Malachite green adsorption onto Fe3O4@SiO2-NH2: isotherms, kinetic and process optimization

Abstract

Higher environmental standards have made the removal of dye from water an important problem for many industrialized countries. Among the removal methods, magnetic adsorbents have received much attention for adsorption of dyes. In this paper, a novel magnetic adsorbent with an amino-modified SiO₂-coated Fe₃O₄ magnetite was prepared. The analysis of Fe₃O₄@SiO₂-NH₂ proved that the nanoparticles were uniform with a diameter of 90 nm. The difference between Fe₃O₄@SiO₂-NH₂ and Fe₃O₄@SiO₂ on the adsorption behaviour of malachite green was studied. Fe₃O₄@SiO₂-NH₂ showed a good capacity for the adsorption of malachite green compared with Fe₃O₄@SiO₂, which was shown to be influenced by the initial concentration and pH. Under the optimal conditions, the removal efficiency of malachite green was over 90% by Fe₃O₄@SiO₂-NH₂, while using Fe₃O₄@SiO₂ efficiency was below 60%. The experimental data fit well with the Freundlich isotherm and the pseudo-second-order kinetic model. In further applications, real samples were treated with Fe₃O₄@SiO₂-NH₂ nanoparticles. All the results demonstrated that the Fe₃O₄@SiO₂-NH₂ nanoparticles could be promising and effective adsorbents.