LAUSR

Abstract Sugarcane leaves biomass (SCL) has been utilized for the removal of Ni2+, Cr3+ and Co2+ ions from polluted water. Qualitative analysis was performed by Fourier Transformed Infra-Red spectroscopy, Raman spectroscopy, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffractometry. Adsorption of the metal-ions was carried out by contacting 50 mL of known concentration of Ni2+, Cr3+ and Co2+ with known amount of SCL at 27 °C, and under varied experimental conditions such as pH, ionic strength, solid-to-liquid ratio, contact time and initial metal ions concentration in batch adsorption experiment. The kinetics, isothermal, as well as the nature of the adsorption were predicted by models such as pseudo-first-order, pseudo-second order, Elovich, Weber-Morris, Freundlich, Langmuir, Temkin and Dubinin-Raduschevich. The thermodynamics of the processes was also predicted. Characterization analyses portrayed the surface of SCL as being porous, oval in shape and composed of hydroxyl and carbonyl groups as the main binding sites. Raman analysis revealed the interaction of the metal ions with the lignin, cellulose as well as hemicellulose components of the adsorbent. Adsorption of Ni2+ and Co2+ ions was favored by increasing pH, while that of Cr3+ ions was mostly favored at pH 4. Metal uptake increased with increasing contact time and concentration up to equilibrium stage. The sorption processes followed the pseudo-second-order kinetics and was monolayer in nature with qmax of 51.3, 62.5, and 66.7 mg/g for the uptake of Ni2+, Cr3+ and Co2+ ions, respectively. The models predicted physisorption as the main process involved. Thermodynamic study showed that the processes were feasible and spontaneous, endothermic, and occurred with increase in randomness at the adsorbate-adsorbent interface, demonstrating a good metal uptake nature of the adsorbent.