Abstract:The kinetics of extractive separation of La(III) and Ni(II) from nitrate medium in the presence of lactic acid (HLac) using di-2-ethylhexyl phosphoric acid (DEHPA) diluted in petrofin was investigated using a cell with constant interfacial area and continuous stirring. The effects of stirring speed, interfacial area, pH, HLac concentration, extractant concentration, concentrations of metal ions and temperature on the extraction rate were examined. Results suggested that the extraction regime is diffusion-controlled. The reaction which occurred at the interface was found to be the rate-determining step. The extraction rates of both metal ions are found to be independent of pH. The extraction rates of La(III) and Ni(II) are first-order dependent with respect to lactic acid and metal ions (La(III) and Ni(II)) concentrations. The extraction rate of La(III) is first-order dependent on DEHPA concentration and for Ni(II), it varies to the power of 1.5. The separation of La(III) and Ni(II) from nitrate solution is possible at low interfacial area and low stirring speed.

Key words: extraction; separation; kinetics; mechanism; La(III); Ni(II)