TiO2膜电极光电催化降解苯甲酸的机理研究

利用自制纳米TiO2薄膜作电极, 对苯甲酸光电催化降解过程进行了系统研究. 同时利用扫描电镜(SEM)、X射线衍射图谱(XRD)和光电流-电压响应谱分析光催化剂的微观性质和光电性能. 选取较高的pH 10.5, 以利于苯甲酸降解中间产物的检测(GC/MS). 通过对比光电催化与单一的TiO2光催化体系中苯甲酸的降解动力学、总有机碳(TOC)的去除率、降解产物的生成(GC/MS)及活性自由基物种的产生(ESR), 提出光电催化降解苯甲酸的具体反应路径和氧化机理. 羟基化的苯甲酸在羟基自由基与活性氧自由基的共同作用下, 经由含六个碳原子的二酸(顺式己二烯二酸), 被进一步氧化成小分子酸和CO2.

Mechanism on Photocatalytic Degradation of Benzoic Acid with TiO2-film Electrode

The supported nano-TiO2 electrode was prepared in laboratory, and the photoelectrocatalytic degradation of benzoic acid under UV irradiation was investigated detailedly. The micro-structure and photoelectrocatalytic property of TiO2-film were characterized by scanning electron microscopy, X-ray diffractometry and photo-current response. A value of pH 10.5 was chosen to detect more intermediates generated during the photoelectrocatalytic degradation of benzoic acid by GC/MS. The degradation kinetics, removal yield of total organic carbon, degraded intermediates and the formation of active radical species in different experimental conditions were examined by HPLC, TOC, GC/MS and spin-trap ESR spectrometry. According to above experimental results, the mechanism of benzoic acid photocatalytic degradation was deduced initially. Due to the combined effect of hydroxyl and active oxygen radicals, the hydroxylated benzoic acid, via cis,cis-muconic acid, was decomposed into low molecular weight acid and CO2.