Purification of Wet Process Phosphoric Acid by Solvent Extraction using Cyclohexanol

Abstract

Solvent extraction using organic solvents is an important technology for the purification of wet process phosphoric acid (WPA). In this study, the purification process of WPA, using a new type of solvent extraction system, cyclohexanol diluted in kerosene, was investigated. The equilibrium phase diagram of the system H₃PO₄-H₂O-solvent mixtures at 313.2K was obtained. The effects of extraction time, phosphoric acid concentration, cyclohexanol concentration, temperature, phase ratio on extraction efficiency were studied. The extracted species was shown to be 2H₃PO₄ · 2C₆H₁₂O. The extraction process of H₃PO₄ is exothermic and the enthalpy change, △H, was obtained. Via a cross-current three-stage extraction, the solvent mixtures have a high efficiency for phosphoric acid purification from the actual industrial WPA with an H₃PO₄ extraction yield of 90.2% at room temperature. The study is capable of enriching theoretical foundation and technical guidance for the phosphoric acid purification process.