Study on the Purification Process of Phosphoric Acid Using Organic Solvents: A Case of Wet-process Phosphoric Acid Based On Karatau Phosphorites

This article presents research data on the processes used to produce concentrated phosphoric acid from Karatau phosphate rock.

The study investigated the purification of wet-process phosphoric acid using liquid-liquid extraction with organic solvents. To determine the composition of extractable complexes formed during the extraction of phosphoric acid with tributyl phosphate and n-butyl alcohol, infrared spectroscopy was employed. In addition, physicochemical transformations under thermal exposure were analyzed using differential thermal analysis.

The effect of magnesium salts and sulfuric acid impurities on the distribution factor of phosphoric acid was investigated. Increasing the initial concentration of phosphoric acid from 5.38% to 25.61% P₂O₅ at 25°C led to an increase in the distribution factor from 0.178 to 0.436 for n-butyl alcohol, from 0.06 to 0.183 for isoamyl alcohol, and from 0.120 to 0.320 for tributyl phosphate. Increasing the temperature from 25°C to 60°C had little to no impact on the distribution factor. The results showed that the distribution factors of phosphoric acid are influenced by its initial concentration, particularly in the presence of sulfuric acid. Among the solvents tested, n-butanol demonstrated the highest extraction efficiency. The phosphoric acid concentration was increased to 56%–63% P₂O₅, with sulfuric acid impurity levels reduced to ≤ 0.002%.

The results of the study demonstrate a significant contribution to the field of optimizing phosphoric acid extraction using organic solvents. One of the innovative aspects of the work is the analysis of extraction mechanisms using various solvents, including n-butanol, tributyl phosphate, and isoamyl phosphate. This contribution significantly expands the scientific understanding of extraction processes and opens up new possibilities for optimizing phosphoric acid purification technology.

For the first time, countercurrent extraction and azeotropic distillation were combined to address the issue of equipment corrosion caused by fluorine impurities. The findings of this study can be applied in developing a fundamental technological process for the deep purification of technical-grade phosphoric acid, resulting in the production of pure and highly concentrated phosphoric acid.