, the laws of adsorption and diffusion between oil base and sludge matrix was explored, and the kinetic characteristics and mechanism of scCO2 extraction were qualitatively described and quantitatively reveal; ③Considering the economy of the extraction process and taking the highest extraction rate as the objective function, the optimization model of extraction conditions was established to provide theoretical and technical supports for the design, optimization and industrial application of scCO2 extraction oily sludge process.

    Preparation of magnetic biochar and its application in polluted water
    SONG Shaohua, XU Jinlan, SONG Xiaoqiao, YU Yuan
    2022, 41(12):  6586-6605.  doi:10.16085/j.issn.1000-6613.2022-0369
    Abstract ( 46 )   HTML ( 0)   PDF (1612KB) ( 33 )  
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    The preparation method and required raw materials of magnetic biomass charcoal are introduced, especially the application in polluted water.The preparation methods of magnetic biochar including impregnation-pyrolysis, liquid-phase reduction, co-precipitation and physical mixing are expounded, and the advantages and disadvantages of various preparation methods are pointed out. The influencing factors and mechanism of the adsorption of pollutants by magnetic biochar are mainly analyzed. It is found that the pyrolysis temperature and dosage of magnetic biochar, the pH value of the solution, the reaction time, the initial concentration of pollutants, the adsorption temperature and other competing ions in the solution have a certain influence on the adsorption effect of pollutants. Moreover, its adsorption mechanism is complex, and the key adsorption mechanisms include physical adsorption, ion exchange, electrostatic adsorption, co-precipitation, and surface complexation. The application of magnetic biochar in polluted water is summarized in detail. Magnetic biochar has been widely used to remove various pollutants in water, including heavy metals, inorganic anions, antibiotics, pesticides, organic dyes and nuclear pollutants. In addition, the regeneration and recovery of magnetic biomass carbon are evaluated.

    Research progress of collagen-derived carbon in water treatment
    CHEN Yiping, HUANG Yaoyi, ZHENG Chaohong
    2022, 41(12):  6606-6614.  doi:10.16085/j.issn.1000-6613.2022-0271
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    Collagen-derived carbon has many advantages, such as wide source of raw materials, low cost, adjustable porous structure, excellent conductivity, high defect density and rich heteroatom doping. The research status of collagen-derived carbon at home and abroad is reviewed in this paper. The commonly used precursor materials, such as shrimp shell, fish scale, crab shell, oyster shell, animal skeleton and animal skin, are summarized. And then, the effects of different activation and modification methods, including calcium carbonate/hydroxylapatite self-activation, synergy activation of hydroxylapatite/calcium carbonate and KOH, potassium compound-assistant synthesis, on pore structure and chemical functional groups of collagen-derived carbon are analysed and compared. Additionally, the application of collagen-derived carbon in water treatment, involving adsorption and catalysis, is emphatically analysed. Finally, in view of the problems in the water treatment process, the corresponding countermeasures and the development trend are prospected, which could provide the theoretical basis for the application of collagen-derived carbon in practical wastewater treatment.

    Recent development on boron-doped diamond anodes in electrochemical degradation of emerging antibiotic pollutants
    ZHAI Chongyuan, ZHAO Dandi, HE Yapeng, HUANG Hui, CHEN Buming, GUO Zhongcheng
    2022, 41(12):  6615-6626.  doi:10.16085/j.issn.1000-6613.2022-0247
    Abstract ( 50 )   HTML ( 6)   PDF (2135KB) ( 40 )  
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    Antibiotics are considered as a kind of emerging organic contaminants in water environment, which have features of difficult to naturally degrade, environmental irritation, biological toxicity and drug resistance, etc. Therefore, the elimination of antibiotics in water environment has become the focus of environmental researchers in recent years. Benefitting from excellent physical and chemical properties, boron-doped diamond (BDD) electrode has been regarded as the most ideal and efficient electrode material for electrocatalytic oxidation of organic pollutants. However, there is lack of summary for the current research status of BDD anode in emerging antibiotic pollutants. This review firstly discusses the degradation process and mechanisms of organic pollutants involving oxidation species during electrocatalytic oxidation on BDD anode, and then analysis the research progress of electrocatalytic degradation of emerging antibiotic pollutants in recent years. In the following, the key influencing factors on electrocatalytic degradation process of antibiotics are discussed, and the development progress of BDD anode materials is further summarized. At the same time, the combined techniques based on electrocatalytic oxidation on BDD anode are also summarized. Finally, the problems existing in electrocatalytic degradation of antibiotic pollutants with BDD anode and key development direction in the future are further prospected.

    Research progress on degradation of antibiotics by activated persulfate oxidation
    QI Yabing
    2022, 41(12):  6627-6643.  doi:10.16085/j.issn.1000-6613.2022-0195
    Abstract ( 45 )   HTML ( 0)   PDF (646KB) ( 33 )  
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    The degradation of antibiotics by advanced oxidation process based on SO4-· has attracted much attention due to its economical, efficient, environmentally friendly, safe and stable advantages. Presently, degradation of antibiotics by activated persulfate (PS) contains external energy and catalyst activation. Besides, the hybrid technologies derived from combination of different methods of activated persulfate have emerged. The single external energy activation for PS are heat, microwave, ultrasound, light, electrode and plasma activation, et al. The external energy activation of PS has simple and green processes without secondary pollution. However, it also has some disadvantages such as high energy consumption and operation cost. The external catalysts for activating PS include transition metals, carbon materials and metal-organic frameworks, et al. The external catalyst activation has advantages of high catalytic activity and high degradation of antibiotics but its disadvantages exist in poor stability, low recovery ratio and high preparation cost of catalyst. The different degradation methods of antibiotics by activated PS are reviewed. Then, the research progress on degradation of antibiotics by activated PS are summarized. The advantages and disadvantages of degradation of antibiotics by activated PS are also given. Finally, the development trends on degradation of antibiotics by activated PS are outlooked. It can provide direction and guidance for subsequent research.

    Research progress of NO x removal by combination of atmospheric pressure dielectric barrier discharge and catalysis
    ZHANG Wei, WANG Zongyu, GUO Yu, YANG Mengfei, LI Zhengkai, CHANG Chao, ZHANG Jifeng, JI Yulong
    2022, 41(12):  6644-6655.  doi:10.16085/j.issn.1000-6613.2022-0351
    Abstract ( 43 )   HTML ( 0)   PDF (2672KB) ( 56 )  
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    Driven by the concept of green ecology and sustainable development strategy, exhaust emissions to the environment has attracted much attention. As one of the main pollutants of exhaust gas, NO x is the focus and difficulty of exhaust gas pollutant control. The advantages, disadvantages and application status of traditional post-treatment de-NO x technologies are introduced. The basic researches of dielectric barrier discharge are reviewed. The synergistic de-NO x performance and mechanism by DBD and catalyst are analyzed. It is pointed out that:①the DBD power supply and the reactor structure are the key factors restricting the de-NO x performance; ②the de-NO x performance of DBD only is not satisfactory, but the combination of DBD with catalytic packed bed exhibits excellent de-NO x efficiency and high N2 selectivity; ③the researches on de-NO x mechanism of plasma-assisted catalyst mainly include plasma characteristic parameter diagnosis, fluid model verification, plasma propagation mechanism analysis and in-situ characterization. However, the research on the theoretical calculation of plasma catalysis is limited. Therefore, we propose that the future development of DBD de-NO x technology should be based on ①the high-power and high-efficiency power supply to improve the NO x treatment capacity; ②the reactor structure optimization to improve the de-NO x efficiency and N2 selectivity; ③suitable design and construct of the de-NO x catalyst for DBD environment; ④the comprehensive analysis of the de-NO x mechanism of DBD synergistic catalyst.

    Research status of recycling and utilization of valuable metals in tungsten residue
    PENG Wei, HUANG Jian, WANG Zhenjie, LIU Anrong
    2022, 41(12):  6656-6663.  doi:10.16085/j.issn.1000-6613.2022-0380
    Abstract ( 47 )   HTML ( 12)   PDF (491KB) ( 25 )  
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    The smelting of tungsten ore is bound to produce a large amount of tungsten residue. As a dangerous solid waste, the residue is rich in valuable metals. Direct accumulation in the tailings pond will not only pollute the environment and occupy land, but also cause waste of metal resources. Therefore, it is necessary to use suitable sorting technology to treat and recover valuable metals such as Sn, W, Sc, Fe, Mn, Ta and Nb in tungsten residue. On the one hand, it can reduce the discharge of tungsten residue from the source, and on the other hand, it can increase the recycling rate of valuable metals. The article elaborated on the separation and recovery of different valuable metals in tungsten residue, and compared the advantages and disadvantages of different methods. At the same time, it also pointed out the current situation that tungsten residue is used to produce different special materials. On this basis, the future development direction of tungsten residue treatment technology is prospected, which provide reference for better comprehensive utilization of tungsten residue.

    Study on the adsorption characteristics of methylene blue by soft manganese ore-oil sludge-based activated carbon
    FAN Xiangru, YANG Yijin, GUO Xujing, ZHANG Quanbi
    2022, 41(12):  6664-6671.  doi:10.16085/j.issn.1000-6613.2022-0304
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    Activated carbon was prepared from oily sludge and pyrolusite, which was used to adsorb methylene blue in water, and its adsorption performance and mechanism were explored. SEM, BET, XPS and FTIR were used to characterize the micro-morphology and phase structure of activated carbon. Two-dimensional correlation spectroscopy (2D-COS) in combination with FITR was used to explore the adsorption point and mechanism of activated carbon and methylene blue. The results showed that activated carbon was a mesoporous material with a specific surface area of 464.4m2/g, which contained a large number of oxygen-containing functional groups. The adsorption process of methylene blue by activated carbon, which was monolayer adsorption controlled by chemical adsorption, accorded with pseudo-second-order kinetic equation and Langmuir model. Combined with the results of FTIR and moving-window 2D-COS analysis, more functional groups participated in the adsorption process of methylene blue with lower concentrations, in which contain oxygen was dominant. The π-π interaction played a primary role in higher concentrations of methylene blue. The adsorption mechanism included hydrogen bonding, oxygen-containing functional groups and π-π interaction.

    Research on the application of hydrate-based method in the treatment of actual complex wastewater and high salt wastewater
    SUN Huilian, SUN Lingjie, ZHAO Yang, SUN Xiang, ZHANG Lunxiang
    2022, 41(12):  6672-6679.  doi:10.16085/j.issn.1000-6613.2022-0319
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    The treatment of complex wastewater and high salt wastewater is the current difficulty in the field of wastewater treatment. The traditional wastewater treatment technology has the disadvantages of complex operation and high energy consumption. An innovative hydrate-based method was proposed in this study to treat actual complex wastewater and high salt wastewater. The feasibility of this technology was confirmed by measuring the concentration of pollutants in purified water through hydrate dissociation. Combined with the petroleum refining wastewater and laboratory wastewater from Sinopec Zhenhai refining & chemical company and Dalian hydrology bureau, the experiment was conducted under atmospheric pressure and 275.15K. The treatment effect of R141b hydrate on wastewater was evaluated by measuring the removal efficiency, water yield, and enrichment factor. The electrical conductivity, total organic carbon and ion concentration before and after treatment were measured to reflect the removal capacity of different kinds of pollutants. Vacuum filtration combined with centrifugal separation was used as the post-treatment method to improve the removal efficiency of pollutants in wastewater. The results showed that the hydrate-based wastewater treatment method can remove inorganic salts and organic pollutants in wastewater simultaneously. The removal efficiency of each pollutant reached more than 75%, with the water yield reaching about 78.9%. For copper ions with high concentrations in laboratory wastewater, the removal efficiency reached 90.8%. The hydrate-based wastewater treatment technology proposed in this study will promote the development of complex wastewater and high salt wastewater treatment.

    Effect of organic load fluctuation frequency on aerobic granular sludge
    LI Dong, GAO Feiyan, XIE Yibo, LI Zhu, ZHANG Jie
    2022, 41(12):  6680-6688.  doi:10.16085/j.issn.1000-6613.2022-0226
    Abstract ( 36 )   HTML ( 1)   PDF (2901KB) ( 26 )  
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    In order to explore the influence of organic load fluctuation frequency on aerobic granular sludge (AGS) under low-intensity influent conditions, three parallel cylindrical sequencing batch reactors(SBR), R1, R2 and R3, were operated by constant organic loading rate (OLR) and two alternating OLR modes respectively, fed with synthetic water. Their high and low OLR were 0.67gCOD/(L∙d)/0.67gCOD/(L∙d), 0.74gCOD/(L∙d)/0.56gCOD/(L∙d) and 0.74gCOD/(L∙d)/0.56gCOD/(L∙d) respectively. The fluctuation frequency of organic load was defined as the number of OLR high-low fluctuation every 12 days, R1’s OLR did not fluctuate, R2 and R3 completed OLR high-low fluctuation every 12 days and 4 days respectively, and their fluctuation frequencies were 0, 1 and 3 respectively. The results showed that the average particle sizes of R1, R2 and R3 were 318.86μm, 426.71μm and 593.06μm, respectively. The extracellular polymeric substance (EPS) content (VSS) were 71.97mg/g, 75.88mg/g and 80.35mg/g, PN/PS were 4.24, 5.14 and 5.72, respectively, indicating that the granules had higher hydrophobicity and stability when the fluctuation frequency was 3. In addition, the internal carbon storage rates (CODin) of R1, R2 and R3 were 97.06%, 98.37%, 98.91%, respectively, and the internal carbon storage rate (SND) efficiencies were 44.74%, 58.20%, 64.42%, respectively. The average total phosphorus (TP) removal efficiencies were 86.82%, 89.36% and 92.65%, respectively, the average total nitrogen (TN) removal efficiency were 71.69%, 74.31% and 78.55%, respectively, indicating that the granules had higher carbon source utilization efficiency and pollutant removal ability when the fluctuation frequency was 3.

    Goethite promotes the removal of nitrogen and carbon in the anaerobic digestion of waste activated sludge
    XIAO Cancan, YANG Yafei, ZHANG Yaobin
    2022, 41(12):  6689-6697.  doi:10.16085/j.issn.1000-6613.2022-0282
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    The development of anaerobic digestion of waste activated sludge (WAS) is limited due to its low energy conversion rate, and the high concentration of organic matter in the sludge also inhibits nitrogen removal. Theoretically, organic matter and ammonium could be removed through dissimilatory iron reduction in an anaerobic digestion system containing Fe(Ⅲ) (hydr) oxides, which however remains to be verified. Therefore, in this study goethite was added to the sludge anaerobic digestion system to explore the effect of Fe(Ⅲ) (hydr) oxide on the simultaneous removal of carbon and nitrogen. The results showed that with the increase of goethite dosage, the concentration of organic matter in the reactor gradually decreased. The cumulative methane production reached 695.1mL when 50mmol/L goethite was added, which was 30.3% higher than that of the control group without goethite. The TS and VS removal rates of the 50mmol/L goethite-added group were also increased by 21.1% and 33.8%, respectively, demonstrating that goethite could accelerate sludge reduction. Goethite also promoted the removal of total nitrogen and the removal efficiency was 21.0% in 50mmol/L goethite-added reactor. The above results showed that goethite can remove nitrogen and carbon simultaneously in sludge anaerobic digestion.

    Adsorption characteristics of CO2/H2O with low humidity
    REN Kexin, LU Junhui, WANG Suilin, TANG Jinjing
    2022, 41(12):  6698-6710.  doi:10.16085/j.issn.1000-6613.2022-0246
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    Carbon capture, utilization and storage is an essential way to achieve the goal of carbon peak and neutrality, the gases exhaust from power industry and coal supercritical water gasification systems after condenser of carbon capture are mainly CO2/H2O with 1%—5% H2O, which needs to separate using by adsorption. To purify and reutilize the low-moisture CO2/H2O, the adsorption breakthrough curve, temperature profiles, adsorption capacity of binary CO2/H2O at different temperature (303K, 313K) and H2O mole fraction (0.7%—3.0%) were studied experimentally for four adsorbents of activated carbon, activated alumina, zeolites 3A and 13X. The separation factor and isosteric heat of binary CO2/H2O were also analyzed. Results show that as adsorption time increases, the bed temperature and the concentration of each component present the same trend. As the inlet temperature increases, the saturation time of H2O decreases. As the mole fraction of H2O increases, the adsorption of CO2 was inhibited due to competitive adsorption, and the saturated time of H2O in activated carbon and activated alumina increases, but that of H2O in zeolite 3A and 13X decreased. The adsorption amounts of H2O increased with the increase of H2O concentration, while the isosteric heat decreased with the adsorption amounts, which presented the opposite for CO2. Zeolite 3A had the smallest CO2 adsorption amounts and the largest CO2/H2O separation factor. When H2O mole fraction was less than 1%, the separation factor of zeolite 13X, which had the largest CO2 adsorption amounts, was greater than that of activated alumina. Therefore, the zeolite 3A and 13X were suitable for the separation of CO2/H2O with low moisture.

    Improved capture capacity of SeO2 by sorbents with anti-sintering at high temperature
    YANG Xiaoyu, YU Mengzhu, HUANG Yaji, LI Jinlei, ZHU Zhicheng, LI Zhiyuan, WANG Sheng, LI Qiubai
    2022, 41(12):  6711-6722.  doi:10.16085/j.issn.1000-6613.2022-0234
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    Selenium (Se) capture capacity by different oxides (MgO, Fe2O3, Al2O3 and CaO) at 700—1100℃ were performed by a gas-solid instant reaction system to determine characteristics of adsorption products. Then, corresponding typical minerals and bicomponent composite sorbents with anti-sintering were chosen to improve Se capture capacity at high temperature. Results showed that the capacity of CaO was highest before 900℃, but noticeably decreased to 167.59μg/g as temperature rose to 1100℃. Capture capacity of γ-Al2O3 was greater at high temperature, which could reach 415.04μg/g at 1100℃ likely due to its great pore structure. Calcite, one of typical Ca-based minerals, indicated great high-temperature capture capacity because of its great anti-sintering and pore structure, and the capacity could be improved to 1064.97μg/g at 1100℃. Capture capacity of bicomponent composite sorbents at high temperature presented some improvement. Capacity of Ca-Al based sorbent increased slightly, while that of Ca-Si based sorbent was much higher than that of monocomponent based sorbents, which increased by 1787.21μg/g than that of CaO.

    Removal of emulsified water in oil by glass fiber coalescer
    HAN Fen, YANG Na, SUN Yongli, JIANG Bin, XIAO Xiaoming, ZHANG Lyuhong
    2022, 41(12):  6723-6732.  doi:10.16085/j.issn.1000-6613.2022-0292
    Abstract ( 43 )   HTML ( 0)   PDF (3982KB) ( 42 )  
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    With the advancement of oil-water separation technology and the development of new materials, the technology of removing emulsified water in oil by coalescence has been realized. In this paper, hydrophilic glass fibers were used as coalescing element to remove emulsified water (d95=10μm) in white oil. The apparent flow rate (5—30m/h) of the feed in the coalescer, the initial water content of the oil (500—4000μL/L), the thickness of the coalescer bed (100—400mm) and the porosity (0.80—0.95) were investigated on the coalescence separation efficiency by experiments, and the response surface method was used to analyze the synergistic effects between the variables to determine the optimal operational conditions, and the grain dimeter separation efficiency under the conditions was analyzed. The experimental results demonstrated that when the apparent flow rate was 14m/h, the initial water content was 1278μL/L, the bed thickness was 275mm, the porosity was 0.85, and the highest separation efficiency was 95.18%. Compared with the predicted value of the response surface (95.02%), the relative error was only 0.17%, which indicated that the regression model had high reliability and good reproducibility of the experiments. The analysis of the inlet and outlet particle size showed that the separation effect of the coalescer increased with the increase of the water droplet size, and the effective separation particle size was >5μm. The research results in this paper have practical application value for the selection of coalescers and the design of operating parameters for separating emulsified water from refined oil products with large density differences by using glass fibers as coalescing elements.

    Fermentation wastewater treatment and high-quality protein production by Chlorella pyrenoidosa under fed-batch mode
    QI Zhenhua, ZHOU Rong, BAI Yanan, LI Yuqin, TANG Yufang
    2022, 41(12):  6733-6743.  doi:10.16085/j.issn.1000-6613.2022-0443
    Abstract ( 43 )   HTML ( 2)   PDF (1770KB) ( 23 )  
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    The feasibilities of fermentation wastewater treatment and high-quality protein production by Chlorella pyrenoidosa was investigated. The removal rate of TP, TN, NH3-N, COD and BOD separately reached 99.5%, 95.1%, 99.4%, 98.2% and 99.7% by C. pyrenoidosa under fed-batch treatment mode, which was 1.47, 1.45, 1.22, 1.13, and 1.19-fold more than batch treatment mode, respectively. The effluent quality of fermentation wastewater treated with C. pyrenoidosa met discharge standard of GB 25463—2010. The biomass and protein yield of C. pyrenoidosa subjected to fermentation wastewater treatment were separately 48.53g/L and 27.20g/L. The proportions of 18 amino acids and essential amino acids in C. pyrenoidosa protein were separately 58.56% and 26.44%. The amino acid score was 65.3, which indicated that C. pyrenoidosa protein was a high-quality single-cell protein source. Additionally, C16—C18 occupied approximate 86% of total fatty acids and also the contents of linoleic acid and linolenic were separately 27.06% and 25.82% in C. pyrenoidosa. Synchronously, the safety indexes of heavy metals and microorganisms of C. pyrenoidosa complied with GB 13078—2017 health standards for fodder. The digestibility of dry matter, crude protein, crude fat, and starch of C. pyrenoidosa in simulative pig intestinal gastric juice in vitro were separately 79.02%, 90.17%, 92.93%, and 87.81%. The bioavailability of small intestinal Caco-2 cells to peptides, triglycerides, free fatty acid, and carbohydrates of digestive C. pyrenoidosa were separately 97.57%, 85.79%, 91.55% and 35.22%, which were roughly equivalent to the digestibility and bioavailability of other feed protein such as corn and soybean. The outcomes of this work could provide a basis for industrial wastewater treatment coupling co-production of high-value fine chemicals by other microalgae.