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Updated: Jul 15, 2026
Pretreatment of Lignocellulosic Biomass with Low-cost Ionic Liquids
Published on: August 10, 2016
Addition of Sodium Fluoride to an Ionic Liquid Innovative System in the Reused Pretreatment to Enhance Cellulose
Manita Kuntapa1,2, Chakrit Tachaapaikoon3,4, Kaokanya Sudaprasert5
1Energy Technology Program, School of Energy, Environment and Materials, King Mongkut's University of Technology Thonburi, 126 Pracha Uthit Rd., Bangmod, Thung Khru, Bangkok, 10140, Thailand.
Abstract:
Eco-friendly ionic liquids (ILs) are widely used in lignocellulosic biomass pretreatment. With their rather high cost, ILs must be reused in pretreatment processes. By pretreating with reused [BMIM]BF4:DMSO: NaF and [BMIM]BF4:DMSO for 22 rounds, the residual solid lignin contents of raw corn cobs samples are 6.94% ± 0.11% and 11.87% ± 0.22%, respectively, compared with 19.19% ± 0.41% in raw corn cobs, demonstrating the superior delignification performance of [BMIM]BF4:DMSO: NaF. Moreover, the residual lignin content remained consistently low throughout the reuse cycles for [BMIM]BF4:DMSO: NaF, increasing only slightly from 6.62% ± 0.15% in the first cycle to 6.94% ± 0.11% in the 22 rounds, whereas a more pronounced increase was observed for [BMIM]BF4:DMSO, from 9.28% ± 0.19% to 11.87% ± 0.22%. The crystallinity index (CI) of a raw corn cob sample is 40.56 ± 0.02, whereas that of a corn cobs sample pretreated by reused [BMIM]BF4:DMSO: NaF and [BMIM]BF4:DMSO for 22 rounds is 22.10 ± 0.01 and 39.00 ± 0.01, respectively. This comparison suggests that the crystalline lignocellulose of a corn cob sample is regenerated into an amorphous form more by [BMIM]BF4:DMSO: NaF pretreatment than by [BMIM]BF4:DMSO pretreatment, verifying that [BMIM]BF4:DMSO: NaF performs well in delignification and cellulose separation. This conclusion is also supported by the peak of F- detected through ion chromatography analysis because F- in reused [BMIM]BF4:DMSO: NaF solution can increase lignocellulose denaturation. Consequently, the cellulose conversion of the enzymatic hydrolysis of the 22nd reuse of [BMIM]BF4:DMSO: NaF, 85.82% ± 0.12%, is higher than that of [BMIM]BF4:DMSO, 26.55% ± 0.10%. Moreover, the [BMIM]BF4:DMSO: NaF has successfully reused because the solid lignin separated at 40 °C, suggesting that the [BMIM]BF4:DMSO: NaF can be used in the next round of pretreatment. By considering the function of [BMIM]BF4:DMSO: NaF, the combination between [BMIM]BF4 and DMSO: NaF mechanism explanation of reused pretreatment is first reported in lignocellulosic pretreatment.
