RECOVERY OF NI2+ BY DI-(2-ETHYLHEXYL) PHOSPHORIC ACID (HDEHP)
Abstract
This paper dealts with solvent and bulk liquid membrane extraction of Ni2+ from its chloride solutions by HDEHP in n-heptane. Effects of extraction time, initial pH and Ni+ concentration in the feed as well as HDEHP concentration in the organic phase were investigated. Solvent extraction equilibrium was established within 10 minutes. Ni2+ showed to be extracted into the organic phase preferentially as complexes. The Ni2+ extraction yield decreased with increasing initial Ni2+ concentration, with decreasing pH and/or HDEHP concentration. The later is not only due to shifting equilibrium of Ni2+ extraction reaction, but also due to concurent extraction of HCl. Results of bulk liquid membrane extraction could be described by the kinetics of interfacial pseudo-first order reactions. Observed rate constants were determined ~ 2,30.10-2 ÷ 2,68.10-2 min-1 for concentration range [Ni2+]0 ~ 10-3 ÷ 10-2 mol/l.