Preparation of montmorillonite-pillared graphene oxide with increased single- and co-adsorption towards lead ions and methylene blue
To prevent the aggregation of graphene oxide (GO) during storage or application, montmorillonite (MMT) was used as the modifier, and MMT-pillared GO (GM) was prepared. The features of GM were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersion X-ray spectrometry, atomic force microscopy and X-ray diffraction measurements. Then, a batch system was applied to study the adsorption behaviors of lead ions (Pb2+) and methylene blue (MB) by GM in single and binary systems. The results showed that GM possessed a higher Brunauer–Emmett–Teller (BET) specific surface area than GO. In a single system, the maximum adsorption capacities of GM for MB and Pb2+ were 350 and 285 mg g−1, respectively. With increasing the storage days, the BET specific surface area and the maximum adsorption capacity of GM remained approximately unchanged, while that of GO dramatically decreased. For a binary system, the presence of MB in water provides additional binding sites for Pb2+, promoting the adsorption of Pb2+ on GM. The presence of Pb2+ in water would compete with MB on GM during the adsorption process, resulting in a decrease in the adsorption of MB. The adsorption results recorded under different conditions indicated that this experiment was capable of the simultaneous removal of Pb2+ and MB using GM as the adsorbent. In addition, the pillared structure of GM greatly enhanced the noncovalent adhesion.