Optimization of Aqueous NH4+/NH3 Photodegradation by ZnO/Zeolite Y Composites Using Response Surface Modeling

Abstract

Abstract In this study, ZnO/Zeolite Y composites were synthesized by the solid state dispersion method and employed in order to investigate their photocatalytic performance in NH4+/NH3 removal from an aqueous solution. FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, SEM and EDX analyses were applied to characterize these composites. The three-factor, three-level Box-Behnken experimental design (BBD), as one of the response surface methodology (RSM), was used to achieve maximum removal of aqueous NH4+/NH3 under optimum conditions by ZnO/Zeolite Y composites. The effects of parameters such as ZnO loading (10–50 wt %), initial pollutant concentration (25–315 mg/L) and solution pH (3–11) as well as their interactions were determined on removal of NH4+/NH3 by the mentioned method. It was found that pH of the solution with the percentage contribution of 86.79 %, was the most important parameter among the others. A second-order polynomial equation was well fitted on the experimental data with the determination coefficient value of 0.9932 and the adjusted determination coefficient value of 0.9864. It could not describe only 0.68 % of observed changes in the response. The predicted removal percentage of NH4+/NH3 at the optimal conditions (pH = 11, NH4+/NH3 initial concentration (207.21 mg/L) and ZnO loading (45.02 wt %)) was achieved 62.26 %, which was in agreement with its experimental value (65 %) obtained in similar conditions.