Optimization of Struvite Crystallization and Heavy Metal Recovery in Wastewater Using Response Surface Methodology

In this study, the recovery of heavy metal (Cu2+, Pb2+, and Zn2+) concentrations and the yield of struvite from MAP precipitation in the wastewater were optimized by SRM (surface response methodology). Struvite was a major mineral precipitated with an impurity of sylvite (KCl) as confirmed by the XRPD Rietveld method, and struvite crystal has a prism-like shape morphology according to the SEM/EDX analysis. The SRM estimates that the concentration of Pb2+ has a significant effect of retarding the yield of the struvite mass, while insignificant effects were related to the Cu2+ and Zn2+ concentration. The optimum yield of struvite was reached at 8.342 mg, of which 59.4564 ppm of Cu2+ 70.7930 ppm of Pb2+ and 77.2114 ppm of Zn2+ could be recovered from wastewater. These optimized conditions could be valuable input data for engineering-design software in an equipment of the effluent treatment plant.