Hebei Messi Biology Co., Ltd. stated that magnesium carbonate is a white odorless powder with two common forms: amorphous powder and monoclinic crystal. Due to its special structure and properties, magnesium carbonate is widely used in medicine, cosmetics, rubber industry, printing industry and other fields. Industrial-grade magnesium carbonate can be used as an excellent filler and reinforcing agent for rubber products, and can also be used for heat-insulating and high-temperature fireproof insulation materials. Pharmacopoeia-grade magnesium carbonate can be used as an additive for beverages and daily chemical products and a gastric acid neutralization inhibitor. An appropriate amount of additives is added to the magnesium bicarbonate solution, and magnesium carbonate whiskers of different specifications are obtained by controlling the conditions for the crystallization of magnesium carbonate. There is no literature report on spherical and radial magnesium carbonate and its preparation method.
The purpose of the present invention is to provide a preparation method for spherical and radial magnesium carbonate. The process uses soluble magnesium salt and soluble carbonate as raw materials, and surfactant as additive. In an aqueous solution system, the reaction temperature is controlled between 15 and 75°C, and the reaction is carried out under stirring for 2 to 20 minutes. After the reaction is completed, the precipitate is left to stand for 1 to 6 days, washed and dried to obtain spherical and radial magnesium carbonate products.
When preparing magnesium carbonate, the soluble magnesium salt, soluble carbonate and surfactant are first prepared into aqueous solutions with concentrations of 0.5 mol/L to 1.5 mol/L, 0.5 mol/L to 2 mol/L and 2 mmol/L to 2 mol/L, respectively. Then, the soluble magnesium salt solution, the soluble carbonate solution and the aqueous solution of the surfactant are mixed and reacted under stirring. When the surfactant is a polymer, an aqueous solution with a concentration of 1 to 5 g/L is prepared. The amount of the soluble magnesium salt and the soluble carbonate is controlled between 1:2 and 1:0.5, and the concentration of the surfactant in the entire reaction system is 2 mmol/L to 0.5 mol/L. When the surfactant is a polymer, the concentration of the surfactant in the entire reaction system is between 0.1 and 1 mg/L.
There are two ways to mix the soluble magnesium salt solution, the soluble carbonate solution, and the aqueous solution of the surfactant: first mix the soluble magnesium salt solution and the solution of the surfactant, then add them to the reactor simultaneously with the soluble carbonate solution, and react under stirring; or add the soluble magnesium salt solution and the soluble carbonate solution to the aqueous solution of the surfactant at the same time, and react under stirring. After the reaction is completed, the precipitate is allowed to stand for 1 to 6 days, and then a combination of re-pulping and rinsing is adopted: first re-pulping and washing 1 to 3 times, then rinsing with distilled water until no chloride is detected in the washed water, and then rinsing with ethanol; finally drying at 15 to 75°C. The soluble magnesium salt used in the present invention is magnesium chloride, magnesium sulfate, magnesium nitrate or magnesium acetate; the soluble carbonate used is sodium carbonate, ammonium carbonate or potassium carbonate.
The morphology of magnesium carbonate can be controlled by changing the type and amount of surfactant and the stirring speed of the reaction solution: when the surfactant is any one of sodium tartrate, sodium alginate, sodium silicate, SrCl2, CaCl2, MnCl2, and LiCl, and the reaction stirring speed is controlled at 100 to 600 rpm, the obtained magnesium carbonate product is spherical.
When the surfactant is any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, hexadecyl trimethyl ammonium bromide, potassium hydrogen phthalate, sodium tartrate, sucrose, glucose, β-cyclodextrin, soluble starch, sodium citrate, polyacrylamide, glycerol, polyethylene glycol, ethanol, flocculant 1010f, and flocculant 1019s, and the reaction stirring speed is controlled at 500 to 900 rpm, the obtained magnesium carbonate product is radial.
The spherical and radial magnesium carbonate products prepared by the present invention have a chemical formula of MgCO3·XH2O, wherein x=2-5, and a purity of 95-99.9%, according to XRD analysis and chemical analysis. The appearance is fine sand-like, and the filtering performance is significantly better than that of ordinary magnesium carbonate, thereby improving the problem that ordinary magnesium carbonate is filtered slowly due to excessively fine particles. The product can be used as an additive in industries such as plastics, rubber, and papermaking, and can also be used as an intermediate raw material for preparing high-purity magnesium oxide and other magnesium products.