Influence of aqueous chloride and bromide ions on bisphenol A degradation efficiency with zinc oxide nanoparticles

Abstract Zinc oxide (ZnO) nanoparticles (NPs) have been widely investigated for applications in photocatalytic degradation of organic pollutants in wastewater. Despite the advantages of robust ZnO material, its photocatalytic activity is greatly affected by environmental factors. Halogen ions are commonly found in wastewater, which directly affect the pollutant aggregation and sedimentation, therefore it is necessary to discuss their effect on the photocatalytic degradation. The current study assesses the halogen ions effect on the photocatalytic degradation of bisphenol A (BPA) using different dosage of sodium chloride (NaCl) and sodium bromide (NaBr). The microstructural characterization of ZnO NPs was conducted by transmission electron microscopy and hydrodynamic size was analyzed through dynamic light scattering. The effective BPA degradation with ZnO NPs was observed and pseudo-first-order kinetics was calculated. The increase of ZnO NPs dosage from 10 to 100 mg L − 1 enhanced the degradation rate constant of BPA up to 0.089 min − 1 (14.8 folds). In order to evaluate the role halogen ions to degrade BPA, NaBr and NaCl were used. The degradation rate was reduced to 0.0034 min − 1 after the addition of NaBr due to the increase in hydrodynamic particle size, thereby restricting the light adsorption capacity. Noteworthy, upon addition of NaCl up to 500 mM concentration, only a slight decrease on BPA degradation rate was observed. Therefore, this study unveils the role of chloride ions as an effective medium for BPA degradation by ZnO NPs, without aggregation, and provides a novel platform for the treatment of organic pollutants in saline water.