Facile synthesis and selective adsorption properties of Sm2CuO4 for malachite green: Kinetics, thermodynamics and DFT studies

Abstract

Tetragonal-phase Sm2CuO4 nanoparticles were synthesized using the simple solution method (SSM), then used as highly efficient selective adsorbent towards malachite green (MG) in aqueous solutions. The Sm2CuO4 samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectrum (DRS), and standard Brunauer–Emmett–Teller (BET) methods. The maximum adsorption capacity (Qm) of each sample was determined by adsorption isotherms at different adsorbent doses of 0.03–0.07 g and temperatures of 298, 318, and 338 K. Sm2CuO4 showed a very large Qm (7.18 g/g) towards MG at room temperature. The thermodynamic parameters were determined through the fittings of the temperature-dependent isotherms, and the kinetic parameters through time-dependent adsorption isotherms. A careful analysis of the data suggested that the adsorption process followed a pseudo-second-order reaction. Finally, the competitive ion (CI) experiments and DFT studies indicated that highly efficient selective adsorption mechanism was achieved through the strong O-Cu and O-Sm coordination bonds between Sm2CuO4 and MG.