CoO_x-TiO_2催化臭氧氧化草酸的研究

Performance investigation of catalytic ozonation of oxalate by CoO_x-TiO_2

采用溶胶凝胶的方法制备CoOx-TiO2催化剂,对臭氧流量、催化剂投量、反应温度、草酸初始浓度、pH值等影响草酸去除率的因素进行了研究,并探讨了催化机理.实验结果表明,溶液初始pH值对草酸的去除率有显著的影响,溶液初始pH值为3时,草酸具有去95.7%的最高去除率.催化氧化过程中草酸被彻底矿化为CO2和H2O.通过叔丁醇实验和电子顺磁共振波谱仪(ESR)证明,在催化过程中有羟基自由基的生成,但羟基自由基并不是主要的氧化剂.草酸可能首先在催化剂表面发生吸附或者络合,然后被羟基自由基或者臭氧分子直接氧化.

CoOx-TiO2 was prepared by sol-gel method. The effects of ozone flow, catalyst dosage, reaction temperature, initial concentration of oxalate and pH value on the removal rate of oxalate were discussed. The catalytic mechanism was also investigated. The catalytic ozonation was remarkable affected by pH value. The best removal rate of oxalate reached to 95.7% was found when pH value was 3. Oxalate was absolutely mineralized into CO2 and H2O in catalytic ozonation. Through TBA experiment and ESR, hydroxyl radicals which generated in catalytic process weren＇t the main oxidant. Oxalic acid may first be adsorbed or chelated on the surface of catalyst, and then oxidized by hydroxyl radicals or ozone molecules directly.