Mechanistic insight into active chlorine species mediated electrochemical degradation of recalcitrant phenolic polymers

Abstract

Degradation of recalcitrant phenolic syntan by electro-oxidation was investigated. The kinetics of degradation of phenolic syntan was followed both in terms of TOC and COD measurements. The generation of oxidants such as Cl₂, HOCl and free radicals of oxychloride in the presence of NaCl electrolyte was also monitored and their role in the oxidation of organics was discussed. The generation of ˙ClO free radicals was ascertained by electron spin resonance (ESR) spectroscopy coupled with the spin trapping technique. The effect of pH, electrolyte concentration and current density on the degradation of phenolic syntan was discussed. Also, the current efficiency (CE) and energy consumption (EC) were estimated. It was observed that the oxidation of phenolic syntan was proportional to the current density and electrolyte concentration. The kinetics of the degradation of phenolic syntan was found to follow first order rate equation with an R² value of 0.9966. The intermediate compounds formed during electrooxidation were characterised using AOX, FT-IR and NMR techniques and the degradation pathway proposed. These results clearly suggest the effectiveness of the electrochemical technique for the treatment of wastewater containing a high concentration of phenolic syntan.