磷化纳米零价铁去除水中重金属离子性能及其界面反应机制

The use of nZVI for the removal of heavy metals is one of the hot topics in pollution control technology field. But the electrons from the nZVI could be consumed by heavy metals, medium molecules, and intermediate species simultaneously during the treatment of heavy metals by nZVI, leading to the low utilization and poor selectivity of electrons. The surface/ interface modification of nZVI is one of the effective strategies to solve this problem. Recently, we found that both the electrons utilization and electrons selectivity of nZVI were improved significantly over the phosphated nanoscale zero-valent iron (P-nZVI) during removal of typical heavy metal ions in aqueous solution. In order to verify the interface reaction and its mechanism of P-nZVI and heavy metal ions, this project aims to systematically characterize the micro-structure morphologies of the P-nZVI by modern analysis technologies; to investigate the phosphated layer structure of P-nZVI, the surface phosphate functional group, the adsorption/ coordination configuration of typical heavy metal ions, and electron transfer pathway by using DFT simulation; to study the adsorption/ reaction/ selectivity performance of different heavy metal ions with P-nZVI; to analyze the change of iron/ heavy metals, the generation and consumption of active species on the surface/ interface and in the solution during the reaction of heavy metals and P-nZVI; to reveal the "structure-performance" relationship of heavy metal ions removal with P-nZVI; to clarify the effects of environmental factors on the removal of heavy metals by P-nZVI; and to provide theoretical support for the green and efficient nZVI-based heavy metal pollution control technology.

利用纳米零价铁(nZVI)去除重金属是污染控制领域的热点之一。但污染控制过程中nZVI的电子被重金属、介质分子、中间物种等同时消耗，存在着电子利用率低/选择性差的问题。表面改性nZVI是解决该问题的有效途径。近期我们发现磷化纳米零价铁(P-nZVI)去除水中典型重金属离子的电子利用率/选择性显著提升。为探明P-nZVI去除重金属性能和反应机制，本项目将系统表征P-nZVI结构及形貌；通过DFT模拟P-nZVI磷化层及表面官能团与典型重金属离子吸附/配位构型和电子转移途径；研究不同重金属离子与P-nZVI的表界面吸附/反应/选择性规律；分析P-nZVI与重金属作用过程中材料表界面和溶液相铁/重金属的形态/价态、及活性物种种类/浓度变化规律；揭示P-nZVI去除重金属离子的“结构-性能”关系；阐明环境因素对P-nZVI去除重金属性能的影响；为发展绿色高效nZVI重金属污染控制技术提供理论支持。

本项目可控合成系列磷酸化纳米零价铁材料，系统表征P-nZVI结构及形貌；通过DFT模拟P-nZVI磷化层及表面官能团与典型重金属离子吸附/配位构型和电子转移途径；研究不同重金属离子与P-nZVI的表界面吸附/反应/选择性规律；分析P-nZVI与重金属作用过程中材料表界面和溶液相铁/重金属的形态/价态、及活性物种种类/浓度变化规律；揭示P-nZVI去除重金属离子的“结构-性能”关系；阐明环境因素对P-nZVI去除重金属性能的影响。项目通过液相合成法在陈化阶段加入磷酸根前驱体，制备表面磷酸根修饰的纳米零价铁(P-nZVI)，磷酸根修饰改变铬酸根离子在nZVI表面的吸附配位模式，为铬酸根还原提供双电子通道，同时抑制溶解氧还原、产氢等副反应，提升nZVI还原去除Cr(VI)的电子选择性；通过液相合成法在硼氢化钠还原前加入磷酸根前驱体与三价铁离子混合，制备含径向裂纹的纳米零价铁(CnZVI)，直接“打破”nZVI致密的氧化层，构建贯通表面氧化层与内部铁核的传质通道，实现多种重金属离子快速去除；通过机械球磨法制备磷原子取代的零价铁，优化铁核内部电子结构，加速电子传输，促进洛克沙胂降解与无机砷固定。项目的完成为发展绿色高效的重金属污染控制技术提供理论支持。