Highly efficient removal of nickel and cadmium from water using sawdust-derived cellulose nanocrystals

Bioresources are renewable raw materials which can be utilised for multiple purposes including the development of various materials for water treatment. In this study, cellulose nanocrystals (CNC) derived from sawdust was modified and utilised as coagulants for the removal of Ni2+ and Cd2+ ions from water. The modified CNC was characterized using Fourier transform infra-red, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and zeta potentiometer. Analyses revealed that the modified CNC is porous and exhibited narrow particle size distribution and needle-like morphology. The functional group responsible for the coordination and removal of the metals was mainly carboxylate anion (COO2-). Zeta potential measurement showed a reduction in negative surface charge value of modified CNC. The effects of solution pH, CNC coagulant dosage and initial metal concentration were investigated using jar test experiment. Results revealed that the removal of metal ions increased with an increase in the coagulant dosage and solution pH, and that the best pH for the investigation was pH 7.10. Metal removal efficiency, however, reduced with an increase in the initial concentration of the metal ions. Experimental uptake values of 956.6 mg Ni/g and 2207 mg Cd/g were obtained, which in comparison with uptake values of other cellulosic materials gives indication that CNC derived from sawdust is highly competitive material for the amelioration of water containing metals.