Nanomaterials For Efficient Detection And Removal Of Pollutants From Drinking Water:Structural Design And Mechanism Study

As a newly developed science, nanoscience has drawn more and more attentions in recent years. Nanoscience as a21st century frontier science, are leading the development of many disciplines, especially the interdiscipline. Nanotechnology has been widely appllied in environmental science, especially, by providing new materials, process and technology. For example, nanotechnology can be used in the inspection of pollutants in water, the treatment of raw water, the deep purification of drinking water, sewage treatment, water regeneration and recycle, and so on. As compared to the traditional method, nanotechnology and related process take less field area with less manpower and energy consumption. Thus, nanotechnology has been shown great superiority and application potential in the inspection of pollutants as well as in the water treatment. The main contents of this thesis are as follows:the design and synthesis of new nanocomposites; the study of the application of the nanocomposites for pollutant detection and water treatment; the study and discussion of the related reaction kinetics and mechanisms.1. The synthesis of a water dispersible magnetite graphene-layered double hydroxide (MG-LDH) nanocomposite for the removal of arsenate from waterAs a toxic element, arsenic (As) can generate many illness such as cancer and melanosis. The As contaminated water is a widespread problem which has been drawn more and more attentions all over the world. Herein, we designed and synthesized a magnetite graphene-layered double hydroxide (MG-LDH) nanocomposite based on a large number of screening experiments. The obtained MG-LDH was applied for removal of As from water. The results showed an enhanced adsorption capacity toward As by the MG-LDH as compared to the pure nano LDH. This composite material can be dispersed in water and also can be easily separated from water by a external magnet, leading to an enhanced efficiency. On one hand, the incropration of the MG can enhance the surface area of the composites which provides more active adsorption sites; on the other hand, the introduction of mechanically and chemically stable graphene can improve their mechanical strength. The results demonstrated fast and efficient adsorption of arsenate by the MG-LDH, suggesting that MG-LDH can be potential material for the preconcentration of arsenate from the contaminated water. 2. Chloridion intercalated layered double hydroxide (LDH-Cl) nanoplates for the treatment of sewage prepared in laboratory and the contaminated groundwaterArsenic (As) contaminated groudwater are mainly caused by nature process and human activities. The As contaminated groudwater was found widespread in the world, such as in Hungary, Argentina, Mexico, Chile and China, and recently in Bangladesh and Vietnam. The environmental protection agency (EPA, USA,2001) and the world health organization (WHO,1993) have revised the drinking water standard of the arsenic from50to10mg/L. Hence, it is very urgent to develop new technology and materials for the watertreatment in order to meet the new increasingly strict drinking water standard. In this work, we choose As as the target pollutant and As sewage prepared in laboratory for the experiments. Based on experimental results, we gradually screen out suitable nanomaterials or nanocompo sites and apply them to the treatment of actual contaminated groundwater. At last, we screen out a chloridion intercalated layered double hydroxide (LDH-Cl) nanoplates for the treatment of both As and natural organic matter (NOM) contaminated groundwater. The results demonstrated that most of the As (>98%) and NOM (>94%) are removed by the LDH-Cl, and the treated groundwater mmets the drinking water national standard. The adsorption process was studied by techniques of XRD, FTIR, XPS, SEM, TEM and EXAFS, which provides the theoretical foundation for the application of this material in commercial watertreatment.3. An efficient surface-enhanced Raman scattering (SERS) substrate based on biomass-derived carbon film supported Au nanoparticles (Au NPs) for the detection of pollutants in water.The application of surface-enhanced Raman scattering (SERS) technique has provided new techniques and methods for the cost-effective detection of pollutants. The design and fabrication of novel cheap and efficient SERS substrates are of great significance for the application of SERS techniques. Herin, we designed and synthesized a porous carbon film incorporated with Au nanoparticles (Au NPs) as SERS substrate by using a cheap biomembrane as raw material, and their SERS activities were studied. The results demonstrated the predominant sensitivity toward Rhodamine6G (R6G) by this substrate with very low detection limit (1×10-9M). Moreover, great reproducibility and small relative standard deviation (RSD)(16.3%) obtained from the intensity of the main Raman peaks also verified the good SERS signal. The good SERS signals can be attributed to the densely packed Au NPs in the porous carbon film, in which the strong electromagnetic field was generated. Moreover, there is no surfactant exist in the substrate which avoid the undesired signals. The results showed a green and cost-effective method for the synthesis of ultrasensitive SERS substrate and their great application potential in the pollutant detection.