【作者】 王丹；

【导师】 徐小逊； 朱启红；

【作者基本信息】 四川农业大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 重金属已经成为制约污泥农用的主要障碍之一,开展污泥中重金属的去除修复是当前环境污染防治领域的重要课题之一。阻垢剂因具有较强的金属去除能力在土壤修复领域开始引起关注,而污泥具有与土壤相似的物理和化学性质,因此利用阻垢剂去除污泥中重金属的可行性值得探讨,各因素之间交互作用对重金属去除效率的影响及淋洗剂对污泥性质的影响有待进一步阐明。针对以上问题,本研究以羧乙基硫代丁二酸（CETSA）和衣康酸丙烯酸共聚物（IA-AA）作为淋洗材料,系统地分析它们对污泥中重金属的去除效果及对污泥性质的影响,以期为污泥后续合理利用提供环境友好的技术方案。主要结果如下:（1）两种淋洗剂能够有效去除污泥中的镍（Ni）、铅（Pb）、锌（Zn）、镉（Cd）和铬（Cr）五种重金属,其去除率随淋洗液浓度(10-100 g L^-1)和淋洗时间（10-1440 min）增加而显著增加（P<0.05）,随pH（2-8）和固液比（1:10-1:80）的降低而明显增加（P<0.05）。两种淋洗剂对五种重金属的去除均符合准二级动力学方程。（2）响应面优化（RSM）结果表明,淋洗液浓度是控制CETSA去除重金属的主要因素,其次为淋洗液pH和淋洗时间。然而,淋洗液pH是控制IA-AA去除重金属的主要因素,其次为淋洗时间和IA-AA浓度,且IA-AA浓度和淋洗液pH两因素间存在显著交互效应（P<0.05）。优化模型得到重金属去除的最佳淋洗参数,在此条件下其总去除率分别达到68.63%和97.47%,分别达到《农用污泥污染物控制标准》B级和A级标准。（3）污泥中重金属的淋洗去除主要机制为酸溶作用、静电吸附和螯合反应。随着淋洗液的加入,溶液中质子化（H⁺）严重,金属从污泥胶体中溶解和解吸;同时,淋洗系统中的污泥颗粒表面带上正电荷,降低其对重金属的吸附力,解离出来的金属离子与淋洗剂中羧基或磺酸基官能团因库仑力相互吸引;此外,酸性条件下可交换态重金属是可溶解的,此种形态重金属与淋洗剂中羧基和磺酸基发生螯合反应。（4）淋洗后,污泥中重金属的较易萃取组分（可交换态和可还原态）被有效去除,主要以氧化态和残渣态的较稳定形态存在,其可迁移能力差且生物可利用度较低,一定程度上降低了污泥土地利用的风险。（5）淋洗过程对污泥环境质量产生不同程度的影响。淋洗后污泥pH、碱解氮（AN）含量以及CETSA处理后的污泥中全氮（TN）和速效磷（AP）虽有下降但降幅较小,分别为0.26-0.81个单位、4.7%-24.8%、1.21%和5.75%。IA-AA淋洗后全氮（TN）、全磷（TP）和全钾（TK）含量以及CETSA淋洗后全磷（TP）和速效钾（AK）无显著变化（P>0.05）。有机质（SOM）的含量在淋洗后增加了6.9%-14.4%,IA-AA淋洗后速效磷（AP）含量以及CETSA淋洗后全钾（TK）亦有所增加,分别为6.42%和10.79%。（6）傅里叶红外光谱（FT-IR）谱图表明,淋洗后部分峰有位移、峰强减弱的现象,可忽略不计,表明CETSA和IA-AA对污泥体系的化学环境造成一定的影响,但并未造成污泥结构的破坏。扫描电子显微镜与能谱（SEM-EDS）分析证实两种材料淋洗对污泥形貌与骨架仅有微小的影响。CETSA淋洗后,污泥聚集体呈独立小颗粒物质分散分布,颗粒轮廓不清。IA-AA淋洗后与原始污泥整体形状并无明显变化,但是结构更加松散,表面更加光滑。淋洗后污泥中部分元素浓度明显下降,而C的重量百分比却明显增加。X射线衍射（XRD）结果表明淋洗过程对污泥矿物组成成分及晶体结构产生较小影响。更多还原

【Abstract】 Heavy metals have become one of the main obstacles restricting sludge agriculture,and it is one of the important topics in the field of environmental pollution prevention and control to carry out the removal and remediation of heavy metals in sludge.Scale inhibitor has attracted attention to the field of soil remediation because of its strong metal removal ability,and sludge has similar physical and chemical properties to soil.Therefore,it is worth exploring that the feasibility of using scale inhibitor to remove heavy metals in sludge.The effect of interaction between factors of heavy metal removal efficiency and the effect of washing agent on sludge properties needs to be further elucidated.In this study,carboxyethylthiobutyric acid（CETSA）and itaconic-acrylic acid copolymer（IA-AA）were used as eluent materials to systematically analyze their effects on the removal of heavy metals in sludge and on the properties of sludge,providing an environmentally friendly technical scheme for the subsequent rational utilization of sludge.The main results are as follows:（1）CETSA and IA-AA have good washing effect on nickel（Ni）,lead（Pb）,zinc（Zn）,cadmium（Cd）,and chromium（Cr）.The removal rates increased significantly（P<0.05）with the increase in washing solution concentration(10-100 g L^-1)and washing time（10-1440 min）,with the decrease of pH（2-8）and solid-liquid ratio（1:10-180）（P<0.05）.Kinetic studies suggested thatthe removals of five heavy metals with CETSA and IA-AA washing were fitted well with pseudo-second-order kinetic models.（2）Response surface optimization（RSM）results showed that washing solution concentration was the main factor to control CETSA remove heavy metals,followed by pH of washing solution and washing time.Nevertheless,pH of washing solution was the main factor to control IA-AA remove heavy metals,followed by washing time and IA-AA concentration,and there is a significant interaction effect（P<0.05）between pH of washing solution and IA-AA concentration.The optimum washing parameters of heavy metals were obtained by the optimization model,and the total removal rate reached 68.63%and 97.47%in this condition,respectively.Finally sludge treated reached the B and A grade standards of Control stanards of pollutants in sludge for agricultural use.（3）The main mechanisms of heavy metal washing removal of sludge are acid dissolution,electrostatic adsorption and chelation reactions.As the washing solution was added,the protonation（H⁺）in the solution was severe,the metal was dissolved and desorbed from the sludge colloid.At the sametime,the surface of the sludge particles was positively charged and reduce their adsorption force to heavy metals,the dissociated metal ions inter attraction with the carboxyl or sulfonic groups of the solutiont due to coulombic force.In addition,the exchangeable heavy metals were soluble in acidic conditions and chelat with the carboxyl and sulfonic groups in the solution.（4）The easier extractable components（exchangeable and reducible）of heavy metals were effectively removed after CETSA and IA-AA washing,then the heavy metals components of sludge are mainly stable forms of oxidation state and residue state.They have poor transportability and low bioavailability,which reduce the risk of sludge land use to some extent.（5）The washing process will have different effects on the environmental quality of sludge.The pH and alkali-hydrolyzed nitrogen（AN）content in the sludge decreased 0.26-0.81 units and 4.7-24.8%after washing.The total nitrogen（TN）and available phosphorus（AP）after CETSA treatment were decreased but less by 1.21%and 5.75%,respectively.There were no significant changes in total nitrogen（TN）,total phosphorus（TP）,and total potassium（TK）contents after IA-AA treatment,as well as total phosphorus（TP）and available potassium（AK）after CETSA washing（P>0.05）.The content of organic matter（SOM）increased by 6.9-14.4%.Available phosphorus（AP）content after IA-AA and total potassium（TK）after CETSA also increased 6.42%and 10.79%,respectively.（6）The Fourier transform infrared spectroscopy（FT-IR）of sludge before and after CETSA and IA-AA washing showed that some characteristicpeaks position displacement and peak strength weakening,which is negligible,indicating the washing have a certain impact on the chemical environment of the sludge system,but have not caused the destruction of the sludge structure.Scanning electron microscopy and energy spectrum（SEM-EDS）analysis confirmed there were only minor effects on the sludge morphology and skeleton.The sludge aggregates showed independent small particle material dispersion distribution and the particle profiles not clear after CETSA washing.There was no obvious change in the overall shape of the original sludge,but the structure was more loose and the surface was more smooth after IA-AA washing.The concentration of some elements in sludge decreased significantly,while the weight percentage of C increased significantly.The results of X ray diffraction（XRD）showed that CETSA and IA-AA have little effect on sludge during washing process.更多还原