Photoelectro-Fenton mineralization of phenol through optimization of ferrous regeneration

Abstract

The degradation of phenol in acidic solution at pH3 has been investigated under various photo- and electrochemical conditions. A laboratory-scale reactor on which were mounted net electrodes (RuO2/IrO2-coated Ti anodes (DSA) and stainless steel cathodes) and 254nm UV lamps was established to effectively reduce ferric reagents. The experimental results of the photoelectron-chemical reaction suggested that the current efficiency of reducing ferric ion was improved by increasing the number of electrodes used, and the UV lamps were important to inducing the reduction of ferric carboxylates, which were the major intermediates that were formed upon a particular degree of phenol oxidation. Accordingly, the addition of an initial concentration of 400ppm ferrous salt and 10,200ppm hydrogen peroxide (in a continuous mode) resulted in the removal of over 92% of TOC (initial phenol = 2,000ppm, TOC = 1,532ppm) by 4h of the photoelectro-Fenton and the sequential 2h of the photo-Fenton processes. HPLC was utilized to monitor the formation of aromatic and carboxylate byproducts, and revealed that the aid of photo irradiation eliminated most of the oxalate residue from the final solution, which would have contributed to the 25% of the TOC that was inactive in the electrolytic system.