Degradation of phenol using low concentration of ferric ions by the photo-Fenton process

In this study, phenol was degraded by the photo-Fenton process at pH 3, 5 mg/L Fe(III), 1080 mg/L H2O2 using 3 UV lamps (365 nm). In the UV/H2O2 system, the degradation of phenol is inefficient, and only around 25% of the phenol is degraded in 1 h. The efficiency of the photo-Fenton system considerably exceeded that in UV/H2O2 and Fenton-like systems. The removal efficiency of COD by the photo-Fenton process was 98% respectively, but only 63% in the Fenton-like system. The effect of oxalate on the degradation of phenol was also investigated. The removal efficiency of phenol was highest at a molar concentration ratio of oxalic acid to ferric ions ([Ox]/[Fe3+]) of 2. Increasing the amount of dissolved oxygen promoted the degradation of phenol. Even when concentration of added ferric ions in the photo-Fenton system was low, the COD removal efficiency was still satisfactory. The intermediate organic acids during the degradation of phenol were formic acid, acetic acid, oxalic acid and succinic acid. The pathway of phenol degradation in the photo-Fenton process is proposed from experimental results and the literature.