Morphology of aluminum phosphate by the Al-EDTA mediated particle formation in aqueous solutions at high temperatures

The morphology of aluminum phosphate, formed by homogeneous precipitation in aqueous solutions using Al-ethylenediaminetetraacetic acid (Al-EDTA) complex in the presence of H2O2, was investigated under several temperature conditions, and pH, Al-EDTA, and H2O2 concentrations. Spherical particles of AlPO4·xH2O (x = 1.04–1.90) were formed at pH 4–8 at 125–200 °C. Since nonspherical precipitates were observed in the absence of EDTA or H2O2, the formation of the spherical particles at pH 4–8 is attributed to the slow release of Al3+ ions by the degradation and/or dissociation of Al-EDTA with H2O2 under hydrothermal conditions. The size of the spherical particles obtained with Al-EDTA depends on the concentration of the Al-EDTA chelate and H2O2, and also on temperature; the size distribution of the particles decreased significantly with the H2O2 concentration and temperature.