Photocatalytic Degradation of Pentachlorophenol Using ZnO Nanoparticles: Study of Intermediates and Toxicity

Abstract

The photocatalytic degradation of pentachlorophenol (PCP) was carried out using ZnO nanoparticles (NPs) in the presence of sunlight. The effect of different ZnO NPs sizes was synthesized by sol–gel method as well as loading of ZnO NPs on degradation of PCP was investigated. The results showed that the sunny condition was the best to achieve higher efficiency due to the fact that higher energy of photon was available to accelerate rate of reaction. The highest degradation efficiency of PCP was achieved by smaller size of ZnO NPs as 20 nm with band gap and surface area as 3.198 eV and 26.23 m2/g, respectively. The optimum loading of ZnO NP to achieve higher efficiency of 99.6% was 1.0 g/l under 2 h of irradiation time. The photodegradation of PCP followed a pseudo-first order reaction and the observed rate constant was dependent on the ZnO NP loading. The pathway of PCP degradation was suggested according to the HPLC analysis where PCP was converted to nontoxic compounds such as acetic acid and oxalic acid. The toxicity of PCP before and after degradation was evaluated which indicated the removal of toxicity after degradation as sequence with degradation efficiency and confirmed within fragmentation of PCP degradation.