Application of vinyl monomers functionalized cellulosic biopolymer for removal of dissolved toxic metal ions from polluted water samples

• Cellulosic fibers were graft copolymerized with acrylonitrile and acrylamide from their binary monomer mixtures.
• Further cyanide groups were converted into amidoxime functional groups through reaction with NH2OH·HCl.
• The resulted functionalized fibers were characterized by FT-IR, SEM and TGA techniques.
• The functionalized fibers were applied to remove toxic metal (Zn2+, Cd2+ and Pb2+) ions from wastewater.
• Langmuir model fits better with the equilibrium data than other adsorption isotherm studied.

In the present study, a binary vinyl monomer mixture of acrylonitrile (AN) and acrylamide (AAm) was graft copolymerized onto cellulosic fibers using ascorbic acid and hydrogen peroxide as redox initiator. The grafted fibers were further reacted with aqueous solution of hydroxylamine hydrochloride at pH 10.0 to convert them into amidoxime derivative. These resulting functionalized cellulosic fibers were characterized by various techniques such as FT-IR, TGA, and SEM studies. The functionalized fibers were used for removal of toxic metal ions from aqueous solution through adsorption process. The adsorption process follows pseudo-second-order kinetics and relative adsorption rate of various metal ions were found in the order of Pb2+ > Zn2+ > Cd2+. Langmuir, Freundlich and Dubinin–Radushkevich models were used to show the adsorption isotherm. Langmuir model fits better with the equilibrium data. The maximum monolayer capacity qm calculated using the Langmuir isotherm for Zn2+, Cd2+ and Pb2+ metal ions were 55.72, 106.72 and 200 mg/g respectively. From thermodynamic parameters ΔH° and ΔG° values were obtained. The adsorption process has been found to be exothermic in nature.