基于催化臭氧氧化去除煤化工废水中污染物——苯系物

苯、甲苯、乙苯和二甲苯(BTEX)是煤化工废水中典型的难降解有机污染物,通常情况下BTEX较难通过传统的化学氧化技术去除。笔者自主制备了多孔臭氧催化剂,并对催化剂进行表征分析;考察了催化臭氧化降解BTEX的最佳反应条件,并对不同反应体系中自由基的激发情况进行比对;在此基础上探究催化臭氧化对BTEX的去除机理,为BTEX在实际处理过程中的技术应用提供理论基础。XRD分析结果表明,多孔臭氧催化剂含有氧化铝、氧化硅等,且含有沸石结构的化合物。XPS分析结果表明,所合成的催化剂含Si、O、Cu、Fe、Mn、Al等元素。SEM结果表明,催化剂由许多不规则的细小块状粉末构成,且表面非常蓬松,堆叠成多级结构,使催化剂呈多孔性。比表面积分析表明,催化剂的比表面积为20.8 m~2/g,孔隙直径主要集中在3.8 nm。使用该催化剂对BTEX进行催化臭氧化试验,结果表明,反应温度为30℃、溶液pH=8、臭氧投加量为3.5 mg/L、催化剂投加量为5 g/L时,BTEX的降解效果最佳。在该反应体系中有机物去除率为99.1%,其中苯、甲苯、乙苯、二甲苯的去除率分别为95.6%、98.2%、100%、100%。ESR分析结果表明,催化臭氧化反应体系中羟基自由基和超氧自由基的激发强度明显高于臭氧氧化反应体系,这是因为本文制备的催化剂含有Al、Fe、Mn、Cu氧化物,使催化反应过程中负载的金属氧化物价态间相互变化,转移的电子可促进臭氧分子分解,从而产生更多的自由基。催化臭氧化技术是以羟基自由基为主导,超氧自由基、催化剂吸附为辅助,协同实现煤化工废水中典型有机污染物BTEX的高效去除。 Benzene,toluene,ethylbenzene and xylene( BTEX) are typical refractory organic pollutants in coal chemical wastewater,which are usually difficult to be removed by traditional chemical oxidation technology.In this experiment,a porous ozone catalyst was prepared independently and the catalyst was characterized and analyzed.The best reaction conditions of degradation of BTEX by ozone catalytic oxidation were studied,and the excitation of free radicals in different reaction systems was compared.Based on this,the mechanism of the removal of BTEX by the ozone catalytic oxidation method was explored,which provided a theoretical basis for the technical application of BTEX in actual treatment process. The analysis results of XRD show that the porous ozone catalyst contains alumina and silica,and the catalyst contains compounds with a zeolite structure.XPS analysis results show that the synthesized catalyst contains Si,O,Cu,Fe,Mn,Al and other elements.The SEM results show that the catalyst is composed of many irregular small powders and its surface is very fluffy. The stacked multi-stage structure makes the catalystporous. The specific surface area analysis shows that the catalyst is porous with a specific surface area of 20.8 m~2/g,and the pore diameter is mainly concentrated at 3.8 nm.The experimental results of ozone-catalyzed oxidation of BTEX with this catalyst show that the degradation effect of BTEX is the best when the reaction temperature is 30 ℃,the solution pH is 8,the ozone dosage is 3.5 mg/L and the catalyst dosage is 5 g/L.In this reaction system,the removal rate of organic matter is 99.1%,and the removal rates of benzene,toluene,ethylbenzene and xylene are 95. 6%,98. 2%,100% and 100%,respectively. The ESR analysis results show that the excitation intensity of hydroxyl radicals and superoxide radicals in ozonation system is significantly higher than that in ozonation system.