Diluent effect on the distribution ratio and separation factor of Ni(II) in the liquid–liquid extraction from aqueous acidic solutions using dibutyldithiophosphoric acid

The liquid–liquid extraction of Ni(II) from aqueous H2SO4 medium and its separation from Zn(II) were studied using dibutyldithiophosphoric acid (DBDTPH) as an extracting agent in three different diluents (CCl4, CHCl3 and isobutylmethyl ketone, IBMK). Distribution curves, which are shown as the plots of Ni(II) concentration in the organic phase vs. its concentration in the aqueous phase, indicated similar extraction patterns among the three diluents studied; however, their positions were displaced from one diluent to the next. CCl4 provided a higher partition (i.e., a better extraction) than did the other two. For the separation factor, the results are presented as the plots of molar fraction of Ni(II) in organic phase vs. its molar fraction in aqueous phase. Separation factor was strongly dependent on the diluent. While a poor separation was achieved when using IBMK as diluent, CCl4 and CHCl3 resulted in a good separation of Ni(II) from Zn(II), which were similar to each other. For a better result in the liquid–liquid extraction of nickel using such complexing agents as DBDTPH, diluent properties have to be consulted.