Nanoplatelet forms of metal hydroxide and metal oxide are provided, as well as methods for preparing same. The nanoplatelets are suitable for use as fire retardants and as agents for chemical or biological decontamination.

Nanoplatelet forms of metal hydroxide and metal oxide are provided, as well as methods for preparing same. The nanoplatelets are suitable for use as fire retardants and as agents for chemical or biological decontamination.

Nanoplatelet forms of metal hydroxide and metal oxide are provided, as well as methods for preparing same. The nanoplatelets are suitable for use as fire retardants and as agents for chemical or biological decontamination.

A treatment method for a magnesium slag, comprises: Step a, producing magnesium particles and a crude solution of magnesium slag by digesting and sifting a magnesium slag; Step b, filtering the crude solution of magnesium slag sifted in Step a, so that mixed chlorides are obtained after a moisture in a filtrate is removed; Step c, obtaining a high purity magnesium oxide by dissolving a filter residue obtained in Step b via an ammonium sulfate method and a magnesium precipitation reaction as well as post-treatment. With the method, utilization of magnesium slag can reach up to more than 90% with a higher recycling rate, while the discharge of solid wastes can be reduced greatly which solid wastes are less contaminative to the environment, so that the contamination to the environment is greatly reduced and the required energy saving and emission reduction are also achieved.

The invention relates to chemical technology for producing high-purity magnesium oxide used in the pharmaceutical, cosmetic, and food industries, in the production of ceramics, glasses, optical materials, electronic materials, catalysts, polymer materials, transformer steel.

High-purity magnesium oxide having a specific surface area, determined by the BET method, in the range from 5 to 70 m.sup.2/g, an average particle size (d50), determined by laser diffraction, of not more than 5 m, characterized in that it has a mass fraction of impurity elements of each of Pb, Cd, As, Hg of not more than 0.1 ppm, a mass fraction of impurity elements of each of Ba, Zn, Ti, Mn, Co, Mo, V, Sb, Sr of not more than 1 ppm, a mass fraction of impurity elements of each of Al, F of not more than 5 ppm, a mass fraction of impurity elements of each of P, Cr, Ni, K, Li of not more than 10 ppm, a mass fraction of Fe of not more than 50 ppm, a mass fraction of Si of not more than 0.01%, a mass fraction of impurity elements of each of Ca, B of not more than 0.02%, a mass fraction of sulphates SO.sub.4.sup.2k of not more than 0.02%, a mass fraction of Na impurity of not more than 0.05%, a mass fraction of chloride impurity of not more than 0.05% and includes primary particles and agglomerates consisting of primary particles.

High-purity magnesium oxide is obtained by calcination of magnesium hydroxide obtained by reacting a purified concentrated aqueous solution of magnesium chloride with an aqueous solution of sodium hydroxide in a continuous manner at a temperature of 40-90 C., stirring at a speed of 20-300 rpm at a molar ratio of OH.sup.:Mg.sup.++ ions within the range (1.92.1):1 with the continuous supply of a suspension of magnesium hydroxide seed crystals into the reaction mass in an amount of 5-200% of the total mass of the supplied initial reagents, and the magnesium hydroxide seed crystals are pre-treated with a concentrated aqueous solution of magnesium chloride, after interaction of the reagents, a suspension of magnesium hydroxide is sent for aging at a temperature of 40-90 C., then hydrothermal crystallization of magnesium hydroxide particles is carried out in the presence of dihydric alcohol: ethylene glycol or propylene glycol, at a temperature in the range from 120 to 220 C., pressure in the range from 0.1 to 2.3 MPa, and a duration ranging from 1 to 10 hours, the resulting suspension of magnesium hydroxide is filtered, washed, and calcination of magnesium hydroxide is carried out at a temperature of 700-1100 C.

The obtained high-purity magnesium oxide has high chemical purity, adjustable specific surface area, pore volume and pore size distribution, par

The invention relates to chemical technology for producing high-purity magnesium oxide used in the pharmaceutical, cosmetic, and food industries, in the production of ceramics, glasses, optical materials, electronic materials, catalysts, polymer materials, transformer steel.

High-purity magnesium oxide having a specific surface area, determined by the BET method, in the range from 5 to 70 m.sup.2/g, an average particle size (d50), determined by laser diffraction, of not more than 5 m, characterized in that it has a mass fraction of impurity elements of each of Pb, Cd, As, Hg of not more than 0.1 ppm, a mass fraction of impurity elements of each of Ba, Zn, Ti, Mn, Co, Mo, V, Sb, Sr of not more than 1 ppm, a mass fraction of impurity elements of each of Al, F of not more than 5 ppm, a mass fraction of impurity elements of each of P, Cr, Ni, K, Li of not more than 10 ppm, a mass fraction of Fe of not more than 50 ppm, a mass fraction of Si of not more than 0.01%, a mass fraction of impurity elements of each of Ca, B of not more than 0.02%, a mass fraction of sulphates SO.sub.4.sup.2k of not more than 0.02%, a mass fraction of Na impurity of not more than 0.05%, a mass fraction of chloride impurity of not more than 0.05% and includes primary particles and agglomerates consisting of primary particles.

High-purity magnesium oxide is obtained by calcination of magnesium hydroxide obtained by reacting a purified concentrated aqueous solution of magnesium chloride with an aqueous solution of sodium hydroxide in a continuous manner at a temperature of 40-90 C., stirring at a speed of 20-300 rpm at a molar ratio of OH.sup.:Mg.sup.++ ions within the range (1.92.1):1 with the continuous supply of a suspension of magnesium hydroxide seed crystals into the reaction mass in an amount of 5-200% of the total mass of the supplied initial reagents, and the magnesium hydroxide seed crystals are pre-treated with a concentrated aqueous solution of magnesium chloride, after interaction of the reagents, a suspension of magnesium hydroxide is sent for aging at a temperature of 40-90 C., then hydrothermal crystallization of magnesium hydroxide particles is carried out in the presence of dihydric alcohol: ethylene glycol or propylene glycol, at a temperature in the range from 120 to 220 C., pressure in the range from 0.1 to 2.3 MPa, and a duration ranging from 1 to 10 hours, the resulting suspension of magnesium hydroxide is filtered, washed, and calcination of magnesium hydroxide is carried out at a temperature of 700-1100 C.

The obtained high-purity magnesium oxide has high chemical purity, adjustable specific surface area, pore volume and pore size distribution, par

There is provided a magnesium oxide powder, where D.sub.50 is 10 m or less, D.sub.50 being a particle size at which a cumulative size based on a volume-based cumulative particle size distribution curve by sieving test is 50%, a ratio D.sub.90/D.sub.10 is 10 or less, D.sub.90 and D.sub.10 being particle sizes at which cumulative sizes based on the volume-based cumulative particle size distribution curve by sieving test are 90% and 10%, respectively, and a citric acid activity is in a range of 500 seconds or more and 2,500 seconds or less.

There is provided a magnesium oxide powder, where D.sub.50 is 10 m or less, D.sub.50 being a particle size at which a cumulative size based on a volume-based cumulative particle size distribution curve by sieving test is 50%, a ratio D.sub.90/D.sub.10 is 10 or less, D.sub.90 and D.sub.10 being particle sizes at which cumulative sizes based on the volume-based cumulative particle size distribution curve by sieving test are 90% and 10%, respectively, and a citric acid activity is in a range of 500 seconds or more and 2,500 seconds or less.

The invention provides a method of producing an annealing separator, an annealing separator and a grain-oriented magnetic steel. An annealing separator obtained by the method has high purity and excellent dispersibility and bonding strength, thus allowing formation of a uniform, dense forsterite layer on the surface of a grain-oriented magnetic steel. The method of producing an annealing separator comprises the following steps: step (1) in which magnesium oxide and an ammonium salt solution are mixed and reacted to prepare a magnesium salt solution and ammonia, and then the purified magnesium salt solution and the ammonia are reacted to obtain magnesium hydroxide, step (2) in which one portion of the obtained magnesium hydroxide is subjected to high temperature ageing at 155 to 230 C. while another portion of the obtained magnesium hydroxide is subjected to low temperature ageing at 10 to 100 C., and step (3) in which the magnesium hydroxides aged under the different conditions are mixed and burned to obtain magnesium oxide for use as an annealing separator.

The invention provides a method of producing an annealing separator, an annealing separator and a grain-oriented magnetic steel. An annealing separator obtained by the method has high purity and excellent dispersibility and bonding strength, thus allowing formation of a uniform, dense forsterite layer on the surface of a grain-oriented magnetic steel. The method of producing an annealing separator comprises the following steps: step (1) in which magnesium oxide and an ammonium salt solution are mixed and reacted to prepare a magnesium salt solution and ammonia, and then the purified magnesium salt solution and the ammonia are reacted to obtain magnesium hydroxide, step (2) in which one portion of the obtained magnesium hydroxide is subjected to high temperature ageing at 155 to 230 C. while another portion of the obtained magnesium hydroxide is subjected to low temperature ageing at 10 to 100 C., and step (3) in which the magnesium hydroxides aged under the different conditions are mixed and burned to obtain magnesium oxide for use as an annealing separator.