硫酸根自由基是一类新型的强氧化性自由基，氧化能力与羟基自由基相当，但最适pH更宽，在水中寿命更长，因此对有机污染物降解效果更好，是目前国际上的研究热点。目前，获得硫酸根自由基的主要方法是使用金属氧化物活化过硫酸盐或过二硫酸盐，然而该方法需要额外投加化学试剂，不但增加运行成本，而且带来很大的二次污染风险。由于硫酸根在各类水体中十分常见，浓度范围很宽（从几个毫克每升到几十克每升），研究团队以光催化反应热力学原理为指导思想，首次提出使用具有宽带隙和高价带的光催化剂磷酸铋纳米线对硫酸根进行活化，在中性pH条件下原位生成硫酸根自由基的概念和方法（i-PCAS），并从多个角度证实了这一方法的可行性和有效性。i-PCAS只需利用水中已有的硫酸根离子产生硫酸根自由基，完全不需要额外使用过硫酸盐或过二硫酸盐，降低处理成本的同时有效避免了二次污染。这一成果为人们提供了更加简单、绿色、廉价的方法和途径获得硫酸根自由基，从而实现水中有机污染物的高效去除。

该项研究得到国家自然科学基金、城市水资源与水环境国家重点实验室自主课题、我校环境生态研究院创新基金和“青年拔尖人才计划”等项目支持。

论文链接：http://pubs.acs.org/journal/esthag

Abstract

The advanced oxidation process (AOP) based on SO4•– radicals has been receiving growing attention in water and wastewater treatment. Producing SO4•– radicals by activation of peroxymonosulfate or persulfate faces the challenges of high operational cost and potential secondary pollution. In this study, we report the in situ photochemical activation of sulfate (i-PCAS) to produce SO4•– radicals with bismuth phosphate (BPO) serving as photocatalyst. The prepared BPO rod-like material could achieve remarkably enhanced degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of sulfate, indicated by the first-order kinetic constant (k = 0.0402 min–1) being approximately 2.1 times that in the absence (k = 0.019 min–1) at pH-neutral condition. This presented a marked contrast with commercial TiO2 (P25), the performance of which was always inhibited by sulfate. The impact of radical scavenger and electrolyte, combined with electron spin resonance (ESR) measurement, verified the formation of •OH and SO4•– radicals during i-PCAS process. According to theoretical calculations, BPO has a sufficiently high valence band potential making it thermodynamically favorable for sulfate oxidation, and weaker interaction with SO4•– radicals resulting in higher reactivity toward target organic pollutant. The concept of i-PCAS appears to be attractive for creating new photochemical systems where in situ production of SO4•– radicals can be realized by using sulfate originally existing in aqueous environment. This eliminates the need for extrinsic chemicals and pH adjustment, which makes water treatment much easier, more economical, and more sustainable.

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