Studies on obtaining of aluminium ammonium calcium phosphates

Aluminium ammonium calcium phosphates were prepared with the use of AlCl3, CaCO3, H3PO4. The influence of the process parameters (pH 5 ± 3, the molar ratios of Ca2+:Al+3:PO4−3 in the substrates, respectively 0.31:0.62:1; 0.5:0.5:1; 0.72:0.36:1, temperature 40 ± 20 °C) on the phase composition and the product properties was determined. The process parameters that enable to obtain the material with expected physicochemical properties were determined based on the statistical evaluation of the experiments (fractional factorial design at three levels 3(k−p)27). The phase composition of the obtained samples was studied with the use of XRD analysis. The specific surface area was calculated with the use of SBET method and the particle size was determined by the laser scanning microscopy. The materials with the molar ratio of Al3+/NH4+ and Al3+/Ca2+ in the range of 0.70–27.93 and 0.47–24.48, respectively, with an absorption oil number of 95–157 g/100 g paraffin oil, the SBET within 25–118 m2/g, the pore volume within 0.14–0.74 cm3/g and the particle size in the range of 168–285 nm were obtained.