Extraction and Mechanisms of Acid Dyes Into a Room Temperature Ionic Liquid

Investigation of liquid-liquid extraction of acid dyes is carried out by using ionic liquid - 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM] [PF₆]) as extraction phase. Effects of its process parameters are studied such as extraction phase ratio, pH of the aqueous phase, concentration of salt. Important results are obtained that acid dyes can be extracted with [BMIM] [PF₆] quantitatively, however, different acid dyes proceed through different mechanisms. The anion-exchange extraction process is predominantly responsible for the extraction of acid yellow RN, while the ion-pair process is for acid brilliant red B. The pH value has a great impact on the removal efficiency of the acid dyes. This pH swing effect may be a good solution for the recovery of acid dyes after extraction.