| It has been an attractive trend for the materials science to pursue new technologies for preparing novel functional materials by means of the chemical compositions, special structures and physical-chemical characteristics of natural minerals.The structure-property relationship between the natural minerals and the as-synthesized advanced functional materials is especially emphasized, and the potential application of the obtained functional materials is a key research focus. The development of porous materials experienced from natural zeolites to mesoporous materials and macroporous materials.For porous materials, Si and Al act as the basic compositions in the framework. With regard to the traditional approaches, Si and Al sources in the preparation of porous materials are mainly chemical reagents, which are of high cost and baffle the industrial production of porous materials.On the basis of their special structures and compositions,layered silicate minerals usually act as a preferred candidate for the preparation of novel porous materials.In this thesis, based on a comprehensive review of the research and current issues of porous materials,we have conducted a detailed study of porous material with bimodal pore size distribution, ordered mesoporous material and zeolite by means of the special layered structure and the rich Si, Al contents of the natural minerals.The structures and properties of the obtained products are characterized by X-ray diffraction(XRD), scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),thermogravimetric-differential scanning calorimeters(TG-DSC), solid-state nuclear magnetic resonance(NMR), fourier transform infrared spectroscopy(FT-IR), Photoluminescence(PL), N2 adsorption-desorption measurement, water adsorption capacity and compression strength techniques.Porous materials with bimodal pore size distribution of micropores (0.36nm) and mesopores(3.8nm),specific surface area of 400m2·g-1 and pore volume of 0.80ml·g-1 are synthesized through mechanochemically activating and acid-leaching of layered silicate minerals.The effect of grinding time and leaching time on porous properties of the synthesized materials are mainly investigated. The results show that the grinding process induces the crystal structure of layered silicates becoming amorphous, which is beneficial to the following leaching process.The octahedral metal ions are leached out by H+ions through ion exchange. Consequently, the residual voids after leaching form micropores and the SiO4 tetrahedrons layers form mesopores through structure rearrange and condensation. Compared with the leaching time, the grinding time shows more significant effect on the porous properties of the resulting porous materials.The difference of layered silicate minerals in chemical compositions and layer types (type 1:1 and type 2:1)result in the various change behaviors of structure and porous properties of the layered silicates, and finally result in discrepancy of porous properties for the resulting porous materials.Ordered mosoporous material MCM-41,with huge specific surface area of 1100m2·g-1, pore volume of 1.00ml·g-1 and pore size of 2.80nm, is successfully synthesized via hydrothermally heating acid-leached layered silicates.The obtained MCM-41 has fine thermal stability and the endurable temperature is up to 940℃.Charge density matching and polymerization of silicate species determine the final structure of the resulting product.This technique realizes the synthesis of ordered mesoporous material MCM-41 in low surfactant concentration through cooperative formation mechanism according to the charge density matching rule. H3SiO4- and H4SiO4 are main species existed in the alkaline solution. The polymerization and assembly of these species result in the formation of the final product MCM-41 which mainly contains Q3(Si(SiO)3OH) and Q4(Si(SiO)4) structures.The component of pore wall of MCM-41 synthesized from different layered silicates is amorphous SiO2.The layer type of silicates shows little influence on the final structure of ordered mosoporous materials.It should be emphaseized that the SiO4 tetrahedrons contained in layered silicates are regarded as the essential ingredient for the preparation of ordered mesoporous materials. The structural evolution from layered silicates to ordered mesoporous materials involves the transformation from layered crystal structure to disordered porous structure, and finally to ordered mesoporous structure. Taking ordered mesoporous materials as host matrix, various kinds of functional composites have been succussfully synthesized by incorporating various guest molecules into the channels of the host matrix. The properties of the obtained composites were superior to that of the host matrix or the guest molecules.SnO2/MCM-41 composite is synthesized by hydrothermal method taking SnO2 nanoparticles as guest and as-prepared MCM-41 as host matrix. The result shows that most SnO2 nanoparticles exist in the channels of the host matrix without damaging the mesoporous structure of the host matrix, except that little amount of Sn atoms is incorporated into the framework of the host matrix. Taking the channels of the host matrix as "micro-reactor",the PL property of SnO2/MCM-41 composite could be modulated by varying the Sn/Si molar ratios.The PL intensity of SnO2/MCM-41 composite is nearly 8 times as that of the pure SnO2 nanoparticles.Zeolite 4A molecular sieve powder is synthesized using layered silicates (taking kaolin as an example) as raw material via hydrothermal method. The obtained 4A molecular sieve particles show cubic morphology with the particle size of about 4μm. The water adsorption capacity and compression strength of the final desiccant are 21.0wt% and 51.0N/particle, respectively, which meet the standard of HG/T 2524-93 (water adsorption capacity≥20 wt% and compression strength≥50N/particle).4A molecular sieve powder and desiccant also can be successfully prepared in the pilot test, and the properties of the desiccant meet the application standard. The preparation is processed in low hydrothermal condition without any additional silica and alumina sources. The purity and morphology of the 4A molecular sieve powder could be modulated by adjusting the involved parameters, and the excellent properties of the desiccant product could be obtained through optimizing the crystalline degree of the 4A molecular sieves.Based on the special layered structure and chemical compositions of layered silicates, the aim of this thesis is to synthesize porous materials and functional composites with unique structures and excellent properties through mechanochemical activation and leaching method as well as hydrothermal treatment.Moreover, the potential application of the prepared products in desiccant field is exploited. The standpoint of this thesis is to develop a new method for the preparation of functional materials from natural minerals, investigate the physical and chemical behaviors during the preparation process, establish a structure-property relationship between the natural minerals and the obtained functional materials, and finally expand the unprecedented applications of the functional materials.All of these will provide basic fundamental and technical support for the integration of resources and materials. |
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