高过氢电位电极去除酸性溶液中Cr3+机理研究

During the process of treating Cr3+ wastewater using electrochemical method, the phenomenon of low current efficiency, low removal efficiency, high energy consumption exist due to low electrode hydrogen evolution potential and confused removal mechanism. The main work of the present study is to prepare stainless steel net coated with single walled carbon nanotubes electrode with different physical and chemical properties. According to the relationship between different electord and hydrogen evolution potential, the effect regulation of electrode physical and chemical properties to hydrogen evolution potential was studied. Then, the electrode with high hydrogen evolution potential is prepared. Different complexing agents which have different complexation ability with Cr3+ forming [Cr(H2O)6-xLx]3-x (L, complexing agent) are selected to break the steady stucture of [Cr(H2O)6]3+. Optimal [Cr(H2O)6-xLx]3-x geometry construction of Cr3+ easily reduced is select through detecting the intermediate products and its geometric construction by UV-vis, single crystal cultivation and X-radial single crystal analysis methode, analyze the existence mode and valence state of Cr on the surface of electrode by XRD and XPS technique, and also combining the removal efficiency of Cr3+. At last, combining the chemical physical and chemical reaction between Cr3+ and complexing agents, the removal mechinism process of Cr3+ from solution to electrode surface is studied. The main purpose of this study is hopeful to provide a theoretical basis for using this method to remove Cr3+ from acidic wastewater.

电化学法处理酸性Cr3+废水过程中，存在去除率低、能耗大、电流效率低等现象，本质上是电极析氢电位较低、Cr3+去除机理不清。项目拟通过制备具有不同物理化学性质沉积单壁碳纳米管的不锈钢网片电极，通过考察不同电极与析氢电位的对应关系，探求电极物理化学参数对析氢电位的影响规律，制备具有高过氢电位的电极，降低析氢等副反应发生；选择与Cr3+具有强烈作用的络合剂打破[Cr(H2O)6]3+稳定正八面体结构，采用UV-vis、单晶培养、X射线单晶分析等手段研究Cr3+和不同络合剂形成的中间产物及其结构，利用XRD、XPS技术分析电极表面Cr的存在形态和价态，依据Cr3+去除率，遴选Cr3+易被还原的[Cr(H2O)6-xLx]3-x几何结构，结合Cr3+与络合剂可能发生的化学反应，揭示Cr3+的去除机理，为电化学法去除Cr3+的工程应用提供理论基础和科学依据。

利用电沉积技术，通过对单壁碳纳米管（SWCNTs）进行改性，制备了含有不同官能团的（-OH, -COOH, -SO3H）的SWCNTs钛网电极（SWCNTs@Ti）。并通过SEM，CV，极化曲线等分析手段，得到了电极物理化学参数与析氢电位的内在关系。以SWCNTs-COOH@Ti为电极，研究了其对水体中Cr3+， Cd2+，及甲基橙去除的影响因素、去除性能、机理及电极再生过程。研究发现：1）对SWCNTs进行不同的预处理，可使得SWCNTs表面携带不同的官能团，通过电泳沉积技术，可制备携带不同官能团的电极，经SEM、CV、极化曲线分析发现，不同官能团的引入可改变电极的析氢析氧电位，SWCNTs-COOH@Ti网电极具有较高的析氢析氧性能。2）不同络合剂（甲酸铵、甲酸和草酸）以及溶液pH、电解质浓度、硼酸浓度等参数对水溶液中Cr3+的去除具有显著的影响。3）SWCNTs-COOH@Ti电极对水体中的Cd2+具有良好的去除效果，在pH为8.0、应用电压为2.5 V、NaNO3浓度为20 g•L-1、镉初始浓度为20 mg•L-1条件下，Cd2+去除率可达90%以上，实验后电极经酸泡方式可以实现再生。4）在pH为2.0、应用电压为2.0 V、NaSO4浓度为1 g•L-1时，甲基橙具有最佳的去除效果；去除机理分析表明，甲基橙被降解为了小分子物质，同时SWCNTs电极可重复使用。