The present application pertains to methods for making metal oxides and/or citric acid and/or capturing carbon dioxide. In one embodiment, the application pertains to a process for producing calcium oxide, magnesium oxide, or both from a material comprising calcium and magnesium. The process may include reacting a material comprising calcium carbonate and magnesium carbonate. Separating, concentrating, and calcining may lead to the production of oxides such as calcium oxide or magnesium oxide. In other embodiments the application pertains to methods for producing an alkaline-earth oxide and a carboxylic acid from an alkaline earth cation-carboxylic acid anion salt. Such processes may include, for example, reacting an alkaline-earth cation-carboxylic acid anion salt with aqueous sulfur dioxide to produce aqueous alkaline-earth sulfite or bisulfite and an aqueous carboxylic acid solution. Other useful steps may include desorbing, separating, and/or calcining.

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.

Compositions comprising highly reflective microcrystalline/amorphous materials are provided. In some instances, the highly reflective materials are microcrystalline or amorphous carbonate materials, which may include calcium and/or magnesium carbonate. In some instances, the materials are CO.sub.2 sequestering materials. Also provided are methods of making and using the compositions, e.g., to increase the albedo of a surface, to mitigate urban heat island effects, etc.

A method including precipitating a precipitate including one or more divalent cation carbonates from a solution including the divalent cation of each of the one or more divalent cation carbonates, and storing at least a portion of the precipitate downhole by placing the at least the portion of the precipitate downhole via a well. Precipitating can include contacting the solution with a gas, such as atmospheric air, including carbon dioxide (CO.sub.2). The method can further include separating the precipitate from the solution, and forming a slurry including the at least a portion of the precipitate. Placing the at least the portion of the precipitate downhole via the well can include pumping the slurry downhole via the well. A system is also provided. Via the system and method, CO.sub.2 can be sequestered downhole.

The present invention relates to the use of solid metal materials for catalyzing the hydration of carbon dioxide. It also relates to methods of and apparatus for hydrating carbon dioxide and capturing carbon. The solid metal materials may be nickel nanoparticles. The invention finds particular application in the sequestration of carbon dioxide either at the point of release or from the atmosphere.

The present invention provides a new carbon dioxide fixation apparatus. The carbon dioxide fixation apparatus (1) of the present invention includes: a first reaction vessel (10); a carbon dioxide fixing agent feeding unit (110); and a gas-liquid mixing unit. The first reaction vessel (10) can contain a carbon dioxide fixing agent, the carbon dioxide fixing agent feeding unit (110) can feed the carbon dioxide fixing agent into the first reaction vessel (10), and the gas-liquid mixing unit can mix a gas containing carbon dioxide into the carbon dioxide fixing agent.

The present disclosure is directed to a method for reducing bacteria in a precipitated calcium carbonate (CaCO.sub.3) slurry, the method including: adding water to calcium oxide (CaO) to form Ca(OH).sub.2; treating the Ca(OH).sub.2 with CO.sub.2 gas to form a slurry including precipitated CaCO.sub.3; neutralizing the slurry; and exposing the slurry that was neutralized to ozone in an amount sufficient to reduce bacteria in the precipitated calcium carbonate slurry. Oral care compositions including the precipitated calcium carbonate of the disclosed process are also described.

The current invention relates to methods of the recovery and re-use of minerals obtained from the combustion of the residues of a process to recycle paper.

The present invention relates to a method and a process of preparing precipitated calcium carbonate of high purity by extracting calcium ion contained in an alkali ion-containing inorganic material such as mineral, steelmaking slag and waste concrete with the use of an acidic aqueous solution, separating other metal ions from the extracted solution, preparing an alkaline earth metal hydroxide using an alkaline aqueous solution and then contacting the same with carbon dioxide.

The present invention provides a process for preparing a precipitated calcium carbonate product. The process comprises the steps of 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, based upon moles of Ca(OH).sub.2 prior to or during carbonation; 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, wherein the precipitated calcium carbonate seeds have a D50 that is less than the D50 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.