Title: Optimization of the Turbidity Removal Conditions from TiO<sub>2</sub>Solution Using a Response Surface Methodology in the Electrocoagulation/Flotation Process
Abstract: The removal of turbidity from <TEX>$TiO_2$</TEX> wastewater by an electrocoagulation/flotation process was studied in a batch reactor. The response surface methodology (RSM) was applied to evaluate the simple and combined effects of the three main independent parameters, current, NaCl dosage and initial pH of the <TEX>$TiO_2$</TEX> solution on the turbidity removal efficiency, and to optimize the operating conditions of the treatment process. The reaction of electrocoagulation/flotation was modeled by use of the Box-Behnken method, which was used for the fitting of a 2nd order response surface model. The application of RSM yielded the following regression equation, which is an empirical relationship between the turbidity removal efficiency of <TEX>$TiO_2$</TEX> wastewater and test variables in uncoded unit: Turbidity removal (%)=69.76+59.76Current+11.98NaCl+4.67pH+5.00Current<TEX>${\times}$</TEX>pH-160.11<TEX>$Current^2-0.34pH^2$</TEX>. The optimum current, NaCl dosage and pH of the <TEX>$TiO_2$</TEX> solution to reach maximum removal rates were found to be 0.186 A, 0.161 g/l and 7.599, respectively. This study clearly showed that response surface methodology was one of the most suitable method to optimize the operating conditions for maximizing the turbidity removal. Graphical response surface and contour plots were used to locate the optimum point.