318results about "Magnesium hydroxide" patented technology

The invention belongs to the technical field of synthesis of magnesium hydroxide flame retardants, and provides a synthesis method and flame-retardant application of hexagonal flaky magnesium hydroxide, and the synthesis method comprises the following steps: step 1, dissolving a mineralizer, a crystal form control agent and magnesium chloride in water in proportion; step 2, putting a certain amount of the mixed solution into a high-pressure reaction kettle for hydrothermal reaction; step 3, after the reaction is finished, taking out the cooled solution from the high-pressure reaction kettle, and filtering and separating out a white product; 4, drying the sample, and grinding to obtain pure magnesium hydroxide powder; through reasonable process design and optimization, the prepared magnesium hydroxide not only has regular morphology and better dispersity, but also has excellent performance in the field of flame retardance of high polymer materials, meets the requirement of environmental protection, has the production advantages of low cost and high efficiency, and is suitable for industrial production. The method not only can effectively improve the overall utilization rate of salt lake resources, but also has remarkable economic and application values, and has wide industrial application prospects.

The invention relates to a method for recovering metal cations from wet-process phosphoric acid, and belongs to the technical field of wet-process phosphoric acid. The technical problem to be solved by the invention is to provide a method for recovering metal cations from wet-process phosphoric acid. The method comprises the steps of extraction, washing 1, reverse extraction, metal ion recovery, washing 2 and the like. The specific reverse extraction method is adopted, the metal cations are recovered from the wet-process phosphoric acid, various metal ions can be effectively separated, the recovery rate of all metal elements is high, and the product value is high. And the associated metal elements in the wet-process phosphoric acid can be classified and recycled by adopting one stripping agent, the method is simple and low in cost, and the recycled associated metal elements can be effectively separated and utilized in a high-quality mode.

The invention relates to a method for preparing hexagonal flaky magnesium hydroxide through a hydration modification one-step method, and belongs to the technical field of inorganic material preparation. Hyperbranched sodium polyacrylate containing phosphonic acid and ammonium phosphonate salt is synthesized and serves as a crystal forming agent for magnesium hydroxide crystal growth, the hyperbranched sodium polyacrylate can coordinate with magnesium ions, uniform growth of all crystal faces of the magnesium hydroxide crystal is promoted, and the magnesium hydroxide crystal growth rate is increased. And the hyperbranched structure can better and moderately wrap the formed magnesium hydroxide crystal, so that the uniform growth property of the crystal face is improved. In addition, ammonium phosphate groups and carboxylate in the crystal forming agent have good wetting dispersity, agglomeration of magnesium hydroxide crystals is weakened, and the particle size distribution uniformity is improved. According to the method, the magnesium oxide powder and the crystal forming agent are ground and then subjected to the hydration reaction, the hexagonal flaky magnesium hydroxide is synthesized through a one-step method, and the prepared magnesium hydroxide is in a regular hexagonal flaky shape, has uniform particle size distribution, and has relatively high purity and relatively low impurity content.

The invention discloses a crosslinked polyethylene low-smoke halogen-free flame-retardant power cable which comprises the following hierarchical structures: a conductor layer; an insulating layer; a shielding layer; the shielding layer takes polyethylene as a matrix and comprises the following components in parts by weight: 70-78 parts of matrix, 20-25 parts of carbon black and 2-5 parts of nano montmorillonite modified lignin, the thickness of the shielding layer is 0.8-1.2 mm, the shielding layer and the insulating layer are molded through a co-extrusion process, and the interface gap is less than or equal to 0.1 mm. The nano montmorillonite modified lignin is adopted as a core flame retardant, the addition amount is reduced by 10%-15% compared with that of a traditional halogen-free flame retardant, by taking a 120 mm civil cable as an example, 18 parts of modified lignin replace 25 parts of a traditional flame retardant with the same flame retardant effect, the raw material cost is reduced by 8%-12%, lignin is derived from agricultural and forestry wastes, dependence on a petroleum-based material is reduced, and the environment-friendly flame-retardant cable material is suitable for industrial production. The gradient cooling process shortens the cooling time by 20%-30% compared with the traditional single-section cold water cooling process, and meanwhile, the pre-crosslinking process reduces the subsequent forming internal stress and reduces the rejection rate.

The invention belongs to the technical field of inorganic flame retardants, and discloses a nano hexagonal flaky magnesium hydroxide flame retardant and a preparation method thereof. Comprising the following steps: respectively preparing a soluble magnesium salt solution and a precipitant aqueous solution, respectively carrying out preheating treatment, respectively and continuously conveying and mixing to obtain a mixed solution, carrying out ultrasonic treatment and reaction to obtain magnesium hydroxide nano slurry, and carrying out ultrasonic dispersion, filtration and drying to obtain the nano hexagonal flaky magnesium hydroxide. Controllable preparation of the nanoscale hexagonal magnesium hydroxide flame retardant is achieved for the first time, compared with an ultrasonic intermittent method, the nanoscale hexagonal magnesium hydroxide flame retardant has the advantages of being short in reaction period, high in reaction efficiency and uniform in reactant mixing, the preparation period is remarkably shortened to 3 hours, particle size distribution is optimized to be narrow amplitude, PDI is 0.300-0.999, generated magnesium hydroxide particles are in a regular nanometer hexagonal sheet shape, the particle size distribution is optimized to be small, and the particle size distribution is uniform. The dispersity and compatibility of the polymer in a polymer matrix are greatly improved, and excellent cost benefits and market competitiveness are shown in industrial production.

The invention relates to the technical field of flame retardants, in particular to a magnesium hydroxide flame retardant suitable for a high-speed extrusion cable and a preparation method of the magnesium hydroxide flame retardant. According to the preparation method, magnesium hydroxide is induced to form a flaky crystal structure with a high radius-thickness ratio through the synergistic effect of polypropylene carbonate and tetrabutylammonium bromide, and multi-scale regulation and control of particle morphology and interface characteristics are realized in combination with surface modification of sodium stearate. The flame retardant shows excellent dispersion stability and interfacial compatibility in high-speed extrusion processing, and solves the problems of poor processing suitability and insufficient flame retardant efficiency caused by non-uniform dispersion and friction heat accumulation of the traditional magnesium hydroxide flame retardant.

The invention relates to the technical field of hydrometallurgy, in particular to a method for selectively separating calcium sulfate in a complex reaction system. The method comprises the following steps: adding a soluble sulfate solution and a precipitant solution into a base solution in a parallel flow manner, and reacting to obtain mixed slurry containing fibrous calcium sulfate; and separating the mixed slurry containing fibrous calcium sulfate to obtain fibrous calcium sulfate crystals, metal hydroxides and purified liquid. According to the method, on the basis of wastewater treatment through a traditional precipitation method, fibrous calcium sulfate is separated from other substances in a complex system by controlling growth of calcium sulfate crystals, the environmental influence caused by solid waste is reduced while the industrial wastewater containing sulfate radicals is treated at low cost, and finally resourceful treatment of the industrial wastewater is achieved.

A method of photocatalytic degradation includes contacting a nanocomposite with a solution including one or more pollutants. The nanocomposite is a graphite-phase carbon nitride copper oxide and magnesium aluminum oxide (g-C3N4@CuO / MgAl2O4) material and includes a graphite-phase carbon nitride (g-C3N4) in an amount of 2 to 20 percent by weight (wt. %), copper oxide in an amount of 1 to 10 wt. %, and magnesium aluminum oxide (MgAl2O4) in an amount of 75 to 95 wt. % based on a total weight of the g-C3N4@CuO / MgAl2O4 material. The method further includes irradiating the nanocomposite with light having a wavelength of 400 to 800 nm in the absence of UV light to photocatalytically degrade the one or more pollutants in the solution.

The invention belongs to the technical field of inorganic chemical material preparation, and discloses a high-selectivity crystallization and impurity migration inhibition method of high-purity magnesium hydroxide. The method comprises the following steps: a phenylphosphonic acid surface modifier is introduced in the initial stage of crystallization, molecules of the phenylphosphonic acid surface modifier selectively occupy high-activity Mg < 2 + > sites of a magnesium hydroxide crystal face through bidentate coordination, and a molecular-level interface barrier with steric hindrance and electrostatic repulsion effects is formed, so that a Ca < 2 + > migration path is specifically blocked, and Mg < 2 + > crystallization is not influenced. The preparation method of the high-purity magnesium hydroxide is high in selectivity, high in efficiency, low in cost and environmentally friendly, the interface adsorption behavior of calcium ions is accurately intervened in the initial stage of crystallization through a molecular level surface engineering means, the technical bottleneck that impurity migration and lattice doping are difficult to control in a traditional process is fundamentally solved, and the preparation method is suitable for industrial production. And a brand new technical path is provided for green manufacturing of high-performance inorganic functional materials.

The invention relates to the technical field of inorganic material synthesis, in particular to a preparation method of a controlled-release magnesium hydroxide fertilizer. Comprising the steps of primary magnesium precipitation, hydrothermal treatment, secondary magnesium precipitation, anaerobic heat treatment and pulping. According to the method, firstly, crystal defects are eliminated through hydro-thermal treatment, crystal seeds with complete crystallinity are obtained, then the crystal seeds are added into a magnesium precipitation reaction system, the principle of Gibbs free energy minimization is followed, newly generated magnesium hydroxide tends to precipitate on the surfaces of the crystal seeds, under the interference effect of a crystal form regulator, the newly generated magnesium hydroxide crystal has many defects, and the magnesium precipitation effect is good. And then oxygen-free heat treatment is carried out, so that the defects of the magnesium hydroxide on the surface layer are further increased, and the initial dissolution and release capacity is improved. The controlled-release magnesium fertilizer which is high in early-stage release speed and long-acting in later-stage slow release is synthesized by utilizing a crystal defect engineering tool, and is different from a traditional coating scheme, and a brand new thought is provided for the design of the controlled-release fertilizer.

The invention relates to micron-sized hexagonal flaky magnesium hydroxide with controllable particle size by using sodium hydroxide and bittern as raw materials and a preparation method thereof, belonging to the technical field of inorganic material preparation. The preparation method of the granularity-controllable micron-sized hexagonal flaky magnesium hydroxide with sodium hydroxide and bittern as raw materials comprises the following three steps: preparation of a magnesium hydroxide precursor, hydrothermal synthesis and post-treatment. According to the micron-sized hexagonal flaky magnesium hydroxide which takes sodium hydroxide and bittern as raw materials and is controllable in particle size, the particle size distribution tested by a laser particle analyzer is as follows: D10 is 0.96-1.18 mu m, D50 is 1.83-2.13 mu m, and D90 is 3.85-4.44 mu m.

A CO2 capture process comprising: -Hydrating quicklime materials (16) and / or quick dolomitic lime materials (16') to produce hydrated materials (17); - Transferring at least a portion of the heat generated during the hydration to at least one energy distribution unit (20); - Controlling at least one secondary working medium flow (52.1, 52.2, 52.3) and / or at least one secondary electric power flow (62) between at least one energy distribution unit (20) and at least one energy utilization unit (30.1, 30.2, 30.3, 30.4); -Capturing at least some CO2 from at least one stream containing CO2 (71, 71*) to reduce the CO2 content in said stream, in at least one CO2 treatment unit (35.1, 35.2, 35.3).

The invention relates to the field of preparation of battery materials and precursors of the battery materials, and discloses a method for efficiently preparing battery-grade manganous-manganic oxide by using electrolytic manganese residue leachate and a harmless treatment method for tail liquid of the battery-grade manganous-manganic oxide. Treating the manganese residue leachate concentrated water obtained in the previous step with ammonia water and oxygen to prepare battery-grade manganous-manganic oxide; adjusting the pH value of the filtrate obtained in the previous step to prepare magnesium hydroxide; the filtrate obtained in the previous step is subjected to evaporative crystallization, ammonium sulfate is prepared, finally, harmless treatment of preparation of battery-grade manganous-manganic oxide from the manganese residue leachate and the tail liquid of the battery-grade manganous-manganic oxide is achieved, and the recovery efficiency of valuable components is greatly improved.

The application discloses a preparation method of low-chlorine magnesium oxide. The method comprises the following steps: adding high-chlorine magnesium hydroxide slurry into an electrolytic cell, adding an anode liquid into an anode chamber, adding a cathode liquid into a cathode chamber, and adding a reinforcing agent into the high-chlorine magnesium hydroxide slurry. A direct current electric field is applied between the anode and the cathode by using a pulse power source to remove chlorine. Under the action of the electric field, the negative-charged chlorine ions move to the anode chamber by electromigration, and the chlorine moves to the cathode chamber by electrodialysis in the form of chlorides or other soluble ions, so as to reduce the concentration of the chlorine ions in the high-chlorine magnesium hydroxide slurry. After the chlorine is removed, the magnesium hydroxide is filtered and calcined to obtain the low-chlorine magnesium oxide. The method has the advantages that the high-energy-consumption processes such as ball milling and calcining in the traditional chlorine removal process of magnesium hydroxide are avoided, the harm of the chlorine ions to the equipment is reduced, the chlorine ions in the magnesium hydroxide are removed only by electromigration and electrodialysis, and the green and efficient preparation of the low-chlorine magnesium oxide is realized.

The invention provides an electrochemical method for removing magnesium and extracting lithium from salt lake brine, which comprises the following steps: feeding the salt lake brine into a single-chamber electrolysis chamber, and carrying out electrolytic reaction in the single-chamber electrolysis chamber; the anolyte after electrolysis is sent out from the single-chamber electrolysis chamber and collected, and the collected anolyte is sent into the single-chamber electrolysis chamber again to participate in the electrolytic reaction; the electrolyzed catholyte is sent out from the single-chamber electrolysis chamber and filtered, hydroxyl ions in the electrolyzed catholyte react with magnesium ions in the salt lake brine to generate magnesium hydroxide precipitates, and the filtered lithium-ion-rich salt lake brine is evaporated and concentrated to obtain a lithium-ion-rich brine concentrated solution; sodium carbonate is added into the lithium-rich brine concentrated solution for a lithium precipitation reaction, lithium carbonate precipitates are obtained, and lithium carbonate is obtained after the lithium carbonate precipitates are centrifuged, washed and dried. The invention further provides a magnesium and lithium separation system of the electrochemical salt lake brine magnesium removal and lithium extraction method. The method realizes efficient separation of lithium and magnesium in the salt lake brine and extraction of lithium.

The invention provides a method for preparing magnesium hydroxide from chlorine-alkalized brine, which comprises the following steps: taking a sodium hydroxide solution as a precipitator, enabling small-particle magnesium hydroxide as a seed crystal to participate in crystallization reaction of magnesium-containing crude brine again, increasing the particle size of magnesium hydroxide particles, and enabling a small part of large-particle magnesium hydroxide to return to a reaction mixer; according to the method disclosed by the invention, no auxiliaries or flocculants are added, under the condition that the concentration of magnesium ions in the raw material of the crude brine is extremely low, magnesium hydroxide particles with relatively large agglomerated particles are continuously generated, and the production cost of a brine refining process is effectively reduced; the particle size of magnesium hydroxide particles is increased from 1-5 microns to 15-20 microns, the sedimentation rate of the particles in a solution is greatly improved, the technical problem that magnesium hydroxide is difficult to settle in a chlor-alkali production system is fundamentally solved, and the moisture content of salty mud is reduced from about 50% to 35%-40%.

The invention belongs to the technical field of water treatment brine reuse, and provides an electrochemistry-based brine calcium and magnesium graded extraction process, which comprises the following steps: brine enters a primary electrolysis device for electrochemical reaction, carbon dioxide is introduced, and calcium ions in the brine are precipitated; further entering a primary precipitation separation device, and intercepting and collecting precipitated calcium; then the brine enters a secondary electrolysis device, the density of current applied to an electrode is increased, and magnesium ions in the brine are precipitated; the solution enters a secondary precipitation separation device, and precipitated magnesium is intercepted and recycled; drying the separated calcium and magnesium precipitates to obtain a product; and finally, introducing the reacted effluent into an ion exchange resin chromatographic column to remove untreated calcium and magnesium ions, and applying the obtained hardness-free alkaline water to the hydrogen production industry. By regulating the current density and introducing CO2, calcium and magnesium in various kinds of saline water are respectively precipitated and extracted, and the device is suitable for salt-containing organic wastewater, seawater, seawater desalination concentrated solution, bitter brine and industrial circulating cooling water.

The invention relates to micron-sized hexagonal flaky magnesium hydroxide with bittern as a raw material and a preparation method of the micron-sized hexagonal flaky magnesium hydroxide, and belongs to the technical field of inorganic material preparation, and the preparation method of the micron-sized hexagonal flaky magnesium hydroxide with bittern as the raw material comprises three steps of preparation of a magnesium hydroxide precursor, hydro-thermal synthesis and post-treatment. According to the micron-sized hexagonal flaky magnesium hydroxide prepared by taking the bittern as the raw material, the particle size distribution tested by a laser particle size analyzer is as follows: D10 is 0.71-0.85 mu m, D50 is 1.28-1.47 mu m, and D90 is 3.26-3.65 mu m.

The utility model discloses an ammonia-ammonium chloride catalysis system for decarburization of steel slag solid waste and flue gas, and belongs to the technical field of ferrous metallurgy. The ammonia-ammonium chloride catalysis system for steel slag solid waste and flue gas decarburization comprises a steel slag dissolving tank, an ammonia gas condensation cooler and a decarburization tower which are sequentially connected, the top of the decarburization tower is sequentially connected with an ammonia recovery system, an impurity filtering system and a calcium carbonate extraction system, and the bottom of the decarburization tower is connected with the calcium carbonate extraction system. The calcium carbonate extraction system is connected with the steel slag dissolving tank, and the steel slag dissolving tank is communicated with the ammonia recovery system. According to the technical scheme, the purpose of carbon capture and high-added-value resource reutilization of the steel slag are achieved.

The present disclosure relates to a brine purification device, its purification method and uses thereof. It is disclosed a brine purification device comprising a housing with an inlet configured to receive untreated brine and an outlet configured to discharge purified brine from a purification chamber; wherein the purification chamber within said housing is configured to have two separated hemispheres; wherein the at least one plate comprises a first engraved serpentine flow channel in a first side configured for the flowing of brine and a second engraved serpentine flow channel in the opposite side of the same plate configured for the flowing of a flowing fluid; wherein the two sides of the at least one plate are separated by an anion-exchange membrane in such a way that the untreated brine combine with counter-ions from the flowing fluid through said anion-exchange membrane; wherein the at least one plate is configured for a fluid velocity of 0.007 to 0.015 m / s considering a thickness of 3 to 6 mm.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

The objective of the present invention is to provide a method for producing a core-shell particle without requiring the synthesis of a core particle and the adjustment of the electric charge of the surface of the core particle, and to provide a method for producing a hollow particle without requiring thermal energy in a hollowing step of the core-shell particles. The method for producing the core-shell particle according to the present invention includes a step for forming a shell by directly fluorinating the surface layer of a core particle consisting of a magnesium inorganic salt. Next, the method for producing a hollow particle of a fluoride includes a step for removing only the core particle with an acid from the core-shell particle obtained by the above-mentioned producing method.

The invention relates to an extraction agent and an extraction method, and relates to the technical field of wet extraction of industrial solid waste, and the extraction agent comprises the following components in parts by mass: an extraction main agent, an anti-impurity stabilizer and an extraction aid; the extraction main agent comprises di (2-ethylhexyl) phosphate and mono (2-ethylhexyl) phosphate, the impurity-resistant stabilizer comprises an imidazoline derivative, a triazine derivative and dimethyl methylphosphonate, and the extraction assistant comprises isooctyl alcohol; the extraction method comprises the steps of ash ball preparation, impurity removal, extraction and the like. According to the extraction agent and the extraction method, interference impurities such as trace heavy metal ions, sulfides and cyanides generated due to component fluctuation in the purified ash of the calcium carbide furnace are selectively chelated, the impurities are prevented from being combined with the extraction main agent, and then the anti-interference stability of the extraction agent under the condition that the impurity content of the purified ash of the calcium carbide furnace fluctuates is improved; and the control difficulty in the production process is reduced.

This magnesium oxide powder contains secondary particles in which a plurality of primary particles of magnesium oxide having a crystal phase and a grain boundary phase are at least partially fused together by the grain boundary phase, and a median diameter obtained by a laser diffraction scattering method is 300 µm or less.

To provide a method for producing particles of magnesium hydroxide by which the particles of the magnesium hydroxide can simply be grown by using a magnesium hydroxide material containing a prescribed amount of silicon.SOLUTION: The present disclosure relates to a process for producing particles of magnesium hydroxide. The manufacturing method according to the first disclosure includes a mixture forming step. In the mixture formation step, a mixture is formed by mixing a magnesium hydroxide material containing 100ppm or more and a slurry containing a seed crystal of magnesium hydroxide. The production method according to the first disclosure includes an aging method. In the aging method, the mixture is aged to grow the seed crystals and form particles of the magnesium hydroxide having a larger particle size than the seed crystals.SELECTED DRAWING: None

Disclosed herein are acid-base leaching methods and systems. Specifically, the systems and methods can include reacting a feed material comprising at least two metals selected from the group consisting of iron, magnesium, and calcium with a weak acid to produce a first leachate comprising ions of the at least two metals and an insoluble product; reacting the first leachate with a base to produce a first solid product comprising a first metal and a second leachate comprising ions of a second metal different from the first metal; and reacting the second leachate with the base to produce a second solid product comprising the second metal and a third leachate.

A method of making a material for capturing carbon dioxide from the earth's atmosphere, comprises producing an acid and a base with an electrochemical acid-base generator; dissolving a mineral in the acid to produce a mineral rich solution, separating silica from the mineral rich solution to form a silica depleted solution; adding a first portion of the base to the silica depleted solution to remove impurities by precipitation, adding a second portion of the base until ferrous hydroxide (Fe(OH)2) precipitates, then pausing base addition and removing the ferrous hydroxide precipitate from the solution. Then adding a third portion of the base to the iron-depleted solution to precipitate magnesium hydroxide (Mg(OH)2) and / or calcium hydroxide (Ca(OH)2). Then recovering a salt solution and directing the recovered salt solution to the electrochemical acid-base generator to produce a new acid and a new base. The magnesium hydroxide and / or calcium hydroxide may be used to capture and sequester carbon dioxide from a CO2-containing gas (e.g., air) by forming a carbonate or from the ocean by forming bicarbonate.

The present invention relates to a method for recovering valuable materials from waste. The method for recovering valuable materials from waste comprises the steps of: (a) pulverizing waste, which is generated from an evaporator or a crystallizer among equipment of a zero liquid discharge process for desulfurization wastewater, and then injecting same into a dissolution tank so as to dissolve same in a solvent and separating same into a gypsum (CaSO4) precipitate and a supernatant from which the gypsum has been removed; (b) dissolving, in a desulfurization tank, barium chloride (BaCl2) in the supernatant from which the gypsum has been removed, and separating same into a barium sulfate (BaSO4) precipitate and a supernatant from which the barium sulfate has been removed; (c) dissolving, in a hydroxide tank, sodium hydroxide (NaOH) in the supernatant from which the barium sulfate has been removed, and separating same into a magnesium hydroxide (Mg(OH)2 precipitate and a supernatant from which the magnesium hydroxide has been removed; and (d) injecting, into a salt pond, the supernatant from which the magnesium hydroxide has been removed, so as to recover sodium chloride (NaOH).

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 m2 / g, an average particle size (d50), determined by laser diffraction, of not more than 5 μm, 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 SO42−k 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−:Mg++ ions within the range (1.9÷2.1):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, particle size distribution and activity.

A process for recovering titanium dioxide from a titanium-bearing material, the process including the steps of: leaching the titanium-bearing material in a first leaching step at atmospheric pressure and at a temperature of 70 to 97° C. with a first lixiviant to produce a first leach solution comprising undissolved first leach solids that include a titanium content and a first leach liquor, the first lixiviant comprising hydrochloric acid at a concentration of less than 23% w / w; separating the first leach liquor and the undissolved first leach solids; leaching the first leach solids in a second leaching step at atmospheric pressure and at a temperature of 60 to 80° C. with a second lixiviant in the presence of a Fe powder reductant to produce a second leach solution comprising undissolved second each solids and a second leach liquor that includes a leached titanium content and iron content, the second lixiviant comprising a mixed chloride solution comprising less than 23% w / w hydrochloric acid and an additional chloride selected from alkali metal chlorides, magnesium chloride and calcium chloride, or mixtures thereof; separating the second leach liquor and the undissolved second leach solids; and thereafter separating the titanium dioxide and the iron content from the second leach liquor by precipitation, and regenerating the second lixiviant for recycle to the second leaching step.