Method for producing dipotassium hydrogen phosphate or potassium dihydrogen phosphate from residual raffinate and producing potassium sulfate as a byproduct

By subjecting residual raffinate to precipitate defluorination, extraction, washing, and neutralization, dipotassium hydrogen phosphate or potassium dihydrogen phosphate is prepared, with potassium sulfate as a byproduct. This solves the problems of waste of residual raffinate and high cost of traditional preparation methods, and achieves efficient resource recovery and low-cost production.

CN118026117BActive Publication Date: 2026-07-17SICHUAN UNIV +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
SICHUAN UNIV
Filing Date
2024-03-14
Publication Date
2026-07-17

AI Technical Summary

Technical Problem

In existing technologies, treating residual acid as waste not only increases the cost of wet phosphoric acid purification technology, but also wastes non-renewable phosphoric acid resources. Furthermore, traditional methods for preparing dipotassium hydrogen phosphate and potassium dihydrogen phosphate suffer from high raw material costs and high energy consumption.

Method used

Using the residual acid from the purification of wet-process phosphoric acid as raw material, dipotassium hydrogen phosphate or potassium dihydrogen phosphate is prepared through steps such as precipitant defluorination, extraction, washing, reaction and neutralization, with potassium sulfate as a byproduct. The precipitant used is potassium carbonate, dipotassium hydrogen phosphate or potassium dihydrogen phosphate, and the extractant is a mixture of trioctyldecyl tertiary amine and tributyl phosphate with kerosene. The reaction conditions, such as temperature and pH, are optimized.

Benefits of technology

This method enables the efficient utilization of residual acid, improves the recovery rate of phosphorus pentoxide and sulfuric acid, reduces production costs, provides a new way to utilize phosphorus resources, and is suitable for industrial production.

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Abstract

A method for producing dipotassium hydrogen phosphate or potassium dihydrogen phosphate and potassium sulfate as a byproduct from the residual acid of purified wet-process phosphoric acid, comprising the following steps: (1) Defluorinating the residual acid with a precipitant to obtain defluorinated residual acid, and then extracting the defluorinated residual acid to obtain an extractant and a residual phase containing phosphoric acid and impurities; (2) Washing the extractant containing phosphoric acid and impurities with water to obtain purified phosphoric acid-containing extractant and washing liquid; (3) Reacting the residual phase with potassium hydroxide aqueous solution to obtain a reaction solution. When preparing dipotassium hydrogen phosphate, the pH of the reaction solution is 9-12, and when preparing potassium dihydrogen phosphate, the pH of the reaction solution is 4-8; (4) Neutralizing the purified phosphoric acid-containing extractant with the reaction solution, and then separating the extractant from the neutralization solution; (5) Cooling the neutralization solution to crystallize, and then separating the crystals from the mother liquor. The obtained crystals are dipotassium hydrogen phosphate or potassium dihydrogen phosphate; (6) Concentrating the mother liquor separated in step (5) until a small amount of crystals precipitate, and then cooling to crystallize. The separated crystals are potassium sulfate.
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