Individual and simultaneous adsorption of Ni (II), Cd (II), and Zn (II) ions over polyamide resin: Equilibrium, kinetic and thermodynamic studies

Heavy metal pollution is a serious environmental issue worldwide with rapid increase in global industrial activities (Podder and Majumder [2016]: Water Conserv Sci Eng 1, 103-125). In this study, aromatic polyamide (PA) containing the azomethine group (Vidhyadevi et al. [2012]: Sep Sci Technol 48, 1450-1458) was used as an adsorbent for the individual and simultaneous adsorption of Ni (II), Cd (II), and Zn (II) ions from their aqueous solutions. Equilibrium, kinetic, and thermodynamic analyses of Ni (II), Cd (II), and Zn (II) ions adsorption were also carried out. The kinetic study on heavy metal ions adsorption suggests that the adsorption follows pseudo-second-order kinetic model. The thermodynamic study results revealed that the process is spontaneous and exothermic in nature. In the multicomponent adsorption system, adsorption of one metal ion was considerably reduced by the presence of other ions in the solution due to competition for the active sites on PA. The adsorption of heavy metal ions over PA was confirmed through FT-IR, SEM, and EDX analyses. The adsorption capacity of PA was found significantly higher than other adsorbents. The PA could be regenerated and reused even after five cycles for the Ni (II), Cd (II), and Zn (II) ions suggesting that adsorption using the PA is a reversible process.