Decolorization of soluble dyes by extraction using hydrophobic ionic liquid [Bmim]PF₆

Extraction of dyes into hydrophobic ionic liquid-[BmimlPF₆ is investigated. The ionic liquid extraction system is successfully used in the extraction of dyes. The effects of some parameters, such as the extraction phase ratio, pH of the aqueous phase, system temperature and the addition of dicyclohexyl-18-crown-6 in organic phase are studied in detail. Acid dyes can be extracted by [Bmim]-PF₆ quantitatively, the acid dyes can be extracted more than 95 percent. For reactive dyes, however, the percentage removal is 64.9 percent. When the phase ratio V₀/V_aq = 1 : 10, ionic liquid reaches its critical saturation point. With the pH of the aqueous phase adjusted from pH 1.50 to pH 12.5, the removal efficiency of acid yellow dye RN is reduced from 99.8 percent to 13.4 percent. The higher the system temperature, the higher becomes the removal efficiency. Moreover, the addition of dicyclohexyl-18-crown-6(CE) can enhance the removal efficiency of reactive black KN-G2RC and reactive yellow M-5R from 31.5 percent and 5.5 percent to 81.6 percent and 82.7 percent, respectively.