Copper adsorption onto synthesized nitrilotriacetic acid functionalized Fe3O4 nanoparticles: kinetic, equilibrium and thermodynamic studies

The continuous discharge of heavy metals into the near water bodies causes great harm to the human and aquatic ecosystem. Several adsorbent have been developed and applied for effective removal of metal ions from water. In this paper nitrilotriacetic acid (NTA) functionalized Fe3O4 nanoparticles (Fe3O4-NTA) were developed by coprecipitation method with iron salt and NTA, shown to be effective removal of Cu(II) ions from aqueous solution. The functionalized nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), X ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Brunauer-Emmett-Teller Surface area analyzer (BET), and pHzpc. The various effecting factors of Cu(II) ions adsorption from aqueous solution such as contact time, adsorbate dose, and pH were investigated. The kinetics models such as pseudo-first-order, pseudo-second-order, Elovich, and intra-particles diffusion were applied on experimental Cu(II) adsorption. The kinetic data showed pseudo-second-order model was found to be better agreement with correlation coefficient, R2 = 0.997-0.999 at 60-12 mg L−1. The equilibrium adsorption data modeled with Langmuir, Freundlich, and Dubinin-Radushkevich isotherms found to be better fitted with Langmuir reveal the monolayer adsorption of Cu(II) ions on the surface of Fe3O4-NTA with maximum adsorption capacity of 34.63, 38.8 and 40.24 mg L−1 at 298, 303 and 308 K, respectively. The positive value of ΔH° (35.127 kJ mol−1) and ΔS° (176.031 kJ mol−1 K−1) indicates the endothermic nature of Cu(II) adsorption onto Fe3O4-NTA. The negative value of ΔG° (7.365-8.005 kJ mol−1) indicates spontaneous nature of adsorption.