| Lead as a heavy metal material has a close relationship with human life. It is used in the manufacture of the battery, the explosion proof agent, building material, cable jacket and so on. However, with the development of society, the pollution of lead is increasing,which is harmful to human health.Therefore, more and more scholars of domestic and foreign pay attention to lead removal and migration process in the environment.Recent years, a new carbon nano material, graphene oxide(Graphene, oxide GO) and its derivatives, shows a strong adsorption capacity for a variety of heavy metal ions in the water. Graphene oxide is a single layer or multilayer nano material formed by the fracture of the substrate with graphite under the action of strong oxidant.After strong oxidation, there are a large number of carbonyl(C=O), carboxyl(O-C=O), hydroxyl(C-O), epoxy group(-O-) and other oxygen functional groups on the surface and edge of GO sheet.The adsorption of graphene oxide mainly depends on the complexation between the oxygen functional groups and the heavy metal ions in water.Graphene oxide can be reduced to reduced graphene oxide(rGO, Graphene Oxide reduced) in a variety of ways. The remarkable feature of the reduction process is the disappearance ofthe oxygen containing functional groups on the GO surface.Therefore,the adsorption capacity of GO is different before and after reduction.Although there are many methods for the reduction of graphene oxide, the process of microbial reduction of GO under anaerobic condition is more universal. Based on the consideration ofthe applicability of heavy metal ion adsorption treatment technology on GO, It is necessary to studythe GO material itself and the adsorption and desorption of heavy metal ions on GO under typical reduction conditions.In the light of the environmental stability of lead oxide(GO) with lead ionsin the reduction of groundwater. This experiment used one of the three major toxic heavymetal lead as the target pollutants by in anaerobic conditions adding sulfide simulated groundwater common sulfate reducing conditions, to study the influence of the Na2 S reduction to the graphene oxide adsorption lead ion and desorption processes under anaerobic conditions. By using X ray photoelectron spectra, Fourier transform infrared spectroscopy-attenuated total reflectance, X- ray diffraction and Surface- enhanced Raman scattering, the mechanism of adsorption and desorption processes were analyzed and compared.The main results are as follows:(1) The adsorption process of GO and rGO reduced by Na2 S was in accord with the Langmuir isotherm model. And the maximum adsorption capacity was 937.65 and92.99 mg·g-1, respectively. The adsorption capacity of lead ion on GO was decreased after reduction.(2) The reduction by Na2 S can lead the release of Pb from the surface of graphene oxide under anaerobic conditions. There was 19.9%~35.5% of Pb released from spent GO as Pb2+ in the presence of Na2 S in anaerobic controls.(3) Spectral analysis showed that the adsorption of lead ions on the graphene oxide under anaerobic conditions was reduced by Na2 S, which resulted in the reduction of the oxygen functional groups on the GO surface, and cause the desorption of lead ions. And PbS formed in precipitates was detected by XRD.(4) After the GO attached to the lead into the reducing environment, desorption of Pb2+ ions in the form of Pb will lead to the recontamination of water body. |
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