氨基多羧酸化合物改性磁性纳米复合材料对低浓度络合重金属的深度净化机制

Chelated heavy metal is one of major pollutants in industrial wastewater, which poses severe threats for human health and ecological system. Based on the wastewater characteristic of chelated heavy metals with high concentration chelating agents and low concentration heavy metals after conventional treatment of chemical precipitation process, aminopolycarboxylic acid modified magnetic nanocomposites are prepared and used as adsorbents for removing low concentration heavy metal from heavy metal chelates in aqueous solution. The adsorption mechanism of low concentration chelated heavy metal on aminopolycarboxylic acid modified magnetic nanocomposites is described by comparison with surface properties of the adsorbent and speciation of heavy metals, chelating agents and heavy metal chelates in solution before and after chelated heavy metals adsorption, and structural elucidation of chelated heavy metals adsorbed on the adsorbent. The interaction mechanism among heavy metals, chelating agents and active groups of the adsorbent would be elucidated, and the effect of water chemistry conditions on adsorption of chelated heavy metals onto the adsorbent would be also explained. The present study would provide the theoretical basis for the development of the adsorbents with high efficiency for the removal of low concentration chelated heavy metals in aqueous solution, and technical support for treatment of wastewater containing chelated heavy metal.

络合重金属是工业废水主要污染物之一，其对人体健康和生态系统构成严重威胁。针对经传统化学沉淀法处理后的络合重金属废水中络合剂浓度高，重金属浓度低的特点，本项目拟合成氨基多羧酸化合物改性磁性纳米复合材料，并以其为吸附剂研究其对络合重金属废水中低浓度络合态重金属的吸附行为。通过研究吸附前后吸附剂表面化学特性变化，吸附前后吸附体系中重金属、络合剂以及重金属络合形态变化规律以及吸附后吸附剂表面重金属络合物的结构分析，阐明氨基多羧酸化合物改性磁性纳米吸附剂对水中低浓度络合态重金属的吸附机制，揭示吸附剂表面活性官能团与重金属、络合剂之间的相互作用机理，明确水化学条件对低浓度络合态重金属在氨基多羧酸化合物改性磁性纳米吸附剂上吸附的影响，以期为开发对水中低浓度络合重金属废水具有高效净化效果的吸附剂提供理论依据，为络合态重金属废水处理提供技术支撑。

本研究制备了不同氨基多羧酸化合物（如IDA、NTA、EDTA、EGTA和DTPA等）改性磁性硅基或磁性碳基吸附剂，系统研究其对水中Cr(III)和络合态Cr(III)的吸附规律，阐明吸附剂表面活性基团与水中重金属离子之间相互作用关系。研究发现了高盐离子和高浓度络合剂存在抑制氨基多羧酸化合物改性磁性吸附剂对Cr(III)的吸附，但在高盐和高浓度络合剂条件下，氨基多羧酸化合物改性磁性吸附剂对水中低浓度Cr(III)仍具有较好吸附效果，其吸附量随表面氨基多羧酸化合物络合能力的增强而增加，吸附主要机制在于形成“吸附剂表面活性基团-有机络合剂-重金属”三元复合物。研究还发现，高盐离子和高浓度络合剂对氨基多羧酸化合物改性磁性介孔复合材料吸附低浓度Cr(III)影响较小，因此，磁性介孔吸附剂在高盐条件下低浓度络合重金属的吸附去除方面具有潜在优势。本项目研究为低浓度络合态重金属高效吸附去除提供科学依据，为设计和开发对低浓度络合重金属具有高效净化效果的吸附剂提供理论依据和技术支撑。