• 关键词：络合态重金属  重金属沉淀剂  柠檬酸  硫化钠  废水处理

• 基金项目：国家自然科学基金（No.41101299）；广东省重点领域研发计划项目（No.2019B110207001）；广东省科技计划项目（No.2015A020215034）；广东省自然科学杰出青年基金（No.2015A030306005）

• 郑雄开
• 仲恺农业工程学院环境科学与工程学院, 广东省农业产地环境污染防控工程技术研究中心, 广州 510225

• 陶雪琴
• 仲恺农业工程学院环境科学与工程学院, 广东省农业产地环境污染防控工程技术研究中心, 广州 510225

• 杜建军
• 仲恺农业工程学院环境科学与工程学院, 广东省农业产地环境污染防控工程技术研究中心, 广州 510225

• 曾宇飞
• 华南理工大学环境与能源学院, 工业聚集区污染控制与生态修复教育部重点实验室, 广州 510006

• 张博雯
• 广东工业大学土木与交通工程学院, 广州 510006

• 谢莹莹
• 韩山师范学院化学与环境工程学院, 潮州 521041

• 邹梦遥
• 仲恺农业工程学院环境科学与工程学院, 广东省农业产地环境污染防控工程技术研究中心, 广州 510225

• 卢桂宁
• 华南理工大学环境与能源学院, 工业聚集区污染控制与生态修复教育部重点实验室, 广州 510006

• 摘要：土壤淋洗废液中污染物的选择性去除是实现淋洗液回收的关键.本文以硫化钠（Na₂S）、乙基黄原酸钾（PEX）、二甲基二硫代氨基甲酸钠（DTC）作为重金属沉淀剂处理电子垃圾污染土壤模拟淋洗废液，在筛选出Na₂S作为理想重金属沉淀剂的基础上，研究初始pH值、反应温度、沉淀剂浓度等因素对Na₂S分离络合态重金属的影响，并通过软件模拟和产物表征等方式推测反应机理.结果表明：Na₂S对柠檬酸络合态重金属的分离顺序依次为Cu、Pb、Cd，符合硫化物溶度积原则；反应温度、初始pH值对Na₂S处理络合态重金属无显著影响，重金属去除率均保持在90%以上，柠檬酸的回收率约为95%；Visual MINTEQ模拟结果显示，S^2-投加前液相中重金属主要以H₂CA^-、HCA^2-和CA^3-结合形式存在，S^2-投加后液相中重金属则以HS^-和S^2-结合形式存在；扫描电镜及能谱（SEM-EDS）表明，S^2-与金属阳离子按物质的量比1：1生成硫化物沉淀物，沉淀主要呈团聚、成簇和圆片状存在；X射线衍射（XRD）分析结果表明，沉淀产物中存在CuS、CdS、PbS和CuPbS₂.本研究结果可为化学沉淀法处理重金属污染土壤淋洗废液提供技术参考.

• Abstract：Selective removal of pollutants from soil leaching wastewater is the key step to recovery of eluent. Sodium sulfide (Na₂S), potassium ethylxanthate (PEX), and sodium dimethyl dithiocarbamate (DTC) were used as heavy metal precipitants to treat simulated wastewater from leaching electronic-waste contaminated soil. Based on the screening experiments that identified Na₂S as an ideal heavy metal precipitant, the effects of initial pH value, reaction temperature and precipitant concentration on the separation of complexed heavy metals in Na₂S were investigated. The reaction mechanism was investigated by software prediction and product characterization. The results showed that the separation order of citric acid complexed heavy metals by Na₂S was Cu, Pb and Cd, in line with the sulfide solubility. The reaction temperature and initial pH value had no significant effect on the complexed heavy metals treated by Na₂S. The removal rate of heavy metals was above 90%, and the recovery of citric acid remained about 95%. The results of predition by Visual MINTEQ software show that before S^2- addition metal cations were mainly associated with H₂CA^-、HCA^2- and CA^3-, while after S^2- addition, metal cations have been bonded with HS^- or S^2-. The scanning electron microscopy and Energy dispersive spectrum (SEM-EDS) indicated that sulfide precipitation mainly existed in agglomerated, clustered and disc-shaped forms with a 1:1 molar ratio between S^2- and other metal cations; The result of X-Ray diffraction (XRD) analysis revealed the main precipitated product was the mixtures of CuS, CdS, PbS and CuPbS₂. These collective results provide a newly technical knowledge for the leachate recovery from the heavy-metal-leaching wastewater.

• Key words：chelated heavy metal  heavy metal precipitant  citric acid  sodium sulfide  wastewater treatment

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