Application of cotton stalk biochar as a biosorbent for the removal of malachite green and its microwave-assisted regeneration

摘要

In this study, cotton stalk (CS) biochar was used as a sorbent for the removal of malachite green from wastewater. Batch sorption experiments revealed that dye removal increases along with rise in initial dye concentration, temperature of the sorption process, and sorbent weight. Dye removal was observed in the range of 35-40 mg/g for 100 mg/L initial dye concentration. Freundlich and Temkin isotherm models were used for modelling the sorption process. Furthermore, thermodynamic study indicated that the process is endothermic and that the spontaneity of sorption gradual rise with temperature. The changes in enthalpy and entropy were determined to be 57,697.25 J/mol and 177.768 J/mol, respectively. Pseudo-second-order kinetics was found to be suitable for the sorption process. Dynamic study revealed that film diffusion is the governing diffusion in the sorption process. Additionally, microwave-assisted heating was employed to regenerate the spent CS biochar, and a yield of 21-76 was obtained depending on the power of the microwave. It was observed that high-power regeneration distorts the pores; thereby, lowering the dye sorption capacity of the regenerated biochar. GRAPHICS .