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近年来,药物和个人护理产品(pharmaceuticals and personal care products, PPCPs)在环境中的频繁出现引起了越来越多的关注。PPCPs可对水生生物和人类造成慢性毒性和内分泌紊乱,甚至引起致病菌耐药性的发生,对人体健康和生态系统构成潜在的严重威胁。布洛芬(ibuprofen, IBP)是目前世界上应用最多的一种非甾体抗炎药,也是在城镇污水处理厂二级出水中检出频率最高的一种PPCPs[1]。因此,探索从水环境中去除以布洛芬为代表的PPCPs技术已经成为环境领域的研究热点[2-3]。
目前, PPCPs的去除技术主要有生物技术[4-5]、臭氧氧化技术[6-8]、膜技术[9-11]、活性炭吸附技术[12-13]等。生物技术对PPCPs的降解效果并不稳定,这种现象与微生物的降解特性和PPCPs的结构有关[14]。膜技术与臭氧氧化技术对PPCPs的去除效果受PPCPs的种类和浓度影响[15]。活性炭可有效去除部分PPCPs,但对于极性化合物的去除效果有限,并且其他竞争物质的出现也会对活性炭的吸附能力产生影响[16]。
电催化强化技术在难降解废水的深度处理中表现出高效的污染物去除能力。CHEN等[17]通过O3+H2O2强化电催化体系对地表水中的氧氟沙星进行降解,发现O3单独和O3+H2O2强化电催化体系均可快速氧化氧氟沙星,与单独臭氧氧化(30%)相比,O3+H2O2体系显著提高了氧氟沙星的矿化率(55%)。BAVASSO等[18]采用O3强化电催化对利尿酮进行了去除,结果表明,在200 mA电流和酸性pH条件下,在2 h内可实现利尿酮的快速降解和矿化,这与羟基自由基的大量产生密不可分。SANTANA-MARTINEZ等[19]评价了H2O2强化电催化法的氧化效率,结果表明,在pH为3、电流密度为60 mA·cm−2、H2O2流速为4.7 L·min−1和电解质浓度为0.05 mol·L−1的条件下,苯酚的最高矿化率约为75%,其出水的原始毒性显著降低。综上所述,电催化强化对水体中的PPCPs类污染物具有高效的去除效率,然而电催化强化体系对布洛芬的深度去除效果和机制研究还很缺乏。因此,本研究设计了3种电催化强化处理体系,考察了H2O2浓度、O3投加量、腐殖酸等因素对IBP去除效果的影响,基于布洛芬的降解产物,阐明了IBP的降解机理。本研究以期为电催化强化体系去除以布洛芬为代表的PPCPs类污染物提供参考。
电催化强化对布洛芬的去除效果及机制
Removal effect and mechanism of ibuprofen by enhanced electrocatalysis
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摘要: 对比研究了O3 + H2O2电催化、 O3电催化和H2O2电催化这3种电催化强化体系对水中难降解污染物布洛芬的去除效果,并且进一步阐明了布洛芬的降解机制。结果表明:经30 min反应后,3种电催化强化体系对布洛芬的去除率分别达到93.2%、84.5%和52.7%,均高于在单独电催化条件下的去除率(46.2%)。尺度排阻色谱-紫外分析结果表明3种电催化强化体系对大分子(28 800 Da)和小分子(2 900 Da)有机污染物均有较好的去除作用。腐殖酸的存在会显著降低布洛芬的去除率。荧光光谱分析结果表明,类腐殖酸和溶解性微生物副产物是限制布洛芬去除的主要原因。硬度离子的存在对布洛芬去除影响较大,在CaCO3的质量浓度为15 mg·L −1时,O3 + H2O2体系对水中布洛芬的去除率相比去离子水溶液时下降了26.6%。研究阐明了布洛芬的降解路径,布洛芬在降解过程中产生了13种中间产物,反应中通过脱羧、脱甲基等一系列反应,最终将污染物氧化为CO2和H2O。Abstract: In this study, the performance of O3+H2O2 enhanced electrocatalysis, O3 enhanced electrocatalysis and H2O2 enhanced electrocatalysis on ibuprofen removal from water was compared, and the degradation mechanism was analyzed. The results showed that after 30 min reaction, the removal rates of ibuprofen by these three types of enhanced electrocatalysis were 93.2%, 84.5% and 52.7%, respectively, which were higher than 46.2% by electrocatalysis alone. The three enhanced electrocatalysis systems had good removal effects on macromolecular (28 800 Da) and small molecular (2 900 Da) pollutants detected by size exclusion chromatography-UV. Humic acid in water significantly reduced the removal effect of ibuprofen. Fluorescence spectrum analysis showed that the humic acid like and soluble microbial by-products were the main reason for restricting ibuprofen removal. The hardness of water significantly reduced the removal efficiency of ibuprofen. The removal rate of ibuprofen by O3+H2O2 enhanced electrocatalysis decreased by 26.6% at the 15 mg·L−1 CaCO3 in comparison with that in deionized aqueous background solution. The degradation path of ibuprofen was clarified, 13 intermediate products were produced during the degradation process of ibuprofen. In the reaction, the ibuprofen was finally oxidized to CO2 and H2O through a series of reactions such as decarboxylation and demethylation.
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Key words:
- electrocatalysis /
- ibuprofen /
- organic matters /
- degradation /
- molecular weight
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表 1 高效液相色谱串联飞行时间质谱检测到布洛芬在反应过程的中间产物
Table 1. Intermediate products of ibuprofen in the reaction process detected by high performance liquid chromatography-time-of-flight mass spectrometry
序号 名称 化学式 m/z 保留时间/min 1 2-(3-羟基-4-异丁基苯基)丙酸 C13H18O3 222 2.5 2 2-羟基-2-(4-异丁基苯基)丙酸 C13H18O3 222 6.6 3 4-(1-羟乙基)苯甲醛 C9H10O2 150 13.9 4 2-(4-甲基苯基)丙酸 C9H8O3 164 8.2 5 1-(4-异丁基苯基)乙醇 C11H13O2 178 11.7 6 1-(4-(1-羟乙基)苯基)-2-甲基丙烷-1-酮 C12H16O2 192 2.7 7 4-(1-羟基-2-甲基丙基)苯乙酮 C12H16O2 192 14 8 1,2,4-苯三酚 C6H6O3 126 1.7 9 邻苯二酚 C6H6O2 110 2.1 10 4-乙基苯酚 C8H10O 122 2.4 11 对苯二酚 C6H6O2 110 1.8 12 4-乙基苯甲醛 C9H10O 134 3.5 13 1-乙基-4-(2-甲基丙基)苯 C12H18 162 3.9 -
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