Wastewater Flocculation Using a New Hybrid Copolymer: Modeling and Optimization by Response Surface Methodology

A new hybrid inorganic-organic copolymer, aluminum chloride-poly(acrylamide-co-acrylic acid), was prepared using the free radical polymerization method and employed in this study. The hybrid copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS). This hybrid copolymer was used in the flocculation of wastewater as a new flocculant. The design variables in the flocculation experiments were hybrid copolymer dosage and wastewater pH. The central composite design (CCD) for the response surface methodology (RSM) approach was used to develop a mathematical model and to optimize the parameters of the flocculation process in terms of optimal removal of chemical oxygen demand (COD), total suspended solids (TSS), and turbidity. After applying the analysis of variance (ANOVA) of all quadratic models, it was found that the obtained value of the correlation coefficient (R-2) was more than 0.98 for all models. The optimum hybrid copolymer dosage was 125 mg/l and the optimum pH 7.55. Under these optimum values, the wastewater treatment achieved 97%, 98.6%, and 88.6% removal of turbidity, TSS, and COD, respectively.