Thermodynamics and solution chemistry of struvite

Abstract

The key feature of this paper is the combined removal of magnesium, ammonium and phosphate from a representative synthetic solution of piggery effluent. The byproduct of this recovery process is struvite, commercially used as slow-release fertiliser. A thermodynamic model was developed relating to all the complexes of magnesium, ammonium and phosphate using gPROMS process software. A laboratory-based batch experiment confirmed 80% recovery of phosphate using this crystallization technique. The batch experiment was conducted at constant pH using synthetic solution made up of analytical-grade MgCl2 and NH4H2PO4. Borosilicate glass grindings of 5 g were used as seeds in this batch experiment. Basic solution characteristics of piggery effluent are reported in this paper.