Efficient Removal of Ni(II) and Co(II) Ions from Aqueous Solutions Using Silica-based Hybrid Materials Functionalized with PAMAM Dendrimers

Abstract

ABSTRACT Many techniques of metal ions removal have been already implemented; however, there is still need for novel, efficient, and non-toxic adsorbents dedicated to heavy metals. In a recent study, the adsorptive properties of four hybrid materials consisting of silica platform surface grafted with poly(amidoamine) dendrimers (PAMAM) with different amino-terminal components, toward two heavy metal ions: Ni(II) and Co(II), were examined. The materials showed maximal scavenging properties at pH 5.4. To determine the adsorptive nature of the hybrid materials, experimental isotherms were fitted by the Langmuir, the Freundlich, and the Dubinin–Radushkevich models. All materials exhibited adsorption capability best described by the Langmuir model. The calculated adsorption capacities qm ranged between 86.7 and 116.6 mg g−1 for Ni(II) ions and 32.8 and 101.1 mg g−1 for Co(II) ions, which strictly indicate the influence of grafting agent structure on adsorptive properties of hybrid materials. The values of mean free energy E and adsorption enthalpy ΔH° jointly indicated the physical nature of adsorption processes. From the thermodynamic studies, the values of ΔH°, ΔS°, and ΔG° were obtained, indicating the spontaneous and endothermic character of investigated Ni(II)/Co(II) metal ions adsorption process on SiO2–dendrimer hybrid materials. Moreover, the materials exhibited selectivity toward Ni(II) ions.