TiO_2-AC电催化氧化含酚废水

Electro-oxidation of phenolic wastewater with TiO_2-AC filling in a packed bed electrochemical reactor

采用溶胶凝胶法制备了TiO2负载型活性炭颗粒。使用X-射线衍射仪(XRD)、电子扫描显微镜(SEM)对其进行物相组成及微观形貌分析,结果表明,TiO2晶粒主要以锐钛矿及金红石相填充于AC孔径之中,并形成均匀连续的负载膜;以TiO2-AC/AC分别作为填充床电化学反应器的填充物质对苯酚废水进行了电催化氧化对比性研究,引入表征填充床电化学反应器传质特性的传质系数km计算阳极和粒子电极对苯酚废水的氧化选择系数;实验结果表明,在苯酚废水浓度600 mg/L,操作电压为4.0 V,30 A/m2电流密度,流速0.6 L/h反应条件下以TiO2-AC为填充颗粒时填充床电化学反应器体系的传质系数4.032×10-6m/s大于以AC为填料时填充床电化学反应器的传质系数3.281×10-6m/s,电化学反应电荷控制阶段进程延长0.21 h,苯酚废水COD的去除率由73.2%提高至80.4%,体系电流效率亦由40.2%增加至49.5%,能耗降低2.01 kWh/kg COD;TiO2-AC/AC作为填充床电化学反应器填充颗粒对苯酚废水的选择氧化系数分别为0.74和0.80;紫外吸收光谱表明,TiO2-AC/AC作为填料电催化氧化苯酚废水过程中表现出不同的降解路径。

TiO2-AC was prepared in our laboratory via a sol-gel method,its phase composition and microtopography were characterized by X-ray diffraction( XRD) and scanning electron microscope( SEM) techniques.The results showed that a continuous uniform distribution membrane would be formed by anatase and rutile TiO2 filled in the apertures of active carbon. A comparative study with a packed bed electrochemical reactor between TiO2-AC and AC was conducted to investigate the phenol oxidation character of this new filling. Mass transfer coefficient(km) for packed bed reactor mass transfer representation was introduced to calculate oxidation selectivity coefficient of anodes(metal electrode) and particle electrodes toward phenolic wastewater. Experiments showed that when TiO2-AC were used as filling particles the mass transfer coefficient was 4. 032 × 10- 6m /s larger than operated with AC 3. 281 × 10- 6m /s under the working conditions: phenol concentration of 600 mg /L,voltage of4. 0 V,current density of 30 A /m2 and flow rate of 0. 6 L /h. Furthermore,an extended 0. 21 h charge control period was observed after the impregnation of TiO2,COD removal efficiency improved greatly from 73.2 % to80. 4 % and average current efficiency(ACE) changed from 40. 2 % to 49. 5 %,as well as a decreased specific power consumption(Esp) 2.01 kWh/kg COD during phenol electro-oxidation. Oxidation selectivity coefficient of TiO2 loaded AC and AC toward phenolic wastewater were 0. 74 and 0. 80,respectively. Ultimately,UV curves for these two fillings at different oxidation times indicating different electro-catalysis path ways in phenol degradation.