Effect of operational conditions on removal of 4-chlorophenol in water using UV/NiO process

Abstract

This study present the removal of 4-chlorophenol (4-CP) from water by nickel oxide (NiO) nanoparticles. Photodegradation was compared using different processes in a batch reactor with medium-pressure mercury lamp irradiation. The effects of operating conditions such as feed concentration of reactants, catalyst load, pH, and half-life time on photodegradation system were evaluated. The results showed that photodegradation using UV/NiO system in the presence of H2O2 were much more effective than using either UV/H2O2 or UV/NiO processes. The optimum conditions for the complete degradation of 4-CP were achieved at a neutral pH, with 0.2 mol l-1 H2O2, and 0.05 g l-1 of NiO. However, no significant pH effects were observed in the range of 4-10. Also, the best TOC removal and Cl- ions formation results were achieved by combined system with 48 and 80%, respectively. The illuminated NiO nanoparticles had lower influence on the degradation of 4-CP but dramatically promoted the mineralization of 4-CP. For all these reactions, the degradation rates are evaluated by determining their first-order rate constants and half-life times. The reaction rate constants ranged from 0.0003 min−1 by direct photolysis to 0.029 min−1 and 0.083 min−1 using UV/NiO in absent and presence of H2O2, respectively.