Research of the Process for Thermal Dehydration of Orthophosphate is Sodium Phosphate from Central Kyzylkum

This research is on the process for high-temperature dehydration of sodium orthophosphates with the ratio Na2O:P2O5 = 0.73 in pH = 6.3. Temperature parameters for the formation of sodium tripolyphosphates form I and form II using physico-chemical methods are established. It shows the synthesis possibility of sodium tripolyphosphate in the set form. Dried samples of a mixture of 1 mole of dihydrogen phosphate and 2 moles of sodium hydrogen phosphate was prepared and heated for 1 hour at temperatures of 360 to 560оС. During dehydration at temperature 360°C, only phase II is formed, which is characterized by intense peaks 4,6911, 2,6898, 4,5091, 2,6215, 2,5843, 4,4572, 4,4181, 3,0612 Å. Similar peaks are characteristic in the form I of sodium tripolyphosphates. Difference in the x-ray peaks are 4,6911 and 2,6898 Å. Form II has a maximum value of the peaks at 4,6911 Å, and form I has a maximum value at 2,6902 Å. X-ray of sodium tripolyphosphates form II and form I are almost the same. In IR spectrum Na5P3O10 four groups of absorption bands in the intervals 570-750, 890-1015, 1095-1215 and 1255-1285 cm-1 were identified, indicating the long-chain structure of the anion compound. Structure Na5P3O10 consists of the continuous P–O–P chains arranged along the cleavage of the fiber, in which each phosphorus atom is in tetrahedral coordination. On derivatograms there are many exo and endoeffective. Endoeffect at 163 and 267оС corresponds to the formation of Nа2H2P2O7. At 163оС weight loss makes 12.00%, while 267оС 17,15%. Theoretical losses are 11.96% and 17.1%. Thermo chemical transformations at temperature 300-400°C are accompanied by removal of 0.5 mol water and formation Na5P3O10 II. At temperature 450-620°C, reactions transform the form II into form I. At temperature above 620°C sodium hexametaphosphates of amorphous structure is formed.