硫（IV）自氧化体系降解典型有机溴类污染物及溴转化研究

Org-bromine pollutants are extensively detected in natural waters. Compared to hydroxyl radicals, sulfate radicals are more effective in the degradation of org-bromine pollutants. However, bromate and brominated disinfection by-products would form during the reaction of sulfate radicals and bromine-containing compounds. Auto-oxidation of S(IV) systems which can produce a series of reactive radicals such as sulfate radicals are usually achieved through the activation of sulfite by transition metals. Due to the fact that sulfite would consume some necessary bromine-containing intermediates for the formation of bromate and brominated disinfection by-products, it is reasonable to propose that auto-oxidation of S(IV) systems might control the formation of bromate and brominated disinfection by-products during the degradation of org-bromine pollutants. Five different auto-oxidation of S(IV) systems and five different org-bromine compounds will be selected in this study. The degradation efficiency of org-bromine pollutants in the selected systems will be evaluated and the mechanisms will be disclosed, along with studying the influences of some operational parameters and water matrices. Kinetic models for the degradation of org-bromine pollutants in the selected auto-oxidation of S(IV) systems will be also developed. Then the application of auto-oxidation of S(IV) systems in the degradation of org-bromine pollutants will be comprehensively evaluated based on the test of toxicity and biodegradability. Additionally, the transformation of bromine during the degradation of org-bromine pollutants in the auto-oxidation of S(IV) systems will be also disclosed. The progressing of this study will offer a new method to treat org-bromine pollutants with controlling the formation of bromate and brominated disinfection by-products with making clear the related hydro-chemical process and mechanism, which is important to optimize the technological parameters.

有机溴类污染物在天然水体中广泛检出。硫酸根自由基相对于羟基自由基在降解有机溴类污染物时效果更优，但是硫酸根自由基可与溴经过系列反应生成溴酸根和溴代消毒副产物。硫（IV）自氧化体系可由过渡金属活化亚硫酸根生成硫酸根自由基在内的多种自由基，具有同步降解有机溴类污染物并控制溴酸根和溴代消毒副产物生成的潜力。本项目拟选择五种硫（IV）自氧化体系和五种典型有机溴类污染物为研究对象，系统研究各体系降解有机溴类污染物的效果及机理，明确工艺参数和水质参数的影响，构建动力学模型，分析各污染物的降解路径，并结合毒性和可生化性进行综合评估；阐明各体系在反应时的溴转化过程，在此基础上开发同步降解有机溴类污染物并控制溴酸根和溴代消毒副产物生成的高级氧化技术。本研究可为有机溴类污染物的处理提供一种新方法，并揭示其水化学过程与机理，为参数优化提供基础。

硫酸根自由基可有效降解有机溴类污染物（Org-Br），但是硫酸根自由基与溴经过系列反应会生成溴酸根和溴代副产物。基于过渡金属活化亚硫酸盐的硫（IV）自氧化体系可生成硫酸根自由基和羟基自由基，且亚硫酸根可消耗活性溴进而可能在降解Org-Br的同时抑制溴酸根和溴代副产物生成。针对上述假设，本项目选择四溴双酚A、1,3,6,8-四溴咔唑、溴氰菊酯、十溴二苯醚和2,4,6-三溴苯酚为典型Org-Br，重点研究了铁离子[Fe(II)/Fe(III)]及其金属氧化物活化亚硫酸盐降解Org-Br并控制溴酸根及溴代副产物的效果及机理。结果表明：硫（IV）自氧化体系可有效去除溶液中的Org-Br，硫酸根自由基和羟基自由基在十溴二苯醚、2,4,6-三溴苯酚、四溴双酚A和溴氰菊酯的降解中发挥重要作用，而1,3,6,8-四溴咔唑主要通过体系内原位生成的铁系絮凝剂去除。本项目系统研究了多种操作参数和水质参数对Org-Br去除的影响：增加Fe(II)/Fe(III)和亚硫酸盐虽然能够促进Org-Br去除，但过量的Fe(III)和亚硫酸盐会消耗溶液中的自由基；溶解氧是硫（IV）自氧化体系产生硫酸根自由基的必要条件，亚硫酸氢根易与Fe(III)络合而促进自由基生成进而导致大部分Org-Br在pH4~6的降解效果较优；光照能够改变体系内自由基的贡献，并提升体系的处理效率；分次投加亚硫酸盐可提升体系内亚硫酸盐的利用效率；共存腐殖酸、碳酸氢根和氯离子由于可竞争自由基，进而会降低以自由基氧化为主的Org-Br的去除效果。此外，本项目以Fe(III)/亚硫酸盐为典型硫（IV）自氧化体系，建立了污染物降解的响应面回归模型；结合密度泛函理论计算结果和产物鉴定提出了5种Org-Br的降解路径，发现C-Br键的脱溴和羟基化取代是硫（IV）自氧化体系降解Org-Br的重要初始路径；溶液中的溴离子虽然能够被硫酸根自由基转化为溴自由基，但溴自由基会被亚硫酸盐快速还原为溴离子进而不会产生溴酸根、溴代甲烷和溴乙酸等副产物；硫（IV）自氧化体系可有效降低多种Org-Br毒性并提高其可生化性。本项目证实了硫（IV）自氧化体系可在降解Org-Br的同时控制溴素根和溴代副产物生成，相关的理论研究可为该体系应用推广提供基础。