Efficient Extraction of [Bmim]BF₄ by Organic-Aqueous System of NaBr-H₂O and CH₂Cl₂

The homogeneous [Bmim]BF4-NaBr-H2O system will be obtained in the industrial synthesis of [Bmim]BF4, and the extraction of [Bmim]BF4 from such a system remains to be challenging. In this work, dichloromethane (CH2Cl2), is used as the organic phase to extract and separate [Bmim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) from the reaction solution. Dichloromethane, serving as the extracting agent, effectively facilitates the purification and component separation of the ionic liquid [Bmim]BF4 postreaction, enhancing the reaction efficiency and product purity. The influence of operating parameters, including initial concentration of the ionic liquid (IL), temperature, O/A ratio (the volume ratio of organic phase to aqueous phase), and initial concentration of NaBr, on IL separation and extraction were investigated. It was found that the recovery ratio of IL and the separation factor could reach 90.3% and 133.19 at optimized extraction conditions. Moreover, this method was appropriate for the extraction of [Bmim]BF4 at different concentrations. As a result, this work developed an optimized extraction scheme to maximize the yield of [Bmim]BF4 using an organic and aqueous two-phase system of NaBr-H2O and CH2Cl2, which could provide essential technological parameters for the efficient extraction of [Bmim]BF4 in the NaBr-H2O-CH2Cl2 two-phase system.