Quantitative recovery and regeneration of acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulphate via industrial strategy for sustainable biomass processing.

Quantitative recovery is necessary for scale-up application of acidic ionic liquids (AILs). Ultrafiltration and bipolar membrane electrodialysis (BMED) was employed for the recovery and regeneration of acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulphate (Bmim[HSO4]) after biomass pretreatment. Ultrafiltration was designed for the purification of BMED feed solution. During BMED treatment, Bmim+ retention with OH- generation occurred in mixing section and SO42- immigration with H+ generation occurred in aciding section. Resulting aqueous Bmim[OH] in mixing section and H2SO4 in aciding section could be utilized for quantitative synthesis of Bmim[HSO4]. Influence of BMED operating mode and major parameters including BMED feed concentration and current density of BMED module were studied in detail. The highest recovery ratio for Bmim+ and SO42- reached 96.2% and 96.0%. And the lowest energy consumption of specific Bmim[HSO4] recovery approached 9.0 kw∙h/kg. Insight gained from this study suggested a sustainable biomass processing methodology using AILs.