Effective removal of Cu (II) ions from aqueous solution by amino-functionalized magnetic nanoparticles

A novel magnetic nano-adsorbent (MNP-NH2) has been developed by the covalent binding of 1,6-hexadiamine on the surface of Fe3O4 nanoparticles for removal of Cu2+ ions from aqueous solution. Various factors affecting the uptake behavior such as contact time, temperature, pH, salinity, amount of MNP-NH2 and initial concentration of Cu2+ were investigated. The kinetics was evaluated utilizing the Lagergren pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models. The equilibrium data were analyzed using Langmuir, Freundlich, and Dubinin–Radushkevich isotherms. The adsorption was relatively fast and the equilibrium was established within 5 min, and its kinetics followed the pseudo-second-order mechanism, evidencing chemical sorption as the rate-limiting step of sorption mechanism. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities was 25.77 mg g−1 at pH 6, and 298 K. Thermodynamic parameters showed that the adsorption process was spontaneous, endothermic and chemical in nature. The successive adsorption–desorption studies indicated that the MNP-NH2 sorbent kept its adsorption and desorption efficiencies constant over 15 cycles. Importantly, MNP-NH2 was able to remove 98% of Cu2+ from polluted river and tap water.