Solar-assisted photochemical and photocatalytic degradation of phenol

Photocatalytic (TiO2, air and solar radiation) and photochemical (H2O2 and solar radiation) mineralizations of phenol solutions (up to 500mgdm(-3)) in a batch reactor using concentric solar radiation were studied. A compound parabolic reflector as a concentrating reflector was used to obtain concentrated solar radiation in both cases. Considerable enhancement (Five-fold) in the rate of degradation was obtained when concentrated solar radiation was used instead of plain solar radiation in photocatalytic degradation. The effect of initial phenol concentration, intensity and presence of anions has been studied in both the cases. Low concentrations of intermediates were observed, during the reaction, over the entire range of phenol concentrations studied in the case of photocatalytic degradation using Degussa-P25 TiO2 as photocatalyst and in the absence of anions; whereas significant quantities of intermediates were observed in the case of the photochemical degradation. The presence of anions generally had a detrimental effect on the mineralization process in both cases. Different anions showed different effects. Total organic carbon (TOC) variations with time were also studied. A rational explanation has been given for the decrease in the rate in the presence of anions. (C) 2001 Society of Chemical Industry.