Study on the degradation mechanism of phenol in a new electrochemical oxidation system
一种新型电化学体系降解苯酚的机理研究

By using a self-made carbon/polytetrafluoroethylene (C/PTFE) O2-fed as cathode and Ti/IrO2/RuO2 as anode, the mechanism of electrochemical oxidation of phenol in the diaphragm cell was studied. The result indicated that the two-electron reduction from O2 to hydrogen peroxide (H2O2) was produced at the C/PTFE O2-fed electrode, and the accumulated H2O2 in the cathodic compartment reached to the steady concentrations of 8.3mg?L-1 after 80 min Furthermore, hydroxyl radical (HO?) was examined in the cathodic compartment by electron spin resonance spectrum (ESR). Hydroquinone, which was produced by the reaction between HO? and phenol and examined by high-performance liquid chromatography (HPLC), provedthat HO? was one of oxidizing agents resulting in phenol degradation. The degradation of phenol was supposed to be cooperative oxidation by direct or indirect electrochemical oxidation at the anode and H2O2, HO? produced by oxygen reduction at the cathode. At the beginning, the main intermediates from the phenol oxidation of the cathodic compartment were ring compounds (hydroquinone and benzoquinone). Then they were broken to yield CO2 and short chain acids, such as maleic, fumaric, crylic, malonic, oxalic, acetic and formic acids. Based on the intermediates analysis, a general degradation pathway of phenol was proposed. And the different pathway of phenol degradation between the cathodic compartment and the anodic compartment was compared.