The application of eggshells and sugarcane bagasse as potential biomaterials in the removal of heavy metals from aqueous solutions

Lead and cadmium are amongst some of the most hazardous and carcinogenic heavy metals to contaminate water sources in the industrial sector. As such, there have been several research efforts to remediate this worldwide environmental concern. The main objective of this study was to determine the efficacy of using two natural agricultural waste materials, sugarcane bagasse and eggshells, in removing Pb (II) and Cd (II) from aqueous solutions. The biosorbents were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The functional groups present in eggshells was carboxylic and carbonyl groups with hydroxyl and carbonyl groups present for bagasse. Crystallographic information revealed both an amorphous and a crystalline phase for bagasse with a crystalline phase for eggshells. The effect of particle size and pH was investigated where a higher removal rate was obtained with increasing pH with no significant difference observed with the particle size. Sorption equilibrium and kinetics were also studied by varying the initial concentration and contact time, respectively. The Langmuir and Freundlich models were applied for the mathematical description of the isotherms. The applicability of the Langmuir isotherm implied a monolayer formation of metal ions onto the surface of the adsorbents. The maximum amounts of Pb and Cd adsorbed based on 1 g of biosorbent were found to be 277.8 and 13.62 mg/g for eggshells and 31.45 and 19.49 mg/g for bagasse, respectively. The pseudo-second order model was used to describe the kinetics of the adsorption process for Pb and Cd ions. Based on the above findings, this study has demonstrated the efficacy of both adsorbents and presents it as a viable adsorbent for the biosorption process.