可见宽波响应的光电催化氧化去除废水中络合态重金属的协同作用机制

Removal of heavy metals complexes from wastewater was one of the problems in the environment field of mining and metallurgy. Photoelectrocatalytic oxidation is a new type of wastewater treatment technology with characteristics of light and electrocatalytic, and energy saving and high efficiency without secondary pollution. A new type of doping non-metallic Zn2SnO4 and Bi2MoO6 membrane visible-light photocatalytic electrode was proposed to solve the problems that the low solar energy utilization and the light quantum efficiency in this study. The degradation behaviors of heavy metal-inorganic complexes, heavy metal-organic complexes and heavy metal-organic-inorganic complexes using visible light electrode was investigated. Meanwhile the degradation difference on electrode surface between a variety of complexing agents coexisting and free complexing agent in wastewater was studied. Furthermore, the interaction between heavy metals and complexing agents was discussed. Based on the study of the distribution characteristic of intermediate and final products, the effects of hydrochemical control conditions on the removal of complex heavy metals were clarified. The relationship between heavy metals, complexing agents and interface and the synergetic mechanism of photoelectrocatalytic oxidation to complex heavy metals was revealed. The research results will provide a theoretical basis and guidance for the development of photoelectrocatalytic oxidation technology for the removal of metal complex.

如何去除废水中络合态重金属是矿冶领域环境治理的难题之一。光电催化氧化是一种兼具光、电催化特点，节能高效无二次污染的水处理技术。针对目前光催化过程中存在的太阳能利用率及光量子效率低等问题，本项目拟通过研究获得在可见宽波范围内具有良好响应的新型非金属掺杂锡酸锌系及钼酸铋系薄膜光催化电极，构建电助光催化体系处理络合态重金属废水。通过研究可见光电极对重金属-无机络合物、重金属-有机络合物以及重金属-有机-无机络合物的降解行为，明确多种络合剂共存下电极表面与水中游离络合剂的降解差异及重金属的电沉积规律；通过研究外加电压及水化学条件等因素对降解过程中中间产物和最终产物的分布特性，明确光电作用下降解与回收络合重金属的控制因素，阐明重金属、络合剂以及导电体界面之间的相互作用机理，揭示络合态重金属在光电催化氧化作用下的化学转性及其降解与回收的作用机制，研究结果为开发高效处理络合重金属废水提供理论与技术基础。

本项目以废水中重金属离子及难降解有机污染物为研究对象，围绕高性能光电催化电极的制备及污染物去除过程开展了大量研究工作：1）制备了Zn2SnO4基、ZnFe2O4基、Bi2MoO6基、BiOI基及Bi12TiO20复合光电极，探究了不同电极材料的制备机理及及其光电催化性能；2）建立了光电催化氧化体系，研究了Cr(VI)、As(III)及难降解有机污染物的脱除过程，明确了不同因素对复杂体系中重金属离子去除的影响机制以及电极再生的控制因素，揭示了重金属、有机物以及电极表面活性基团之间的相互作用机理，为实现光电催化协同去除重金属离子及有机污染物提供了理论依据，为其工业应用提供了技术支撑。.研究取得下列结果：.1）在光照激发下Zn2SnO4/CdS复合材料中Zn2SnO4的光生电子转移至CdS，产生大量的羟基自由基和超氧自由基，在同步处理有机物和重金属离子的混合废水时表现出良好的催化性能，在2 h内对甲基橙和Cr(VI)的去除率分别达到92.48%和98.81%。ZnFe2O4/Ag/AgCl表面的Fe元素是As(III)的活性吸附位点，Ag是过硫酸盐的活性吸附位点，两者有效缩短污染物分子与活性物种（•OH、O2•−、SO4•−和1O2）的距离，有利于As(III)的快速氧化。.2）ZnFe2O4@PANI可在30 min内去除50 mg/L的As(III)，能够促进催化剂表面Fe(IV)的生成，使As(III)快速氧化。ZnFe2O4/g-C3N4活化草酸盐体系能够在80 min内去除60 μM的Cr(VI)，在60 min内去除60 μM的As(III)。.3）2%Tm3+掺杂改性的Bi2MoO6光电极，其降解MB的效率提高了26%。在FTO上涂覆催化剂获得Yb-BVO-BO薄膜电极，其对MB的降解速率常数达到0.845 h-1。BiOI/WO3-120s薄膜电极降解效率是纯WO3电极的3.6倍，h+和·OH是主要活性物质。Ti3C2Tx/BTO/FTO光阳极在120 min后对MB的降解率达85.4％，动力学常数为0.01595 min-1，具有良好的污染物去除作用。