Functionalized polyacrylamide/graphite composites - Biodegradable adsorbents for the removal of synthetic dye from aqueous solution

Eco friendly, biodegradable functionalized polyacrylamide/graphite composites have been used to adsorb synthetic dye from aqueous medium. The polymer composites have been synthesized and characterized with FT-IR, 1H and 13C NMR. The composite's adsorptive features have been analyzed using different parameters. The efficiency of adsorption process is determined using kinetic, equilibrium and thermodynamic analysis. The equilibrium uptake capacity was obtained from Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models. The correlation coefficients indicate that the Langmuir model show satisfactory fit for the uptake of dye. The adsorption process follows pseudo second order in addition to intraparticle diffusion model with a good correlation coefficient. The thermodynamic parameters ΔG, ΔH and ΔS show that the adsorption process is spontaneous (ΔG < 0), endothermic (ΔH > 0) and had decreased entropy (ΔS > 0). The equilibrium and kinetic experiments confirm that the temperature and pH play an important role i.e., the dye uptake increases with increased temperature and decreased pH. FTIR and desorption studies confirm the involvement of functional groups in adsorption mechanism.