Wang Hui, Bian Zhao-Yong
College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
Huan Jing Ke Xue. 2010 Jun;31(6):1506-12.
Using a self-made Pd/C gas-diffusion electrode as the cathode and Ti/IrO2/RuO2 as the anode, the degradation of phenol was investigated in an undivided electrolysis device by the electrochemical oxidation process. Hydroxyl radical (*OH) was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The result indicated that the Pd/C catalyst in Pd/C gas-diffusion electrode system accelerated the two-electron reduction of O2 to H2O2 when feeding air, which is in favor of producing *OH. After 120 min electrolysis in Pd/C gas-diffusion electrode system, the steady concentration of H2O2 was 7.5 mg/L. The removal efficiency of phenol and COD reached about 97.2% and 50% after 120 min electrolysis, respectively, which suggested that most of phenol were oxidized to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the ratio of BOD5/COD of the solutions was 9.1 times larger than the initial ones. Hence the electrochemical oxidation can enhance the biodegradation character of the phenol solution. The degradation of phenol was supposed to be cooperative oxidation by direct and/or indirect electrochemical oxidation at the anode and H2O2, *OH produced by oxygen reduction at the cathode. UV-Vis and GC-MS identified catechol, hydroquinone, and benzoquinone as the main aromatic intermediates, and adipic, maleic, fumaric, succinic, malonic, and oxalic acids as the main aliphatic carboxylic intermediates. A reaction scheme involving all these intermediates was proposed.
以自制的 Pd/C 气体扩散电极作为阴极，Ti/IrO₂/RuO₂作为阳极，在无隔膜电解装置中通过电化学氧化过程研究了苯酚的降解情况。采用电子自旋共振光谱（ESR）测定反应混合物中的羟基自由基（*OH）。结果表明，在通入空气时，Pd/C 气体扩散电极体系中的 Pd/C 催化剂加速了 O₂的两电子还原生成 H₂O₂，这有利于产生 *OH。在 Pd/C 气体扩散电极体系中电解 120 min 后，H₂O₂的稳定浓度为 7.5 mg/L。电解 120 min 后，苯酚和 COD 的去除率分别达到约 97.2%和 50%，这表明使用 Pd/C 气体扩散电极时，大部分苯酚被氧化为中间体。此外，溶液的 BOD₅/COD 比值比初始值大 9.1 倍。因此，电化学氧化可以增强苯酚溶液的生物降解特性。苯酚的降解被认为是阳极的直接和/或间接电化学氧化以及阴极氧还原产生的 H₂O₂、*OH 的协同氧化作用。紫外可见光谱（UV-Vis）和气相色谱-质谱联用（GC-MS）鉴定出邻苯二酚、对苯二酚和苯醌为主要的芳香族中间体，己二酸、马来酸、富马酸、琥珀酸、丙二酸和草酸为主要的脂肪族羧酸中间体。提出了一个涉及所有这些中间体的反应方案。
