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 H(2)O(2), was investigated under several temperature conditions, and pH, Al-EDTA, and H(2)O(2) concentrations. Spherical particles of AlPO(4)center dot xH(2)O (x = 1.04-1.90) were formed at pH 4-8 at 125-200 degrees C. Since nonspherical precipitates were observed in the absence of EDTA or H(2)O(2), the formation of the spherical particles at pH 4-8 is attributed to the slow release of Al(3+) ions by the degradation and/or dissociation of Al-EDTA with H(2)O(2) under hydrothermal conditions. The size of the spherical particles obtained with Al-EDTA depends on the concentration of the Al-EDTA chelate and H(2)O(2), and also on temperature; the size distribution of the particles decreased significantly with the H(2)O(2) concentration and temperature. (c) 2006 Elsevier Ltd. All rights reserved.