Removal of molybdenum(VI) from aqueous solutions using nano zero-valent iron supported on biochar enhanced by cetyl-trimethyl ammonium bromide: adsorption kinetic, isotherm and mechanism studies

A new carbonized pomelo peel biosorbent (MCPP) modified with nanoscale zero-valent iron (NZVI) and cetyl-trimethyl ammonium bromide was prepared and employed for the adsorption of molybdate (Mo(VI)) from aqueous solution. We investigated the effects of various conditions on Mo(VI) adsorption and evaluated the results based on adsorption kinetics models and isotherm equations. The kinetic data fitted to the pseudo-second-order model. The Langmuir model best described the adsorption of Mo(VI) on MCPP. The values of changes in Gibbs free energy, standard enthalpy, and standard entropy revealed that the adsorption process was feasible, spontaneous and endothermal. X-ray diffraction, Fourier transform infrared and X-ray photoelectron spectroscopy measurements suggested that Mo(VI) adsorption occurred via both the reduction and surface adsorption. Thus, biochar, prepared from fruit residue, can be applied to remove Mo(VI) from aqueous solutions. More importantly, our results provide a sustainable approach for Mo(VI) removal from wastewater by means of functional modification.