Extraction of chromium (VI) from multicomponent acidic solutions by emulsion liquid membranes using TOPO as extractant.

Experimental results for the extraction of chromium (VI) from multicomponent acidic solutions by emulsion liquid membrane (ELM) using trioctylphosphine oxide (TOPO) as extractant are presented. The membrane phase consists of kerosene as diluent, TOPO as extractant, ECA 4360J (a nonionic polyamine) as surfactant and (NH(4))(2)CO(3) solution as stripping phase. Effects of various parameters such as mixing speed, type and concentration of stripping solution, surfactant and extractant concentrations, and volume ratio of the membrane phase to internal stripping phase on Cr (VI) extraction were studied and optimum conditions were determined. Results show that with proper adjustment of experimental conditions for the extraction of Cr (VI) can be enhanced to a great extent. This study also examined the effects of concentrations of acid and metal ions in the feed phase for the extraction of Cr (VI) ions. The results also showed that by appropriate selection of the extraction and stability conditions, nearly all of the Cr (VI) ions (100-500 mg/L) present in the acidic feed solution containing 1000 mg/L from each of Cu (II), Zn (II), Co (II), Ni (II) and Cd (II) ions were extracted within a few minutes. Concentration variations of Cr (VI) and other ions in the acidic solutions were determined by atomic absorption spectrophotometry.