Abstract: A new extraction process for wet-process phosphoric acid by tributyl phosphate（TBP）+methy isobutyl ketone （MIBK）（abbreviated as TM） mixer was proposed.The miscibility of TBP and MIBK as well as phase equilibrium of wet-process phosphoric acid extraction by TM were also investigated.The solubility parameter of pure TBP or pure MIBK at 10~ 50 ℃ and the phase equilibrium data of TM/H₃PO₄/H₂O ternary system at 25 ℃ and 50 ℃ when the mass fraction of TBP was at 10%～90% were determined.Experimental results showed that there was almost no effect of temperature on the solubility parameter of TBP and MIBK and they were miscible at any temperature, because their solubility is very close; temperature had little effect on phase equilibrium of wet-process phosphoric acid extraction by TM；composition of TBP and MIBK had certain effect on equilibrium.The higher content of TBP，the wider extraction range；on the contrary，the extraction range was narrower；TM′s extraction range was between pure MIBK and pure TBP.The results and data laid the theoretical foundation for extraction and purification of wet-process phosphoric acid by TM.

Key words: TBP, MIBK, phosphoric acid, solubility parameter, phase equilibrium, wet-process phosphoric acid