Trimeric Surfactant Modified Montmorillonite Immobilized in Alginate Beads: An Efficient Adsorbent for Removal of Cu2+ and Methyl Orange from Aqueous Solution

Abstract

Trimeric surfactant modified montmorillonite immobilized in alginate beads (CA/3RenQ-Mt) sorbent was synthesized to simultaneously remove Cu²⁺ and methyl orange (MO) from aqueous solution. The CA/3RenQ-Mt was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), zeta potential analysis and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The adsorption of Cu²⁺ and MO by CA/3RenQ-Mt was studied by the operational variables including contact time, pH and temperature. The results showed CA/3RenQ-Mt exhibited higher affinity to both Cu²⁺ and MO compared to sodium montmorillonite (Mt-Na), trimeric surfactant modified montmorillonite (3RenQ-Mt) or calcium alginate (CA). The pseudo-first-order kinetic model and Langmuir isotherm model were found to describe the MO adsorption well; the pseudo-second-order kinetic model and Freundlich isotherm model fitted well with the Cu²⁺ adsorption. The adsorption of MO onto CA/3RenQ-Mt is an endothermic spontaneous process, and ion-exchange was the dominant adsorption mechanism. Accordingly, the adsorption of Cu²⁺ on CA/3RenQ-Mt involved endothermic spontaneous chemical adsorption by means of coordination/chelation between Cu²⁺ and the oxygen atoms of carboxyl and hydroxyl groups of alginate. In general, CA/3RenQ-Mt can be applied as multifunctional adsorbent to remove heavy ions and anion dyes from aqueous solution.