| Abstract:The silicate minerals have many extraordinary properties, such as huge specific surface area, high adsorption capacity, and abundant surface active sites and so on; therefore, it has been an important research focus for the development and utilization of silicate minerals that constructs the system of the integration of resources and materials. Our country is abundant in silicate minerals; however, the level of comprehensive utilization is too lower. Consequently, it is meaningful to optimize the silicate mineral resources utilization and promote the economic development that prepares minerals-based functional composites with high-performance at a low cost. This thesis focuses on the palygorskite clay mineral with a fibrous microstructure. Firstly, the palygorskite-based functional composites are prepared and the enhanced properties are realized by means of the surface activation and nanocrystallization modification. Secondly, a route that synthesize of ordered mesoporous materials and in-situ encapsulation nanoparticles using palygorskite as silicon and aluminum resources is proposed due to the silicate minerals has the same silicon-oxide skeleton with porous silica material. Finally, a novel microcapsules based on the self-assembly of mesoporous silica nanospheres in the emulsion phase is constructed, which will provide technical reference for the designing of silicate minerals-based microreactors. The main research contents and results of this thesis are as follows:In order to make better use of the unique surface properties of palygorskite, the palygorskite-based functional composites are prepared by surface functionalization of palygorskite with functional nanoparticles under the preservation of its fibrous morphology. The palygorskite is activated to increase its specific surface area and silicon hydroxyl to improve the adsorption capacity for metal cations, the palygorskite-based functional composites are successfully prepared via in-situ precipitation of loading ZnO?NiO?CuO nanoparticles onto activated palygorskite being as carrier. These samples are characterized by X-ray diffraction (XRD) and transmission electronic microscope (HRTEM) and the results show that the drawbacks of agglomeration of photocatalyst can be avoided and the size of nanoparticles can be restrained by loading photocatalyst nanoparticles onto the surface of palygorskite nanofibers. The ZnO/palygorskite composites demonstrate enhanced antibacterial activity with a minimum inhibitory concentration against E. coli of0.1g/L, which is lower than that of pure ZnO of0.25g/L. The enhanced antibacterial activity of ZnO/palygorskite composites can be ascribed to the synergistic effect between the high adsorption capacity of palygorskite clay carriers and the antibacterial property of ZnO nanoparticles. The Pd-CuO/palygorskite composites are obtained after the CuO/palygorskite composites modified with PVP-Pd solution. The results show that CuO nanoparticles are successfully anchored onto the surface of palygorskite fibers and uniformly dispersed, and the structure of palygorskite is well maintained after loading. The Pd-CuO/palygorksite composites display significantly high degradation ability for MO under UV irradiation, up to98%in20minutes; the enhanced photocatalytic activity of Pd-CuO/ATP composites can be interpreted by the fact that synergetic effect between the high adsorption capacity and active sites of palygorskite and the efficient electron-hole separation at the coupled Pd-CuO/ATP photocatalyst interface due to the introduction of Pd.The ordered mesoporous material is successfully synthesized from structure modulation of palygorskite based on its layered structure. Through the optimization of different pretreatment to palygorskite, the highly ordered Al-MCM-41mesoporous material can be obtained with alkaline leached palygorskite as source and cetyltrimethylammonium bromide (CTAB) as template via hydrothermal reaction, and the obtained Al-MCM-41mesoporous material has a high specific surface area of1044m2/g. The in-situ encapsulation route is proposed on the base of mesoporous materials incorporation of nanoparticles, which may avoid the problems of aggregation and blocked pores during the post-synthesis process. Taking CuO nanoparticles as guest, the CuO/Al-MCM-41composites are prepared by in-situ incorporation of CuO nanoparticles into the Al-MCM-41matrix. The effect of different copper sources and copper loading amount on the microstructure of mesoporous materials are investigated, the SAXRD, TEM and N2adsorption-desorption results manifest that the CuO/Al-MCM-41composites have high degree of channel order and specific surface area and the majority of CuO nanoparticles are incorporated into the pores of Al-MCM-41. H2temperature programmed reduction (H2-TPR) measurement results demonstrate that the in-situ synthesized sample has a lower reduction temperature than that of post-synthesized sample, confirming that the CuO nanoparticles in the in-situ synthesized sample can be reduced easier, meaning that the in-situ synthesized sample has a better redox property. Taking Au nanoparticles as another guest, the Au/Al-MCM-41composites are prepared by in-situ encapsulation of Au nanoparticles into the Al-MCM-41, Using this in-situ encapsulation route, the size of gold nanoparticles can be well controlled close to3nm, and ensure that the gold nanoparticles can be well confined in the pores of Al-MCM-41. The mechanism of the in-situ assembling gold nanoparticles into mesoporous materials reveals that the formation of the rod-like micelles by CTAB stabilized AuCl4" is the key for in-situ encapsulation. The proposed in-situ encapsulation technique guarantee that the nanoparticles can be well embedded in the mesopores, and ensure that the composites have an enhanced performance and expanded application.In order to study the behavior of self-assembly and property of interface of mesporoues materials, the mesoporous silica nanospheres with a size of60nm and MCM-41-like hexagonal structure are prepared with TEOS as silicon source, CTAB and Brij56as templates. A novel colloidosome microcapsules with mesoporous membrane is constructed by the self-assembly of various mesoporous silica in the emulsion phase, the particles-stabilized emulsion overcome the drawback of toxicity in the surfactant-stabilized emulsion. The optical microscope test results demonstrate that the mesoporous silica nanoparticles with template can stabilize the water-in-oil (W/O) and oil-in-water (O/W) emulsions, while the mesoporous silica nanoparticles with template removal can only stabilize the oil-in-water (O/W) emulsion to form the colloidosome microcapsules. The type of colloidosomes of water-in-oil or oil-in-water can be switched by the degree of the hydrophilic or hydrophobic surface properties of the mesoporous silica nanoparticles, the relative hydrophilic nanoparticles are willing to stabilize the oil-in-water emulsion, while the hydrophobic nanoparticles are inclined to stabilize the water-in-oil emulsion. By fixing the ratio of water and oil in the water-in-oil emulsion, and changing the amount of modified mesoporous silica nanoparticles, the size of colloidosomes can be effectively controlled from about300micrometers to120micrometers, and all the colloidosome microcapsules can maintain the regular and stable spherical shape. Meanwhile, the semipermeability and adsorbability of the mesoporous colloidosomes are demonstrated by the diffusion of fluorescent dye in the oil and water phase. Au/meso-SiO2composites are synthesized via post-synthesis route, and the composites are applied as emulsifiers to stabilize the water-in-oil emulsion to construct the interfacial catalytic reaction system. The Pickering emulsion-based interfacial catalytic system can overcome the drawback of the low efficiency in the single phase catalytic system due to the different solubility of substrate, and as well solve the problems of aggregation and difficult separation of substrate and product, and also provide theoretical and technical reference for the construction of microreactors based on silicate minerals.This thesis aims to study the fine processing and high-value utilization of palygorskite clay. It detailedly studies the mechanism and routes of preparation palygorskite-based functional composites via surface nanocrystallization modification to decorate functional nanoparticles, the designed synthetic method will provide the new concept and technical reference for the synthesis of functional composites using others relevant silicate minerals. Furthermore, this thesis develops a new synthetic route of preparation ordered mesoporous material and in-situ encapsulation nanoparticles using palygorskite caly mineral, clarifies the structure evolution of silicate mineral during the process of fabrication mesoporous material, establishes the reaction model of the ordered mesoporous material in-situ encapsulation nanoparticles, constructs the relation between the microstructure and property of the composite, explores the potential application of the composite being as catalyst, the proposed technique that produce the ordered mesoporous material and in-situ assemble nanoparticles using clay minerals can provide fundamental basis for the synthesis mesoporous composites using others minerals. Finally, this thesis creates a novel microcapsule structure based on the self-assembly of mesoporous silica spheres in the emulsion phase, it can not only offers new idea for the system of multi-phase interfacial catalytic reaction, but also supplies technical reference for the microreactor based on silicate minerals. |
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