The role of the struvite crystallization process on the adsorptive removal of phosphate using MgFe layered double hydroxide

This study aimed to investigate the role of the struvite crystallization process as an auxiliary process to optimize the adsorptive removal of phosphate using MgFe layered double hydroxide (LDH) and to obtain an environmentally friendly value-added Material by transforming phosphate-loaded particles into struvite. According to the experimental results, optimal conditions for the phosphate removal were determined as initial pH of 11.0, initial phosphate concentration of 600 mg P/L, particle amount of 4.0 g, contact time of 90 min, and temperature of 20 °C. Derived from the results, the main mechanisms involved in the removal process were proposed and the removal properties of the particle were determined with emphasis on kinetics, isotherms and thermodynamic. Treatment of phosphate-loaded particles with NH₄Cl to obtain struvite compound (MgNH₄PO₄.6H₂O) resulted in further decrease in the P concentration remaining from the adsorption process (78 mg P/L) to 3.8 mg/L. This result indicated that almost all the initial phosphate (600 mg P/L) was removed due to the combined effect of adsorption and struvite crystallization processes. XRD and EDS analyses confirmed the presence of constituting elements of struvite compound in the elemental composition of the NH₄Cl-treated particle, revealing that the resulting material predominantly consisted of struvite crystals.