Evaluation and mechanism of cationic/anionic dyes extraction from water by ionic liquids

Dispersive liquid–liquid micro-extraction (DLLME) using three different imidazolium-based ionic liquid (IL) was applied for extraction of recalcitrant dyes, Eriochrome black T (anionic azo dye), and Crystal Violet (cationic triphenylmethane dye) from aqueous solutions, not previously reported. Effects of process parameters such as initial dye concentration, pH of aqueous phase, amount and type of IL on fraction extracted, and distribution ratio of dyes were studied. Further, dyes interaction with ILs and extraction mechanism were explored. Considering the high cost of ILs, regeneration and reuse study for ILs was also performed using reverse DLLME. The fraction extracted for both the dyes with all the ILs varied significantly with pH change. Maximum dyes fraction extracted were observed nearly at neutral pH (pH =7). However, the fraction extracted were different for different IL.