Montmorillonite/graphene oxide nanocomposite as superior adsorbent for the adsorption of Rhodamine B and Nickel ion in binary system

Abstract

A series of montmorillonite reduced graphene oxide (MrGO) composites were synthesized using different ratios (5, 10, 15 and 20) of montmorillonite (MMt) to GO. The synthesized composites were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, surface area analyzer (BET), and Fourier transform- infrared spectroscopy. The adsorption capacity and efficiency of the synthesised composites were examined towards removal of Rhodamine B (RhB) and Nickel ion (Ni2+). The results were compared with that of GO and commercial MMt clay. The kinetic sorption models were evaluated, and it was observed that sorption follows the pseudo-second-order kinetics. Adsorption isotherm was best fit into the Langmuir model (R2 = 0.996 for RhB & 0.957 for Ni2+). Among all the synthesized composites, MrGO-2, a composite of GO and montmorillonite with (1:10) ratio, showed maximum activity towards the adsorption of Rhodamine B and Ni2+ calculated to be 625 mg/g and 178 mg/g respectively at neutral pH condition. From the calculated ΔG0 (−3.99 & −0.71 kJ mol−1), ΔH (28.6 & 4.61 kJ mol−1) and ΔS (−107.5 & −17.8 J mol−1 K) values for RhB & Ni2+ respectively, it can be unambiguously inferred that the adsorption process was feasible, endothermic and exhibiting least randomness, respectively. The prepared MrGO composites showed good adsorption capacity towards efficient removal of RhB and Ni2+ in single as well as binary system.