Photocatalytic degradation of pentachlorophenol by visible light N-F-TiO2 in the presence of oxalate ions: optimization, modeling, and scavenging studies

The efficiency of heterogeneous photocatalysis using N-F-TiO2 as photocatalyst to degrade a priority pollutant, pentachlorophenol (PCP), in the presence of oxalates (OA) was investigated in detail. Response surface methodology was used to optimize the effect of three variables (catalyst concentration, OA/PCP ratio, and pH) on the photocatalytic degradation of pentachlorophenol. A quadratic model was established as a functional relationship between three independent variables and the degradation efficiency of PCP. The results of model fitting and statistical analysis demonstrated that the pH played a key role in the degradation of PCP. Within the studied experimental ranges, the optimum conditions for maximum PCP degradation efficiency (97.5 %) were: catalyst concentration 600 mg L-1, OA/PCP ratio 2, and pH 10. The contribution of HO center dot, O-2(center dot-), and e(-) produced during the photocatalytic treatment was investigated with the addition of scavengers. The photocatalytic degradation was essentially proceeded through an oxidative mechanism at both acid and alkaline pH values by HO center dot and O-2(center dot-) radicals attack. It was found that O-2(center dot-) were the major reactive species involved in PCP degradation in pH 4 and HO center dot in pH 10.