The effect of thiol ligands on the adsorption behavior of silver ions on functionalized nanomagnetic graphene oxides

Abstract

The magnetic graphene oxides (MGO) were modified with l-cysteine (Cys), glutathione (GSH), and thioglycolic acid (TGA) as the thiol ligands. using field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, and Brunauer Emmett Teller (BET) surface area analysis, the structural and magnetic properties of the as-prepared samples have been studied. The results affirmed the successful synthesis of functionalized adsorbents. The adsorbents presented here have been reported for the first time to remove Ag ions from dilute aqueous solutions. The influence of the adsorption conditions (pH, contact time, and initial concentration) was investigated. The experimental data were consistent with both the pseudo-second-order kinetic model and the Langmuir isotherm model indicating chemisorption monolayer adsorption with the fast kinetics. The maximum adsorption capacity for MGO-TGA, MGO-Cys, and MGO-GSH based on the Langmuir isotherm model was found to be qm = 67.16, 53.42, and 43.73 mg/g, respectively. The calculated separation factors (0 < RL < 1) revealed that the adsorption process was favorable for three adsorbents. The large surface area of the adsorbents (57.244, 37.006, and 15.676 m2/g, for MGO-TGA, MGO-Cys, and MGO-GSH, respectively), along with the presence of thiol ligands on them, significantly affects the adsorption behavior. Therefore, these adsorbents offer an effective and rapid process for adsorbing silver ions from low concentration aqueous solutions.