Preparation And Characterization Of Organic-inorganic Multi-alkoxy Silicon Hybrid Membranes

There have been many methods for introducing the inorganic particles into organic network to achieve hybrid, such as blending, sol-gel and in-situ polymerization. In this hybrid, organic components and inorganic components can combine with each other well. Thus, the hybrid materials may own the merits of both the organic and inorganic material, such as high mechanical, chemical and thermodynamic stabilities. When hybrid materials are used for preparation of ion-exchange membranes, the high swelling performance following with high ion exchange capacities (IEC_p) should be settled. On the other hand, the membrane permeability and selectivity can be improved because of the introduction of inorganic components. Therefore, organic-inorganic hybrid materials are developing rapidly these years.In the thesis, we have prepared several organic-inorganic non-ion exchange hybrid membranes, as well as some cation exchange hybrid membranes, through the sol-gel process and blending. Some physical and chemical properties of test were carried out. Especially for the cation exchange hybrid membranes, they were firstly used to recover sodium hydroxide from the mixture of NaOH and Na2WO4 through diffusion dialysis (DD). The main experiment and data are as following:(1) A type of hybrid membranes were prepared using the ethylenediamine (EDA), chloromethyl triethoxysilane (CMTES) and poly (vinyl alcohol) (PVA). Firstly, multi-alkoxy silicon small molecular was synthesized through EDA and CMTES. Then the sol-gel process was carried out between PVA and the multi-alkoxy silicon small molecular. The experimental conditions, such as the content of the silicon, the solvent and catalyst, have been investigated. The thermal, mechanical and chemical stabilities of the membranes, as well as the pervapration performance, were investigated. As a result, the membrane produced with catalyst potassium hydroxide and solvent ethanol exhibited the better properties.(2) Organic-inorganic cation exchange hybrid membranes have been prepared through sol-gel reaction of poly (acrylic acid -co-methacryloxypropyl trimethoxy silane (poly (AA-co-γ-MPS)) in presence of poly (vinyl alcohol) (PVA). The effect of the content of the polymer poly (AA-co-γ-MPS) to the membrane was investigated. The membranes have good thermal stabilities and the Td values are in the range of 264 - 270°C. With increasing poly(AA-γ-MPS) content, water content (W_R) gradually decreases from 81.6% to 70.8% while the practical cation exchange capacities (IEC_P) increases from 0.76 mmol/g to 0.90 mmol/g. The hybrid membranes have been used to recover sodium hydroxide from the mixture of NaOH and Na₂WO₄ through diffusion dialysis (DD). The dialysis coefficient of OH^- (UOH), as well as the separation factor (S), is at high level ( UOH: 0.010– 0.042m/h). The hybrid membrane containing 50wt% poly(AA-co-γ-MPS) has the highest separation factor of 95.7 at 35°C.(3) A type of hybrid membrane were prepared using acrylic acid (AA), methacryloxypropyl trimethoxy silane (γ-MPS) and sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO). The effect of the blending mode and the content of SPPO were investigated. Some test was carried out, and the feasibility of application in alkali recovery was discussed.