Removal of heavy metal ions using cellulose nanocrystals and succinic anhydride-modified cellulose nanocrystals prepared from bleached soda bagasse pulp

Abstract

Cellulose nanocrystals (CNC) and succinic anhydride-modified CNC from bleached soda bagasse pulp under different parameters were used to remove Cd+2 and Pb+2 heavy metal ions from aqueous solution. The aim was to modify the chemical structure of cellulose nanocrystal using succinic anhydride and to investigate the effect of CNC and succinic anhydride-modified CNC on the adsorption capacity of heavy metal ions. The adsorption parameters included pH (3, 5, 6, and 8), contact time (30, 60, and 90 min), and initial metal ion concentration (40, 120, 200, and 280 ppm). It was found at all pHs that the adsorption capacity of the succinic anhydride-modified CNC adsorbent was much higher than that of the default CNC adsorbent, and this difference was greater at higher pHs. The results showed that the maximum metal ion adsorption was obtained at pH 6 for Pb+2 and Cd+2 ions. Both types of CNC had a higher adsorption capacity for lead ions than cadmium ions. To investigate the kinetic models of adsorption, the pseudo-first-order and pseudo-second-order kinetics model were used. Adsorption on unmodified adsorbent gave a better fit to the Langmuir model than the Freundlich model for both Pb+2 and Cd+2 metals. In addition, the adsorption mechanism was changed by modifying the adsorbent, and then it had better fit to the Freundlich adsorption model. Adsorption of cadmium and lead metals by adsorbents fit better to the pseudo-first-order kinetics model.