刘婷,郝秀珍,刘存,周东美,孙倩.羟基铁柱撑蒙脱石同时吸附水溶液中Cd(Ⅱ)和As(Ⅴ)的研究[J].环境科学学报,2020,40(7):2468-2476
羟基铁柱撑蒙脱石同时吸附水溶液中Cd(Ⅱ)和As(Ⅴ)的研究
- Study on the simultaneous adsorption of Cd(Ⅱ) and As(Ⅴ) in water solution simultaneously by hydroxy-iron-pillared montmorillonite
- 基金项目：中国科学院南京土壤研究所"一三五"计划和领域前沿项目（No.ISSASIP1619）；现代农业产业技术体系建设专项资金项目
- 刘婷
- 1. 中国科学院南京土壤研究所土壤环境与污染修复重点实验室, 南京 210008;2. 中国科学院大学, 北京 100049
- 郝秀珍
- 中国科学院南京土壤研究所土壤环境与污染修复重点实验室, 南京 210008
- 刘存
- 中国科学院南京土壤研究所土壤环境与污染修复重点实验室, 南京 210008
- 周东美
- 中国科学院南京土壤研究所土壤环境与污染修复重点实验室, 南京 210008
- 孙倩
- 1. 中国科学院南京土壤研究所土壤环境与污染修复重点实验室, 南京 210008;2. 中国科学院大学, 北京 100049
- 摘要：为同时去除水溶液中的Cd（Ⅱ）和As（Ⅴ），采用羟基铁柱撑改性获得改性蒙脱石，并深入研究了其吸附性能和吸附机理.同时，采用BET比表面积、SEM、XRD和XPS等手段分析了改性前后蒙脱石的结构特征；采用批实验分别研究了改性蒙脱石对水体中Cd（Ⅱ）和As（Ⅴ）的吸附动力学和热力学特征，并探讨了Cd（Ⅱ）-As（Ⅴ）复合体系中镉、砷相互作用对改性蒙脱石等温吸附镉、砷的影响.结果表明，改性蒙脱石的比表面积较改性前增加了28.2%，XPS测试结果表明改性蒙脱石成功引入羟基铁.改性蒙脱石单一吸附Cd（Ⅱ）和As（Ⅴ）的最优初始pH分别为6.5和5.5，且25℃时分别在10 h和5 h内达到吸附平衡，吸附过程均符合准二级动力学方程；Langmuir等温吸附模型能更好地描述改性蒙脱石对Cd（Ⅱ）的吸附，最大吸附量为21.36 mg·g-1，该吸附过程是离子交换和化学络合共同作用的结果；Freundlich等温吸附模型能更好地解释改性蒙脱石对As（Ⅴ）的吸附，最大吸附量为11.45 mg·g-1，该吸附过程是化学络合作用的结果（改性剂投加量均为2 g·L-1）.在Cd（Ⅱ）-As（Ⅴ）复合体系中，镉、砷之间存在相互作用，pH为5.5时，吸附量高于改性蒙脱石对单一Cd（Ⅱ）和As（Ⅴ）的吸附量，分别增加了14.4%和23.7%，表明合成的羟基铁柱撑蒙脱石对镉、砷复合污染农田具有同时去除Cd（Ⅱ）和As（Ⅴ）的修复潜力.
- Abstract：Hydroxy-iron pillared montmorillonite was synthesized for the simultaneous removal of Cd(Ⅱ) and As(Ⅴ) in solution. The adsorption performance and underlying reaction mechanism were thoroughly investigated. The structural properties of montmorillonite before and after modification were analyzed by BET, SEM, XRD, and XPS. Batch adsorption experiments were carried out to investigate the kinetics and thermodynamic characteristics of Cd(II) and As(V) adsorption on the modified montmorillonite from aqueous solution. The effects of cadmium and arsenic interaction on their co-adsorption by modified montmorillonite in the Cd(Ⅱ)-As(Ⅴ) binary solution were also investigated. The specific surface area of the modified montmorillonite increased by 28.2%, and the successful intercalation of hydroxy iron pillars was evidenced by XPS. The results showed that the optimal adsorption pH for Cd(II) and As(V) alone by hydroxy-iron-pillared montmorillonite at 25℃ were 6.5 and 5.5, respectively. The adsorption equilibria for Cd(II) and As(V) on the modified montmorillonite were reached within 10 h and 5 h, respectively, while both adsorption processes followed pseudo-second-order kinetics. The adsorption isotherms of Cd(II) on modified montmorillonite can be well described by the Langmuir model with a maximum adsorption capacity of 21.36 mg·g-1, reflecting the combined actions of ion exchange and chemical complexation as the main adsorption mechanism. The Freundlich model better explained the adsorption isotherms of As(V) on the modified montmorillonite with a maximum adsorption capacity of 11.45 mg·g-1, indicating that the adsorption interaction was dominated by chemical complexation. In the Cd(II)-As(V) binary system, the interaction between cadmium and arsenic enhanced the adsorption of each other on modified montmorillonite at pH 5.5 by 14.4% and 23.7%, respectively, suggesting a potential application of the synthesized hydroxy-iron-pillared montmorillonite as a promising soil remediation material for simultaneous removal of cadmium and arsenic in polluted farmland.
