Change of acidity of the environment in the process of decomposition of apatitis sulfuric acid

An experimental study of the decomposition process of Kovdorsky apatite with certain particle sizes, in a 1 dm3 batch reactor with stirring of the reaction mixture, initial phosphoric acid concentration 17% by weight, in the system: Apatite-H3PO4 - H2SO4-H2O. Sulfuric acid was introduced in stoichiometric amount at the beginning of the process. The process was carried out at a ratio L:S 2.5:1, at a temperature of 78- 82 °C. The process was monitored by the method of joint determination of sulfuric and phosphoric acids by titrimetric analysis of the composition of the reaction mixture in the presence of methyl orange, and then phenolphthalein. Determined the concentration of phosphoric acid, the concentration of excess or deficiency of sulfuric acid and the concentration of monocalcium phosphate gel were determined. The acidity of the reaction mixture was recorded according to the indications of a Ph-meter (pH-105 MA with a combined glass electrode - ESK-10603). In the system: Apatite-H3PO4-H2SO4-H2O, when analyzing the obtained experimental values of these parameters, it was shown that during the process the pH of the reaction mixture rises to pH 6...