Magnesium dihydrogen phosphate is a common plastic stabilizer, flame retardant materials and pesticide intermediates, in many fields can play an indispensable role. And magnesium oxide is an important factor affecting the quality of magnesium dihydrogen phosphate, the following 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) and phosphoric acid neutralization to produce magnesium dihydrogen phosphate. Reaction equation is: MgO + H3PO4 + H2O → Mg (H2PO4) 2-2H2O in the neutralization reaction tank add phosphoric acid heated to 80-90 ℃, under constant stirring slowly add magnesium oxide (magnesium hydroxide or magnesium carbonate) for the reaction, when the PH ≈ 3 to stop adding materials, natural clarification or filter filtration, the clear liquid will be evaporated and concentrated to the emergence of the crystal seed, the slurry sent to cooling After crystallization, centrifugal separation, drying, packaging, that is, to obtain Mg (H2PO4)2-2H2O products.
Due to the high cost of magnesium oxide, some enterprises use magnesium hydroxide or magnesium carbonate for substitution as a neutralization reaction. The following provides a process for preparing magnesium dihydrogen phosphate using magnesium hydroxide as an example, comprising the following steps:
Taking the magnesium hydroxide filter cake formed in the process of lithium extraction from the brine of a salt lake as a raw material, removing impurities from said magnesium hydroxide filter cake in order to extract the magnesium hydroxide material in said magnesium hydroxide filter cake, the mass fraction of cl- in said magnesium hydroxide material being 0.001% or less; mixing said magnesium hydroxide material with the phosphoric acid solution in accordance with the ratio of the moles of magnesium hydroxide and phosphoric acid of 1:2, and reacting according to the reaction equation : Mg(OH)2+2H3PO4+H2O→Mg(H2PO4)2-2H2O undergoes a neutralization reaction to form a magnesium phosphate solution; said magnesium phosphate solution is subjected to a crystallization process to form a magnesium dihydrogen phosphate crystalline primary body, and said magnesium dihydrogen phosphate crystalline primary body is subjected to a separation process, a drying process, to produce magnesium dihydrogen phosphate crystals.
According to an embodiment of the present invention, decontaminating said magnesium hydroxide filter cake comprises the following steps:
Adding water to said magnesium hydroxide filter cake, stirring and mixing to form a first thick consistency; heating said first thick consistency to 40-50°C and then stirring said first thick consistency for 20-40min to form a second thick consistency; press-filtering said second thick consistency to form a second filter cake; and employing demineralized water to wash said second filter cake in order to form a third filter cake and to use it as a magnesium hydroxide material.
During the course of said neutralization reaction being carried out, the reaction temperature is controlled at 80 to 90°C. At the end of said neutralization reaction, the pH value of the magnesium phosphate solution formed is 3 to 3.5. the crystallization process is cooling crystallization, and the crystalline solution in said cooling crystallization is cooled to 25 to 35°C. The separation process is centrifugal separation. The drying process is airflow drying, and the drying temperature in said airflow drying is 50 to 55° C. and the pressure is less than 0.01 mpa. the mass fraction of water in the first thick mass is 60 to 80%.
Hebei Messi Biology Co., Ltd. states that magnesium dihydrogen phosphate of excellent quality can be prepared by the said process of preparing magnesium dihydrogen phosphate, which is suitable for use in medicine, industry and agriculture. The use of waste magnesium hydroxide filter cake from the production process of lithium extraction from brine in a salt lake as raw material not only solves the problem of burying the waste magnesium hydroxide filter cake in the process of lithium extraction from brine, but also effectively saves the cost of the preparation of magnesium dihydrogen phosphate crystals. At the same time, the preparation process of the provided magnesium dihydrogen phosphate is simple, low energy consumption, in line with the concept of green circular economy.