Magnesium dihydrogen phosphate is a common plastic stabilizer, flame retardant material and pesticide intermediate, and can play an indispensable role in many fields. Magnesium oxide is an important factor affecting the quality of magnesium dihydrogen phosphate. Hebei Messi Biology Co., Ltd. will take you to understand the application of magnesium oxide in magnesium dihydrogen phosphate.
Magnesium dihydrogen phosphate is generally produced by neutralization method, that is, magnesium oxide (magnesium hydroxide or magnesium carbonate) is neutralized with phosphoric acid to obtain magnesium dihydrogen phosphate. The reaction equation is: MgO+H3PO4+H2O→Mg(H2PO4)2·2H2O. Add phosphoric acid to the neutralization reaction tank and heat to 80-90℃. Slowly add magnesium oxide (magnesium hydroxide or magnesium carbonate) under constant stirring to react. When PH≈3, stop adding, clarify naturally or filter by filter. Evaporate and concentrate the clear liquid until crystal seeds appear. Send the slurry to cool and crystallize, centrifuge, dry and package to obtain Mg(H2PO4)2·2H2O product.
Due to the high cost of magnesium oxide, some companies use magnesium hydroxide or magnesium carbonate as a substitute for neutralization reaction. The following is a preparation process of magnesium dihydrogen phosphate using magnesium hydroxide as an example, including the following steps:
Use the magnesium hydroxide filter cake formed in the process of extracting lithium from salt lake brine as a raw material, remove impurities from the magnesium hydroxide filter cake to extract the magnesium hydroxide material in the magnesium hydroxide filter cake, and the mass fraction of cl- in the magnesium hydroxide material is less than 0.001%; mix the magnesium hydroxide material with phosphoric acid solution according to the molar ratio of magnesium hydroxide to phosphoric acid of 1:2, and neutralize according to the reaction equation: Mg(OH)2+2H3PO4+H2O→Mg(H2PO4)2·2H2O to form a magnesium phosphate solution; the magnesium phosphate solution is subjected to a crystallization process to form a magnesium dihydrogen phosphate crystal body, and the magnesium dihydrogen phosphate crystal body is subjected to a separation process and a drying process to obtain magnesium dihydrogen phosphate crystals.
According to one embodiment of the present invention, the impurity removal treatment of the magnesium hydroxide filter cake includes the following steps:
Add water to the magnesium hydroxide filter cake, stir and mix to form a first viscous substance; after heating the first viscous substance to 40-50°C, stir the first viscous substance for 20-40 minutes to form a second viscous substance; filter the second viscous substance to form a second filter cake; wash the second filter cake with desalted water to form a third filter cake and use it as a magnesium hydroxide material.
During the neutralization reaction, the reaction temperature is controlled to 80-90°C. At the end of the neutralization reaction, the pH value of the formed magnesium phosphate solution is 3-3.5. The crystallization process is cooling crystallization, and the crystal liquid in the cooling crystallization is cooled to 25-35°C. The separation process is centrifugal separation. The drying process is airflow drying, and the drying temperature in the airflow drying is 50-55°C and the pressure is less than 0.01mpa. The mass fraction of water in the first viscous substance is 60-80%.
Hebei Messi Biology Co., Ltd. stated that the preparation process of magnesium dihydrogen phosphate can produce high-quality magnesium dihydrogen phosphate, which is suitable for use in medicine, industry and agriculture. The waste magnesium hydroxide filter cake in the production process of lithium extraction from salt lake brine is used as a raw material, which not only solves the landfill problem of waste magnesium hydroxide filter cake in the brine lithium extraction process, but also effectively saves the preparation cost of magnesium dihydrogen phosphate crystals. At the same time, the preparation process of magnesium dihydrogen phosphate provided is simple and energy-saving, which conforms to the concept of green circular economy.