Nowadays phosphate salts are widely used in agriculture as well as in many industries: chemical, food, pharmaceutical, electronic, textile, etc. Chemically pure and high-purity phosphates are often required for industrial use. For example, for use in the food and pharmaceutical industries, phosphates are required to be free from toxic impurities of arsenic, lead, d-metals and fluorine. In the world production of phosphates, the share of food phosphates is up to 5%. World consumption of food phosphates is increasing by an average of 3.5% per year, and the total demand for food phosphates in Ukraine is estimated at about 40 thousand tons / year.
Until now, there is no food phosphates produced in Ukraine. This puts our country in economic dependence on imports and increases the cost of production. At the same time there are own powerful deposits of natural phosphorites in Ukraine (to 1.03 billion tons of Р2О5).
Classical methods for obtaining chemically pure ammonium phosphates and alkali metals are based on neutralization of food orthophosphoric acid solutions or its reactive types with chemically pure carbonates or hydroxides of alkali metals, followed by evaporation of salt solutions for their crystallization. It is obvious that the high cost of such phosphates is determined by the cost of precursors used for their synthesis. The development of alternative technologies that would allow obtaining cheaper chemically pure phosphate salts, forms quite relevant scientific and technical problem.
In our opinion, unlike the already known methods of obtaining high-purity phosphate salts, it is advisable to pre-purify the synthesis precursors, using, for example, the method of coprecipitation. This method is less energy consuming than isohydric or isothermal crystallization. Considering the relatively high cost of chemically pure carbonates and hydroxides of sodium or potassium, it is also advisable to use the method of conversion of ammonium phosphate salt using cheaper chemically pure salts of sodium and potassium than their carbonates and alkalis. It should also be noted that food orthophosphates can be considered as raw material for another class of nutritional supplements - sodium, potassium or calcium pyrophosphates.
As a result of research devoted to synthesis processes of phosphate salts of sodium, potassium, ammonium and calcium, the technological schemes of chemically pure ortho- and pyrophosphates of sodium, potassium, ammonium and calcium obtaining for their use as nutritional supplements are suggested
