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药品和个人护理用品(PPCPs)作为一种新型有机微污染物,近年来受到了人们的广泛关注[1-3]. 其中,三氯生(triclosan,TCS)是一种多环芳烃类广谱抗菌剂,被广泛用于各类生活用品(如肥皂、清洁剂、牙膏、洗发水等)中[4]. 当前,随着TCS产品的普及,其在生产和使用过程中已不可避免地进入自然水体. 研究表明,全球范围地表水中的TCS浓度已高达ng·L−1至μg·L−1级别.TCS易通过生物富集和生物放大作用对摄入它的水生物种和哺乳动物造成内分泌干扰和毒性损伤,且能够诱导抗性基因的产生和传播,对人体健康和生态系统的潜在威胁不容忽视. 早在2016年,美国食品和药物管理局已开始禁止含TCS抗菌皂和沐浴露的销售,欧盟也于同年通过了禁用含TCS杀菌液的议案. 然而,我国对TCS的管控相对滞后[5].
传统的污水生物处理工艺对TCS的去除效率不佳,且在其处理过程中易产生危害性更大的亲脂性甲基衍生物[6]. 吸附技术处理水中TCS具有能耗低、反应过程不生成有毒物质的优点,但处理费用昂贵,并存在材料再生过程的二次污染隐患[7]. 相比之下,高级氧化技术因其高效、矿化率高、二次污染小等优势成为该领域研究的热点. 目前,国内对TCS废水的高级氧化处理已有较多报道,如臭氧氧化[8]、紫外/过氧化氢[9]、紫外/过硫酸盐[10]以及光催化氧化[11-12]等技术已被证实可有效削减水中的TCS.
过氧乙酸(peracetic acid,PAA)通常作为一种高效漂白、除菌剂被广泛用于食品加工、医疗制药、水产养殖等领域中,具有耐储存、pH依赖性低、氧化能力强、不产生有害消毒副产物、对人体危害小、成本低等特点[13]. 与过氧化氢相比,PAA是一种具有潜力的活性自由基前驱体,其氧化还原电位高达1.96 V[14],但过氧键能(38 kcal·mol−1)却远低于过氧化氢(51 kcal·mol−1)[15],理论上更易被活化.近两年,已有研究报道紫外光、过渡金属(Fe2+、Co2+、Mn2+)可在广泛pH条件下活化PAA,并获得丰度较高的活性物种(如羟基自由基HO·、有机自由基CH3C(=O)O·、CH3C(=O)OO·等)[16],将此类技术用于水中TCS去除的研究还未见报道.
为探讨PAA高级氧化体系去除水体中TCS的可行性,本研究采用价格低廉、来源广泛且二次污染较小的过渡金属离子Fe2+与PAA构建均相氧化体系(Fe2+/PAA),考察反应初始pH、PAA投加量、共存阴阳离子和天然有机物(NOM)对TCS去除效率的影响. 此外,通过自由基选择清除试验鉴别体系中的主要自由基物种,并利用超高效液相色谱-四极杆飞行时间质谱仪(UPLC-Q-TOF-MS)对反应过程中产生的中间产物进行分析,进而推断TCS在Fe2+/PAA体系中的转化途径.
亚铁联合过氧乙酸降解水中的三氯生
Degradation of triclosan by Fe2+-peracetic acid system in water
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摘要: 研究了Fe2+/过氧乙酸(Fe2+/PAA)高级氧化体系对水中三氯生(TCS)的降解.考察了初始pH、PAA投加量、常见阴阳离子(HCO3−,Cl-,Fe3+,Cu2+)和天然有机物(NOM)对TCS降解的影响,探讨了TCS在该体系中的降解机理和转化途径. 结果表明,TCS在Fe2+/PAA体系中的降解符合准一级反应动力学,其反应速率常数为0.46 min−1. 在TCS浓度为1 μmol·L−1,初始pH值为3.5、Fe2+投加量为10 μmol·L−1、PAA投加量为1 mmol·L−1、反应温度为25 oC、反应时间为20 min的条件下,TCS去除率高达95%.水中的NOM通过自由基竞争抑制TCS的降解,而共存阴阳离子的影响较小. HO•氧化是TCS降解的主要途径,但有机自由基对其的氧化作用亦不容忽视. 基于TCS降解过程中检出的4种产物,提出了它的转化途径,包含醚键断裂、羟基化和脱氢.Abstract: The degradation of triclosan(TCS)by activated peracetic acid(PAA)using Fe2+ was investigated in this study. The effects of operational parameters such as initial pH, PAA dosage and common water matrix on the degradation of TCS were investigated. Finally, the degradation mechanism and transformation pathway of TCS were studied. Results indicated that the TCS degradation by Fe2+/PAA followed the pseudo first-order kinetic model(k = 0.46 min−1). 95% of TCS was removed in 20 min under the conditions of TCS initial concentration of 1 μmol L−1, inital pH of 3.5, Fe2+ dosage of 10 μmol L−1, PAA dosage of 1 mmol L−1, temperature of 25 oC and reaction time of 20 min. The presence of NOM inhibited the TCS degradation through radical competition, while the co-existing inorganic anions and metal cations had no obvious influence on the removal of TCS. The oxidation of TCS by HO• was the major pathway during its degradation, while the organic radicals might also be the important active species. According to four identified intermediates, the transformation pathway of TCS by Fe2+/PAA was proposed including ether bond cleavage, hydroxylation and dehydrogenation.
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Key words:
- ferrous ion /
- peracetic acid /
- advanced oxidation /
- triclosan
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表 1 TCS在Fe2+/PAA体系中的降解产物
Table 1. Degradation products of TCS in Fe2+/PAA system
序号
Serial number质荷比(m/z)
Mass to charge ratio分子式
Formula结构式
StructureTCS 287 C12H7Cl3O2 1 143 C6H5ClO2 2 161 C6H4Cl2O 3 317 C12H5Cl3O4 4 319 C12H7Cl3O4 -
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