A novel bio-nanocomposite, FeS encapsulated chitosan grafted polyacrylamide, was successfully synthesized using a grafting technique that employs microwave irradiation. Employing FTIR, SEM, XRD, TEM and SAED analysis, the synthesized nanocomposites were characterized. Thermodynamic and kinetic studies were accomplished using the batch mode via the eosin yellow adsorption from aqueous solution using the nanocomposite. The adsorption process was tailored to the pseudo-second-order kinetic model and the Freundlich isotherm model. The enthalpy change, ∆H° (-12.243 kJ/mol), was an exothermic process. The Gibbs energy, ∆G° (from -5.492 kJ/mol.K to -5.078 kJ/mol.K for temperatures from 300 K to 318 K respectively) values were indications of a thermodynamically feasible reaction process which was spontaneous within the temperature domain. The change in entropy, ∆S° (-0.023 kJ/mol), showed reduced randomness during the adsorption process. The mean free energy of adsorption was 0.408 kJ/mol, which was an indication of physisorption. These results show the possible use of the graft copolymer as an adsorbent in water treatment.