Development of deep eutectic solvents for pretreatment of sugarcane bagasse and corncob

Abstract

Lately, deep eutectic solvent (DESs) being an innovative and green solvent is becoming more popular due to growing environmental concern arising from the uses of conventional organic solvents. In view of this, four deep eutectic solvents based on choline chloride namely DES1 (Choline chloride - Urea), DES2 (Choline chloride - Oxalic acid, DES3 (Choline chloride - Glycerol and DES4 (Choline chloride - Ethylene Glycol were synthesized, characterized and used for pretreatment of sugarcane baggasse and corn cob respectively. The physicochemical and thermal properties of the synthesized DESs, like density, pH, viscosity, refractive index, surface tension, and thermal conductivity were found to be affected by the components and molar ratios of the DESs. The characterization result revealed that the viscosity of the DESs drops drastically as temperature rises. DES3 has the highest viscosity of 499.4 cPs followed by DES2, DES1 and DES4 having 305.72 cPs, 188.50 cPs and 131 cPs respectively. The untreated (raw) corn cob and sugarcane baggasse which contains 20.65 % and 19.06 % lignin were subjected to pretreatment using the synthesized DES1-DES4 under the same conditions in order to remove lignin. Lignin content reduced by 72 % for corncob and 83.26% for sugarcane baggasse compared to conventional solvents having a range of (41-63 %) lignin removal. Regarding lignin removal and holocellulose content, the DESs tested in this study demonstrated their potential for use as biomass pretreatment solvents, with DES1 and DES2 performing better in terms of percentage lignin removal for both sugarcane bagasse and corncob, respectively.