| 摘要 |
<p>A process for recovering phosphoric acid from an aqueous solution thereof comprises treating the solution with an extracting solvent capable of extracting phosphoric acid from an aqueous solution thereof having a concentration of H3PO4 above a threshold value of 35%, whose capacity for extracting phosphoric acid from water varies inversely to a temperature and which does not extract phosphoric acid from an aqueous solution thereof having a concentration below a threshold value of 35%, a temperature of the treatment being low enough for the formation of a clear homogeneous extract phase distinct from a residual aqueous phase, separating the extract phase from the aqueous phase, raising the temperature of the extract phase to that at which it separates into a lower layer containing phosphoric acid and an upper layer containing solvent, and separating the lower layer from the upper layer. Suitable solvents may be ester, ketones, glycol ethers and ethers, such as ethers and esters containing 2-15 carbon atoms. Ethers specified are diethyl, di-isopropyl, di-n-butyl, isopropyl-n-butyl, di-n-amyl and di-isoamyl ethers. During the heating to separate the aqueous acid from the solvent a small amount of water or purified phosphoric acid may be added. The lower temperature for the extraction of the acid may be obtained by evaporating in vacuo an adequate proportion of the solvent added to a technical-grade acid.</p> |
