The mechanism of Pb(II) and Cd(II) removal by coffee grounds biochar: Role of KOH modification

Abstract In order to make comprehensive use of coffee grounds, and to investigate the effect of KOH on the surface properties of biochar and the adsorption performance of heavy metal Pb(II) and Cd(II), this paper investigates the surface properties and the adsorption performance of unmodified and modified biochar for heavy metal Pb and Cd ions by means of SEM, elemental analysis, FTIR, XRD and other characterization, adsorption kinetics, adsorption thermodynamic model fitting, and other adsorption experiments. The results show that the modified biochar has the best adsorption performance for heavy metals, the maximum adsorption capacity for Pb(II)and Cd(II) reaches 593 mg/g and 128 mg/g respectively, and the adsorption process is mainly chemical adsorption. An isothermal sorption fit using the Langmuir and Freundlich model can better reflect the sorption behaviour and properties of biochar in coffee grounds. The results show that KOH modification has a good activation on biochar, and KOH- activated biochar from coffee grounds has excellent adsorption performance on Pb(II) and Cd(II).