Single-pot conversion of fruit peel waste to 5-hydroxymethylfurfural catalyzed by modified activated carbon in green solvent: kinetics and thermodynamic study

Abstract

The present study investigates one-pot depolymerization of fruit peel waste, namely pineapple (Ananas comosus) and banana (Musa acuminata) peel, for the formation of reducing sugars (TRS) and finally to 5-hydroxymethylfurfural (HMF). The combination of ionic liquid catalyzed by chemically treated activated carbon during dilute acid hydrolysis of fruit peel wastes for the formation of value-added products was evaluated. Physicochemical changes were also determined using FTIR, XRD, and lignocellulosic composition before and after treatment of biomass species. Percentage change in lignocellulosic composition attributes the reduction in crystallinity toward the amorphous region and, hence, increases product yield. Results also reveal significant changes in biomass matrix under different operating conditions, and maximum product yield was observed to be 47.82% and 42.12% (HMF) for pineapple and banana peel, respectively, using optimized ratio of ionic liquid/catalyst as 20 (IL dose 1.5 g) in a hydrolysis time of 90 min at 110 °C. The addition of dilute acid with an appropriate amount and ratio of ionic liquid further improves product yield. The optimum amount of ionic liquid reduced to 1 g from 1.5 g using 4 mL of H3PO4 acid. Kinetic parameters reveal the in situ view of rate constants with increase in temperature and acid strength and were simulated with the Saemen model with coefficient of determination > 0.94 for the rate of sugar formation and degradation. Thermodynamic parameters were also evaluated under the same reaction conditions and the change in ΔSo revealed invariable phase and volume change throughout the reaction process, whereas change in Gibbs free energy indicates a nonspontaneous process. This study provides sustainable and cost-effective production of value-added products with application in biorefinery.