Purification Of Dihydric Phosphate

The glass made from metaphosphate, in which the total content of transition metal ions as impurity is less than 5 ppm, can be used to produce glass of high-power laser due to its excellent optical transmission. So the related preparation technique of the high-purity metaphosphate is important for military industry.In general, A1(PO₃)₃ or KPO₃,Which is one of the basic materials for making phosphate glass, can be obtained by heating the mixture of Al(OH)₃ and NH₄H₂PO₄ or KH₂PO₄. In this paper, NH₄H₂PO₄ or KH₂PO₄ in which the total content of Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺ and Mn²⁺ as impurity is less than 5 ppm has been prepared by ion exchange chromatography method.The main content in this paper included:1,A chelating resin D751 was selected to purify NH₄H₂PO₄. Under the optimum conditions, the total impurity content in the NH₄H₂PO₄ was reduced with the D751 from 13.51 ppm to less than 5 ppm. The static of the resin adsorption capacity and regeneration properties have been measured.2,By using of three ion exchange resins to purify NH₄H₂PO₄, including strongly acid cation exchange resins D001, 732 and 742, those three resins selectively adsorbed transition metal ions and didn't adsorb alkaline earth metal.The results showed that the content of all transition metal ions including Fe³⁺ ,Co²⁺,Ni²⁺,Cu²⁺,Cr³⁺ and Mn²⁺ in NH₄H₂PO₄ was more than 5 ppm. The static of the resin adsorption capacity and regeneration properties have been measured.3,By using of a chelating resin D751 to purify KH₂PO₄, under the optimum conditions, the total impurity content in the KH₂PO₄ was reduced with the D751 from 41.48 ppm to less than 5 ppm. The static of the resin adsorption capacity and regeneration properties have been measured.4,We measured the high-purity Al(PO₃)₃ content of phosphorus and aluminum. It was better that the content of phosphorus was measured by quinoline phosphomolybdate gravimetric method and the content of aluminum was measured by complexometric titration method. The methods were high-accuracy. After testing, the purity of Al(PO₃)₃ was more than 95%.