Magnesite is rich in domestic resources, but due to the unreasonable traditional mining and beneficiation methods, it has caused serious waste of resources. According to the requirements of modern development of circular economy, it is necessary to realize the high-energy comprehensive utilization of magnesite.
Magnesite is mainly used as refractory materials, followed by chemical raw materials, building materials, and refining of magnesium metal. At present, the utilization of magnesite is developing in the direction of high-end and synthetic, especially the demand for sintered magnesite with high purity, high volume density and large crystals is increasing. Continuously improving the deep processing level of magnesite materials, improving product grades, and increasing product added value are the development trends of market competition.
The comprehensive utilization of magnesite is to transform it into high value-added products such as nano magnesium oxide and nano magnesium hydroxide through a series of chemical methods and physical treatment technologies. The following is an overview of the basic steps of the conversion process:
Preparation of nano magnesium oxide
1. Mining and crushing of magnesite: First, magnesite is collected from the mine, and then it is initially physically crushed to reduce the size of the mineral particles.
2. Acid leaching purification: The crushed magnesite is treated with an acidic solution such as hydrochloric acid or sulfuric acid to remove impurities such as calcium, iron and other elements to obtain a pure magnesium salt solution.
3. Precipitation and separation: Alkaline substances (such as sodium hydroxide) are added to the purified magnesium salt solution to promote the precipitation of Mg2+ ions as magnesium hydroxide. Subsequently, the magnesium hydroxide precipitate is separated by filtering and washing.
4. Pyrolysis to produce magnesium oxide: The obtained magnesium hydroxide is calcined under high temperature conditions, generally at a temperature exceeding 500°C, to decompose it into magnesium oxide (MgO). By controlling the calcination conditions, such as temperature, atmosphere and time, nano-scale magnesium oxide particles can be obtained.
5. Subsequent treatment: The calcined magnesium oxide is further refined by grinding, grading and other steps to improve the dispersion and purity of nanoparticles.
Preparation of nano magnesium hydroxide:
If the target product is nano magnesium hydroxide, it can be achieved by optimizing the process parameters by direct precipitation method:
1. Fine regulation: During the precipitation process, the pH value, reactant concentration and reaction rate are precisely controlled, and advanced technologies such as ultrasound and microwave assistance are used to promote the uniform formation of crystal nuclei and the growth of crystals to obtain nano-scale magnesium hydroxide.
2. Subsequent treatment: The product also needs to be refined through steps such as cleaning and drying to ensure that its purity and particle size distribution meet the requirements.
This comprehensive utilization of magnesite not only improves the efficiency of resource utilization, but also promotes a win-win situation of environmental protection and economic benefits. These nanomaterials have broad application prospects in catalysts, adsorbents, biomedicine, electronic materials and other fields.
Magnesite resources are a non-renewable and indispensable strategic resource. Restricting and reducing mining and improving resource utilization should be the focus of future work. To this end, we put forward suggestions for the sustainable development of domestic magnesite resources.
1. Increase financial and technical investment in improving the utilization rate of magnesite. Increase the investment in the separation and purification of low-grade magnesite. It can not only improve the comprehensive utilization rate of magnesite, but also solve the problem of shortage of superior magnesite raw materials.
2. Vigorously promote mineral processing technology and make comprehensive use of medium and low-grade ores. At present, relevant enterprises have gradually realized that relying solely on raw ore production raw materials can no longer maintain the supply of superior raw materials. Only by beneficiating and purifying the raw ore can we produce superior-grade primary raw materials. Ensure the normal production of raw materials.
3. Increase the energy conservation and consumption reduction and environmental pollution control efforts in the processing of magnesite resources, maximize resource utilization, reduce energy consumption and pollution, and enable my country’s magnesite resources to achieve healthy and sustainable development.
4. Develop magnesium salt fine chemical products. Low-grade magnesite can be used to prepare high-purity magnesium oxide, magnesium hydroxide, basic magnesium carbonate, magnesium sulfate, magnesium nitrate and other magnesium salt products through mineral processing and purification, changing the production situation of magnesium salt enterprises that mainly produce low-value-added magnesium salt products and enhancing corporate competitiveness.
5. In the mining and processing of magnesite resources, we must accelerate the pace of using mature high-energy equipment and eliminate backwardness. Research and promote mature light-burned magnesium oxide roasting technology and kilns, such as promoting suspension kilns and multi-layer furnaces for the production of light-burned magnesium oxide. Only by establishing a large-scale concentrated production base of light magnesium oxide and forming economies of scale can we make reasonable investments, thereby adopting mature roasting technology and kilns to solve the problem of energy conservation and emission reduction from the source.
6. The comprehensive utilization of magnesite resources is diversified and the utilization rate is greatly improved; the scale of products is appropriately expanded on the basis of the quality stability of magnesia raw materials such as light-burned magnesia (powder), heavy-burned magnesia, mid-range magnesia, high-purity magnesia, and fused magnesia. A new series of superior synthetic magnesia, such as magnesia-calcium sand, magnesia-calcium iron sand, magnesia-marine sand, magnesia-aluminum spinel sand, magnesia-chrome sand, fused spinel sand, and forsterite sand, has been rapidly developed.