A method of preparing a transparent zinc carbonate is disclosed. The method includes dissolving a zinc source in aqueous ammonium carbonate, removing metal impurities from the solution, injecting CO.sub.2 into the zinc ammonia carbonate solution, heating a resulting slurry to a temperature of about 100° C. or more until the ammonia is substantially absent from the solution, and drying the resulting zinc carbonate at a temperature from around 150° C. to 300° C. for a length of time that removes water, but retains a significant part of the CO.sub.2 content. The ammonia and the carbon dioxide are present in the aqueous solution in a ratio by moles or by weight effective to dissolve the zinc. A nano zinc oxide can be prepared by drying the zinc carbonate at a temperature of 300-400° C. for a length of time sufficient to remove substantially all of the CO.sub.2.

Aspects of the invention include methods of removing carbon dioxide (CO.sub.2) from a CO.sub.2 containing gas. In some instances, the methods include contacting CO.sub.2 containing gas with a bicarbonate buffered aqueous medium under conditions sufficient to produce a bicarbonate rich product. Where desired, the resultant bicarbonate rich product or a component thereof may then be stored or further processed, e.g., combined with a divalent alkaline earth metal cation, under conditions sufficient to produce a solid carbonate composition. Aspects of the invention further include systems for practicing the methods, as well as products produced by the methods.

Aspects of the invention include methods of removing carbon dioxide (CO.sub.2) from a CO.sub.2 containing gas. In some instances, the methods include contacting CO.sub.2 containing gas with a bicarbonate buffered aqueous medium under conditions sufficient to produce a bicarbonate rich product. Where desired, the resultant bicarbonate rich product or a component thereof may then be stored or further processed, e.g., combined with a divalent alkaline earth metal cation, under conditions sufficient to produce a solid carbonate composition. Aspects of the invention further include systems for practicing the methods, as well as products produced by the methods.

A reduced-carbon footprint concrete composition includes CO.sub.2-sequestering aggregate that sequesters carbon dioxide (CO.sub.2) from a CO.sub.2 containing gas and cementitious material. The reduced-carbon footprint concrete composition has a reduced carbon footprint relative to an ordinary concrete composition.

A reduced-carbon footprint concrete composition includes CO.sub.2-sequestering aggregate that sequesters carbon dioxide (CO.sub.2) from a CO.sub.2 containing gas and cementitious material. The reduced-carbon footprint concrete composition has a reduced carbon footprint relative to an ordinary concrete composition.

Methods of producing solid CO.sub.2 sequestering carbonate materials are provided. Aspects of the methods include introducing a divalent cation source into a flowing aqueous liquid (e.g., a bicarbonate rich product containing liquid) under conditions sufficient such that a non-slurry solid phase CO.sub.2 sequestering carbonate material is produced. Also provided are systems configured for carrying out the methods.

Methods of producing solid CO.sub.2 sequestering carbonate materials are provided. Aspects of the methods include introducing a divalent cation source into a flowing aqueous liquid (e.g., a bicarbonate rich product containing liquid) under conditions sufficient such that a non-slurry solid phase CO.sub.2 sequestering carbonate material is produced. Also provided are systems configured for carrying out the methods.

Effluent water is combined with carbon dioxide sourced from a carbon dioxide-containing emission stream to produce a reaction solution. The pH of the reaction solution is controlled to induce precipitation of a carbonate salt from the reaction solution.

Effluent water is combined with carbon dioxide sourced from a carbon dioxide-containing emission stream to produce a reaction solution. The pH of the reaction solution is controlled to induce precipitation of a carbonate salt from the reaction solution.

Provided herein are methods of removing carbon dioxide from an aqueous stream or gaseous stream by: contacting the gaseous stream comprising carbon dioxide, when present, with an aqueous solution comprising ions capable of forming an insoluble carbonate salt; contacting the aqueous solution comprising carbon dioxide with an electroactive mesh that induces its alkalinization thereby forcing the precipitation of a carbonate solid from the solution and thereby the removal of dissolved inorganic carbon by electrolysis; and removing the precipitated carbonate solids from the solution, or the surface of the mesh where they may deposit. Also provided herein are flow-through electrolytic reactors comprising an intake device in fluid connection with a rotating cylinder comprising an electroactive mesh, and a scraping device and/or liquid-spray based device for separating a solid from the mesh surface.