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Preparation of magnesium oxide nanoparticles from hydromagnesite

Magnesium oxide nanoparticles (MgO) are a new type of highly functional fine inorganic materials with some optical, thermal, electrical, magnetic, mechanical and chemical properties different from the native ones due to the special effects of surface effect, volume effect, quantum size effect and macroscopic quantum tunneling effect of nanomaterials. In recent years, it has important applications in antimicrobial agent, catalyst, adsorbent, advanced ceramics, optoelectronic materials, refractory materials, fillers, pharmaceuticals and other fields. Magnesium oxide nanoparticles usually have different morphological characteristics, and the different morphological characteristics lead to different properties, the main forms are powder, film, sheet, rod, tube, filament, etc., and some special morphologies.

The currently reported preparation methods of magnesium oxide nanoparticles are mainly divided into gas phase method, solid phase method and liquid phase method, among which solid phase method and liquid phase method are the most common, and the solid phase method mainly includes mineral calcination method, mechanical crushing method and solid phase chemical reaction method. The liquid phase method mainly includes precipitation method, sol-gel method, electrochemical method, metal alcohol salt hydrolysis method, hydrothermal method, dolomite carbonization method, microwave method, microemulsion method, etc. Among them, mineral calcination method is one of the commonly used methods for large-scale preparation of magnesium oxide due to abundant raw materials and low cost, but the commonly used minerals are usually magnesite, which usually requires complex pretreatment process before calcination, and most of the produced magnesium oxide is low-end. And although the magnesium oxide produced in the liquid phase method is of high quality, the method requires a large amount of chemical reagents, even introducing organic impurities to cause pollution, and the high equipment requirements and costs make industrial production challenging. Therefore, the search for low cost, non-polluting and suitable method for industrial production of high quality magnesium oxide products is an important task at present.

Water magnesite is a natural alkali carbonate mineral with abundant reserves. the mineral was first discovered in Tibetan Bangor Lake and other areas in the late 1950s. The resource content of hydromagnesite in China has been proven to be more than 100 million tons, which is a rare large deposit, mainly distributed in the northern Tibetan salt lake area and some salt lake areas in Qinghai. Water magnesite texture pure, white color, with \”snow-white\” or \”white-flower\” called, its chemical formula is 4MgCO-Mg (OH)-4H2O, in which CaO and other impurities content is low, has little effect on the general application, is the preparation of flame retardant, active magnesium oxide, heavy magnesium carbonate, nano magnesium hydroxide and other magnesium products of high quality mineral raw materials. However, it has not been well exploited due to geographical and traffic constraints, and studies on the preparation of magnesium oxide nanoparticles with different properties from hydromagnesite have not been reported.

Messi Biology used Tibetan magnesite from Bangor Lake as raw material to prepare magnesium oxide nanoparticles with different properties by the process of \”calcination, hydration and calcination\”. The effects of different calcination temperatures and times on the morphology, crystallinity, grain size and specific surface area of magnesium oxide and the effects of secondary \”hydration+calcination\” on the morphology of magnesium oxide were investigated.

Messi Biology prepared magnesium oxide with different morphologies by controlling the calcination temperature and time under the simple process of \”calcination-hydration-calcination\” with natural hydromagnesite from Bangor Lake, Tibet, without adding any reagent. The effects of different calcination temperature and time on the morphology, crystallinity, grain size and specific surface area of magnesium oxide were investigated. The products were characterized by TGDTG, BET, XRD, SEM, TEM and other testing instruments. The results showed that the increase of temperature or calcination time helped to improve the crystallinity of magnesium oxide, promote the crystal growth and reduce the specific surface area. The mesoporous mesh magnesium oxide with a specific surface area of 188.3 m2/g could be obtained by calcination at 650 ℃ for 1 h. The rod-shaped and dumbbell-shaped magnesium oxide nanoparticles could be obtained by calcination at 850 ℃ for 4 h. The high specific surface area mesoporous mesh magnesium oxide could be obtained as flake magnesium oxide after \”hydration+calcination\” again.

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