Green synthesis of calcium and phosphate compounds by varying ph value and ca/p atomic ratio using aqueous precipitations

Using an aqueous synthesis with varying pH values and changing ion source of calcium-to-phosphorus atomic ratios to clarify precipitations was the purpose of this study. The precipitation procedures were processed in two ways; firstly, a pH range of 3.0 to 12.0 was controlled while the ion source of relative Ca/P ratio was kept at 2.0. Secondly, the reaction was kept alkaline with a pH of 12.0 and the value range of Ca/P ratios in the precursor ion-solutions was 1.0 to 3.0. The physicochemical properties were measured to characterize the various precipitates. Results showed that when the pH was varied, the morphology of the precipitates gradually changed to micrometer column-like shape under acidic condition and nano-scale globular-like shape in alkaline environments. By controlling the pH and Ca/P ratio of ion-sources in aqueous reactions, precipitates in biphasics of calcium carbonate/apatite and calcium hydroxide/apatite were obtained with nanometer-scale morphologies. The precipitation procedures that are used in the synthesis of the biphasics provide a simpler, safer, less expensive and more environmentally friendly than the co-precipitation by sintering processes.