199 results about "Calcium Compounds" patented technology

The invention relates to the technical field of rare earth ore concentrate treatment, in particular to a rare earth ore concentrate treatment method. The treatment method of the rare earth concentrate comprises the following steps that the rare earth concentrate, a calcium-containing compound, silicon dioxide and carbon powder are mixed and roasted, and roasted ore is obtained; water is added into the roasted ore for size mixing, and size is obtained; and acid is added into the slurry for reaction, solid-liquid separation is carried out, and acid leaching residues and rare earth chloride feed liquid are obtained. The method has the advantages of being simple in technological process, high in rare earth recovery rate, short in reaction time, environmentally friendly, low in cost and diversified in rare earth grade applicability. The silicon dioxide can increase the decomposition activity of bastnaesite and monazite in the rare earth ore, rare earth compounds easy to leach can be generated, and therefore the decomposition rate of the rare earth ore concentrate is increased, and calcium can also play a role in fixing fluorine. According to the method, the rare earth decomposition rate is 98% or above, and the rare earth leaching rate is 96% or above.

The invention discloses a composite heavy metal adsorbent synthesized through mineral conversion and a preparation method of the composite heavy metal adsorbent, and belongs to the technical field of deep processing of natural nonmetallic minerals and preparation of heavy metal adsorption functional materials, and the main preparation method comprises the following steps: S1, crushing and crushing natural clay minerals, and sieving with a 80-mesh sieve to obtain mineral powder; s2, mixing the obtained mineral powder with a calcium compound, and carrying out ball milling; s3, adding a boron compound, and continuing ball milling; s4, adding water into a solid material obtained by ball milling according to a solid-to-liquid ratio of (1: 5)-(1: 20), putting into a microwave hydrothermal reaction kettle, adding an organic auxiliary agent, carrying out gradient heating to 100-200 DEG C, reacting for 30-120 minutes, then naturally cooling to room temperature, separating, drying and crushing; according to the invention, natural clay raw ore is taken as a raw material, and the borate-silicate composite adsorption material is prepared in a preparation mode of combining solid-phase reaction and microwave hydrothermal treatment, so that high-concentration and low-concentration heavy metal ions are efficiently removed.

The invention discloses a composition for promoting cartilage repair and maintaining joint health as well as a preparation process and application thereof, and relates to the technical field of functional foods. The composition is prepared from the following components in parts by weight: 21.1 to 90 parts of a multi-protein complex, 0.1 to 3 parts of cherry powder, 0.01 to 2 parts of N-acetylglucosamine, 0.01 to 2 parts of radix puerariae powder, 0.1 to 1.5 parts of a calcium compound and 0.01 to 0.2 part of rhizoma curcumae longae, the multi-protein compound is prepared from 0.1 to 10 parts of ray collagen peptide, 1 to 30 parts of bone collagen peptide powder and 20 to 50 parts of fish collagen peptide. The composition provided by the invention can promote cartilage repair, achieves the purpose of daily maintenance of joint health, and has a good application prospect.

The invention discloses a calcium-containing antarctic krill oligopeptide nutritional composition for promoting bone cell growth and application thereof, and belongs to the technical field of functional foods.The calcium-containing antarctic krill oligopeptide nutritional composition is composed of antarctic krill oligopeptide and a calcium compound, and the mass ratio of the antarctic krill oligopeptide to the calcium compound is (0.5-5): 1; or the composition is composed of the euphausia superba oligopeptide, the calcium compound and the vitamin D, and the mass ratio of the euphausia superba oligopeptide to the calcium compound to the vitamin D is (0.5-5): 1: (2.5 * 10 <-5 >)-(15 * 10 <-5 >); the mass of the calcium compound is calculated according to the content of the calcium element in the antarctic krill oligopeptide; the antarctic krill oligopeptide is obtained by treating antarctic krill, antarctic krill powder or defatted antarctic krill powder by utilizing an enzymolysis method; the content of a peptide fragment with the molecular weight of less than 1000Da in the antarctic krill The raw materials of the nutritional composition are easy to obtain, the safety is high, and the nutritional composition can be used for preparing products with the effect of promoting bone cell growth.

An application and a composition of bioremediation agents and cremated remains forming underwater sanctuaries and structures by coral reefs comprising a homogenous mixture of calcium compounds, clay, cement, earthworm enzymes, and human / animal ashes. The composition will benefit nearby reefs with added calcium for rehabilitating reefs and earthworm enzymes with detoxifying properties. The underwater sanctuaries and structures will provide habitats for wildlife.

The present invention relates to the technical field of adsorbents, and specifically discloses a pressure swing adsorption hydrogen purification adsorbent for synthesizing morpholine and a preparation method thereof. The specific preparation method comprises the following steps: Step a: grinding the binder into powder for standby; Step b: mixing 13X molecular sieve, binder, structure stabilizer and calcium compound in a certain proportion, and forming a spherical compound A after mixing; Step c: pre-drying the spherical compound A, followed by roasting, washing, drying and activation to obtain the adsorbent. The pressure swing adsorption hydrogen purification adsorbent for synthesizing morpholine provided by the present invention has good adsorption effect, can tolerate high concentration of CO2, and a structure stabilizer is added to the adsorbent, so that the prepared adsorbent has a stable structure and can tolerate the influence of gas flow scouring, particle and bed vibration on the adsorbent. Finally, the preparation method of the adsorbent of the present invention is simple and easy for industrial production.

The invention provides an efficient defluorination process for a sedimentation tank, and belongs to the technical field of wastewater defluorination, and the efficient defluorination process specifically comprises the following steps: introducing fluorine-containing wastewater into a premixing tank, adding an alkaline calcium compound to adjust the pH value, then adding cationic polyacrylamide, and carrying out a flocculation reaction to obtain a flocculation liquid after the reaction is completed; and enabling the flocculated liquid to flow into a sedimentation tank, adding hydrochloric acid to adjust the pH value, carrying out static settlement, then adding a composite fluorine removal agent, carrying out static settlement, carrying out solid-liquid separation in a sedimentation area, carrying out regular cleaning on settled sludge, and enabling effluent of supernate to enter a clean water tank, so as to obtain a purified water body. The defluorination process for the sedimentation tank has an excellent defluorination effect and meets the deep defluorination requirement that the concentration of effluent is lower than 1.0 mg / L. Meanwhile, the treated settled sludge has good sedimentation performance, the occurrence of sludge runout is reduced, and the treatment amount and treatment cost of the sludge are reduced.

A thermostabilizing agent is used in the production of olefinic hydrocarbons. A carrier for a thermostabilizing agent is obtained by mixing a product of rapid partial dehydration of gibbsite having the formula Al2O3·nH2O, where 0.43≤n≤1.5, and calcium compounds, and forming, drying and sintering granules at a temperature of 900-1400°С. The carrier contains, in terms of oxides: 10-36 wt% calcium oxide, and the remainder aluminium oxide. The percentage of pores having an effective radius of 60-70 nm is 70-78%. The thermostabilizing agent has a specific surface area of 8.0-35.0 m2 / g and a crush strength of 15-33 MPa. The technical result is the creation of a thermostabilizing agent that has a high specific surface area, high thermal stability, a constant phase composition, and high strength.

The invention provides a method for synergistically preparing calcium fluoride and a molecular sieve based on multi-element industrial waste, and belongs to the technical field of industrial waste recycling. The method comprises the following steps: respectively taking an electrolytic aluminum industry byproduct fluorine-containing waste electrolyte cryolite and lithium slag after lithium extraction of lithium ore as raw materials, performing acid leaching on the electrolyte cryolite, adding a calcium compound, separating to obtain calcium fluoride solid and a mixed solution containing aluminum chloride and sodium chloride, and adding an alkaline solution into the mixed solution to obtain an aluminum hydroxide product. And carrying out alkaline leaching on the lithium slag to obtain a mixed solution containing sodium silicate and sodium metaaluminate, and proportionally synthesizing the mixed solution with the obtained aluminum hydroxide and sodium hydroxide solution to obtain the 4A zeolite molecular sieve product. The calcium fluoride and the zeolite molecular sieve are cooperatively prepared by adopting multi-element industrial waste, and the problems that electrolyte cryolite cannot be completely applied to the aluminum electrolysis process, the lithium slag treatment cost is high and the like in the prior art are solved.

The invention relates to a method for separating sodium and potassium from mixed sulfate containing sodium and potassium, which comprises the following steps: mixing the mixed sulfate containing sodium and potassium, a calcium-containing compound and water, dissolving and reacting to obtain potassium-removed mother liquor and double salt precipitate; performing first crystallization on the potassium-removed mother liquor to obtain a sodium sulfate product; mixing the double salt precipitate with water for elution treatment to obtain a potassium sulfate solution; performing secondary crystallization on the potassium sulfate solution to obtain a potassium sulfate product; according to the method, efficient separation of sodium and potassium in the mixed sulfate containing sodium and potassium is achieved, the purity of the obtained sodium sulfate product is preferably as high as 99.0% or above, the potassium content in potassium sulfate is preferably as high as 54.2 wt% or above based on the mass content of potassium oxide, the whole technological process is short, potassium chloride does not need to be added, the separation cost is low, waste gas, waste liquid and solid waste are not generated, and the method is suitable for industrial production. And green resource utilization of the mixed sulfate containing sodium and potassium is realized.

The invention discloses a polyaryletherketone composite implant material and a preparation method and application thereof, and belongs to the technical field of medical materials.The preparation method of the polyaryletherketone composite implant material comprises the following steps that a carbon fiber reinforced polyaryletherketone substrate with the surface provided with a groove structure and conductivity is prepared; based on a precipitation method, a calcium compound, a magnesium compound and a phosphoric acid aqueous solution are used for preparing white calcium stone; the preparation method comprises the following steps: carrying out surface modification on the white calcium phosphate by utilizing polydopamine, so as to obtain modified white calcium phosphate; adding the modified white calcium phosphate and a degradable piezoelectric polymer into a solvent, and mixing to obtain a mixed solution; and coating a carbon fiber reinforced polyaryletherketone substrate with the mixed solution, and performing drying and annealing treatment to form a coating, thereby obtaining the polyaryletherketone composite implant material. According to the invention, the degradable piezoelectric composite coating doped with the white phosphorus calcium stone, which has piezoelectric characteristics and ion release capability, is constructed, so that double biomimetic effects of an electric signal and a chemical signal in a bone healing microenvironment are realized.

The invention belongs to the technical field of biological materials, and discloses a PEEK bone implant material of a piezoelectric catalysis biological heterojunction and a preparation method of the PEEK bone implant material, the material comprises a PEEK bone implant loaded with the biological heterojunction, the biological heterojunction is composed of BiVOO and a chalcogenide calcium compound in a molar ratio of 1-3, and the chalcogenide calcium compound is calcium sulfide, calcium selenide or calcium telluride; during preparation, the BiVO / CaX biological heterojunction is firstly prepared by a hydrothermal method or an in-situ composite method, then PEEK is sequentially subjected to acetone, ethanol and deionized water cleaning, sulfuric acid ultrasonic treatment for 5-10 minutes and dopamine modification, the biological heterojunction is in contact with the modified PEEK at 4 DEG C for 12 hours to complete loading, and improvement means can be introduced into part of schemes. The material has the acoustic catalytic antibacterial function and the bone repair promoting function, the antibacterial effect can be regulated and controlled through ultrasound, the process is simple, and the reaction condition is mild; the multi-drug-resistant bacterial infection can be dealt with, and the heterojunction loading stability and the material cell compatibility are improved.

Separating the specific gravity gt of the solid-liquid mixture type underflow red mud discharged in aluminum oxide production from liquid; continuously grading and separating out ferric oxide, trace heavy metal minerals and rare earth from the 5 g / cm < 3 > material, and carrying out solid-liquid separation treatment; the separated materials with the specific gravity smaller than or equal to 5 g / cm < 3 > are atomized and dispersed into particles and liquid drops, the particles and the liquid drops are quickly freeze-dried to prepare fine particles, and the fine particles are divided into sodium aluminosilicate and silicon oxide mixed particles, calcium compound mixed particles and crystallized sodium hydroxide, sodium aluminate and ice crystal particles through multi-stage specific gravity classification in the environment with the temperature smaller than-5 DEG C; and sublimating and dehydrating the separated sodium aluminosilicate and silicon oxide mixed particles and calcium compound mixed particles to form powder materials, and melting sodium hydroxide, sodium aluminate and ice crystal particles at normal temperature to form a solution containing sodium aluminate and sodium hydroxide.

The invention relates to the technical field of ceramic substrates, and provides a heat-resistant multilayer ceramic substrate and a preparation method thereof. The heat-resistant multilayer ceramic substrate comprises the following raw materials in parts by weight: 75-80 parts of aluminum oxide, 1-3 parts of a sintering aid, 82-92 parts of a solvent, 8-14 parts of a binder, 0.5-1.5 parts of a dispersant and 2-6 parts of a flexibilizer. The toughening agent comprises a core-shell structure compound and a calcium-containing compound; the core layer of the core-shell structure compound is titanium dioxide, and the shell layer of the core-shell structure compound is zirconium oxide. According to the technical scheme, the problem that the fracture toughness of the heat-resistant multilayer ceramic substrate is low in the prior art is solved.

The invention provides a method for accelerating carbon dioxide mineralization and sequestration based on a calcium ion-containing aqueous solution, and relates to the technical field of carbon dioxide capture, utilization and sequestration. The method comprises the following steps: selecting a calcium-containing compound, dissolving the calcium-containing compound in water, and uniformly stirring and mixing to obtain an initial aqueous solution; the calcium ion concentration in the initial aqueous solution is within a preset calcium ion concentration range; an alkaline regulator is added into the initial aqueous solution, a target aqueous solution is obtained, and the pH value of the target aqueous solution is within a preset pH value range; injecting the target aqueous solution into formation water of a target formation through injection equipment; carbon dioxide to be sealed is injected into the formation water, and calcium ions in the target water solution and carbonate ions generated after the carbon dioxide is dissolved in the formation water are subjected to mineralization reaction to form calcium carbonate precipitates. According to the method, CO2 dissolution and carbonate conversion are effectively promoted, generation of calcium carbonate precipitates is greatly accelerated, and the key bottleneck of slow reaction kinetics of a traditional mineralization method is overcome.

A method for producing calcium phosphate crystals according to the present invention comprises a step (S11) for preparing a weakly basic phosphoric acid solution containing a complex comprising a rare earth element ion and a coordination compound having a ligand coordinated to the rare earth element ion and a step (S12) for adding a calcium-containing compound to the weakly basic phosphoric acid solution and hydrolyzing. Some of the plurality of calcium ions contained in the structure of the calcium phosphate crystals are substituted by the rare earth element ion.

The invention relates to the technical field of medical materials, in particular to a composite root canal filling agent premixed with a calcium silicate-niobium compound as well as a preparation method and application of the composite root canal filling agent. The composite root canal filling agent comprises (a) a calcium silicate compound, (b) a phosphate compound, (c) a calcium compound, (d) a niobium compound, (e) a radiation-resistant material, (f) a water-miscible non-aqueous phase solvent and (g) an organic matter, the total mass of the component (a), the component (b), the component (c), the component (d), the component (e) and the component (g) accounts for 60-95% of the total mass of the filling agent, and the total mass of the component (a), the component (b), the component (c), the component (d), the component (e) and the component (g) accounts for 20-30% of the total mass of the filling agent. And the component (f) accounts for 5-40% of the total mass of the filling agent. The filling agent is fast in solidification, good in biological activity, excellent in antibacterial performance and convenient to popularize and apply.

The application relates to the technical field of composite materials, and discloses a prefabricated air-permeable coiled material and a preparation method thereof. From top to bottom, the prefabricated air-permeable coiled material comprises a surface layer and a bottom layer. The surface layer comprises the following raw materials in parts by weight: SEBS 30-40 parts, polypropylene 15-22 parts, a first filler 15-25 parts, a softening agent 25-30 parts, an antioxidant 1-3 parts and maleic anhydride grafted polypropylene 1-3 parts. The bottom layer comprises the following raw materials in parts by weight: SEBS 15-22 parts, polypropylene 30-40 parts, a second filler 20-30 parts, a softening agent 25-30 parts and maleic anhydride grafted polypropylene 1-3 parts. The first filler and the second filler are both calcium-containing compounds. Through the technical scheme, the problems of poor air permeability, wear resistance and mechanical properties of the prefabricated coiled material in the related art are solved.

The invention relates to an N-doped self-supporting porous calcium sphere ozonation catalyst, the catalyst is composed of network-shaped porous carbon spheres, and metal active components and non-metal active components dispersed on the network-shaped porous carbon spheres, the network-shaped porous carbon spheres are formed by roasting calcium alginate gel at high temperature, and the metal active components and the non-metal active components are dispersed on the network-shaped porous carbon spheres. The metal active component is a calcium compound, and the non-metal active component is a nitrogen compound and a silicon compound; the catalyst is designed and synthesized based on a cross-linking polymerization instantaneous balling principle of sodium alginate and Ca < 2 + >, and particularly, an auxiliary agent and an N source are introduced into a sodium alginate solution, so that the catalyst is further functionalized, and metal-nonmetal synergistic catalysis is realized. The preparation method of the catalyst is simple in technological process, the catalyst can be rapidly prepared in the crosslinking-roasting process, and the catalyst has good catalytic performance and catalyst stability in deep treatment of salt-containing organic wastewater and is suitable for industrial popularization.

The purpose of the present invention is to provide a novel molded article having antibacterial or antiviral properties, a method for manufacturing the same, and the like. The present invention relates to a molded article 100 which contains a calcium compound 104 and a resin, and has a salt of inositol phosphate 102 with at least one metal element 103 selected from the group consisting of silver, zinc, and copper on a surface 101.

The invention discloses a smoke suppressant and an epoxy resin material, and belongs to the technical field of epoxy resin materials. The smoke suppressant is prepared by heating and mixing a copper-containing compound, citric acid, a calcium-containing compound and water to obtain a gelatinous substance, drying the gelatinous substance and then calcining the gelatinous substance, the molar ratio of the copper-containing compound to the citric acid is (1-5): 1; the molar ratio of copper in the copper-containing compound to calcium in the calcium-containing compound is (6-15): 1; the heating and mixing temperature is 40 DEG C to 100 DEG C. Through the combined action of the smoke suppressant, the epoxy resin, the liquid phosphorus flame retardant and the curing agent, the prepared epoxy resin material can reduce the heat release rate peak value and the total smoke generation amount during combustion at the same time, and then the flame retardant property of the epoxy resin material is improved.

A treatment device for fluorine-containing waste water comprises: a first coagulation treatment unit for performing coagulation treatment on fluorine-containing waste water by using an inorganic coagulant and a calcium compound; the first precipitation treatment unit is used for precipitating and separating the coagulation reaction liquid from the first coagulation treatment unit; a second coagulation treatment unit for performing coagulation treatment by adding an inorganic coagulant to at least a portion of the treated water from the first precipitation treatment unit; the turbidity removal membrane device is used for carrying out membrane separation treatment on the coagulation reaction liquid from the second coagulation treatment unit; a reverse osmosis membrane device which is supplied with the membrane permeated water from the turbidity removal membrane device and separates the membrane permeated water into permeated water and concentrated water; a means for taking out permeated water from the reverse osmosis membrane device; the third coagulation treatment unit is used for performing coagulation treatment on the concentrated water from the reverse osmosis membrane device by using an inorganic coagulant and is separated from the first coagulation treatment unit; and a second precipitation treatment unit for precipitating and separating the coagulation reaction liquid from the third coagulation treatment unit.

The application provides a kind of asphalt pavement crack repair method based on EICP technology, it is related to road engineering field and biomimetic technology field.The repair method is repaired by using repair liquid, the repair liquid is obtained by mixing soybean urease solution and cementing liquid;The cementing liquid is urea, calcium compound and skimmed milk powder, and after adding water, stirring uniformly, wherein the optimum concentration ratio of soybean urease solution and cementing liquid is determined by orthogonal test;The repair method includes repair reaction space construction, repair reaction, maintenance polishing finishing and the like.The application is based on EICP technology, and the existing asphalt road crack repair method and the disadvantages of EICP technology in practical application are optimized, compared with other methods, has the advantages of fast, environmental protection, strong applicability, etc., and also provides a new method for asphalt pavement crack repair.

The invention discloses a method for removing fluorine, phosphorus and boron in wastewater, which comprises the following steps: mixing the wastewater containing fluorine, phosphorus and boron with a calcium-containing compound, and adding a coagulant for primary impurity removal to obtain primary impurity removal liquid; mixing the primary impurity removal liquid with a boron removal agent, adjusting the pH value to be alkaline, and carrying out secondary impurity removal to obtain secondary impurity removal liquid; and mixing the secondary impurity removal liquid with a lanthanum-containing compound, adjusting the pH value to be alkaline, and carrying out third impurity removal to obtain an impurity removal liquid. According to the method, firstly, phosphorus and fluorine in the wastewater are preliminarily removed by using the calcium-containing compound, then boron is removed by using the boron removal agent, and finally, residual boron and fluorine in the wastewater are finely removed by using the lanthanum-containing compound, so that fluorine, phosphorus and boron in the wastewater are effectively removed, and the removal rate is up to 99% or above.

To provide a treatment apparatus for waste water from an exhaust gas treatment facility capable of suppressing blockage of an RO apparatus for brine recovery and stably increasing a recovery rate of waste water from the exhaust gas treatment facility.SOLUTION: A treatment apparatus for waste water from an exhaust gas treatment facility includes a first RO apparatus 4 separating fluorine-containing waste water from an exhaust gas treatment facility into first permeate water and first concentrated water by reverse osmosis treatment, a coagulation sedimentation apparatus 14 precipitating and separating calcium fluoride by adding calcium compounds and coagulants to the first concentrated water, a second RO apparatus 15 separating separated water from the coagulation sedimentation apparatus 14 into second permeate water and second concentrated water by reverse osmosis treatment, and a return piping 16 returning the second permeate water to the pre-stage of the first reverse osmosis membrane apparatus 4.SELECTED DRAWING: Figure 1

The invention discloses modified biochar as well as a preparation method and application thereof. The modified biochar comprises biochar and a calcium-containing compound, wherein the calcium-containing compound is loaded on the biochar, the loading amount of the calcium-containing compound is 10-30% of the mass of the modified biochar, and the calcium-containing compound is at least one of CaO and Ca (OH) 2. According to the invention, the biogas residue is modified by calcium carbonate, so that mesoporous of the biochar in a 4-10nm section is filled. The modified biochar promotes the retention of oxygen-containing functional groups of O-C = O and C = O on the surface, and the modified biochar prepared by the invention still can keep better strength. The invention also provides a method for treating phosphorus-containing wastewater by using the modified biochar and a device for treating phosphorus-containing wastewater, the intermittent adsorption reaction of the biochar shows that the adsorption performance of the modified biochar is superior to that of unmodified biochar, the saturated adsorption capacity of the modified biochar is 18-20 mg-P / g-BC, and the modified biochar is suitable for being applied to a sewage treatment plant.

The invention relates to the field of varnish. In particular, the present invention relates to a dental waterless varnish composition comprising at least one calcium silicate compound, at least one film former and at least one volatile organic solvent wherein the content of the at least one calcium silicate compound is preferably 0.1 wt% to less than 20 wt% relative to the total weight of the composition. The invention also relates to a composition according to the invention for use in the treatment and / or prevention of insufficient mineralization-related pathologies. Finally, the invention also relates to a dental product and a dental adhesive film.

The present application relates to the technical field of rare earth concentrate processing, and particularly relates to a rare earth concentrate processing method. The rare earth concentrate processing method comprises the following steps: mixing and roasting a rare earth concentrate with a calcium-containing compound, silicon dioxide and carbon powder to obtain a roasted ore; adding water to the roasted ore to obtain a slurry; adding acid to the slurry to react, and then performing solid-liquid separation to obtain an acid leaching residue and a rare earth chloride solution. The present application has the advantages of simple process flow, high rare earth recovery rate, short reaction time, green environmental protection, low cost, and diversified applicability of rare earth grade. In the present application, the silicon dioxide can increase the decomposition activity of fluorcarbonate cerium and monazite in the rare earth ore, and can generate a rare earth compound that is easy to leach out, thereby improving the decomposition rate of the rare earth concentrate. Calcium can also play a role in fluorine fixation. The rare earth decomposition rate of the present application is above 98%, and the rare earth leaching rate is above 96%.

The invention relates to a solvent extraction method for removing calcium. In the method, an aqueous extraction solution is dispensed in an organic phase having a lower density than the aqueous extraction solution. The steps of the method include dispensing droplets of an aqueous extraction solution in an upper portion of a solvent extraction unit, passing the droplets through an organic phase towards a bottom of the solvent extraction unit, collecting the droplets at the bottom of the solvent extraction unit into an aqueous phase layer, and removing the aqueous slurry containing the precipitated calcium compound from the bottom portion of the aqueous phase layer at the bottom of the solvent extraction unit. The invention also relates to a solvent extraction unit for carrying out the method according to the invention.

Methods are provided herein comprising: a) calcining limestone in a cement plant to form carbon dioxide and a calcium compound selected from calcium oxide, calcium hydroxide, or combinations thereof; b) treating the calcium compound with N-containing salt in water to produce an aqueous solution comprising calcium salt and N-containing salt; and c) contacting the aqueous solution with carbon dioxide under one or more precipitation conditions to produce a precipitate comprising calcium carbonate and a supernatant aqueous solution wherein the calcium carbonate comprises vaterite.