Distribution of chromium(VI) in various organic solutions during extraction and re-extraction

Equilibrium studies on the extraction of Cr(VI) in various solvent phases have been performed. The organic solvent phase consists of Aliquat-336 (a cationic carrier) dissolved in kerosene/Shellsol TK (as an organic solvent) and hexanol (as a phase modifier). The values of the distribution coefficient for the extraction have been obtained by varying the following experimental conditions: feed solution pH (range 9-12); initial feed phase concentration (25 ppm ≤ Cr(VI) ≤ 1000 ppm); and composition of the organic phase (2 vol % ≤ Aliquat-336 ≤ 50 vol %). Re-extraction of Cr (VI) from the solvent phase was examined with an aqueous solution of HCl or NaCl by varying its pH (range 1-12) and concentration (0.5-2 mol·L^-1). The values of the partition coefficient for this process are also presented. The extraction and re-extraction reaction coefficients were calculated by combining the experimental data and the kinetic expressions for the interfacial reactions. These values are presented and compared with the literature values.