A temperature-mediated precipitation of struvite-family crystals in wastewater

Abstract

The paper presents results of the investigation into the temperature mediated mineralogical formation of struvite family crystals in a synthetic wastewater. The scale-forming solution was set-up by mixing solutions of MgCl2 and NH4H2PO4 with Mg+2, NH4 + and PO4 -3 in a molar ratio (MAP) of 1:1:1. The temperature was altered: 30, 35 and 40 OC. The initial pH of the solution was set up in 9.0. SEM (equipped with EDX) analysis revealed that the crystals have a needle like-shaped morphology, and contained Mg, K, P, and O as the main composition. The Rietveld analysis of the XRPD pattern confirmed that the major phase of struvite, and struvite-(K) formed in the precipitating solids. Apparently, bobierrite and newberyte were other phosphate minerals formed at the temperature of 35 OC. Analysis of this experimental data suggested that the temperature-mediated crystallization process yielded a potential optimization of struvite precipitation.