普伐他汀的光催化降解性能及机理研究

摘要

Bi2WO6 was synthesized by hydrothermal method and characterized by XPS, XRD, BET, UV-Vis and SEM. The effects of Bi2WO6 dosage, pH of solution on the photocatalytic degradation of pravastatin (PR) were investigated by photocatalytic performance experiments. And the main active radicals, intermediates and mechanism were ascertained by in situ capture experiments and the identification of intermediates. The toxicities of PR before and after degradation were evaluated by the acute toxicity tests of luminescent bacteria. The results showed that the prepared Bi2WO6 was a flower-like microsphere composed of a large number of nanoplates with orthorhombic crystal. Its mole ratio of elements was Bi:W:O=2.5:1:6.7. Its specific surface area and band gap were 26.67m2/g and 2.74eV, respectively. The optimal conditions for degradation of 10mg/L PR were: 0.4g/L Bi2WO6 and pH 6.5. Under this condition, 80.6% PR could be degraded, and the mineralization rate was up to 40.2%. By the detection of active radicals, demonstrated that h+ was the key active radical while ·OH and ·O-2 played a supplementary role in this photocatalytic process. The mechanism of photocatalytic degradation of PR was proposed based on the identification of active radicals and intermediates formed during this reaction. The C-C bond, C=C bond, and ester bond of pravastatin were destroyed by the oxidation of h+,·OH and ·O-2, and the PR was decomposed into small easily degradable organic compounds. In addition, the results of toxicity test showed that the small molecule products did not possess higher toxicity than the PR original solution.%通过水热法合成Bi2WO6,并利用XPS,XRD,BET,UV-Vis和SEM等方法对样品进行了表征;通过光催化性能实验考察了Bi2WO6投加量,溶液pH值对普伐他汀(PR)降解效果的影响;通过自由基捕获实验及中间产物的鉴定探明了Bi2WO6光催化降解PR过程的主要活性自由基,中间产物及降解机理,并采用发光细菌急性毒性试验评估了PR降解前后的毒性.结果表明,所制备的Bi2WO6是由大量纳米片组成的正交晶系花瓣状微球,各元素物质的量比为Bi:W:O=2.5:1:6.7,比表面积为26.67m2/g,带隙能为2.74eV;光催化性能结果表明,对于10mg/L PR,当溶液pH=6.5,Bi2WO6投加量为0.4g/L时降解效果最佳,降解率可达80.6%,矿化度为40.2%;自由基捕获实验结果表明降解过程中h+起主要的氧化作用,?OH和?O-2的氧化起辅助作用.基于活性自由基和中间产物的鉴别结果提出了Bi2WO6光催化降解PR的机理,即以h+为主,?OH和?O-2为辅联合攻击PR分子中C-C键,C=C双键,酯键等化学键,进而将其分解为易降解小分子有机物.另外,毒性测试结果表明PR经光催化降解后的小分子产物与PR原液相比毒性并没有增强.