The disclosure herein sets forth processes and compositions for producing carbonated materials comprising calcium carbonates through a mechanochemical process. The present disclosure concerns the production of calcium carbonate by sequestrating CO.sub.2. Certain processes herein include providing alkaline-rich mineral materials that include carbonatable solid wastes such as lime kiln dust, cement kiln dust, and coal combustion residues, and simultaneously fractioning the alkaline-rich mineral materials, while contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure. In some embodiments, the alkaline-rich mineral materials are partially carbonated before being used in the processes disclosed herein. After contacting the alkaline-rich mineral materials with a CO.sub.2-containing gas in carbonation reactor at low temperature and ambient pressure, solid calcium carbonate is produced. In aqueous reactors, the solid calcium carbonate is filtered from a solution in which it precipitated, and the remaining solution includes hydroxide as well as alkaline metal ions. The solution filtered from the solid calcium carbonate can be sequentially contacted with a CO.sub.2-containing gas stream to precipitate additional calcium carbonate. The carbonated materials formed from these processes can be used in the form of a slurry, as a moist powder, as a dried powder, as a reactive filler or as a supplementary cementitious material in a mixture that is used to make concrete.

Carbon dioxide may be stored by mineralization. An example method thereof may include: providing a first solution including a first aqueous fluid having dispersed therein a metal salt and a metal catalyst; dispersing carbon dioxide gas in a second solution including a second aqueous fluid, wherein the carbon dioxide gas forms dissolved carbon dioxide; introducing an electrical current to the second solution; generating, using the electrical current, nanobubble carbon dioxide; combining at least a portion of the first solution and at least a portion of the second solution to form a combined solution; and generating mineralized carbon dioxide from the dissolved carbon dioxide and the nanobubble carbon dioxide, wherein the generating at least partially comprises catalytically reacting, using the metal catalyst, the metal salt and one or more of the dissolved carbon dioxide and the nanobubble carbon dioxide, thereby forming the mineralized carbon dioxide.

The present invention provides a process for preparing a precipitated calcium carbonate product comprising the steps of: (a) preparing an aqueous suspension of precipitated calcium carbonate seeds by carbonating a suspension of Ca(OH).sub.2 in the presence of 0.005 to 0.030 moles of Sr, in the form of Sr(OH).sub.2, per mole of Ca(OH).sub.2, (b) dewatering and dispersing the precipitated calcium carbonate seeds prepared in step (a) to obtain an aqueous suspension of precipitated calcium carbonate seeds having a d.sub.50 of less than or equal to 0.1 to 0.3 m and a BET specific surface area of 10 to 30 m.sup.2/g, and (c) forming an aqueous suspension of a precipitated calcium carbonate product by carbonating a slurry of Ca(OH).sub.2 in the presence of 0.5 to 5% by dry weight of the precipitated calcium carbonate seeds obtained in step (b), wherein the precipitated calcium carbonate seeds have a d.sub.50 that is less than the d.sub.50 of the precipitated calcium carbonate product and the precipitated calcium carbonate seeds have an aragonitic polymorph content greater than or equal to the precipitated calcium carbonate product obtained in step (c) characterized in that the dewatering of step (b) is carried out by the use of a tube press.

Techniques for growing crystalline calcium carbonate solids such that the crystalline calcium carbonate solids include a volume of 0.0005 mm.sup.3 to 5 mm.sup.3, include a slaker to react quicklime (CaO) and a low carbonate content fluid to yield a slurry of primarily slaked lime (Ca(OH).sub.2); a fluidized-bed reactive crystallizer that encloses a solid bed mass and includes an input for a slurry of primarily slaked lime, an input for an alkaline solution and carbonate, and an output for crystalline calcium carbonate solids that include particles and an alkaline carbonate solution; a dewatering apparatus that includes an input coupled to the crystallizer and an output to discharge a plurality of separate streams that each include a portion of the crystalline calcium carbonate solids and alkaline carbonate solution; and a seed transfer apparatus to deliver seed material into the crystallizer to maintain a consistent mass of seed material.

Provided is a method for preparing a stable amorphous calcium carbonate (ACC), which can be obtained either in suspension or as a powder. The method comprises stepwise combination of a soluble calcium salt, a soluble carbonate, a first and second stabilizer, and a water miscible organic solvent as described herein. The present invention further relates to stable ACC suspensions and dry powders produced by the method of the present invention.

Techniques for growing crystalline calcium carbonate solids such that the crystalline calcium carbonate solids include a volume of 0.0005 mm.sup.3 to 5 mm.sup.3, include a slaker to react quicklime (CaO) and a low carbonate content fluid to yield a slurry of primarily slaked lime (Ca(OH).sub.2); a fluidized-bed reactive crystallizer that encloses a solid bed mass and includes an input for a slurry of primarily slaked lime, an input for an alkaline solution and carbonate, and an output for crystalline calcium carbonate solids that include particles and an alkaline carbonate solution; a dewatering apparatus that includes an input coupled to the crystallizer and an output to discharge a plurality of separate streams that each include a portion of the crystalline calcium carbonate solids and alkaline carbonate solution; and a seed transfer apparatus to deliver seed material into the crystallizer to maintain a consistent mass of seed material.

Provided herein are integrated biomass combustion-carbonation gas conditioning systems to directly sequester carbon dioxide from biomass-derived CO.sub.2-containing flue gas. The CO.sub.2 is sequestered by mineral carbonation in concrete materials within a carbonation reactor. The mineral carbonation processes sequester CO.sub.2 in concrete materials, aqueous slurries, or aggregates without any additional carbon enrichment process. Contacting a CO.sub.2-containing gas stream from a biomass combustion apparatus with concrete, aggregate, or alkaline solutions, causes a carbonation reaction in which carbonation products such as calcium carbonate (CaCO.sub.3) and alumina silica gel are formed. The carbonation reactions set forth herein are useful for strengthening concrete and concrete components. Certain processes herein condition the biomass-derived flue gas. The conditioning includes condensing the gas to remove acidic gas, and to remove particulates and water. The conditioning includes adjusting the temperature, relative humidity, and gas flow rate of the biomass-derived flue gas without any carbon capture step before entering the carbonation reactor. The permanent storage of CO.sub.2 in concrete materials reduces carbon emissions from biomass combustion systems. The process does so, in certain embodiments, at low temperatures, ambient pressure, and even under dilute CO.sub.2 concentrations in CO.sub.2-containing flue gas streams. For example, the CO.sub.2 concentration in a CO.sub.2-containing flue gas stream from a biomass combustion system may be lower than 20 volume percent (vol %) and be used to produce low-carbon concrete materials.

Dry precipitated calcium carbonate and a slurry of precipitated calcium carbonate (PCC) particles at least partially in the form elongated entities, especially of nanofibers or nanochain like agglomerates constituted by at least two interconnected primary particles, and preferably, with a content of scalenohedron particles, is provided having opacifying properties. The slurry may be produced on site of its use and, due to its high concentration of CaCO.sub.3, may be applied directly after its manufacture.

Provided is a method for preparing a stable amorphous calcium carbonate (ACC), which can be obtained either in suspension or as a powder. The method comprises stepwise combination of a soluble calcium salt, a soluble carbonate, a first and second stabilizer, and a water miscible organic solvent as described herein. The present invention further relates to stable ACC suspensions and dry powders produced by the method of the present invention.

Method of producing hydroxides for use in carbon dioxide mineralization, the method including adding a first amount of sodium hydroxide to a produced oilfield brine to precipitate Mg(OH).sub.2, adding a second amount of sodium hydroxide to precipitate Ca(OH).sub.2, filtering the precipitates, and adding an amount of the filtered precipitates to an aqueous carbon dioxide solution.