RESUMO
The valorisation of wastewaters for minerals recovery and their potential beneficiation has gained enormous attention recently. In this study the removal of phosphate and ammonia from municipal wastewater using activated magnesite resulted in the formation of struvite. The optimum conditions for the synthesis of struvite were 60 min of mixing, 300 rpm mixing speed, 1 g of activated magnesite and room temperature, whilst optimum conditions for the treatment of acid mine drainage (AMD) using the synthesized struvite were 45 min of mixing, 20 g of struvite dosage, 1000 mL, and 300 rpm mixing speed. The efficacy of struvite for neutralisation of AMD and attenuation of inorganic contaminants were ≥98.99% for metals (Al3+, Fe3+, and Mn2+) and ≥30% for SO42-. Traces of other metals such as Zn, Cu, Ni, Pb, and Cr were significantly attenuated. Phosphate was fully attenuated from the aqua-sphere. PHREEQC predicted the removal of minerals as oxy-(hydro)-sulphates, oxy-(hydro)-phosphate, metals hydroxides, and other complexes. FE-SEM equipped with FIB and an EDX, XRD, XRF, and FTIR confirmed the synthesis of struvite and fate of chemical species after treatment. This study confirmed the feasibility of recovering phosphate and ammonia as struvite which can be employed for the treatment of AMD.
