Bulk liquid membrane for the recovery of chromium(VI) from a hydrochloric acid medium using dicyclohexano-18-crown-6 as extractant-carrier

The solvent extraction and transfer of chromic acid from hydrochloric acid medium through a bulk liquid membrane containing dicyclohexano-18-crown-6(L ) were studied. Extraction experiments pointed out that chromium(VI) was co extracted with the chloride ion which formed the complex ion pair L(H3O+)Cr O3Cl- in the organic phase. The Donnan equilibrium isotherm based on the ex traction, stripping, and CrO3Cl- hydrolysis equilibria allowed prediction o f the performance of the semipermeable membrane to concentrate chlorochromi c acid in the receiving phase. Transport experiments confirmed the ability of the liquid membrane to recover chlorochromic acid in pure water. The tra nsport kinetics was modeled by using the two-film theory applied to the liq uid membrane.