METHOD FOR TREATMENT OF WET-PROCESS PHOSPHORIC ACID Russian patent published in 2006 - IPC C01B25/46 

FIELD: inorganic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for preparing phosphoric acid with low content of impurities and used in producing phosphate salts of technical and nutrition quality by using liquid extraction with tributyl phosphate and the following separation of an aqueous and organic phases and re-extraction of phosphoric acid from organic phase with water. Extraction and re-extraction are carried out in pulsation columns by mixing aqueous and organic phases to form emulsion under air effect at the extraction temperature 30-50°C and the re-extraction temperature 40-80°C followed by separation of the re-extraction process for some steps. At the first step the preliminary washed out extract is prepared and then it is fed to the step for preparing purified phosphoric acid and polluted acid recovered to the stage for extraction with tributyl phosphate. The total water flow feeding to the re-extraction step is divided for three parts in the following ratio: V₁:(V₂ + V₃) = 1:(2.5-10) and (V₂ : V₃) = 1:(1-2.5). Extract is mixed with the first part of water and after separating phases is fed successively to mixing with other part and then with the third part of water for preparing purified and highly purified phosphoric acids. Mixing the first part of water with extract is carried out in the volume ratio of phases = 1:(20-55), and mixing the second and third part of water with extract is carried out in the ratio = 1:(5-20). Proposed method provides decreasing the content of impurities in highly purified phosphoric acid preparing at the third step of re-extraction by 2-fold, i. e. to enhance quality of acid.

EFFECT: improved treatment method of phosphoric acid.

7 cl, 2 tbl, 2 ex