微生物絮凝剂对猪粪沼液中铜的去除作用机理研究

The copper ion in pig manure biogas slurry （PBS）seriously exceeded the standards and there is a huge risk of heavy metal pollution in returning PBS to the farmland. In order to solve these problems, the project utilized the environmental-friendly and high-efficient microbial flocculants to remove copper ion from PBS. Firstly, by using the response surface methodology, we optimized the influence of pH, stirring speed, stirring time and additive amount of microbial flocculants on the removal of copper ion, and determined the optimal conditions of the reaction system. Then, the removal efficiency of copper ion by microbial flocculation is determined from both of the adsorption and transformation. The main ways of removal copper ion were determined by quantifying the relative contribution of the adsorption and transformation to the removal of copper ion. Finally, the whole process of removing copper ion by microbial flocculants was simulated by proposing adsorption kinetics model, and the main features of removal were analyzed. Furthermore, using environmental scanning electron microscopy and other analytical methods, the internal reason of the removal of copper ion from PBS by microbial flocculants was analyzed from the aspects of binding bonds type, chemical group type, structure of microbial flocculants and element content change, and then the mechanism of removal of copper ion by microbial flocculants was elucidated. The project aims to enrich the existing basic theory of heavy metal removal from biogas slurry and provides a new way for the removal of heavy metals from biogas slurry. This project is of important theoretical significance and has practical application value for promoting the biogas slurry safe returning to farmland and sustainable development of biogas engineering.

猪粪沼液中Cu离子含量严重超标，还田利用存在巨大的重金属污染风险。为了解决这一问题，本项目利用环保高效的微生物絮凝剂去除猪粪沼液中Cu离子。项目首先通过响应曲面法优化pH、搅拌速度、搅拌时间和微生物絮凝剂添加量4个关键因素对Cu离子去除的影响，确定反应体系的最佳条件；然后从吸附作用和转化作用两方面明确微生物絮凝剂对Cu离子的去除效能，通过量化两者对去除Cu离子的相对贡献，确定去除作用的主要方式；最后通过吸附动力学等模型模拟去除Cu离子的全过程，分析去除作用的主要特征，利用环境扫描电镜等分析方法，从结合键类型、化学基团种类及数量、絮体微观结构和元素含量变化等方面共同解析去除作用的内在原因，阐明微生物絮凝剂对猪粪沼液中Cu离子的去除作用机理。本项目旨在丰富现有的沼液重金属去除理论，为沼液的重金属去除提供新途径，对促进沼液安全还田和沼气工程的持续发展具有重要理论意义和实践应用价值。

猪粪沼液中Cu离子含量超标，还田利用存在巨大的重金属污染风险。因此，本项目研究了微生物絮凝剂对猪粪沼液中Cu离子的去除作用机理，为沼液的重金属去除提供新途径，对促进沼液安全还田和沼气工程的持续发展具有重要理论意义和实践应用价值。主要研究结果如下。.（1）响应曲面法优化得出反应体系最佳条件为：絮凝剂添加量50mL、pH8.7、搅拌速度300rpm和搅拌时间120s。该优化条件下Cu2+去除率为84.8%。方差分析结果表明该模型具有极显著性（P <0.0001），自由度为14，F检验值为7.58，拟合度R2=0.8834, Cu离子去除率预测值为81.6833%，略低于试验值84.8%。.（2）研究表明Langmuir吸附等温模型比Freundlich吸附等温模型更好的拟合絮凝剂对Cu2+的吸附。在优化条件下絮凝剂对Cu2+的吸附中，Ce与Ce/qe均具有良好的线性关系，R2=0.991，b=2.55，说明絮凝剂和Cu²+离子之间形成了较强结合力的复合体，根据Langmuir吸附等温方程结果，絮凝剂对猪粪沼液中Cu2+的吸附为单层吸附。.（3）研究表明准二级吸附动力学方程比准一级吸附动力学方程更好地拟合试验数据，R²=0.943，优化条件下絮凝剂对Cu2+吸附最大量为20min，吸附率为84.8%，吸附作用方式为化学吸附和离子交换。.（4）研究表明随着EDTA和HCL浓度的增加，Cu2+解吸附率逐渐增大。当EDTA浓度时为0.1mol/L时，EDTA对絮体的解吸附率达59.4%，当HCL浓度时为1 mol/L时，其对絮体的解吸附率达51.5%。EDTA和HCL破坏了絮凝剂与Cu2+间的结合，与Cu2+存在吸附竞争，同时在酸性环境中絮凝剂的官能团容易离解，因此被吸附的Cu2+更容易脱离。.（5）傅里叶红外光谱（FTIR）表明参与絮凝剂吸附Cu2+离子的主要活性官能团有O-H、-N=、N-H、C=N。絮凝剂吸附Cu2+离子过程中有氢键缔合，絮凝剂分子间相互搭接形成整体。研究表明絮凝剂去除Cu2+的絮凝过程以化学吸附为主，同时包含范德华力结合、化学反应、吸附架桥、氢键和静电引力等共同作用。