Microwave-assisted hydrothermal carbonization of furfural residue for adsorption of Cr(VI): adsorption and kinetic study

The existence of heavy metals on the earths surface and disposal of industrial effluents to the environment causes severe health issues that need to be dealt with. Adsorption of Cr(VI) was carefully studied onto the furfural residue in a batch system. Furfural residue was treated in the microwaveassisted HTC with water as an effective medium, and the subsequent solid material was further treated by a low concentration of potassium hydroxide. Under optimum conditions (pH 2, 25 degrees C, and 2.5 g/L adsorbent dosage), 91.72% Cr(VI) was removed at the initial concentration of 100 mg/L to achieve equilibrium condition. The effects directed that a higher adsorption capacity of Cr(VI) (36.91 mg/g) was reached by integrating microwave-assisted treatment at 200 degrees C and 0.05 N KOH concentration. Important parameters like effect of pH, contact time, temperature and solution concentration were optimized to investigate their effectiveness. The experimental adsorption data were best fit for the Freundlich model, which instantly followed the pseudo second-order kinetics model. Investigation of thermodynamic studies demonstrated negative values. The findings of the study suggested the modified hydrochar generated from furfural residue could be considered as an alternative to high-cost adsorbents.