Mechanistic insight into suppression of bromate formation by dissolved organic matters in sulfate radical-based advanced oxidation processes
Mechanistic insight into suppression of bromate formation by dissolved organic matters in sulfate radical-based advanced oxidation processes
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硫酸根高级氧化过程中溶解有机物抑制溴酸盐形成的机理研究
DOI：
10.1016/j.cej.2017.09.159
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发表时间：
2018-02
影响因子：
15.1
通讯作者：
Jiang Jin
中科院分区：
文献类型：
--
作者：
Liu Yongze;Yang Yi;Pang Suyan;Zhang Liqiu;Ma Jun;Luo Congwei;Guan Chaoting;Jiang Jin
硫酸根（SO 4 radical dot−）高级氧化工艺中溴酸盐的生成一直是人们关注的问题。以往的研究表明，溶解性有机物（DOMs）可以有效地抑制溴酸盐的形成，但其机制尚不清楚。在这项工作中，我们发现，在草酸盐（DOM模型化合物）存在下，在UV/过二硫酸盐（PDS）中溴酸盐的释放表现出两相动力学，即，溴酸盐在滞后期检测不到，在第二快速期迅速增加。随着草酸浓度的增加，延迟相持续时间延长，第二快速相溴酸盐生成速率降低。通过包括UV/PDS/Br−体系中涉及的草酸盐与各种反应性自由基的基元反应进行动力学模拟，其中CO2是最终产物（即，模拟结果表明，草酸根清除SO 4自由基dot−对溴酸根生成的抑制作用不大，而清除活性溴原子（Br自由基dot）则起重要作用。此外，在草酸盐与Br自由基反应过程中形成的超氧化物也可以通过还原反应性溴物种来促进溴酸盐的抑制。其他DOM模型化合物对溴酸盐的生成也有一定的抑制作用，其抑制作用顺序为酪氨酸>苯酚>叔丁醇>柠檬酸>甲醇>草酸。这一顺序与它们完全矿化所需的氧化剂量一致，表明它们的氧化中间体不断地抑制活性自由基以抑制溴酸盐的形成。同时，无机溴在动力学运行期间几乎保持恒定。这项工作中获得的这些结果表明，DOMs与反应性溴物种反应产生Br−，从而防止它们进一步氧化为溴酸盐。
Serious concerns have been raised on the formation of bromate in sulfate radical (SO4radical dot−)-based advanced oxidation process. Previous studies have shown that dissolved organic matters (DOMs) can efficiently suppress bromate formation, but the involved mechanisms are not clearly understood. In this work, we found that bromate evolution in UV/peroxydisulfate (PDS) in the presence of oxalate (a DOM model compound) exhibited biphasic kinetics, i.e., bromate was undetectable in the lag phase and rapid increased in the secondary rapid phase. Increasing oxalate concentrations resulted in the increase of duration time of lag phase and the decrease of rate of bromate formation in secondary rapid phase. Kinetic simulation was conducted by including elementary reactions of oxalate with various reactive radicals involved in UV/PDS/Br−system, where CO2was the final product (i.e., no interference by organic intermediates) Simulation results indicated that scavenging SO4radical dot−by oxalate contributed little to the suppression of bromate formation, while scavenging reactive bromine atoms (Brradical dot) by oxalate played an important role. In addition, the superoxide formed during the reaction of oxalate with Brradical dot could also contribute to bromate suppression via reducing the reactive bromine species. Similarly, other DOM model compounds were also observed to inhibit bromate formation, and their effects decreased in the order ofl-tyrosine > phenol >tert-butanol > critic acid > methanol > oxalate under identical conditions. This order was consistent with the amounts of oxidant needed for their complete mineralization, suggesting that their oxidation intermediates continuously scavenge reactive radicals to suppress bromate formation. In parallel, the inorganic bromine during the kinetic runs almost kept constant. These results obtained in this work suggest that DOMs react with reactive bromine species yielding Br−and thus prevent their further oxidation to bromate.
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发表时间：
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期刊：
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