Effect of Alkaline and Oxidative Treatment on Sawdust Capacity to Remove Cd(II) from Aqueous Solutions: FTIR and AFM Study

Two treatments, sodium hydroxide and hydrogen peroxide, were applied to enhance the capacity of fir tree (Abies alba) sawdust to adsorb Cd(II). Fourier transform infrared spectroscopy (FTIR) analysis and atomic force microscopy (AFM) were used to characterize untreated and treated fir tree sawdust. The removal of Cd(II) ions by treated sawdust was dependent on the initial Cd(II) concentration, initial pH, and temperature. Kinetics (pseudo-first-, pseudo-second-order, intra-particle, and film diffusion models) and isotherm models (Langmuir and Freundlich) of the considered biosorption process were examined. The pseudo-second-order model was found to better model the kinetics of Cd(II) adsorption. Maximum adsorption capacities calculated using the Langmuir model are 8.84 and 2.67 mg/g for NaOH and H₂O₂ treated sawdust, respectively, and 2.20 mg/g for untreated sawdust. The results indicate that the two treatments enhanced the adsorption capacity of the studied sawdust.