UV活化亚硫酸盐/过硫酸盐协同矿化难降解有机污染物的机理及模型研究

Degradation of organic contaminants by activation of persulfate has been a hot topic in fields of ecological and environmental sciences. However, the low removal efficiency for nitrobenzenes, organochlorine pesticide/calorinatedbenzenes, perfluorinated compounds by activation of persulfate has restricted its application in wastewater treatment. Recently, the advanced reduction process (ARPs) based on ultraviolet activation of sulfite has shown a great advantage for reducing the electron withdrawing groups by producing the reductive radical, such as hydrated electron and hydrogen radical. More importantly, the reduced organic contaminants exert higher reactivity with sulfate radical. In this study, the combination of ultraviolet-activated persulfate and sulfite is used to enhance the removal and mineralization efficiency of refractory organic pollutants by controlling step and time of these two reactions. The mechanism of reaction between active radicals and refractory organic contaminants in ARPs-AOPs will be well investigated based on kinetics experiment, computational chemistry, and kinetics simulation. In addition, the mechanistic insight into the role of inorganic ions and dissolved organic matter in ARPs-AOPs will be elucidated. Based on the investigation of target contaminants, kinetic models and optimum proposals by quantitative structure-activity relationship will be developed to predict the degradation kinetics and treatment effect for other refractory organic contaminants in ARP-AOPs. The results of this study will be expected to provide theoretical guidance and technical support for broadening the application of sulfate radical-mediated advanced oxidation in wastewater treatment.

活化过硫酸盐降解有机污染物成为生态与环境科学的热点前沿，但对硝基苯类、氯代苯（有机氯）类和全氟化合物等含有吸电基团的污染物去除效率低，限制了过硫酸盐高级氧化技术在水处理中应用。近年来发展的UV/亚硫酸盐高级还原技术产生还原性的水合电子和氢原子自由基，能有效地脱除或还原这几类化合物的吸电基团，被还原后的化合物与硫酸根自由基有更高的反应活性。本项目提出UV活化亚硫酸盐和过硫酸盐协同去除的方法，拟通过调控还原-氧化作用，提高难降解有机污染物的降解和彻底矿化效率。结合实验研究、量子计算化学和动力学软件模拟，阐明还原-氧化协同矿化过程中活性基团与难降解有机污染物的反应机理；揭示无机离子、有机质对协同矿化的影响及作用机制；通过目标污染物的研究，构建定量构效关系的动力学模型、协同矿化调控模型，预测其他难降解有机物降解特征。本研究有望为水处理中难降解有机污染物的去除提供理论指导和技术支持。

本项目针对硝基苯类、氯代苯和全氟化合物一类含有强吸电基团的污染物在氧化去除效率低、限制了过硫酸盐高级氧化技术在水处理中应用问题，提出了通过UV/亚硫酸盐高级还原技术产生水合电子等还原性自由基有效脱除吸电基团的思路。本研究开展了难降解有机污染物在高级还原/氧化体系中降解动力学实验、实际污水中氯离子、硝酸根、硫酸根和碳酸根/碳酸氢根等无机离子、有机质及其分子大小分级对高级氧化和还原降解的影响；通过计算化学解释了有机污染物通过氧化、还原脱氯/氟降解可能途径，从微观层面确定主要降解途径，揭示了还原/氧化降解机理；构建了高级氧化和高级还原的降解动力学预测模型。高级还原体系中硝基苯、氯苯和阿特拉津降解效率高于高级氧化体系，而环境基质中对高级还原体系的抑制率低于高级氧化体系，氯离子对高级氧化体系影响较明显，而硝酸根离子对还原体系影响较大；通过计算化学揭示了还原性水合电子容易通过电子转移攻击氟、氯、硝基等吸电子基团，进而使得其获得电子从碳原子脱除。总结了水合电子与污染物降解动力学与基团的供/吸电子能力之间关系，含有强吸电基团污染物的有较高的动力学常数。通过定量构效模型揭示了污染物经验常数与结构参数之间的内在联系，并可用于提高动力学模型的预测性；构建了基于ELUMO单因子的水合电子还原降解动力学预测模型，高于现有模型的预测性。这些研究可为含吸电子基团的难降解有机污染物有效去除提供了科学基础。