The Research On Preparation Of Nano-Magnesium Hydroxide And Heavy Magnesium Oxide Via Brine And Ammonia

There are abundant brine resources in China, such as desalination concentrated drainage, salt lake brine, oil and gas field water and underground brine. In addition to containing a large amount of NaCl, the brine is also rich in magnesium ions, which can be used as high-quality magnesium source. But at present, the utilization of the brine is in low level, resulting in substantial waste of resources and water pollution. In addition, the technology of developing and manufacturing of magnesium compounds is relatively backward in China, the products produced are mostly primary, low value-added, poor economic benefits and cannot meet the needs of special use. So how to make use of magnesium in the brine to produce high quality magnesium compounds is of great significance.Due to their wide range of uses, magnesium oxide and magnesium hydroxide are becoming hot spots in research. Especially, the output of magnesium oxide product and the amount of fine product are important indicators to measure a country’s national strength. And many industries demand for the products, such as national defense, aerospace, aviation, telecommunications and electronics.The products can also be used as raw materials or auxiliary materials of steel, metallurgy and building materials. Besides, magnesium oxide is also an important raw material in light industry, textiles, adhesives, paints and other field. Accordingly, magnesium hydroxide has a wide range of applications as an excellent flame retardant filled in co-polymer, such as antacids, flue gas desulphurization, environmental protection, and so on. What’s more, magnesium hydroxide can also serve as raw material for manufacturing other magnesium compounds. Because the crystal size distribution of magnesium oxide and magnesium hydroxide have large impact on their applications, the superfine and nano products are the major direction of future research.There are many methods for preparing superfine and nano magnesium hydroxide and magnesium oxide, but the precipitation method is the better one by considering the operation and costs. In this method, magnesium is the raw material, while NaOH, ammonia, lime or other alkaline substances is the precipitant. Ammonia is chosen as the precipitant in this paper, while the intermediates has poor filtration performance when NaOH is the precipitant, and there are many shortcomings when choose lime as precipitant, such as slow reaction rates, long reaction period and high impurity content.In order to improve the further utilization of brine,the magnesium hydroxide and heavy magnesium oxide are synthesised by brine and ammonia in this paper,and the feasibility and process conditions of preparing heavy magnesium oxide are discussed. The main purpose of this paper is as follows:1. Preparation of superfine magnesium hydroxide by brine and ammoniaSuperfine magnesium hydroxide is prepared by brine and ammonia via direct precipitation method with ultrasonic processing.The effect of ultrasonic processing on size distribution of the product is investigated. SEM,XRD and TG-DTA were used to characterize the structure morphology and thermal stability of the product. In addition, the influence of temperature, reaction time, ammonia concentration, concentration of reactants and aging time on the particle size and the yield of the product were discussed to obtain the optimum conditions for preparing superfine magnesium hydroxide. The results show that ultrasonic treatment tends to reduce the product size. And flake magnesium hydroxide can be obtained under optimal conditions, with good dispersibility and the thickness is about 70nm.2. Preparation of nano magnesium hydroxide by brine and ammoniaAs magnesium hydroxide is widely used as flame retardants, its morphology also have influence on the flame-retardant effect while results show that the effect is best when the morphology is Hexagonal. In this paper, flaky nanometer magnesium hydroxide is prepared by the hydrothermal method due to its advantages.Besides, urea, ethanol, PEG200 was added to the reaction as different additive, then the impact of the type and amount of additives on the size distribution, morphology and other properties of product was discussed.3. Preparation of heavy magnesium oxide by brine and ammoniaHeavy magnesium oxide is prepared by precipitation method with brine and ammonia in this paper.In order to obtain the optimum conditions for the preparation of heavy magnesium oxide, the material ratio of reactants, ammonia dropping rate, aging time, calcining temperature, heating rate and calcining time are discussed to explore the impact on the product bulk density, and the relationship between the bulk density and particle size distribution of the product is also analyzed. This paper provide a reference for developing industrial production processes of heavy magnesium oxide.