| Heavy metal ions and dyes are two kinds of typical pollutants in wastewater,and most of them exist in sewage with together. How to effectively remove these two kinds of pollutants has become a hot research. The existing processing methods with ion exchange, precipitation, membrane separation, adsorption and so on, adsorption in the numerous methods for its high efficiency, low secondary pollution and adsorption process is simple and easy operation, are widely used. But the existing adsorption materials just owned single function to remove only one type of pollutant and could not remove other complicated pollutants in wastewater. In this study, we used montmorillonite(MMT) of heavy metal ions adsorption performance, and graphene oxide(GO) of high adsorption capacity and excellent adsorption efficiency for removal of organics, using ultrasonic method in water medium to synthesis the montmorillonite-pillared graphene oxide(GM), and the composition and structure were characterized. Moreover, its adsorption of contaminants in water was also studied.Firstly, we used GO and MMT as a row material and adopt the ultrasonic method in water medium to prepare the GM, We characterized the features of GM composites through fourier transform infrared(FTIR), X-ray diffraction measurements(XRD),scanning electron microscope(SEM), atomic force microscopy(AFM), transmission electron microscopy(TEM) and Brunauer-Emmett-Teller(BET) specific surface area.The results showed that with the increase of concentration of GO, the BET specific surface area of GM increased then decreased, when the quality ratio of GO and MMT was 10%, GM possessed a higher BET specific surface area((973m2·g-1) than GO(612m2·g-1) and MMT(245 m2·g-1).Secondly, A batch systems were applied to study the adsorption behaviors of methylene blue(MB), methyl orange( MO) and Pb2+ by GM in single system. The results exhibited that GM had the best adsorption capacity of three kinds of contaminants than the MMT and the GO, and the adsorption behavior was matchedwith the pseudo-second order model and the Langmuir isotherm. With the maximum adsorption capacities of 250 mg/g for MB, 144.9 mg/g for MO and 232.6 mg/g for Pb2+, and reached the adsorption equilibrium in 50 minutes.Thirdly, GM was studied to adsorb the MB and Pb2+ in binary system, and the adsorption mechanism was explored. The experimental results exhibited that the presence of MB in water would provide additional binding site 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;Its adsorption mechanism were as follows: Pb2+ was bound to the same sites on GM surface as MB, but the total sites available for subsequent MB adsorption remained the same, but a layer of Pb2+ adsorbed on the surface of GM might produce a barrier for MB to connect to the available adsorption sites; while the GM adsorbed MB causing an increase in the surface negative charges, which might favor the adsorption of Pb2+. In addition, MB was adsorbed on the GM surface and produced more organic functional groups in the GM-MB surface, which caused an enhancement in the Pb2+adsorption.Finally, GM was applied to adsorb the MB and MO in binary system, and the adsorption mechanism was explored. The results showed that the adsorption capacities of MB and MO by GM in the binary system were dramatically higher than those in single system; Its adsorption mechanism were as follows: MB and MO were both the noncovalent functionalization molecules, which would likely adsorb on GM through Л-Л bond interactions between the columnar structure of GM and the aromatic ring of the dyes; the electrostatic attraction force between GM and dyes would also accelerate its adsorption capacity. |
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