Efficient Extraction of Phosphoric Acid with a Trialkyl Amine-Based Solvent Mixture

Abstract

Production of phosphoric acid by using wet process technology in China is challenging due to high impurities (P2O5 present is less than 25 wt %). Extraction of phosphoric acid from such low concentration mixtures needs to be improved. Moreover, the separation of chloride and phosphate ions is also important for the subsequent production of phosphate fertilizers. In this study, an organic solvent composed of trialkyl amine (N235), isoamyl alcohol, and sulfonated kerosene was developed to extract phosphoric acid. Pseudoternary phase equilibria, two phase densities, and the viscosities were determined at 298.15 K and atmospheric pressure. Results show that unlike other common organic solvents, the proposed solvent exhibits relatively higher extraction capacity even at low phosphoric acid concentration (P2O5 less than 25 wt %). The separation factor of chloride and phosphate ions reaches up to 39.45 and is several orders of magnitude lager than other common organic solvents including alcohols, cyclohexane, and tri-n-butyl phosphate (TBP). In addition, the solubility of organic solvent in the aqueous phase is close to zero, while the water content in the organic phase keeps nearly constant at a low concentration of around 5 wt %. All of these indicated that the developed solvent mixture is efficient for the extraction of phosphoric acid.

Efficient solvent extraction of phosphoric acid with dibutyl sulfoxide

“…The results indicate that the optimal extraction capacity of DBSO is obtained when the aqueous phosphoric acid concentration is in the range 5.81–19.04 wt%. Meanwhile, a distribution coefficient of 0.711–0.721 for moderate‐concentration phosphoric acid is also far better than that of most solvents, whose distribution coefficients are 0.3 under the same conditions …”

“…Because the organic solvent is a mixture of DBSO, DBS and DBSO 2 , the pseudo‐ternary assumption is employed to treat the DBSO‐based solvent as entirety . The liquid–liquid equilibrium of water–DBSO–phosphoric acid system were studied at 298.15 K and atmospheric pressure and the experimental data are listed in Table .…”

“…Several organic solvents have been investigated and used for the purification of WPA . The problem is that existing organic solvents are inefficient for the extraction of WPA, especially for low‐concentration acid . The existing organic solvents have strong extraction capacity only for high‐concentration acid.…”

“…Chen et al . studied a trialkyl amine‐based solvent mixture which was efficient for the extraction of phosphoric acid, especially for low‐concentration acid.…”

Purification of Crude Phosphoric Acid and Leached Apatite by Solvent Extraction with CYANEX 923 in Kerosene

“…The data obtained show that the change in temperature had nearly no effect within the investigated temperature range. Based on the above experimental results, and considering that the predominant species of phosphoric acid at 7.0 M is the orthophosphoric acid, H 3 PO 4 [8,24] the extraction reaction may be represented at equilibrium by:…”