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 SO₄^2- 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 SO₄^2- 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.