Evaluating the integration of olive tree pruning fractionation with ternary eutectic solvent after aqueous pre-extraction or dilute acid pre-treatment

Developing lignocellulosic biomass fractionation approaches that valorize lignin besides the conventional polysaccharide conversion routes have been a growing interest in achieving full biomass cascade processing. Additionally, integrating and designing technologies that use environmentally friendly and recyclable solvents following green chemistry is required. Within this context, the present work aims at investigating the integration of pre-treatments, such as aqueous pre-extraction or dilute acid pre-treatment, with the fractionation of the olive tree pruning biomass (OTP) assisted by ternary eutectic solvent (ES) composed of cholinium chloride, p-toluenesulfonic acid and ethylene glycol (ChCl:pTSA:EG; 1:1:9). The impact of both technological integrations on lignin isolation yield and on lignin physicochemical, thermal and antioxidant properties were the major parameters under evaluation. Overall, the most efficient integration was accomplished with aqueous pre-extraction plus ternary ES treatment. Around 64.3 % and 36.6 % delignification were achieved with ES, when using solid fractions obtained from aqueous pre-extraction and dilute acid pre-treatment, respectively. The lignin isolated after aqueous pre-extraction and ES treatment showed a remarkable aliphatic OH content (5.72 mmol∙g−1). Finally, the integration of these processes enabled cellulose enrichment of remaining solid fractions that were accessible to enzymes (80.1–90.3 % hydrolysis yield).