磷酸盐改性高岭土对生活垃圾热解过程中重金属的富集

doi:10.16085/j.issn.1000-6613.2022-1708

摘要/Abstract

摘要：

研究了磷酸盐改性高岭土在生活垃圾热解过程中对重金属Cr、Cd、Pb、As的富集作用。相较Na₂HPO₄和Na₃PO₄改性，NaH₂PO₄改性高岭土在生活垃圾热解过程中对重金属的富集作用更强。重金属的固留率随浸渍比的升高先增加后减小，随添加比的升高而增加，在浸渍比为5%和添加比为5%时具有较好的重金属富集作用。无添加剂时，在400~600℃范围内随着温度的升高，热解炭的潜在生态风险指数下降。添加高岭土能有效增加重金属残渣态的含量，从而降低热解炭的潜在生态风险。添加5%浸渍比下NaH₂PO₄改性高岭土（H₂P-kaolin）后热解炭的生态风险随温度的升高略有增加，主要原因是熔融的偏磷酸钠增强物理吸附以及热解炭中重金属磷酸盐的可酸溶性，但综合生态风险均为低风险。由XPS分析得出加入H₂P-kaolin之后，吸附重金属的主要原因是由于高岭土与重金属生成硅酸盐以及NaPO₃、Na₃PO₄与重金属反应生成磷酸盐，其中磷酸盐的作用是吸附能力增强的主要因素。

关键词: 生活垃圾, 热解, 重金属, 高岭土, 磷酸盐

Abstract:

The enrichment of heavy metals Cr, Cd, Pb, and As by phosphate-modified kaolin during the pyrolysis of municipal solid waste (MSW) was investigated. Compared with Na₂HPO₄ and Na₃PO₄modification, NaH₂PO₄ modified kaolin showed stronger enrichment of heavy metals during the pyrolysis of MSW. The retention rate of heavy metals increased and then decreased with the increase of impregnation ratio, and increased with the increase of addition ratio. The better heavy metal enrichment was reached at 5% impregnation ratio and 5% addition ratio. Without additives, the potential ecological risk index of pyrolysis char decreased with increasing temperature in the range of 400—600℃. The addition of kaolin effectively increased the content of heavy metal residue state, thus reducing the potential ecological risk of pyrolytic carbon. The addition of phosphate-modified kaolin led to an increase in the residue state due to the acid solubility of heavy metal phosphate. The ecological risk of NaH₂PO₄-modified kaolin (H₂P-kaolin) at 5% impregnation ratio increased slightly with increasing temperature mainly due to enhanced physical adsorption of molten sodium metaphosphate and acid solubility of heavy metal phosphates in pyrolysis char, but the ecological risk of pyrolysis char was low. The combined ecological risk was low. From the XPS analysis, it was concluded that the main reason for the adsorption of heavy metals after the addition of H₂P-kaolin was due to the formation of silicate from SiO₂ of kaolin with heavy metals and the reaction of NaPO₃ and Na₃PO₄ with heavy metals to form phosphate, of which phosphate was the main factor.

Key words: municipal solid waste, pyrolysis, heavy metal, kaolin, phosphate

中图分类号:

TQ534.9

张杉, 仲兆平, 杨宇轩, 杜浩然, 李骞. 磷酸盐改性高岭土对生活垃圾热解过程中重金属的富集[J]. 化工进展, 2023, 42(7): 3893-3903.

ZHANG Shan, ZHONG Zhaoping, YANG Yuxuan, DU Haoran, LI Qian. Enrichment of heavy metals in pyrolysis of municipal solid waste by phosphate modified kaolin[J]. Chemical Industry and Engineering Progress, 2023, 42(7): 3893-3903.

图/表 14

参考文献 23

1	LEI Ming, Jing HAI, CHENG Jiang, et al. Variation of toxic pollutants emission during a feeding cycle from an updraft fixed bed gasifier for disposing rural solid waste[J]. Chinese Journal of Chemical Engineering, 2018, 26(3): 608-613.
2	VICZEK S A, ALDRIAN A, POMBERGER R, et al. Origins and carriers of Sb, As, Cd, Cl, Cr, Co, Pb, Hg, and Ni in mixed solid waste—A literature-based evaluation[J]. Waste Management, 2020, 103: 87-112.
3	DU Haoran, ZHONG Zhaoping, ZHANG Bo, et al. Comparative study on intercalation-exfoliation and thermal activation modified kaolin for heavy metals immobilization during high-organic solid waste pyrolysis[J]. Chemosphere, 2021, 280: 130714.
4	MISKOLCZI Norbert, Funda ATEŞ, BORSODI Nikolett. Comparison of real waste (MSW and MPW) pyrolysis in batch reactor over different catalysts. Part Ⅱ: Contaminants, char and pyrolysis oil properties[J]. Bioresource Technology, 2013, 144: 370-379.
5	LI Shan, GUO Shengli, HUANG Xiao, et al. Research on characteristics of heavy metals (As, Cd, Zn) in coal from Southwest China and prevention method by using modified calcium-based materials[J]. Fuel, 2016, 186: 714-725.
6	YAO Hong, NARUSE Ichiro. Control of trace metal emissions by sorbents during sewage sludge combustion[J]. Proceedings of the Combustion Institute, 2005, 30(2): 3009-3016.
7	WANG Jiawei, ZHANG Yongsheng, WANG Tao, et al. Effect of modified fly ash injection on As, Se, and Pb emissions in coal-fired power plant[J]. Chemical Engineering Journal, 2020, 380: 122561.
8	ZHA Jianrui, HUANG Yaji, CLOUGH Peter T, et al. Green production of a novel sorbent from kaolin for capturing gaseous PbCl₂ in a furnace[J]. Journal of Hazardous Materials, 2021, 404: 124045.
9	LI Qian, ZHONG Zhaoping, DU Haoran, et al. Co-pyrolysis of sludge and kaolin/zeolite in a rotary kiln: Analysis of stabilizing heavy metals[J]. Frontiers of Environmental Science & Engineering, 2022, 16(7): 85.
10	OLU-OWOLABI Bamidele I, UNUABONAH Emmanuel I. Kinetic and thermodynamics of the removal of Zn²⁺ and Cu²⁺ from aqueous solution by sulphate and phosphate-modified Bentonite clay[J]. Journal of Hazardous Materials, 2010, 184(1/2/3): 731-738.
11	ADEBOWALE K O, UNUABONAH I E, OLU-OWOLABI B I. Adsorption of some heavy metal ions on sulfate- and phosphate-modified kaolin[J]. Applied Clay Science, 2005, 29(2): 145-148.
12	LIN Kunsen, Jiahong KUO, XIONG Kun, et al. Effect of phosphorus concentration on alkali and heavy metals transformation under agglomeration/defluidization during fluidized bed simulated sludge co-combustion[J].Waste and Biomass Valorization, 2020, 11(12): 6903-6916.
13	TANG Ping, ZHOU Yongchao, XIE Zhenmiao. Immobilization of heavy metals in sludge using phosphoric acid and monobasic calcium phosphate[J]. Journal of Zhejiang University SCIENCE A, 2013, 14(3): 177-186.
14	TIAN Tian, LIU Qingsong. Effects of added salts on sewage sludge char characteristics and heavy metal behaviors[J]. Journal of Analytical and Applied Pyrolysis, 2020, 146: 104774.
15	ZHANG Xuezhong, YU Jianfei, JIN Baosheng, et al. Improving the adsorption capacity of the sorbent for gaseous PbCl₂ during incineration by forming Pb₃(PO₄)₂: Preparation of the sorbent and evaluation of adsorption performance[J]. Industrial & Engineering Chemistry Research, 2021, 60(45): 16533-16542.
16	BILLEN P, VAN CANEGHEM J, VANDECASTEELE C. Predicting melt formation and agglomeration in fluidized bed combustors by equilibrium calculations[J]. Waste and Biomass Valorization, 2014, 5(5): 879-892.
17	LIU Changqi, HUANG Yaji, WANG Xinye, et al. Interactions of PbCl₂ capture and CdCl₂ capture by kaolin in the high-temperature PbCl₂-CdCl₂-kaolin reaction system[J]. Fuel, 2021, 286: 119346.
18	ZHU Zhicheng, HUANG Yaji, ZHA Jianrui, et al. Transformation of Cr under sintering of Ca-rich solid waste with kaolin: Analysis of multi-element coupled interactions[J]. Chemosphere, 2022, 287: 132181.
19	汪宁波. 城市生活垃圾热解过程中添加剂对砷的吸附实验及其机理研究[D]. 南京: 东南大学, 2021.
	WANG Ningbo. Experimental study on adsorption of arsenic by additives during pyrolysis of municipal solid waste and its mechanism[D]. Nanjing: Southeast University, 2021 .
20	MOFFAT T P, LATANISION R M, RUF R R. An X-ray photoelectron spectroscopy study of chromium-metalloid alloys—Ⅲ[J]. Electrochimica Acta, 1995, 40(11): 1723-1734.
21	PAPARAZZO E. XPS analysis of oxides[J]. Surface and Interface Analysis, 1988, 12(2): 115-118.
22	ZHANG Han, KE Shujia, XIA Mingwei, et al. Effects of phosphorous precursors and speciation on reducing bioavailability of heavy metal in paddy soil by engineered biochars[J]. Environmental Pollution, 2021, 285: 117459.
23	BREEZE P A, HARTNAGEL H L, SHERWOOD P M A. An investigation of anodically grown films on GaAs using X-ray photoelectron spectroscopy[J]. Journal of the Electrochemical Society, 1980, 127(2): 454-461.

组分	质量分数/%
塑料	50
木屑	30
橡胶	20

组分	质量分数/%
塑料	50
木屑	30
橡胶	20

工业分析（质量分数）/%					元素分析（质量分数）/%								重金属含量/mg·kg^-1
水分	挥发分	固定碳	灰分		C	H	O	N	S	Cl	Cd		Pb	Cr	As
0.59	87.98	9.73	1.70		72.09	10.61	14.22	1.65	1.20	0.23	78		356	120	76

工业分析（质量分数）/%					元素分析（质量分数）/%								重金属含量/mg·kg^-1
水分	挥发分	固定碳	灰分		C	H	O	N	S	Cl	Cd		Pb	Cr	As
0.59	87.98	9.73	1.70		72.09	10.61	14.22	1.65	1.20	0.23	78		356	120	76

名称		方法
F1	可交换态	加入20mL乙酸（0.10mol/L）在25℃下振荡16h
F2	可还原态	加入20mL盐酸羟胺（0.10mol/L，pH 2.0）在25℃下振荡16h
F3	可氧化态	加入5mL过氧化氢（30.00%，体积分数）在25℃下振荡1h，之后在85℃下振荡1h，然后加入20mL 乙酸铵（1.00mol/L，pH为2.0）在25℃下振荡16h
F4	残渣态	按上述热解炭的消解方式