Abstract:

The slow oxygen-limited pyrolysis of attapulgite (ATP) and alkali lignin (AL) was used to prepare biochar/attapulgite (BC/ATP) for the adsorption of sulfadiazine (SDZ) in water. The effects of feedstock ratio and pyrolysis temperature on the content of BC/ATP product composition and adsorption performance were investigated, and the effects of initial pH, BC/ATP dosage, adsorption time and initial SDZ concentration on the removal rate were also investigated. The kinetics of the adsorption process was fitted with the proposed pseudo-first-order, pseudo-second-order and intraparticle diffusion equations, respectively, and the isothermal adsorption curves were fitted with the Langmuir and Freundlich equations. The surface morphology, pore structure and functional groups of BC/ATP were analyzed by SEM, FTIR, XRD, Raman and BET determination. The results show that ATP can effectively promote the secondary pyrolysis of volatile intermediates during pyrolysis, increase the BC yield, improve the BC/ATP adsorption properties, and broaden the pH sensitivity of BC/ATP through the metal ion effect of ATP. The adsorption kinetics of the different composites satisfies the pseudo-second-order kinetic model, and the fitting by the intraparticle diffusion model indicates that this diffusion behavior is not the only factor limiting the adsorption rate, and the isothermal adsorption curves are more consistent with the Langmuir isothermal adsorption model, 0 < R_L < 1, for preferential adsorption, indicating that the adsorption process is easy to proceed with a maximum adsorption capacity of 109.53mg/g. The adsorption mechanism under different pH conditions can be divided into two parts: ① under acidic and neutral conditions, it mainly relies on the electrostatic interaction between the negative charge on the upper BC surface of BC/ATP and SDZ; ② under alkaline conditions, it mainly relies on the metal cation bridging interaction between the metal ions on the surface of ATP and the hydrogen bonding of SDZ.

Key words: kinetic modeling, waste water, composites, pyrolysis, adsorbents, biocarbon, attapulgite

摘要：

利用凹凸棒土（ATP）和碱性木质素（AL）慢速限氧热解制备生物炭/凹凸棒土（BC/ATP）吸附水中的磺胺嘧啶（SDZ），研究原料比例和热解温度对产品组分含量和吸附效果的影响，并探讨初始pH、BC/ATP投加量、吸附时间和SDZ初始浓度等因素对去除率的影响。分别采用拟一级、拟二级和颗粒内扩散方程拟合吸附过程动力学，用Langmuir和Freundlich方程拟合等温吸附线。通过扫描电镜、傅里叶红外光谱、X射线衍射、拉曼光谱和比表面积测定分析BC/ATP的表面形貌、孔结构和官能团。结果表明ATP能有效促进热解过程中挥发性中间产物二次热解，提高BC得率，改善BC/ATP吸附性能，并通过ATP的金属离子作用扩宽BC/ATP的pH敏感度。吸附动力学均符合拟二级动力学模型，且由颗粒内扩散模型拟合说明该扩散行为不是限制吸附速率的唯一因素，等温吸附线更符合Langmuir等温吸附模型，0＜R_L＜1，为优惠吸附，说明吸附过程易于进行，最大吸附量为109.53mg/g。不同pH条件下吸附机理可分为两部分：①在酸性和中性条件下，主要依靠BC/ATP的上BC表面负电荷与SDZ静电作用；②碱性条件下主要依靠ATP表面金属离子与SDZ氢键的金属阳离子桥接作用。

关键词: 动力学模型, 废水, 复合材料, 热解, 吸附剂, 生物炭, 凹凸棒土