Synthesis of novel GA-g-PAM/SiO2 nanocomposite for the recovery of rare earth elements (REE) ions from aqueous solution

Abstract

The study highlights the preparation of novel Gum Arabic (GA) grafted polyacrylamide based silica nanocomposite using in-situ radial graft copolymerization method. The presence of radicals involved in synthesis of GA-g-PAM was detected using DMPO as a spin trapping agent by Electron paramagnetic resonance (EPR) analysis and the possible reaction pathway was proposed. The novel GA-g-PAM/SiO2 nanocomposite was characterized by Elemental analyzer (CHNS/O), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Atomic force microscopy (AFM), Brunauer Emmett and Teller (BET) and zeta potential (ZP) to study the chemical, structural and textural properties of nanocomposite. The successful incorporation of silica in grafted copolymer matrix was confirmed by FTIR and XRD analysis. The results indicated that surface area increased significantly after formation of GA-g-PAM/SiO2 compared to parental polymer (GA) matrix and 273.55 m2/g surface area was determined for GA-g-PAM/SiO2 nanocomposite. The recovery of rare earth elements (REE) from aqueous solution was also investigated using GA-g-PAM/SiO2 nanocomposite. The optimum conditions for REEs adsorption were determined from the batch adsorption experiments. The adsorption kinetics for REEs were well described by pseudo first order model. The adsorption equilibrium data fitted well with Langmuir isotherm except for Sc ions. The thermodynamic studies confirm that the adsorption is spontaneous and endothermic. Desorption studies affirmed the regenerative efficiency of loaded REEs up to three cycles.