Co-hydrothermal valorization of food waste: process optimization, characterization, and water decolorization application

In this study, jackfruit peel (JP) was blended into sugarcane bagasse (SB) powder during co-hydrothermal carbonization (Co-HTC) to improve the physicochemical properties of JP/SB@4:1 hydrochar for the removal of methylene blue (MB), malachite green (MG), and crystal violet (CV) dyes from aqueous solutions. JP/SB@4:1 was systematically characterized. Spectroscopic, morphological, and elemental analyses confirmed successful binding of MB, CV, and MG dyes with JP/SB@4:1 surface. Influence of various parameters such as contact time, pH, initial dyes concentration, and temperature on the adsorption process was studied. The optimized magnitudes for these parameters were found to be 480 min of contact time; pH 6.6 for MB, 7.6 for MG, and 8.3 for CV; and 328K of temperature. Non-linear kinetic and isotherm models were applied to the experimental data. Results revealed the fitting of pseudo-second-order (PSO) and Langmuir isotherm (LIM) models to experimental data, while the maximum monolayer adsorption capacities (q(m)) of JP/SB@4:1 toward MB, CV, and MG were 326.79, 300.87, and 922.29 mg/g, respectively. The adsorption of dyes on JP/SB@4:1 was ascribed to electrostatic interaction, hydrogen bonding, and pi-pi/n-pi interactions. Thermodynamics evaluation showed the feasible, spontaneous, and endothermic adsorption of the dyes.