Enhanced Degradation of Aniline by PS Oxidation in the Presence of UV and Ferric Oxalate

Abstract

Oxidative degradation of aniline by Sodium Persulfate (PS) activated with UV-ferric oxalate[UV-Fe(C2O4)33-] was studied. The effects of Fe(C2O4)33- concentration, PS concentration, and pH on PS activation and aniline degradation were investigated. Results showed that Fe(C2O4)33- concentration and pH determined the reduction process of Fe3+ into Fe2+, which had significant effects on the oxidative degradation of aniline by PS. With an increase in Fe(C2O4)33- concentration, PS decomposition increased; however, when concentrations were>0.75 mmol·L-1, aniline degradation efficiency decreased due to competition with oxalate ions (C2O42-) for SO4·-. Aniline degradation efficiency in processes with different initial Fe(C2O4)33- concentrations followed the sequence:5 mmol·L-1 < 0.25 mmol·L-1 < 0.5 mmol·L-1 < 1 mmol·L-1 < 0.75 mmol·L-1. Neutral and alkaline conditions were not conducive to Fe2+ formation via photochemical reaction. However, with initial pH values of 7 and 9, PS activation efficiency reached 74% and 67% respectively after 300 min due to pH decline during the reaction; aniline removal efficiency was as high as 91% and 97%, respectively, higher than under initial acidic conditions. Furthermore, increased PS concentration was conducive to improvement of aniline degradation efficiency, but when PS concentration was>10 mmol·L-1, the aniline degradation process followed the pseudo first-order reaction kinetics model instead of the second-order reaction kinetics model. PS efficiency for aniline degradation decreased significantly due to the reaction between excessive PS and sulfate radicals.