Photocatalytic degradation of 4-chlorophenol by UV/H2O2/NiO process in aqueous solution

The removal of 4-chlorophenol from aqueous phase continues to be an important environmental issue. in thiswork, the photochemical oxidation of 4-chlorophenol in aqueous solutions in a batch reactor using ultravioletirradiation, hydrogen peroxide and nickel oxide was studied. the efficiency of the system was evaluated withrespect to reaction time, ph, feed concentration of reactants, catalyst load, light intensity, and the reaction rateconstant. the concentrations of 4-chlorophenol and chloride ions were determined by high performance liquidchromatography and ion chromatography, respectively. pure nanosized nickel oxide was characterized by x-raydiffraction and scanning electron microscopy. the results showed that the optimum conditions (the complete4-chlorophenol removal (100%) at 60 min) were obtained at a neutral ph, with 0.2 mol/l h2o2, and 0.05 g/l ofnickel oxide. however, no ph effects were observed in the range of 4–10. analytical profiles on 4-chlorophenoltransformation were consistent with the best line fit of the first-order kinetics. moreover, the degradation rateconstant increased with both uv light intensity and decreasing initial concentration of 4-chlorophenol. finally, theresults of mineralization and chloride ions studies indicated that dechlorination was better accomplished but moretime was required to completely mineralize 4-chlorophenol into water and carbon dioxide.