Optimization of simultaneous removal of phosphate and nitrate in synthetic wastewater by enhanced electrocoagulation process

Abstract

The presence of pollutants such as nitrate and phosphate compounds affects the quality of water resources. This study aims to investigate the simultaneous removal of nitrate and phosphate in a batch reactor using an enhanced electrocoagulation process. Initial concentration, current density, pH, and time were the chosen effective parameters considered in 5 levels. Their effect on the removal efficiency of phosphate and nitrate was evaluated. Experiments were designed by the response surface method (RSM) to save time and costs. For this purpose, first, 30 experiments were modeled by design expert software, and then optimal conditions were determined for variables. The optimal conditions were obtained by the following items: current density 36.5 A/m2, initial concentration 140 mg/L, pH 6, and time 65min. These conditions led to removing 77% of nitrate and 98% of phosphate. Finally, the effect of electrode coating with ZnO nanoparticles performed by the sol-gel method under optimal conditions was considered. Cyclic voltammetry (CV) was used to evaluate the impact of the coating layer. The modified electrode by nanoparticles provides a larger surface area which consumes less energy than a simple electrode.