One-step green separation of durian husk lignocellulose using polyol-based ternary deep eutectic solvent under subcritical carbon dioxide

Abstract

Durian husk is rich in lignocellulose and represents a promising target for recycling and value-added utilization. However, the complex structure of lignin and its protective association with carbohydrates pose significant challenges for efficient component separation. Conventional chemical methods are often operationally complex, energy-intensive, and environmentally unfriendly. In this study, a one-step green separation method was developed using a subcritical carbon dioxide (CO₂) environment in combination with an alcohol-based ternary deep eutectic solvent (DES) composed of choline chloride, ethylene glycol, and 4-chlorobenzenesulfonic acid. This method achieved a delignification rate of up to 91.5% and a cellulose retention rate of 84.7% under mild conditions ranging from 60 °C to 90 °C and varying CO₂ pressures. The separation parameters influenced the crystallinity index, hydrogen bonding interactions, and lignin unit distribution in the cellulose-enriched fraction. Moreover, the incorporation of subcritical CO₂ enhanced the acidity and proton donation capacity, thereby improving reaction efficiency. In summary, this study presents a mild, efficient, and environmentally friendly strategy for the selective separation of lignocellulose from natural biomass.

Keywords

Biomass / Carbon dioxide / Deep eutectic solvent / Delignification rate / Green separation / Lignocellulose

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