Preparation And Functionalization Of Magnesium Carbonate From Magnesite

In this paper, based on the fact that China magnesite resource is the most abundant in the world. Magnesite resource in Liaoning province is not only abundant (accounts for 86.5% of country’s,22.5% of world’s), but also superior in quality. According to the concept of green economy, magnesite as raw material to prepare magnesium carbonate with different shape and size by ammonium nitrate recycling method was presented, and the relationship between the morphology and application performance was explored. Finally, the hierarchical TiO2/SiO2 composites were synthesized by the MCH template recycling method. The main content as follows:(1) Preparation of higher purity magnesium carbonate from magnesite. Caustic calcined magnesia reacted with ammonium nitrate solution under the boiling condition, and magnesium nitrate solution was obtained after dissolving. Then the magnesium nitrate solution react with ammonium bicarbonate or ammonium carbonate solution to prepare MgCO3-3H2O. Ammonium nitrate solution can be recycled. The main study as follows:the influence of solid-to-liquid ratio between caustic calcined magnesia and ammonium nitrate solution, stirring and reaction time in the process of preparation of magnesium nitrate solution; the influence of temperature, stirring speed, reaction time and the seed in the process of preparation of large size MgCO3·3H2O. Finally, the recycling of ammonium nitrate solution performance was simplely studied.(2) To control microstructure of magnesium carbonate. On the one hand, the basic magnesium carbonate with high bulk density and MgCO3·3H2O with low bulk density was prepared by hydrate under hige temperature and directly ball-milled respectively. After calcined, magnesium oxide with low bulk density and high adsorption activity (MgO-L) was obtained, and magnesium oxide with high bulk density and low adsorption activity (MgO-H) was also obtained. On the other hand, different morphology and size of alkali magnesium carbonates were prepared with the aid of small size MgCO3·3H2O; in the process different solvents were added and maturing under 80℃ water bath; the corresponding laws about effect of solvents on morphology are mainly summarized.(3) To prepare Mg(OH)2 with different morphology, magnesium carbonate which morphology is easy to control was calcined to get the corresponding morphology of magnesium oxide; then Mg(OH)2 with different morphology, which morphology is difficult to control, is obtained by vapor-hydrating method. In the vapor-hydrating system the crystalline habit is preliminary researched, and The effect of vapor-hydrating time and temperature on the microstructure and phase structure of Mg(OH)2 is mainly discussed.(4) Synthesis of hierarchical TiO2/SiO2 composites and the research on photocatalytic performance. Taking advantage of synthetic magnesium carbonate with tunable micro size and morphology, controllable magnesium-magnesium bicarbonate liquid phase transformation, and a relatively large solubility product constant-the higher metathesis activity, I choose the flower-like basic magnesium carbonate as a template to synthesize a hierarchical structure of TiO2/SiO2 composite materials to explore the reaction conditions during the synthesis of the composite microstructure and photocatalytic performance. The mole ratio of TBT and TEOS effect on microstructure, phase structure, specific surface area of composite and the influence of photocatalytic performance is mainly studied to determine the optimal mole ratio.