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近年来,随着地表水中微量有机物污染的日益严峻和人们对饮用水水质要求的不断提高,内分泌干扰物的环境风险和安全隐患日益受到重视[1]。在已确定的数百种内分泌干扰物中,双酚A在生活和生产中的应用最为广泛且对环境危害较大,已成为目前备受关注的一类有机污染物[2]。环境调查报告显示,双酚A在我国各类地表径流水体、地下水和沉积物中被频繁检出[3-4]。环境中残留的双酚A具有雌激素效应,其含量在ng·L−1水平即可干扰生物体内分泌系统、生殖系统及免疫系统;同时双酚A的持久性使其可以通过食物链在生物体富集,给人类健康和环境安全构成严重的威胁[5]。由于常规的饮用水处理工艺难以实现水中较低浓度双酚A的高效去除,因此,迫切需要寻找一种高效、经济且无二次污染的方法来去除水体中的双酚A。
光催化技术作为一种利用太阳能的绿色、高效水处理技术,在处理水体双酚A污染领域具有广阔的应用前景。王燚凡等[6]制备的超薄硫掺杂石墨相氮化碳纳米片在可见光下对10 mg·L−1双酚A的降解率为66.39%。KUMAR等[7]制备的ZnO-CdO纳米复合催化剂对水中双酚A和环丙沙星均具有优异的光催化性能。在众多的半导体光催化剂中,基于钛片上原位制备的TiO2纳米管阵列(TiO2 nanotube arrays, TNTAs)具有比表面积大、电荷传输性快和光催化活性高等优点,且能够有效解决粉体光催化剂难以回收和再利用的问题[8]。然而TNTAs禁带宽度较大,仅能被紫外光激发,对太阳光利用率低;且光生电子和空穴易于复合,从而阻碍了其在光催化领域的应用[9]。采用窄禁带半导体掺杂TNTAs构建异质结能够有效地解决上述问题[10-11]。
BiOBr作为一种四方晶系的窄禁带半导体,其中[Bi2O2]2+和双卤素层交替排列形成独特的层状结构,能够有效地促进光生载流子分离,显示出较好的可见光催化活性[12-13]。有研究表明,BiOBr能带结构与TiO2较为匹配,将其复合能够有效地拓展光谱响应范围,抑制光生电子空穴的复合[14-15],目前在较高浓度有机物的光催化降解中已有大量研究报道,HAN等[16]制备的BiOBr/TiO2复合催化剂,在可见光下对废水中的染料和抗生素具有良好的降解效果。MA等[17-18]报道了BiOBr掺杂的TNTAs可明显提高TNTAs对废水中罗丹明B和氯代硝基苯的光电催化性能。但采用BiOBr/TNTAs在可见光下对水中微量双酚A的去除还鲜有研究。尤其对自然水体中各种共存的无机离子和天然有机物,对双酚A光催化降解效果的影响研究更少。
本研究采用阳极氧化法-循环浸渍法制备了BiOBr/TNTAs,考察了BiOBr/TNTAs的表面形貌、光学性能及电化学性能,研究了BiOBr/TNTAs光催化降解水中微量双酚A的性能,并考察了不同水质参数对BiOBr/TNTAs光催化降解双酚A的影响规律,通过自由基淬灭实验探究了反应中发挥作用的主要活性物种,揭示了BiOBr/TNTAs光催化降解双酚A的机理。
BiOBr掺杂TiO2纳米管阵列光催化降解水中微量双酚A的性能及机理
Performance and mechanism of BiOBr modified TiO2 nanotube arrays photocatalytic degradation of trace bisphenol A in water
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摘要: 针对光催化降解水中微量双酚A存在的可见光利用率低、载流子复合效率高和催化剂回收难等问题,本研究采用阳极氧化法和循环浸渍法在钛片上原位制备了BiOBr/TiO2纳米管阵列(BiOBr/TNTAs)复合光催化剂,使用SEM、XRD和XPS等分析方法对催化剂的形貌和结构进行了表征。结果表明,片层状的BiOBr均匀负载在TNTAs表面,形成了稳定的异质结结构。BiOBr/TNTAs在可见光下对水中微量双酚A的去除率和矿化率明显高于TNTAs,且表现出优异的光催化稳定性。水体中共存的各种阴离子和腐殖酸等会通过竞争活性位点或作为自由基清除剂影响双酚A的去除效果。自由基淬灭结果表明,·OH和h+是BiOBr/TNTAs光催化降解双酚A的主要活性物种。光催化活性增强主要归因于BiOBr和TNTAs间p-n异质结的形成,可有效拓展TNTAs的光谱响应范围,从而提高光生电子-空穴的分离效率。Abstract: Due to the low visible light utilization, high photogenerated carriers recombination and difficulties in catalyst recovery in photocatalytic degradation of trace bisphenol A in water, BiOBr/TiO2 nanotube arrays (BiOBr/TNTAs) composite photocatalyst was prepared in situ on titanium plates by anodic oxidation method and cyclic impregnation method. The SEM, XRD and XPS analysis results show that lamellar BiOBr uniformly loaded on the surface of TNTAs and formed a stable heterojunction structure. The removal efficiency and mineralization efficiency of BiOBr/TNTAs were significantly higher than those of TNTAs under visible light. BiOBr/TNTAs shows excellent photocatalytic stability. Various anions and humic acids coexisting in water affected the removal of bisphenol A by competing for active sites or acting as free radical scavenger. The results of free radical quenching experiment show that ·OH and h+ were the main active species for BiOBr/TNTAs photocatalytic degradation of bisphenol A. The enhanced photocatalytic activity was mainly attributed to the formation of p-n heterojunction between BiOBr and TNTAs, which effectively expanded the spectral response range of TNTAs and improved the separation efficiency of photogenerated electron-hole.
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Key words:
- TiO2 nanotube arrays /
- BiOBr /
- photocatalytic degradation /
- visible-light response /
- bisphenol A
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