Effect of water quality in photocatalytic degradation of phenol using zinc oxide nanorods under visible light irradiation

This study investigates the feasibility of photocatalysis in the degradation of phenol as synthetic water resembling produced water. The science of nanomaterials was incorporated by fabricating zinc oxide nanorods as a photocatalyst material under the irradiation of visible light. ZnO nanorods were synthesized using microwave-assisted hydrothermal method. The characteristics and properties of the as-prepared ZnO NRs were investigated. The results show that ZnO nanorods are an effective photocatalyst in the visible region and posed high degradation rate of phenol with a removal efficiency of 78.42 %. The effects of different factors such as water pH, salinity, cations, and anions on the phenol photocatalytic degradation were studied. It was found that the degradation of phenol via ZnO NRs favored acidic conditions with a removal efficiency of 84.3 % at pH 5 whereas the degradation decreased as the water pH increased until reaching 69.4 % at pH 9. In addition, water salinity (as NaCl) showed insignificant effect even at high concentration with a slight improvement in the degradation under lower NaCl concentrations (1–4 %). Mono and di-valent cations (Na⁺, K⁺, Mg²⁺ and Ca²⁺) posed negligible effect on phenol photodegradation. Moreover, the behavior of phenol degradation in the presence of both mono and di-valent anions was found to follow inconsistent pattern in which both chloride and sulfate ions enhanced the degradation rate of phenol with removal efficiencies of 85.1 % and 88.0 %, respectively. Conversely, the phenol photocatalytic degradation rate significantly decreased in the presence of carbonate (35.5 % removal efficiency) and bromide (14.7 % removal efficiency).