Far infrared radiated energy-proficient rapid one-pot green hydrolysis of waste watermelon peel: optimization and heterogeneous kinetics of glucose synthesis

Abstract

For the first time, a one-pot green hydrolysis of waste watermelon (Citrullus lanatus) peel (WWP) was optimized for a maximum glucose yield employing a heterogeneous Amberlyst-15 catalyst. The effects of energy-proficient far infrared radiation (FIRR) on intensification of pretreatment and subsequent solvent-free hydrolysis reactions in the one-pot system have been maximized. The optimal process variables for pretreatment and consequent hydrolysis were 20 min and 10 min batch times, 70 °C and 60 °C reactor temperatures, and 5 and 10 (w/w) water to WWP ratios, respectively. Optimal 2.5 (w/w) NH₄OH loading and 2.5 wt% catalyst concentration for pretreatment and hydrolysis under FIRR resulted in a maximum glucose yield (89.87 mol%), which was superior to that obtained (59.86 mol%) using a conventional thermal source. In comparison with pseudo-homogeneous and Langmuir–Hinshelwood models, the Eley–Rideal model described the hydrolysis kinetics more accurately. Significantly, a higher hydrolysis activation energy (92.02 kJ mol⁻¹) in the conventional system compared to the FIRR mode (activation energy, 59.69 kJ mol⁻¹) clearly demonstrated the superior energy-efficiency of the FIRR system. The energy-proficient fast hydrolysis process is expected to be sustainable and applicable to similar lignocellulosic biomasses.