Adsorption kinetic and equilibrium studies for methylene blue dye by partially hydrolyzed polyacrylamide/cellulose nanocrystal nanocomposite hydrogels

A series of partially hydrolyzed polyacrylamide/cellulose nanocrystal (HPAM/CNC) nanocomposite hydrogels with various amounts of CNCs were used to remove methylene blue (MB) dye from an aqueous solution. The effects of three preparation variables (i.e., HPAM anionicity, content of CNCs, and pH value of prepared solution) on swelling properties and equilibrium adsorption were studied systematically. The results showed that improved swelling properties and enhanced MB adsorption capacity were acquired by raising HPAM anionicity, by increasing CNC's content up to 20 wt.%, and by decreasing pH value of solution. The optimum HPAM/CNC nanocomposite hydrogels had an adsorption efficiency of more than 90%. MB adsorption kinetics followed the pseudo-second-order and Elovich models. The adsorption isotherms of nanocomposite hydrogels could be described very well by the Langmuir equation. A possible adsorption mechanism was inferred based on the results of adsorption kinetics and isotherms to show the synergistic effect of HPAM and CNCs.