农林废弃物基生物炭对重金属铅和镉的吸附特性

doi:10.19741/j.issn.1673-4831.2018.0853

摘要/Abstract

摘要： 以沙柳、水稻和玉米秸秆3种农林废弃物为原材料，于500℃条件下热解制备生物炭，并通过元素分析、比表面积分析仪、扫描电镜（SEM）和红外光谱（FTIR）等分析方法对所制备的生物炭进行表征。探究了溶液初始pH、干扰离子强度和初始吸附剂投加量等因素对3种生物炭吸附Pb²⁺和Cd²⁺作用的影响，讨论了吸附动力学特性及吸附等温特性。结果表明：不同生物质制备出的3种生物炭的碱性和灰分含量由高到低依次为沙柳秸秆生物炭（SWB）、玉米秸秆生物炭（CB）和水稻秸秆生物炭（SB），FTIR检测结果显示3种生物炭表面均含有大量含氧官能团；当溶液pH为3~6时，3种生物炭对Pb²⁺和Cd²⁺吸附量随pH值的增加而升高，对Pb²⁺的吸附效果随着溶液中离子强度的增强而降低，而SWB对Cd²⁺的吸附效果随离子强度的增加而增加；3种生物炭对Pb²⁺和Cd²⁺的吸附过程符合准二级动力学模型，R²均大于0.99，表明生物炭吸附速率主要由化学吸附机制决定；SWB、SB和CB对Cd²⁺的吸附过程既符合Langmuir模型，又符合Freundlich模型，而生物炭对Pb²⁺的吸附过程更适合Langmuir等温模型，表明生物炭对Pb²⁺的吸附近似单分子层吸附，而对Cd²⁺的吸附存在多分子层吸附。

关键词: 农林废弃物, 生物炭, 铅, 镉, 吸附特性

Abstract: The adsorptions of Pb²⁺ and Cd²⁺ in aqueous solutions by biochar derived from salix, straw and corn stalk at pyrolysis temperature of 500℃ were evaluated. The characteristics of adsorbent were mainly observed by scanning electron microscope (SEM), specific surface area analyzer and Fourier transform infrared spectroscopy (FTIR), and the effects of initial pH, ionic strength of Na⁺ and Ca²⁺ and adsorbent dose in sorption experiments were further investigated. Results show that the alkali and ash content of the 3 biochars were salix straw biochar (SWB) > corn stover biochar (CB) > rice straw biochar (SB), and all the surfaces of the 3 biochars contained large number of oxygen-containing functional groups. The adsorption kinetics and adsorption results indicate that when the pH was set between 3 to 6, the adsorption efficiency of biochar to Pb²⁺ and Cd²⁺ increased with the increase of pH value, and the adsorption efficiency to Pb²⁺ decreased with the increase of ionic strength in the solution. While the adsorption efficiency of SWB on Cd²⁺ increases with increasing ionic strength. In addition, the adsorption kinetic results of SWB, CB and SB to Pb²⁺ and Cd²⁺ met quasi-secondary kinetics, and the correlation coefficient R² was greater than 0.99, indicating that the biochar adsorption rate is mainly determined by the chemical adsorption mechanism. Moreover, the adsorption isotherm model of Pb²⁺ and Cd²⁺ show that the adsorption of Cd²⁺ was suitable to be described by both Langmuir and Freundlich isothermal equation, while the adsorption of Pb²⁺ was only well simulated by the Langmuir isothermal equation, indicating that the adsorption mechanism of Pb²⁺ by biochar was similar to that of monolayer adsorption law, but the adsorption process of Cd²⁺ showed multi-molecular layer adsorption mechanism.

Key words: agroforestry wastes, biochar, Pb, Cd, adsorption characteristics

中图分类号:

嵇梦圆, 胡逸文, 梁程, 桑文静, 李登新. 农林废弃物基生物炭对重金属铅和镉的吸附特性[J]. 生态与农村环境学报, 2020, 36(1): 106-114.

JI Meng-yuan, HU Yi-wen, LIANG Cheng, SANG Wen-jing, LI Deng-xin. Adsorption of Lead and Cadmium on Biochars Produced From Agroforestry Wastes[J]. Journal of Ecology and Rural Environment, 2020, 36(1): 106-114.

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