Mineral speciation determination and quantitative x-ray analysis of struvite family crystals precipitated in wastewater

Mineral speciation of struvite family crystals precipitated in a synthetic wastewater containing Mg: NH : PO3 (MAP) ions were determined in the study. The pH levels by KOH addition and MAP ratios were set up to be the parameter dependence on struvite family crystals precipitation. The Rietveld analysis of XRPD pattern confirmed a mixed product of struvite, struvite-(K) and newberyite precipitated in the solution at a molar ratio of 1:1:1 and pH 8. Likewise, a relative abundance of struvite and struvite-(K) precipitated, as pH was elevated from 9 to 10. However, as the MAP ratio increased from 1:1:1 to 1:2:1, struvite product reached up almost 99 wt. % at the pH selected in the study. A minor impurity of sylvite was frequently found in all precipitating solids. Struvite family crystals with different size and morphology were also observed. Obviously, the relatively pure struvite was obtained through increasing amounts of NH in the solution.