催化学报 ›› 2019, Vol. 40 ›› Issue (5): 673-680.DOI: 10.1016/S1872-2067(19)63285-7

• 论文 • 上一篇    下一篇

宽pH条件下运行的太阳光催化钨酸铋降解抗生素诺氟沙星

陈美娟a,b, 黄宇b, 朱威c   

  1. a 西安交通大学, 人居环境与建筑工程学院, 陕西西安 710049;
    b 中国科学院地球环境研究所, 黄土第四纪地质国家重点实验室&气溶胶化学与物理重点实验室, 陕西西安 710061;
    c 香港理工大学, 建设与环境学院, 香港
  • 收稿日期:2018-11-13 修回日期:2018-12-13 出版日期:2019-05-18 发布日期:2019-03-30
  • 通讯作者: 黄宇
  • 基金资助:

    国家自然科学基金(41877481,41503102);中国科学院地球环境研究所黄土第四纪地质国家重点实验室开放课题(SKLLQG1729);中国博士后科学基金(2018M643669);中央高校基本科研业务费专项资金(xjj2018249);中国科学院“百人计划”.

Exploring a broadened operating pH range for norfloxacin removal via simulated solar-light-mediated Bi2WO6 process

Meijuan Chena,b, Yu Huangb, Wei Chuc   

  1. a School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, China;
    b State Key Laboratory of Loess and Quaternary Geology(SKLLQG), Key Laboratory of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi, China;
    c Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
  • Received:2018-11-13 Revised:2018-12-13 Online:2019-05-18 Published:2019-03-30
  • Contact: S1872-2067(19)63285-7
  • Supported by:

    This work was supported by the National Science Foundation of China (41877481, 41503102), the open project of the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Science (SKLLQG1729), the China Postdoctoral Science Foundation (2018M643669), the Fundamental Research Funds for the Central Universities (2018249), and the "Hundred Talent Program" of the Chinese Academy of Sciences.

摘要:

抗生素污染对水生和陆地生态环境系统造成严重的威胁.在世界各地的水性环境中普遍检测到第二代合成氟喹诺酮类抗生素—诺氟沙星.因此,水环境中残留诺氟沙星的去除成为当今研究热点.在现有去除方法中,光催化技术因其采用太阳光作为能源、污染物完全矿化及不产生二次污染等优点而被认为是非常有效的方法,在水处理工业中得到了广泛的关注.已有研究表明,pH值是影响光催化降解污染物的一个重要因素,大多数半导体光催化剂的最佳pH被限制在较窄的近中性范围内.当pH变为酸性或碱性时,污染物的降解速度显著降低.我们研究发现,在太阳光下钨酸铋(SSL/Bi2WO6)催化降解诺氟沙星时,在pH=5.0-10.8表现出较快的去除速率,其中pH=8.6时效果最佳,目前优化降解效果多通过酸碱调整初始溶液的pH至最佳值.进一步研究发现,即使将反应初始溶液pH值调整到最佳,随着诺氟沙星的不断降解,反应溶液的pH值持续降低直至3.0.溶液不断酸化导致偏离最佳条件,从而减缓诺氟沙星的降解.这说明通过简单的酸碱滴定优化溶液初始pH值不能阻止反应过程中溶液的酸化,也不能解决酸化导致的降效问题.基于上述问题,本文提出针对溶液pH值改变对体系效率影响的新方法.
本文以钙钛矿结构的Bi2WO6为光催化剂,诺氟沙星为探针化合物,详细研究了在不同pH值下SSL/Bi2WO6体系催化性能.为描述SSL/Bi2WO6反应的合理性,首先提出了OH-富集Bi2WO6模型,并考察了Mg2+和Ca2+两种离子对反应的影响.在预吸附阶段pH值明显降低,说明溶液中的羟基离子被吸附到Bi2WO6表面.光催化反应开始后,pH值以较低的速率持续降低,说明在降解过程中溶液中的羟基离子可能由于低分子有机酸和二氧化碳的形成而逐渐被消耗.因此,在Bi2WO6表面及其附近维持较高浓度的羟基离子是改善或保持探针快速分解的关键途径.我们在极碱pH环境中引入NH4+缓冲体系,以持续提供羟基离子生成·OH自由基,同时可防止溶液酸化,从而使诺氟沙星的去除率和矿化率在碱性条件下均达到更好的效果.另一方面,在酸性pH条件下,通过加入铁盐(即形成替代的SSL/Fe3+/Bi2WO6过程)显著提高了SSL/Bi2WO6去除诺氟沙星的效率.这主要归因于SSL/Fe3+提供的均匀光敏化机制;同时,Fe3+在SSL/Bi2WO6过程中对电子传递起到辅助作用.SSL/Fe3+/Bi2WO6工艺可以在较宽的酸性pH (2-4)范围内使用,且pH=3.0时性能最好.在SSL/Fe3+/Bi2WO6过程中,诺氟沙星的降解速率随着[Fe3+]的增加而增大,过剂量时降解趋于平稳.

关键词: 钨酸铋, 扩展pH范围, 诺氟沙星, 光催化,

Abstract:

Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norfloxacin degradation over a narrow pH range. To broaden the operating pH range of the SSL/Bi2WO6 process, an NH4+ buffer system and an Fe3+ salt were introduced under extremely basic and acidic pH conditions, respectively. The NH4+ buffer system continuously supplied hydroxyl ions to generate·OH radicals and prevented acidification of the solution, resulting in improved norfloxacin removal and mineralization removal under alkaline conditions. In contrast, the Fe3+ salt offered an additional homogeneous photo-sensitization pathway. The former treatment assisted in norfloxacin decay and the latter increased the collision frequency between the photo-generated hole and hydroxyl ions. Moreover, the effect of parameters such as pH and Fe3+ dosage was optimized.

Key words: Bismuth tungstate, Broadened operating pH, Norfloxacin, Photocatalysis, Water