The study of the partitioning mechanism of methyl orange in an aqueous two-phase system.

An aqueous two-phase system of dodecyl triethylammonium bromide (C(12)NE, cationic surfactant) and sodium dodecyl sulfate (SDS, anionic surfactant) mixture is proposed for the extraction of some dyes and porphyrin compounds. Transparent two phase-systems are formed when the surfactant concentrations and C(12)NE/SDS ratios are in certain regions. In this study, the aqueous two phase-systems were prepared by mixing 0.1 mol l(-1) C(12)NE and SDS with a molar ratio of 1.7:1.0. The results showed that negatively charged chlorophyll (sodium copper chlorophyllin) and positively charged dye (methyl violet) were efficiently extracted into the upper phase. The negatively charged methyl orange (pH>7) was moved into the upper phase mostly while amphoteric methyl orange (pH<3) was distributed in the two phases uniformly. Except for hydrophobic force, charge interaction between solute and surfactant also play an important role in the extraction process.