Starch-graft-polyacrylamide copolymer /Fe3O4 /graphene oxide nanocomposite: synthesis, characterization, and application as a low-cost adsorbent for Ni (II) from aqueous solutions

Starch-g-polyacrylamide copolymer and its nanocomposite with Fe3O4 and graphene oxide have been successfully synthesized. The synthesized samples were characterized using FTIR, XRD, SEM, HRTEM, and VSM. The factors that affect the adsorption efficiency of samples for Ni(II) ions from aqueous solutions as pH, initial Ni(II) ions concentration, contact time and temperature have been examined. The maximum adsorption capacities achieved by the synthesized samples were 195 mg g−1 and 290 mg g−1 for starch-g-polyacrylamide copolymer and its starch-g-polyacrylamide/ Fe3O4/ graphene oxide nanocomposite respectively. Kinetic studies showed that the adsorption was well described by the pseudo–second-order model and the equilibrium adsorption data fitted Freundlich model. Thermodynamic studies showed that the adsorption capacity increases as temperature increase up to 313 K but higher temperatures result in dissolution of starch. Results showed that the adsorption process is spontaneous, endothermic in nature and leads to a greater entropy.