METHODS AND SYSTEMS FOR USING CALCIUM COMPOUND FROM CALCINATED LIMESTONE

Abstract

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.

Description

DETAILED DESCRIPTION OF THE INVENTION Methods and systems for producing calcium carbonate using lime and waste from a cement plant that calcines limestone are provided herein. The products obtained from the calcination of limestone include calcium oxide (lime or quicklime), calcium hydroxide (slaked lime), and waste gas such as carbon dioxide. Unique methods and systems for using lime and CO2 from the cement plant to form calcium carbonate, which can be used in various products as described herein, are provided herein. In some embodiments of the methods provided herein, the calcium oxide and / or hydroxide from the cement plant is treated with nitrogen-containing salts to solubilize the calcium compound in an aqueous solution, which is then treated with carbon dioxide gas to form a precipitate or precipitate comprising calcium carbonate. In some embodiments, calcium carbonate is formed in the polymorphic form of vaterite, or in some embodiments, the calcium carbonate is precipitated calcium carbonate (PCC). The PCC may be in the form of vaterite, aragonite, calcite, or combinations thereof. In some embodiments, the calcium carbonate is in the form of stable vaterite or in a form of reactive vaterite, both of which have been described herein. In some embodiments, the precipitate material comprising reactive vaterite possesses unique properties, including, but not limited to, cementing properties through transformation to aragonite, which sets and cements with high compressive strength. In some embodiments, the transformation of vaterite to aragonite results in cement that can be used to form construction materials and / or cementitious products such as, but not limited to, formed construction materials such as building panels, etc.These are further described herein. In some embodiments, the vaterite in the product is stable (does not transform into aragonite) and can be used as a filler or cementitious complement material (SCM) when mixed with another cement such as Ordinary Portland Cement (OPC). The precipitate material comprising vaterite can also be used as an aggregate where the reactive vaterite containing the precipitate material, after contact with water, transforms into aragonite, which then sets and cements and is subsequently chipped after cementation to form the aggregate.In some embodiments where calcium carbonate is formed as PCC, the PCC material is cementitious or can be used as a filler in products such as paper products, polymer products, lubricants, adhesives, rubber products, chalk, asphalt products, paint, paint remover abrasives, personal care products, cosmetics, cleaning products, personal hygiene products, ingestible products, soil amendment products, pesticides, environmental sanitation products, and combinations thereof. Such use of the precipitated material as a filler in non-cementitious products is described in U.S. Patent No. 7,829,053, issued November 9, 2010, which is incorporated herein by reference in its entirety. The nitrogen-containing salt used to solubilize calcium ions from the calcium compound can result in residual nitrogen-containing salt remaining in the supernatant solution as well as in the precipitate itself after precipitate formation. In some applications, the presence of residual nitrogen-containing salt in the precipitate may be undesirable, as nitrogen-containing salts such as ammonium chloride, ammonium acetate, ammonium sulfate, ammonium sulfite, ammonium hydrosulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or any other organic nitrogen-containing salt or combinations thereof, in the precipitate can be detrimental to the cementitious products thus formed from the precipitate material. For example, chloride in the cementitious product can be corrosive to metal structures used in conjunction with the cementitious products. Furthermore, residual ammonia can contribute to unpleasant odors in the products.Furthermore, the removal of spent and unrecovered residual nitrogen-containing salt from the precipitate and supernatant solution can be economically and environmentally unfeasible. Several methods for removing and optionally recovering this residual nitrogen-containing salt from the supernatant and precipitate are provided herein. Before describing the invention in more detail, it should be understood that this invention is not limited to the particular embodiments described, as these may, of course, vary. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Where a range of values ​​is provided, it is understood that every intervening value, down to the tenth of a unit of the lower limit unless the context clearly indicates otherwise, between the upper and lower limits of that range and any other intervening or established value within that stated range, is included within the invention. The upper and lower limits of these smaller ranges may independently be included within the smaller ranges and are also encompassed within the invention, subject to, or any limit specifically excluded from the stated range. When the stated range includes one or both limits, the ranges excluding either or both of those limits are also included in the invention. Certain intervals are presented herein with numerical values ​​preceded by the term "approximately." The term "approximately" is used herein to provide literal support for the exact number it precedes, as well as for a number that is close to or approximately the number preceding the term. In determining whether a number is close to or approximately the number specifically cited, the unmatched approximation or approximation number may be a number which, in the context in which it is presented, provides the substantial equivalent of the specifically cited number. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art to which this invention pertains. Although any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the invention, representative illustrative methods and materials are described herein. All publications, patents, and patent applications mentioned in this specification are incorporated herein by reference to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated for incorporation by reference. Furthermore, each cited publication, patent, or patent application is incorporated herein by reference for the purpose of disclosing and describing the subject matter in conjunction with which the publications are cited. The citation of any publication is for description prior to the filing date and should not be deemed an admission that the invention described herein is not entitled to precede such publication by virtue of the prior invention. In addition, the publication dates provided may differ from the actual publication dates, which may need to be independently confirmed. It is noted that, as used herein and in the appended claims, the singular forms a, an, and the include plural references, unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional elements. As such, this statement is intended to serve as a basis of precedent for the use of such exclusive terminology as solely, only, and similarly in combination with the recitation of the elements of the claim, or the use of a negative limitation. As will be evident to those skilled in the art upon reading this description, each of the individual modalities described and illustrated herein has discrete components and characteristics which can be easily separated from or combined with MA / a / zuzz / uuuo r 4 the characteristics of any of the other various modalities without departing from the scope or spirit of the invention. Any cited method may be carried out in the cited order of events or in any other order that is logically possible. I. METHODS AND SYSTEMS Methods and systems are provided for utilizing the calcium compound and CO2 from the cement plant undergoing limestone calcination to form calcium carbonate polymorphs. Limestone, as used herein, means CaCO3 and may additionally include other impurities typically present in limestone. The calcium compound, as used herein, includes any calcium compound formed from the calcination of limestone. The methods and systems provided herein utilize CO2 and calcium compound selected from calcium oxide, calcium hydroxide, or a combination thereof from the cement plant that is calcining limestone and forming precipitate material comprising calcium carbonate, such as, but not limited to, reactive or stable vaterite or PCC. These methods and systems are described in more detail herein.The calcium carbonate polymorphs formed herein, such as vaterite, can be used as cement or as a filler. In some embodiments, the calcium compound is selected from calcium oxide, calcium hydroxide, or a combination thereof, and can act as both a source of divalent cations (Ca2+) and a proton-removing agent. In some embodiments, the calcium hydroxide formed by solubilizing calcium oxide in water can provide calcium ions as a source of divalent cations and hydroxide as a source of proton-removing agent and reacts with carbon dioxide to form calcium carbonate precipitates. The vaterite polymorph of the calcium carbonate precipitate can be a stable vaterite that can act as a filler in the products, or it can be a reactive vaterite that can transform into aragonite during the dissolution-reprecipitation process described herein. In some embodiments of the methods provided herein, the calcium compound is selected from calcium oxide, calcium hydroxide, or a combination thereof and treated with the nitrogen-containing salt to solubilize the calcium compound in an aqueous solution, which is then treated with carbon dioxide gas to form a precipitate comprising calcium carbonate. The process may result in residual nitrogen-containing salt remaining in the supernatant solution as well as in the precipitate itself after precipitate formation. Several methods have been provided for removing and optionally recovering the residual nitrogen-containing salt from the supernatant solution as well as the precipitate. In some embodiments, the calcium compound obtained after calcination of the limestone may contain sulfur, depending on the limestone source.Sulfur in the calcium compound can be introduced into the aqueous solution after solubilizing the calcium compound with nitrogen-containing salts. In an alkaline solution, various sulfur compounds containing different ionic sulfur species may be present, including, but not limited to, sulfite (SO32), sulfate (SO42), hydrosulfide (HS), thiosulfate (S2O32), polysulfides (Sn2), thiol (RSH), and similar compounds. The term "sulfur compound," as used herein, includes any sulfur ions contained within the compound. Examples of sulfur compounds are provided herein. Several methods are provided for removing and optionally recovering the residual nitrogen-containing salt from the supernatant solution as well as the precipitate. In one aspect, a method is provided comprising: a) calcining limestone in a cement plant to form a calcium and carbon dioxide compound selected from calcium oxide, calcium hydroxide, or combinations thereof; b) treating the calcium compound with a nitrogen-containing salt in water to produce an aqueous solution comprising a calcium salt and a nitrogen-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. In some embodiments of the above-mentioned aspect, the method further comprises dewatering the precipitate to separate the precipitate from the supernatant of the aqueous solution. In some embodiments of the above-mentioned aspect, the calcium carbonate comprises reactive vaterite.In some forms of the above aspect and form, calcium carbonate comprises more than 50% by weight of reactive vaterite. The above appearance and modalities are illustrated in Fig. 1. It should be understood that the steps illustrated in Fig. 1 may be modified, the order of the steps may be changed, or additional steps may be added or omitted depending on the desired output. As illustrated in Fig. 1, the calcium compound selected from calcium oxide, calcium hydroxide, or combinations thereof, and the CO2 obtained from the cement plant undergoing calcination of limestone (Step A in Fig. 1), are subjected to the methods and systems provided herein to produce the precipitate comprising calcium carbonate. Calcination, or calcination, is a heat treatment process used to thermally decompose limestone. Limestone is a naturally occurring mineral. Its chemical composition can vary from region to region, as well as between different deposits within the same region. Therefore, the calcium oxide and / or calcium hydroxide obtained from calcining limestone from each natural deposit may differ. Typically, limestone may be composed of calcium carbonate (CaCO3), magnesium carbonate (MgCO3), silica (S1O2), alumina (Al2O3), iron (Fe), sulfur (S), or other trace elements. Limestone deposits are widely distributed. Limestone from various deposits can differ in chemical properties and can be classified according to its chemical composition, texture, and geological formation. Limestone can be classified into the following types: high-calcium, where the carbonate content may consist mainly of calcium carbonate with magnesium carbonate not exceeding 5%; magnesium, containing magnesium carbonate from approximately 5 to 20%; or dolomitic, which may contain between 20 and 45% MgCCh, the balance being calcium carbonate. Limestones from different sources can differ considerably in chemical compositions and physical structures. It should be understood that the methods and systems provided herein apply to all cement plants calcining limestone from any of the sources listed above or commercially available. The calcination of limestone is a decomposition process where the chemical reaction for the decomposition of limestone is: CaCOs -> CaO + CO2 (g) Calcium oxide can exist in dry or wet form (e.g., calcium hydroxide) depending on the conditions. The production of calcium oxide (lime and quicklime) depends on the type of kiln, calcination conditions, and the nature of the raw material, i.e., limestone. At relatively low calcination temperatures, the products formed in the kiln may contain both lime and unburned carbonate and can be called incompletely calcined lime. As the temperature increases, highly reactive or lightly calcined lime can be produced. At even higher temperatures, low-reactivity or dead-burned lime can be produced. Dead-burned lime occurs when the reaction front reaches the core of the charged limestone and converts all the carbonate present into lime. A highly productive product can be relatively soft, contain small lime crystals, and have an open porous structure with an easily accessible interior.Such lime can have the optimal properties of high reactivity, high surface area, and low bulk density. Increasing the degree of calcination beyond this state can cause the lime crystallites to grow larger, agglomerate, and sinter. This can result in a decrease in surface area, porosity, and reactivity, and an increase in bulk density. This product may be referred to as low-reactivity or dead-calcined lime. Not limited by any theory, the methods and systems provided herein utilize any or a combination of the lime mentioned above. The production of calcium compounds by calcining limestone can be carried out using various types of kilns, such as, but not limited to, a shaft kiln or a rotary kiln. Calcination equipment is available for calcining limestone in the form of lumps with diameters ranging from several to tens of millimeters. Waste streams of the resulting nitrogen-containing salt are inorganic nitrogen-containing salt, organic nitrogen-containing salt, or combinations thereof. The nitrogen-containing salt as used herein is a salt that partially, completely, or substantially solubilizes or dissolves the calcium compound obtained after calcining the limestone. The calcium compound may be calcium oxide, calcium hydroxide, any other calcium derivative, or combinations thereof. The organic salt containing nitrogen, as used herein, includes any inorganic salt containing nitrogen. Examples of inorganic salts containing nitrogen include, but are not limited to, ammonium halide (halide being any halogen), ammonium acetate, ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite, and the like. In some embodiments, ammonium halide is ammonium chloride or ammonium bromide. Such chemicals are well known in the art and are commercially available. The organic salt containing nitrogen, as used herein, includes any salt of an organic compound containing nitrogen. Examples of organic compounds containing nitrogen include, but are not limited to, aliphatic amines, alicyclic amines, heterocyclic amines, and combinations thereof. Such chemicals are well known in the art and are commercially available. The aliphatic amine as used herein includes any amine of formula (R)n-NH3-n, where n is an integer from 1 to 3, wherein R is independently linear or branched between C1 and C8 and an unsubstituted or substituted alkyl group. An example of the corresponding salt or alkyl amine of formula (R)n-NH3-n is (R)n-NH4-n+Cl' or (R)n-NH4-n+Br. In some embodiments, where R is a substituted alkyl group, the substituted alkyl group is independently substituted with a halogen, hydroxyl group, acid, and / or ester. For example, when R is alkyl in (R)n-NH3-n, the alkyl amine can be a primary alkyl amine, such as, for example, only methylamine, ethylamine, butylamine, pentaamine, etc.; the alkyl amine can be a secondary amine, such as, for example, only dimethylamine, diethylamine, methylethylamine, etc.; and / or the alkyl amine can be a tertiary amine, such as, for example, only trimethylamine, triethylamine, etc. For example, where R is a substituted alkyl, substituted with hydroxyl in (R)n-NH3-n, the substituted alkyl amine is an alkanolamine including, but not limited to, monoalkanolamine, dialkanolamine, or trialkanolamine, such as, for example, monoethanolamine, diethanolamine, or triethanolamine, etc. For example, when R is a substituted alkyl, substituted with a halogen in (R)n-NH3-n, the substituted alkyl amine is, for example, chloromethylamine, bromomethylamine, chloroethylamine, bromoethylamine, etc. For example, when R is alkyl substituted, substituted with acid in (R)n-NH3-n, the substituted alkylamine is, for example, an amino acid. In some embodiments, the aforementioned amino acid has a nonpolar, non-charged alkyl chain; examples include, but are not limited to, serine, threonine, asparagine, glutamine, or combinations thereof. In some embodiments, the aforementioned amino acid has a charged alkyl chain; examples include, but are not limited to, arginine, histidine, lysine, aspartic acid, glutamic acid, or combinations thereof. In some embodiments, the aforementioned amino acid is glycine, proline, or combinations thereof. The alicyclic amine as used herein includes any alicyclic amine of the formula (R)n-NH3-n, where n is an integer from 1 to 3, wherein R is independently one or more all-carbon rings which may be saturated or unsaturated, but do not have aromatic character. Alicyclic compounds may have one or more aliphatic side chains attached. An example of the corresponding salt of the alicyclic amine of formula (R)n-NH3-n is (R)n-NH4-n+C|·. Examples of alicyclic amines include, without limitation, cycloalkylamines: cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, cyclooctylamine, and so on. The heterocyclic amine as used herein includes at least one heterocyclic aromatic ring attached to at least one amine. Examples of heterocyclic rings include, but are not limited to, pyrrole, pyrrolidine, pyridine, pyrimidine, etc. Such chemicals are well known in the art and are commercially available. In some formulations, other examples of solubilizers (used alone or in combination with N-containing salts) include borate. Examples of borates include, but are not limited to, borax, colemanite, ulexite, kernite, boracite, painite, or combinations thereof. As illustrated in step B of Fig. 1, the N-containing salt is exemplified by ammonium chloride (NH4Cl). It should be understood that NH4Cl is for illustrative purposes only and that any other N-containing salt (or any borate) may be used in the methods and systems provided herein. One or more steps may be omitted or modified, or the order of the steps in Fig. 1 may be changed. Calcium oxide and hydroxide are solvated or solubilized by treatment with NH4Cl (new and recycled, as further explained below) when the reaction that may occur is: CaO(s) + 2 NH4CI(aq) 2 NH3(aq) + CaCb(aq) + H2O(I) Ca(OH)2+ 2NH4CI(aq) 2NH3+ CaCI2+ 2H2O In some embodiments, the N-containing salt such as, but not limited to, ammonium chloride solution may be supplemented with anhydrous ammonium or an aqueous ammonium solution to maintain an optimum level of ammonium chloride in the solution. In some embodiments, the amount of the nitrogen-containing salt, such as inorganic nitrogen-containing salt, organic nitrogen-containing salt, or combinations thereof, is in excess of 30% of the calcium compound. In some embodiments, the nitrogen-containing salt is in a ratio of between 0.5:1 and 4:1 (nitrogen-containing salt (or borate) : calcium compound), or 0.5:1 to 2:1, or 0.5:1 to 1.5:1, or 1:1 to 1.5:1, or 2:1 to 4:1, or 2:1 to 3:1, or 2.5:1 to 3:1, or 3:1 to 4:1, or 1.5:1, or 2:1, or 2.5:1, or 3:1, or 3.5:1, or 4:1 with the calcium compound. In some forms, the N-containing salt, such as the inorganic N-containing salt, is in a ratio of between 0.5:1 to 4:1 (Inorganic N-containing salt: calcium compound) or 0.5:1 to 2:1 or 0.5:1 to 1.5:1 or 1:1 to 1.5:1 or 2:1 to 4:1 or 2:1 to 3:1 or 2.5:1 to 3:1 or 3:1 to 4:1, or 2:1, or 3:1, or 4:1 with calcium compound.In some forms, the proportions mentioned above or such proportions herein are molar proportions or weight % proportions. In some embodiments of the methods described herein, non-polyhydroxy compounds are used to form the precipitation material and / or the products provided herein. Agitation can be used to treat the calcium compound, for example, by eliminating hot and cold spots. In some embodiments, the concentration of the calcium compound in water can be between 1 and 10 g / L, 10 and 20 g / L, 20 and 30 g / L, 30 and 40 g / L, 40 and 80 g / L, 80 and 160 g / L, 160 and 320 g / L, 320 and 640 g / L, or 640 and 1280 g / L. To optimize the purification / solvation of the calcium compound, high-shear mixing, wet grinding, and / or sonication can be used to break down the calcium compound. During or after high-shear mixing and / or wet grinding, the calcium compound suspension can be treated with the nitrogen-containing salt and then further contacted with carbon dioxide from the cement kiln exhaust (as shown in Fig. 1). In some embodiments, treating the calcium compound with a nitrogen-containing salt (e.g., ammonium chloride) and optionally ammonium results in the formation of an aqueous solution of calcium salt, nitrogen-containing salt, and optionally solids. In some embodiments, insoluble solid impurities can be removed from the aqueous calcium chloride solution before the aqueous solution is treated with carbon dioxide in the process (step C in Fig. 1). The solids can optionally be removed from the aqueous solution by filtration and / or centrifugation techniques. In some embodiments, the solid impurity may not be removed from the aqueous solution (not shown in Fig. 1), and the aqueous solution containing calcium salts, as well as the solids, are in contact with carbon dioxide to form precipitates. In such embodiments, the precipitate material also comprises solids. In some embodiments, the solids obtained from the solvation of the calcium compound (shown as soluble impurities in Fig. 1) are calcium-depleted solids and can be used as a cement substitute (such as a substitute for Portland cement). In some embodiments, the solids are between 1 and 40% by weight, or between 1 and 30% by weight; or between 1 and 20% by weight; or between 1 and 10% by weight or between 1 and 5% by weight; or between 1 and 2% by weight, in the aqueous solution, in the precipitation material, or a combination thereof. As illustrated in step D in Fig. 1, the following reaction occurs when an aqueous solution comprising calcium salt (and optionally solids) is contacted with carbon dioxide from the cement plant: CaCI2(ac) + 2 NH3(ac) + CO2(g) + H2O CaCO3(s) + 2 NFUCKac) The absorption of CO2 in solution produces CO2-laden water containing carbonic acid, a species in equilibrium with both bicarbonate and carbonate. The precipitation material is prepared under one or more precipitation conditions (as described herein) suitable for forming PCC material or material containing vaterite. The aqueous calcium salt solution, from the treatment of the calcium compound with a nitrogen-containing salt such as an ammonium salt, is contacted with CO2 from the cement plant at any time before, during, or after the calcium salt is subjected to one or more precipitation conditions (i.e., conditions that allow the precipitation of the precipitate material). Accordingly, in some embodiments, an aqueous calcium salt solution is contacted with CO2 before subjecting the aqueous solution to precipitation conditions that favor the formation of the precipitate material comprising PCC or reactive or stable vaterite. In some embodiments, an aqueous calcium salt solution is contacted with CO2 while the aqueous solution is being subjected to precipitation conditions that favor the formation of the precipitate material comprising PCC or reactive or stable vaterite.In some embodiments, an aqueous solution of calcium salt is contacted with CO2 before and while the aqueous solution is subjected to precipitation conditions that favor the formation of the precipitate material comprising PCC or reactive or stable vaterite. In some embodiments, contacting the aqueous solution comprising calcium salt with carbon dioxide from the cement plant is achieved by contacting the aqueous solution to achieve and maintain a desired pH range, a desired temperature range, and / or a desired divalent cation concentration using a convenient protocol as described herein. In some embodiments, the systems include a precipitation reactor configured to contact the aqueous solution comprising calcium salt with carbon dioxide from the cement plant. In some embodiments, the aqueous solution comprising calcium salt can be placed in a water-supported precipitation reactor, wherein the amount of the incorporated aqueous solution comprising calcium is sufficient to raise the pH to a desired level (e.g., a pH that induces precipitation of the precipitate material) such as pH 7 to 14, pH 7.5 to 8.5, pH 7 to 8, pH 8 to 14, pH 9 to 14, pH 10 to 14, pH 11 to 14, pH 12 to 14, or pH 13 to 14. In some embodiments, the pH of the aqueous solution comprising calcium salt, when brought into contact with carbon dioxide, is maintained between 7 and 8.5, 7.5 and 8.5, 7 and 8, 7.6 and 8.5, 8 and 8.5, or 7.5 and 9.5. to form the precipitation material comprising stable vaterite, reactive vaterite, or PCC. In some embodiments, the aqueous solution is immobilized in a column or bed.In such embodiments, water is passed through or over a sufficient quantity of calcium salt solution to raise the pH of the water to a desired pH or to a particular divalent cationic (Ca2+) concentration. In some embodiments, the aqueous solution can be cycled more than once, where a first precipitation cycle removes mainly calcium carbonate minerals and leaves an alkaline solution to which additional aqueous solution comprising calcium salt can be added. Carbon dioxide, when brought into contact with the recycled aqueous solution, allows the precipitation of more calcium carbonate and / or bicarbonate compounds. It will be appreciated that, in these embodiments, the aqueous solution after the first precipitation cycle can be contacted with CO2 before, during, and / or after the addition of the aqueous solution comprising calcium. In these embodiments, the water can be recycled or reintroduced.As such, the order of incorporation of CO2 and the aqueous solution comprising the calcium salt can vary. For example, the aqueous solution comprising the calcium salt can be incorporated into, for example, brine, seawater, or freshwater, followed by the incorporation of CO2. In another example, CO2 can be incorporated into, for example, brine, seawater, or freshwater, followed by the incorporation of the aqueous solution comprising the calcium salt. The aqueous solution comprising calcium salt can be contacted with CO2 using any convenient protocol. Where CO2 is a gas, contact protocols of interest include, but are not limited to, direct contact protocols (e.g., bubbling CO2 gas through aqueous solution), concurrent contacting methods (i.e., contact between unidirectionally flowing liquid and gas phase streams), countercurrent methods (i.e., contact between oppositely flowing liquid and gas phase streams), and the like. Contact can be achieved through the use of infusers, bubblers, fluidic Venturi reactors, sprayers, gas filters, atomizers, trays, or IVIA / a / ZUZZ / UUUO / 4 packed column reactors and the like, in the precipitation reactor. In some embodiments, gas-liquid contact is achieved by forming a solution liquid with a flat jet nozzle, wherein the CO2 gas and the liquid sheet move in countercurrent, cocurrent, or crosscurrent directions, or in any other manner. In some embodiments, gas-liquid contact is achieved by contacting solution liquid droplets having an average diameter of 500 micrometers or less, such as 100 micrometers or less, with a CO2 gas source. The gaseous CO2 stream from the cement plant may be substantially pure CO2 or comprise multiple components, including CO2 and one or more additional gases and / or other substances such as ash and other particulates. A portion of the gaseous CO2 waste stream (i.e., not the entire gaseous waste stream) from the cement plant may be used to produce the precipitate material. In some embodiments, the portion of the gaseous CO2 waste stream employed in the precipitation of the precipitate material may be 75% or less, such as 60% or less, and including 50% or less of the gaseous waste stream. In still other embodiments, substantially (for example, 80% or more) of the entire gaseous CO2 waste stream produced by the cement plant is employed in the precipitation of the precipitate material. Any number of the gas-liquid contact protocols described herein may be used. Gas-liquid contact is continued until the pH of the precipitation reaction mixture is optimum (several optimum pH values ​​are described herein for forming precipitate material comprising, for example, reactive vaterite), after which the precipitation reaction mixture is allowed to be stirred. The rate at which the pH drops can be controlled by incorporating more of the aqueous solution comprising calcium salt during gas-liquid contact. Furthermore, additional aqueous solution can be incorporated after spraying to raise the pH back to basic levels for precipitation of a portion or all of the precipitate material. In either case, precipitate material may form under proton removal from certain species (e.g., carbonic acid, bicarbonate, hydronium) in the precipitation reaction mixture.The precipitate material comprising carbonates can then be separated and optionally, further processed. The rate at which the pH drops can be controlled by adding extra supernatant or an aqueous solution containing calcium salt during gas-liquid contact. Additionally, extra supernatant or an aqueous solution containing calcium salt can be added after gas-liquid contact to raise the pH back to basic levels (e.g., between 7 and 9, 7 and 8.5, or 7 and 8) to precipitate some or all of the precipitate material. In some embodiments, the gas leaving the absorbent or precipitation reactor (shown as scrubbing gas in Fig. 1) is sent to a gas treatment unit for further purification. The mass balance and equipment design for the gas treatment unit may depend on the gas properties. In some embodiments, the gas treatment unit may incorporate an HCl scrubber to recover small amounts of NH3 in the exhaust gas stream that may be present from the CO2 absorption or precipitation stage. NH3 can be captured by the HCl solution through: NH3(g) + HCl(aq) -> NH4Cl(aq) The NH4Cl (aq) from the HCl scrubber can be recycled to solvation step B. In some embodiments, the ammonia-containing exhaust gas stream (shown as scrubbing gas in Fig. 1) may be subjected to a scrubbing process where the ammonia-containing exhaust gas stream is scrubbed with carbon dioxide from the industrial process and water to produce an ammonia solution. The inlets to the scrubber may be carbon dioxide (CO2(g)), the ammonia-containing reactor exhaust gas (NH3(g)), and freshwater (or some other dilute water stream). The outlet may be a flow surface of the scrubbing recirculation fluid (e.g., H3N-CO2(aq) or carbamate), which may optionally be returned to the main reactor for contact with the carbon dioxide and precipitation. The pH of the system may be controlled by regulating the CO2 flow rate. <g) dentro del depurador.The system's conductivity can be controlled by adding diluted feed water to the purifier. The volume can be kept constant using a level sensor in the purifier or its tank. Although ammonia is a basic gas, carbon dioxide gases are acidic gases. In some configurations, acidic and basic gases can ionize each other to increase their solubilities. Without being limited by any theory, the following reaction is considered to be possible: NH3(ac) + CO2(ac) + H2O HCCh' + NH4+ The aqueous solution comprising calcium salt, when it comes into contact with CO2 gas, results in the precipitation of calcium carbonate. The one or more precipitation conditions that result in the formation of stable or reactive vaterite (PCC) in this process are described below. In some embodiments, the precipitate material comprises stable vaterite and / or reactive vaterite (PCC). Stable vaterite, or its grammatical equivalent as used herein, includes vaterite that does not transform into aragonite or calcite during and / or after the dissolution-reprecipitation process in water. Reactive vaterite, or activated vaterite, or its grammatical equivalent as used herein, includes vaterite that results in the formation of aragonite during and / or after the dissolution-reprecipitation process in water. Precipitated calcium carbonate (PCC), as used herein, includes conventional PCC with high purity and particles of millimeter size or smaller.PCC can be in any polymorphic form of calcium carbonate, including but not limited to vaterite, aragonite, calcite, or combinations thereof. In some forms, PCC has a particle size in nanometers or between 0.001 micrometers and 5 micrometers. The precipitate material, comprising reactive vaterite (optionally including solids), undergoes transformation to aragonite and is fixed and hardened into cementitious products (shown as products (A) in Fig. 1). The solids can be incorporated into the cementitious products. This provides the additional advantage of one less solids removal step, minimizing NH4Cl loss and eliminating a potential waste stream, thereby increasing efficiency and improving the economics of the process. In some embodiments, the solid impurities do not adversely affect the transformation and / or reactivity of the vaterite or aragonite. In some embodiments, the solid impurities do not adversely affect the strength (such as compressive or flexural strength) of the cementitious products. In some embodiments, the methods described above also include separating the precipitated material (e.g., drainage) from the aqueous solution (referred to as calcium carbonate cake in Fig. 1) by drainage, optionally rinsing, and optionally drying. The precipitated material can then be used to make cementitious or non-cementitious products (shown as products (B) in Fig. 1). In some embodiments, vaterite in the precipitation material can form under appropriate conditions such that it is reactive and transforms into aragonite through a dissolution-precipitation process (during cementation) in water. The aragonite can impart one or more unique characteristics to the product, including, but not limited to, high compressive strength, a complex microstructure network, and neutral pH. In some embodiments, the vaterite in the precipitation material can form under appropriate conditions such that it is stable and used as a filler in various applications. In some embodiments, PCC in the precipitation material can form under appropriate conditions such that the PCC is highly pure and has a very small particle size. In some embodiments, the calcium bicarbonate cake, as described above, may comprise impurities (e.g., 1 to 2% by weight or more) of ammonium ions (NH4+), sulfur ions, and / or chloride ions (Cl·)-. While rinsing the filter cake of precipitated CaCO3, as described above, may remove some or all of the N-containing salts and / or sulfur compounds, this may result in a dilute concentration of N-containing salts (in the supernatant) which may need to be concentrated before recycling. MA / a / ZUZZ / UUUUO f 4 return to the process. The calcium carbonate slurry can be drained and optionally rinsed to form calcium carbonate slurry (with reduced water) or calcium carbonate cake (as illustrated in Fig. 1), and the water containing the residual nitrogen-containing salt solution, for example, the ammonia salt solution. The residual nitrogen-containing salt solution obtained from the drain, as well as the rinse stream, can optionally be concentrated before being recycled back for solvation treatment with the calcium compound. Additional nitrogen-containing salt and / or ammonia (aqueous or anhydrous solution) can be added to the recycled solution to compensate for the loss of nitrogen-containing salt during the process and bring the concentration of the nitrogen-containing salt to the optimum level. In some embodiments, the salt containing residual nitrogen, such as the ammonium chloride solution illustrated in Fig. 1, can be recovered from the supernatant aqueous solution and concentrated using recovery processes such as, but not limited to, thermal decomposition, pH adjustment, reverse osmosis, multi-stage scintillation, multiple-effect distillation, vapor recompression, distillation, or combinations thereof. Systems for carrying out these processes are commercially available. For example, the pH of the solution can be raised (e.g., with a strong base such as NaOH). This can shift the equilibrium toward volatile ammonia (NH3(aq) / NH3(g)). The removal rates and overall removal could both be improved by heating the solution. In some embodiments, the salt containing residual N can be separated and recovered from the calcium carbonate precipitate by a thermal decomposition process. This process can be incorporated into the process illustrated in Fig. 1 during the separation of the CaCO3 precipitate (step E) and / or after the step of drying or powdering the CaCO3 (step F). Typically, at 338°C, solid NH4Cl can decompose into ammonia (NH3) and hydrogen chloride (HCl) gases. However, at 840°C, solid CaCO3 decomposes into solid calcium oxide (CaO) and carbon dioxide (CO2) gas. NH4Cl(s) NH3(g) + HCl(g) CaCO3(s) → CaO(s) + CO₂(g) In some embodiments, the residual nitrogen-containing salt in the dried CaCO3 precipitate and / or CaCO3 precipitate, such as, but not limited to, ammonium chloride, ammonium acetate, ammonium sulfate, ammonium sulfite, ammonium hydrosulfide, ammonium thiosulfate, ammonium nitrate, ammonium nitrite, or combinations thereof, can be removed by thermal decomposition at a temperature between 150 and 360°C, or between 150 and 200°C, or between 150 and 300°C, or between 300 and 850°C, or between 338 and 840°C. This can be done either during the normal filter cake drying process and / or as a second heat treatment after drying.A desirable temperature range decomposes the residual N-containing salt in the precipitate while preserving the cementitious properties of the reactive vaterite in the precipitate material such that the reactive vaterite remains as reactive vaterite after heating, and after combination with water, successfully transforms into aragonite to form cementitious products.In some embodiments of the above aspect and embodiments, step (i¡¡) of removal and optionally recovery of residual N-containing salt from the precipitate material comprises heating the precipitate material to approximately 150 to 375°C or approximately 150 to 300°C or approximately 290 to 375°C or approximately 300 to 360°C or approximately 300 to 350°C or approximately 310 to 345°C or approximately 320 to 345°C or approximately 330 to 345°C or approximately 300 to 345°C, to evaporate the N-containing salt from the precipitate material without optional recovery by condensation of the N-containing salt.In some embodiments of the above aspect and embodiments, step (iii) of removing and optionally recovering the residual N-containing salt from the precipitate material comprises heating the precipitate material, for a duration of more than approximately 10 min or more than approximately 15 min or more than approximately 5 min or from approximately 10 min to approximately 1 hour or from approximately 10 min to approximately 1.5 hours or from approximately 10 min to approximately 2 hours or from approximately 10 min to approximately 5 hours or from approximately 10 min to approximately 10 hours. In the embodiments, the precipitation material is dewatered (to remove the supernatant aqueous solution) and dried to remove water (e.g., by heating to approximately 100°C) before subjecting the precipitation material to heating step (iii) to remove and optionally recover the N-containing salt. In some embodiments, the precipitation material is partially dewatered (to remove the mass of the supernatant aqueous solution) and partially dried to remove water (or the drying step is omitted) before subjecting the precipitation material to heating step (iii) to remove and optionally recover the N-containing salt. In some embodiments, the reactive vaterite in the precipitation material remains as reactive vaterite after heating.In some embodiments of the foregoing, it is desirable that the reactive vaterite in the precipitation material remain as reactive vaterite so as to preserve the cementitious properties of the material. In some embodiments, the nitrogen-containing salt is evaporated from the precipitation material in a form comprising ammonia gas, hydrogen chloride gas, chloride gas, or combinations thereof. Applicants have found that in some embodiments, maintaining a combination of the amount of temperature and the duration of heating can be critical for removing the nitrogen-containing salt from the precipitation material while still preserving the cementitious properties of the reactive vaterite material. Traditionally, reactive vaterite is highly unstable and readily transforms to aragonite / calcite.However, applicants have found temperature ranges coupled with heating durations that minimize the transformation of reactive vaterite while still removing residual nitrogen-containing salts from the material. In some embodiments of the above embodiments, the vaterite in the precipitation material, after removal of the nitrogen-containing salts, remains as reactive vaterite, which, when combined with water, transforms into aragonite (dissolution-reprecipitation process). This aragonite then binds and cements to form cementitious products. The cementitious products thus formed have minimal or no chloride content and no unpleasant ammonia or sulfur odor. In some embodiments, the chloride content is at or below acceptable ASTM standards for cementitious products. In some embodiments, the temperature conditions mentioned above, optionally coupled with the heating duration, can be combined with pressure conditions that provide an activating force to enhance the thermodynamics of the decomposition of the salt containing residual nitrogen. For example, the heating of the precipitation material can be carried out in a system where the headspace is at a pressure lower than atmospheric pressure. This lower-than-atmospheric pressure can create a driving force for the heating reaction involving gas-phase products (such as, but not limited to, ammonia gas, hydrogen chloride gas, chloride gas, or combinations thereof).Another advantage of operating under reduced pressure or vacuum may be that at lower pressure some sublimation reactions can occur at lower temperatures, thus improving the energy requirements of the heating reaction. In some variations of the thermal decomposition process described above, the ammonium chloride separated as HCl and ammonia gases can be recovered for reuse by either recrystallization of the thermally combined evolved gases or by absorption of the gases in an aqueous medium. Both mechanisms can result in NEUCl, which may be sufficiently concentrated for reuse in the process, as shown in Fig. 1. In some formulations, the nitrogen-containing salt can be separated and recovered in the process described above (or as illustrated in Fig. 1) by the evolution of pH-adjusted NH3 gas from ammonium salt. This process can be incorporated into the process illustrated in Fig. 1 for the separation of the CaCO3 cake. The final pH of the water in the filter cake is typically approximately 7.5. At this pH, NH4+ (pKa = 9.25) may be the predominant species. Increasing the pH of this water can shift the acid-base equilibrium toward NH3 gas, as described in the following equation. NH4+H++ NH3(g) Any source of alkalinity can be used to increase the pH of the filter cake water. In some embodiments, an aqueous solution of calcium oxide and / or hydroxide or limestone slurry can provide the high alkalinity source. In some embodiments, the aqueous fraction of the calcium compound can be incorporated into the rinsing stage of the dewatering process (e.g., filter cake pass) to increase the system pH and lead to the evolution of NH3 gas. Since ammonia has substantial solubility in water, heat and / or vacuum pressure can be applied to drive the equilibrium further toward the gas phase. The ammonia can be recovered for reuse by either recrystallization of ammonia with chloride or by absorption of the ammonia in an aqueous medium.Both mechanisms can result in either ammonia solution or NH4Cl product, which may be concentrated enough to be reused in the process as described in Fig. 1. The calcium carbonate cake (e.g., vaterite or PCC) can be fed to the dryer (step F in Fig. 1) to form calcium carbonate powder containing PCC or reactive or stable vaterite. The powder form of the precipitate material comprising stable or reactive vaterite or PCC can be further used in the applications to form products, as described herein. The cake can be dried using any drying techniques known in the art, such as, but not limited to, a fluidized bed dryer or a vortex fluidizer. The resulting solid powder can then be mixed with additives to manufacture different products described herein. In some embodiments, the water-reduced slurry form or the cake form of the precipitate material is used directly to form products, such as construction panels, as described herein. Optionally, the separated solids can be dried and used as pozol. In some embodiments, the separated solids can be incorporated into the powdered form of the precipitation material, which includes vaterite as a filler or supplementary cementitious material. In the methods provided herein, an aqueous solution comprising water charged with CO2, produced by contact with an aqueous solution comprising calcium salt with CO2 (both obtained from the cement plant), is subjected to one or more precipitation conditions (step D) sufficient to produce a precipitate comprising stable or reactive vaterite or PCC and a supernatant (i.e., the portion of the precipitation reaction mixture left after precipitation of the precipitate). The one or more precipitation conditions favor the production of a precipitate comprising stable or reactive vaterite or PCC. Precipitation conditions include those that modulate the CO2-charged precipitation reaction mixing environment to produce the desired precipitate material. MA / a / zuzz / uuuo r 4 comprises stable or reactive vaterite or PCC. Said one or more precipitation conditions, which may be used in the embodiments of the method described herein, appropriately form stable or reactive vaterite or PCC containing carbonate precipitate material, including, but not limited to, temperature, pH, pressure, ion index, precipitation index, presence of additive, presence of ionic species, concentration of additive and ionic species, agitation, residence time, mixing index, forms of agitation such as ultrasonic, presence of seed crystals, catalysts, membranes or substrates, dewatering, drying, ball milling, etc. In some embodiments, the average particle size of the stable or reactive vaterite or PCC may also depend on one or more precipitation conditions used in the precipitation of the precipitate material.In some forms, the percentage of stable or reactive vaterite in the precipitation material may also depend on one or more precipitation conditions used in the precipitation process. For example, the temperature of the CO2-charged precipitation reaction mixture can be increased to a point at which an appropriate amount of the desired precipitate material is formed. In such cases, the temperature of the CO2-charged precipitation reaction mixture can be raised to a value such as 20°C to 80°C, including 25°C to 45°C, 20°C to 70°C, 20°C to 60°C, 20°C to 50°C, 20°C to 40°C, or 20°C to 30°C. Although a given set of precipitation conditions may have a temperature ranging from 0°C to 100°C, the temperature can be raised in certain ways to produce the desired precipitate material.In certain modalities, the temperature of the precipitation reaction mixture is raised using energy generated from low or zero carbon dioxide emission sources (e.g., solar energy source, wind energy source, hydroelectric energy source, waste heat from the combustion gases of the carbon emitter, etc.). The pH of the CO2-charged precipitation reaction mixture can also be increased to an amount suitable for precipitation of the desired precipitate material. In such embodiments, the pH of the CO2-charged precipitation reaction mixture is increased to alkaline levels for precipitation, where carbonate is favored over bicarbonate. In some embodiments, the pH of the aqueous solution comprising calcium salt that is in contact with carbon dioxide gas has an effect on the formation of reactive vaterite or PCC. In some embodiments, the precipitation conditions required to form the precipitate material comprising reactive vaterite or PCC include conducting the contact step of carbon dioxide with the aqueous solution comprising calcium salt at a pH greater than 7, or pH 8, or pH between 7.1 and 8.5, or pH between 7.5 and 8, or between 7.5 and 8.5, or between 8 and 8.5, or between 7.6 and 8.4, to form reactive vaterite or PCC.The pH can be increased to pH 9 or higher, such as ρH 10 or higher, including pH 11 or higher or pH 12.5 or higher. Higher ionic ratios during precipitation can affect the nature of the precipitate material. Higher ionic ratios can have a considerable influence on polymorph formation. For example, as the magnesium:calcium ratio in the water increases, aragonite may convert to the major polymorph of calcium carbonate in the precipitate material over low-magnesium vaterite. At low magnesium:calcium ratios, low-magnesium calcite may become the major polymorph. In some forms, where Ca2+ and Mg2+ are both present, the ratio of Ca2+ to Mg2+ (i.e., Ca2+:Mg2+) in the precipitate material is 1:1 to 1:2.5; 1:2.5 to 1:5; 1:5 to 1:10; 1:10 to 1:25; 1:25 to 1:50; 1:50 to 1:100. 1:100 to 1:150; 1:150 to 1:200; 1:200 to 1:250; 1:250 to 1:500; or 1:500 to 1:1000.In some forms, the Mg2+ to Ca2+ ratio (i.e., IMg2+:Ca2+) in the precipitate material is 1:1 to 1:2.5; 1:2.5 to 1:5; 1:5 to 1:10; 1:10 to 1:25; 1:25 to 1:50; 1:50 to 1:100; 1:100 to 1:150; 1:150 to 1:200; 1:200 to 1:250; 1:250 to 1:500; or 1:500 to 1:1000. The precipitation rate can also affect the phase formation of the compound, with the fastest precipitation rate achieved by seeding the solution with a desired phase. Without seeding, rapid precipitation can be achieved by rapidly increasing the pH of the precipitation reaction mixture, which can result in more amorphous constituents. At higher pH, precipitation is faster, which can result in a more amorphous precipitate material. The residence time of the reaction mixture after contacting the aqueous solution with CO2 can also affect the phase formation of the compound. For example, in some embodiments, a longer residence time can result in the transformation of reactive vaterite to aragonite / calcite within the reaction mixture. In some embodiments, too short a residence time can result in incomplete formation of reactive vaterite in the reaction mixture. Therefore, residence time can be critical for the precipitation of reactive vaterite. Furthermore, residence time can also affect the particle size of the precipitate. For example, too short a residence time can result in the agglomeration of particles, forming large particles, which is undesirable for PCC formation.Therefore, in some modalities, the residence time of the reaction is between approximately 10 min to 1 hour, or between approximately 15 min to 60 min, or between approximately 15 min to 45 min, or between approximately 15 min to 30 min, or between approximately 30 min to 60 min. In some embodiments, a set of precipitation conditions for producing a desired precipitate material from a precipitation reaction mixture may include, as previously mentioned, temperature and pH, as well as, in some cases, the concentrations of additives and ionic species in the water. The additives are described below. The presence and concentration of additives can also favor the formation of stable or reactive vaterite or PCC. In some embodiments, a medium-chain or long-chain fatty acid ester may be incorporated into the aqueous solution during precipitation to form PCC. Examples of fatty acid esters include, but are not limited to, cellulose such as carboxymethyl cellulose, sorbitol, citrate such as sodium or potassium citrate, stearate such as sodium or potassium stearate, phosphate such as sodium or potassium phosphate, sodium tripolyphosphate, hexametaphosphate, EDTA, or combinations thereof.In some forms, a combination of stearate and citrate can be incorporated during the contact step of the process to form PCC. Precipitation conditions may also include factors such as mixing index, agitation methods such as ultrasonic, and the presence of seed crystals, catalysts, membranes, or substrates. In some embodiments, precipitation conditions include supersaturation, temperature, pH, and / or concentration gradients, or cycling or changing some of these parameters. The protocols employed to prepare the precipitation material according to the invention may be batch, semi-batch, or continuous. Precipitation conditions may differ for producing a given precipitation material in a continuous flow system compared to a semi-batch or batch system. The precipitate, after production from a precipitation reaction mixture, is separated from the reaction mixture to produce the separated precipitate (e.g., wet cake) and a supernatant, as illustrated in step E in Fig. 1. In the systems provided herein, the separation step can be carried out at the separation station. The precipitate can be stored in the supernatant for a period of time after precipitation and before separation (e.g., by drying). For example, the precipitate can be stored in the supernatant for a period of time ranging from a few minutes to hours, or from 1 to 1000 days or longer, at a temperature ranging from 1°C to 40°C, or from 20°C to 25°C.Separation of the precipitate material from the precipitation reaction mixture is achieved using any of several different approaches, including drainage (e.g., gravity settling of the precipitate material followed by drainage), decantation, filtration (e.g., gravity filtration, vacuum filtration, filtration using forced air), centrifugation, pressing, or any combination thereof. Separation of bulk water from the precipitate material produces either a wet cake of precipitate material or dewatered precipitate material. A liquid-solid separator such as the Epuramat Extrem-Separator (ExSep), the Xerox PARC spiral concentrator, or a modification of either the Xerox PARC spiral concentrator or the Epuramat ExSep, can be useful for separating the precipitate material from the precipitation reaction mixture. In some embodiments, the resulting dewatered precipitate material, such as wet cake material (after thermal removal of the nitrogen-containing salt), is used directly to manufacture the products described herein. For example, the wet cake of dewatered precipitate material is mixed with one or more additives, described herein, and spread onto the conveyor belt where the reactive vaterite or PCC in the precipitate material transforms to aragonite and fixes and hardens (and the nitrogen-containing salt is thermally removed). The hardened material is then cut into desired shapes, such as plates or panels described herein. In some embodiments, the wet cake is emptied onto a sheet of paper on top of the conveyor belt. Another sheet of paper may be placed on top of the wet cake, which is then pressed to remove excess water.After the precipitation material sets and hardens (transformation from vaterite to aragonite), it is cut into desired shapes, such as cement boards and drywall, etc. In some embodiments, the quantity of one or more additives can be optimized depending on the desired time required for the transformation from vaterite to aragonite (described below). For example, for some applications, a rapid transformation may be desired, while in others, a slow transformation may be preferred. In some embodiments, the wet cake can be heated on a conveyor belt to accelerate the transformation from vaterite to aragonite. In other embodiments, the wet cake can be poured into molds of the desired shape, and the molds are then heated in an autoclave to accelerate the transformation from vaterite to aragonite (and to remove residual nitrogen-containing salt).As appropriate, the continuous flow process, batch process, or semi-batch process are all within the scope of the invention. In some embodiments, the precipitated material, once separated from the precipitation reaction mixture, is washed with fresh water and then placed in a filter press to produce a filter cake with 30 to 60% solids. The filter cake is then mechanically pressed into a mold, using any convenient means, for example, a hydraulic press, at suitable pressures, for example, ranging from 5 to 5000 psi, such as 1000 to 5000 psi, to produce a shaped solid, for example, a rectangular brick. The resulting solids are then cured, for example, by outdoor placement and storage, or by placement in a chamber where they are subjected to high levels of humidity and heat, etc. These resulting cured solids are then used as building materials or crushed to produce aggregate, etc. In the process involving the use of temperature and pressure, the dehydrated precipitate cake can be dried. The cake is then exposed to a combination of re-watering and elevated temperature and / or pressure for a certain time. The combination of the amount of re-watering, temperature, pressure, and exposure time, as well as the cake thickness, can vary according to the composition of the starting material and the desired results. Several different methods of exposing the material to temperature and pressure are described herein; it will be appreciated that any convenient method may be used. The thickness and size of the cake may be adjusted as desired; the thickness may vary in some embodiments from 0.13 centimeters (0.05 inches) to 12.7 centimeters (5 inches), for example, 0.25 inches (0.1 inches) to 5.08 centimeters (2 inches), or 0.76 centimeters (0.3 inches) to 2.54 centimeters (1 inch). In some embodiments, the cake may be from 1.27 centimeters to 15.24 centimeters (0.5 inches to 6 feet) or even thicker. The cake is then exposed to elevated temperature and / or pressure for a given time, by any convenient method, for example, in a pressure plate press using heated pressure plates.The heat required to raise the temperature, for example, for pressure plates, can be supplied, for instance, by heat from an industrial waste gas stream such as a flue gas stream. The temperature can be any suitable temperature; generally, a higher temperature is desired for a thicker cake. Examples of temperature ranges are 40 to 150°C, 60 to 120°C, 70 to 110°C, or 80 to 100°C. Similarly, the pressure can be any pressure suitable for producing the desired results. Exemplary pressures include 1,000 to 100,000 pounds per square inch (psi), including 2,000 to 50,000 psi, 2,000 to 25,000 psi, 2,000 to 20,000 psi, or 3,000 to 5,000 psi. Finally, the time the cake is pressed can be any time, for example, 1 to 100 seconds, or 100 minutes, or 1 to 50 minutes, or 2 to 25 minutes, or 10,000 days.The resulting hard tablet can then optionally be cured, for example, by placing it outdoors and storing it in a chamber where it is subjected to high levels of humidity and heat, etc. These optionally cured hard tablets are then used as building materials or crushed to produce aggregate. Another method of providing temperature and pressure is the use of a press. A suitable press, for example, a platen press, can be used to provide pressure at the desired temperature (using heat supplied, for example, by a combustion gas or by other process steps to produce a precipitate, for example, from an electrochemical process) for a desired time. A set of rollers can be used similarly. Another way to expose the cake to elevated temperature and pressure is by means of an extruder, for example, a screw extruder. The extruder barrel can be equipped to achieve an elevated temperature, for example, by jacketing; this elevated temperature can be supplied by, for example, combustion gases or similar means. Extrusion can be used as a means of preheating and drying the raw material before a pressing operation. Such pressing can be carried out by means of a compression mold, rollers, molded notched rollers (which can provide virtually any desired aggregate shape), between a belt which provides compression as it travels, or any other method. Alternatively, the extruder can be used to extrude material through a die, exposing the material to pressure as it is forced through the die, and giving it any desired shape.In some formulations, the carbonate precipitate is mixed with fresh water and then fed into the feed section of a rotating screw extruder. The extruder and / or the die may be heated to further aid the process. The screw's rotation carries the material along its length and compresses it as the screw depth decreases. The screw and extruder barrel may also include barrel vents with decompression zones in the screw that align with the barrel vent openings. Particularly in the case of a heated extruder, these vent areas allow steam to escape from the conveyed mass, removing water from the material. The material conveyed by the screw is then forced through the die section, which further compresses and shapes the material. Typical die openings can be circular, oval, square, rectangular, trapezoidal, etc., although any desired shape of the final aggregate can be achieved by adjusting the shape of the opening. The material exiting the die can be cut to any convenient length by any suitable method, such as with a flight knife. The use of a heated die section can further aid product formation by accelerating the transition of the carbonate mineral to a stable, hard form. Heated dies can also be used with binders to harden or fix the binder. Temperatures from 100°C to 600°C are commonly used in the heated die section. In still other applications, the precipitate can be used to fabricate or form structures in situ. For example, roads, paved areas, or other structures can be fabricated from the precipitate by applying a layer of precipitate, as described above, to a substrate, such as a floor or subgrade, and then hydrating the precipitate, for example, by exposing it to naturally occurring water, such as rain, or by irrigation. Hydration solidifies the precipitate into a desired in situ structure, such as a road or pavement. The process can be repeated, for example, where thicker layers of in situ structures are desired. In some embodiments, the production of the precipitate and the final product take place in the same facility. In others, the precipitate is produced in one facility and transported to another for final product manufacturing. The precipitate may be transported as a slurry, a wet cake, or a dry powder. In some embodiments, the resulting dewatered precipitate obtained from the separation station is dried in the drying station to produce a powdered form of the carbonate precipitate comprising stable or reactive vaterite or PCC. Drying can be achieved by air drying of the precipitate. In certain embodiments, drying is achieved by freeze-drying (i.e., lyophilization), where the precipitate is frozen, the surrounding pressure is reduced, and sufficient heat is incorporated to allow the frozen water in the precipitate to sublimate directly into a gas.In yet another embodiment, the precipitate is spray-dried, where the liquid containing the precipitate is dried by feeding it through hot gas (such as the gaseous waste stream from the power plant). The liquid feed is pumped through an atomizer in a main drying chamber, and hot gas is passed as a co-current or counter-current toward the atomizer. Depending on the system's specific drying protocol, the drying station may include a filtration element, freeze-drying structure, spray-drying structure, etc. In some embodiments, the precipitate may be dried using a fluidized bed dryer. In certain embodiments, waste heat from a power plant or similar operation may be used to perform the drying step when appropriate.For example, in some embodiments, dry product is produced by the use of elevated temperature (e.g., from waste heat from a power plant), pressure, or a combination thereof. After drying the precipitate material, the material can then be heated to elevated temperatures to remove nitrogen-containing salt as described herein. The supernatant resulting from the precipitation process, or slurry of precipitate material, can also be processed as desired. For example, the supernatant or slurry can be returned to the aqueous solution of the calcium compound or to another location. In some embodiments, the supernatant can be contacted with a CO2 source, as described above, for additional CO2 sequestration. For example, in embodiments where the supernatant is returned to the precipitation reactor, it can be contacted with a gaseous waste CO2 source sufficiently to increase the concentration of carbonate ions present in the supernatant. As described above, the contact can be conducted using any convenient protocol. In some embodiments, the supernatant has an alkaline pH, and the contact with the CO2 source is carried out in a way that allows the precipitate to be processed to produce the desired aggregate.In some forms, the precipitate can be left outdoors, where rainwater can be used as the source of fresh water, to cause the meteoric water stabilization reaction to occur, hardening the precipitate to form the aggregate. As illustrated in Fig. 1, the methods produce precipitate material (wet, slurry, or dry) comprising reactive or stable vaterite or PCC. The terms composition, precipitate, and precipitate material are used interchangeably herein. The precipitate material formed in the methods and systems provided herein after the removal of the residual nitrogen-containing salt, as described herein, comprises vaterite or PCC. Stable vaterite includes vaterite that does not transform into aragonite or calcite during and / or after the dissolution-reprecipitation process. Reactive vaterite or activated vaterite includes vaterite that results in the formation of aragonite during and / or after the dissolution-reprecipitation process. In some embodiments, the PCC formed is in the form of vaterite.In some embodiments, the methods described herein additionally include precipitation of the material (in dry or wet form) with water, transforming the reactive vaterite into aragonite. In some embodiments, stable vaterite, when brought into contact with water, does not transform into aragonite and remains in the vaterite form or transforms over a long period of time into calcite. Typically, under calcium carbonate precipitation, amorphous calcium carbonate (ACC) may initially precipitate and transform into one or more of its three more stable phases (vaterite, aragonite, or calcite). A thermodynamic driving force may exist for the transformation from unstable to more stable phases, as described by Ostwald in his Step Rule (Ostwald, W. Zeitschrift für Physikalische Chemie 289 (1897)). For this reason, the calcium carbonate phases transform in the order: ACC to vaterite, aragonite, and calcite, where intermediate phases may or may not be present. During this transformation, excess energy is released, as shown in Fig. 2. This intrinsic energy can be harnessed to create a strong aggregation tendency and surface interactions that can lead to agglomeration and fixation or cementation. It should be understood that the values ​​reported in Fig. 2 are well known in the art and may vary. The methods provided herein produce or isolate precipitate material in the form of vaterite or PCC, which may be present as vaterite, aragonite, or calcite. The precipitate material may be in a wet, slurry, or dry powder form. It may be a stable vaterite form that does not readily transform into any other polymorph, or it may be a reactive vaterite form that transforms into aragonite. The aragonite does not further convert to the more stable calcite form. The product containing the aragonite form of the precipitate exhibits one or more unexpected properties, including, but not limited to, high compressive strength, high porosity (low density or light weight), neutral pH (useful as an artificial reef described below), and a microstructure network. Other minor polymorph forms of calcium carbonate that may be present in the carbonate-containing precipitate material besides vaterite include, but are not limited to, amorphous calcium carbonate, aragonite, calcite, a vaterite precursor phase, an aragonite precursor phase, an intermediate phase that is less stable than calcite, polymorphic forms between these polymorphs, or combinations thereof. Vaterite can be present in monodisperse or agglomerated form and can be spherical, ellipsoidal, plate-like, or hexagonal. Vaterite typically has a hexagonal crystal structure and forms polycrystalline spherical particles upon growth. The vaterite precursor form comprises vaterite nanoclusters, and the aragonite precursor form comprises sub-micron to nanocluster aragonite needles. Aragonite, if present in the composition along with vaterite, can be needle-shaped, columnar, or rhombic crystals. An intermediate phase that is less stable than calcite can be a phase between vaterite and calcite, a phase between the vaterite precursor and calcite, a phase between aragonite and calcite, and / or a phase between the aragonite precursor and calcite. The transformation between calcium carbonate polymorphs can occur via a solid-state transition, be solution-mediated, or both. In some cases, the transformation is solution-mediated because this may require less energy than a thermally activated solid-state transition. Vaterite is metastable, and the difference in thermodynamic stability of calcium carbonate polymorphs can manifest as a difference in solubility, with the less stable phases being more soluble (Ostwald, supra). Therefore, vaterite can readily dissolve in solution and transform favorably into a more stable polymorph, such as aragonite. In a calcium carbonate-like polymorph system, two kinetic processes can occur simultaneously in solution: dissolution of the metastable phase and growth of the stable phase.In some forms, aragonite crystals can grow while vaterite is undergoing dissolution in the aqueous medium. In one aspect, reactive vaterite can be activated in such a way that it leads to an aragonite pathway rather than a calcite pathway during the dissolution-reprecipitation process. In some embodiments, the composition containing reactive vaterite is activated in such a way that, after the dissolution-reprecipitation process, aragonite formation is enhanced and calcite formation is suppressed. Activation of the reactive vaterite-containing composition can result in control over aragonite formation and crystal growth. Activation of the vaterite-containing composition can be achieved by various processes. Several examples of vaterite activation, such as, but not limited to, core activation, thermal activation, mechanical activation, chemical activation, or combinations thereof, are described herein.In some formulations, vaterite is activated through various processes such that the formation of aragonite and its morphology and / or crystal growth can be controlled by reacting vaterite with water. The aragonite formed results in higher tensile strength and fracture tolerance for the products formed from the reactive vaterite. In some embodiments, reactive vaterite can be activated by mechanical means, as described herein. For example, compositions containing reactive vaterite can be activated by creating surface defects in the vaterite composition, thereby accelerating aragonite formation. In some embodiments, the activated vaterite is either ball-milled reactive vaterite or reactive vaterite with surface defects that facilitate the aragonite formation pathway. Compositions containing reactive vaterite can also be activated by providing core or chemical activation to the vaterite composition. Such core or chemical activation can be provided by one or more aragonite seeds, inorganic additives, or organic additives. The aragonite seed present in the compositions provided herein can be obtained from natural or synthetic sources. Natural sources include, but are not limited to, reef sand, limestone, hard skeletal material from certain freshwater and marine invertebrate organisms, including pelecypods, gastropods, mollusc shells, and the calcareous endoskeleton of cold- and warm-water corals, pearls, rocks, sediments, gold minerals (e.g., serpentine), and the like.Synthetic resources include, but are not limited to, precipitated aragonite, such as formed from sodium carbonate and calcium chloride; or aragonite formed by the transformation of vaterite to aragonite, such as transformed vaterite described herein. In some embodiments, the inorganic additive or the organic additive in the compositions provided herein may be any additive that activates reactive vaterite. Some examples of inorganic or organic additives in the compositions provided herein include, but are not limited to, sodium decyl sulfate, lauric acid, sodium salt of lauric acid, urea, citric acid, sodium salt of citric acid, phthalic acid, sodium salt of phthalic acid, taurine, creatine, dextrose, poly(n-vinylpyrrolidone), aspartic acid, sodium salt of aspartic acid, magnesium chloride, acetic acid, sodium salt of acetic acid, glutamic acid, sodium salt of glutamic acid, strontium chloride, gypsum, lithium chloride, sodium chloride, glycine, sodium citrate dihydrate, sodium bicarbonate, magnesium sulfate, magnesium acetate, sodium polystyrene, sodium dodecylsulfonate, polyvinyl alcohol, or combinations thereof.In some embodiments, inorganic or organic additives in the compositions provided herein include, but are not limited to, taurine, creatine, poly(n-vinylpyrrolidone), lauric acid, sodium salt of lauric acid, urea, magnesium chloride, acetic acid, sodium salt of acetic acid, strontium chloride, magnesium sulfate, magnesium acetate, or combinations thereof. Without being limited by any particular theory, it is envisioned that vaterite activation by ball mill crushing or by incorporating aragonite seed, inorganic or organic additives, or combinations thereof, can result in the control of aragonite formation during the dissolution-reprecipitation process of activated reactive vaterite. This includes control of properties such as, but not limited to, polymorphism, morphology, particle size, crosslinking, agglomeration, coagulation, aggregation, sedimentation, crystallography, inhibition of growth along a specific crystal face, and post-growth along a specific crystal face, or combinations thereof. For example, aragonite seed, inorganic additives, or organic additives can selectively direct aragonite morphology, inhibit calcite growth, and promote aragonite formation that may not be kinetically favorable. In some embodiments, one or more inorganic additives may be incorporated to facilitate the transformation of vaterite to aragonite. The one or more additives may be incorporated during any step of the process. For example, the one or more additives may be incorporated during contact of the calcium compound solution with carbon dioxide, after contact of the calcium compound solution with carbon dioxide, during precipitation of the precipitate material, after precipitation of the precipitate material in the slurry, in the slurry after dewatering of the precipitate material, in the powder after drying of the slurry, in the aqueous solution to be mixed with the powdered precipitate material, or in the slurry made from the powdered precipitate material with water or any combination thereof.In some formulations, the water used in the process of preparing the precipitate material may already contain one or more additives or one or more additive ions. For example, if seawater is used in the process, then the additive ion may already be present in the seawater. In some forms of the above methods, the amount of one or more additives incorporated during the process is more than 0.1% by weight, or more than 0.5% by weight, or more than 1% by weight, or more than 1.5% by weight, or more than 1.6% by weight, or more than 1.7% by weight, or more than 1.8% by weight, or more than 1.9% by weight, or more than 2% by weight, or more than 2.1% by weight, or more than 2.2% by weight, or more than 2.3% by weight, or more than 2.4% by weight, or more than 2.5% by weight, or more than 2.6% by weight, or more than 2.7% by weight, or more than 2.8% by weight, or more than 2.9% by weight, or more than 3% by weight, or more than 3.5% by weight, or more than 4% by weight. weight, or more than 4.5% by weight, or more than 5% by weight, or between 0.5 to 5% by weight, or between 0.5 to 4% by weight, or between 0.5 to 3% by weight, or 0.5 to 2% by weight, or 0.5 to 1% by weight, or 3% by weight, or 2.5% by weight, or 2% by weight, or 1.5 to 2.5% by weight, or 2 to 3% by weight, or 2.5 to 3% by weight, or 0.5% by weight, or 1% by weight, or 1.5% by weight, or 2% by weight, or 2.5% by weight, or 3% by weight, or 3.5% by weight, or 4% by weight, or 4.5% by weight, or 5% by weight. In some forms of the above methods, the amount of one or more additives incorporated during the process is between 0.5 and 3% by weight or between 1.5 and 2.5% by weight. In some embodiments, the precipitation material is in powder form. In some embodiments, the precipitation material is in dry powder form. In some embodiments, the precipitation material is disordered or not in an orderly arrangement, or is in powder form. In still some embodiments, the precipitation material is in a partially or fully hydrated form. In still some embodiments, the precipitation material is in salt water or fresh water. In still some embodiments, the precipitation material is in sodium chloride containing water. In still some embodiments, the precipitation material is in water containing alkaline earth metal ions, such as, but not limited to, calcium, magnesium, etc. In some embodiments, the precipitation material is non-medical or not for medical procedures. Products made from the compositions or precipitation material provided herein exhibit one or more properties, such as high compressive strength, high durability, high porosity (light weight), high flexural strength, and lower maintenance costs. In some embodiments, the compositions or precipitation material, when combined with water, set, and hardened, have a compressive strength of at least 3 MPa (megapascals), or at least 7 MPa, or at least 10 MPa, or in some embodiments, between 3 and 30 MPa, or between 14 and 80 MPa, or 14 and 35 MPa. In some of the above aspects and modalities, the composition or precipitate material includes at least 10% wt / wt of vaterite; or at least 20% wt / wt of vaterite; or at least 30% wt / wt of vaterite; or at least 40% wt / wt of vaterite; or at least 50% wt / wt of vaterite; or at least 60% wt / wt of vaterite; or at least 70% wt / wt of vaterite; or at least 80% wt / wt of vaterite; or at least 90% wt / wt of vaterite; or at least 95% wt / wt of vaterite; or at least 99% wt / wt of vaterite; or from 10% wt / wt to 99% wt / wt of vaterite; or from 10% wt / wt to 90% wt / wt of vaterite; or from 10% wt / wt to 80% wt / wt of vaterite; or from 10% wt / wt to 70% wt / wt of vaterite; or from 10% wt / wt to 60% wt / wt of vaterite; or from 10% wt / wt to 50% wt / wt of vaterite; or from 10% wt / wt to 40% wt / wt of vaterite;or from 10% wt / wt to 30% wt / wt of vaterite; or from 10% wt / wt to 20% wt / wt of vaterite; or from 20% wt / wt to 99% wt / wt of vaterite; or from 20% wt / wt to 95% wt / wt of vaterite; or from 20% wt / wt to 90% wt / wt of vaterite; or from 20% wt / wt to 75% wt / wt of vaterite; or from 20% wt / wt to 50% wt / wt of vaterite; or from 30% wt / wt to 99% wt / wt of vaterite; or from 30% wt / wt to 95% wt / wt of vaterite; or from 30% wt / wt to 90% wt / wt of vaterite; or from 30% wt / wt to 75% wt / wt of vaterite; or from 30% wt / wt to 50% wt / wt of vaterite; or from 40% wt / wt to 99% wt / wt of vaterite; or from 40% wt / wt to 95% wt / wt of vaterite; or from 40% wt / wt to 90% wt / wt of vaterite; or from 40% wt / wt to 75% wt / wt of vaterite; or from 50% wt / wt to 99% wt / wt of vaterite; or from 50% wt / wt to 95% wt / wt of vaterite;or from 50% wt / wt to 90% wt / wt of vaterite; or from 50% wt / wt to 75% wt / wt of vaterite; or from 60% wt / wt to 99% wt / wt of vaterite; or from 60% wt / wt to 95% wt / wt of vaterite; or from 60% wt / wt to 90% wt / wt of vaterite; or from 70% wt / wt to 99% wt / wt of vaterite; or from 70% wt / wt to 95% wt / wt of vaterite; or from 70% wt / wt to 90% wt / wt of vaterite; or from 80% wt / wt to 99% wt / wt of vaterite; or from 80% wt / wt to 95% wt / wt of vaterite; or from 80% wt / wt to 90% wt / wt of vaterite; or from 90% wt / wt to 99% wt / wt of vaterite; or 10% wt / wt of vaterite; or 20% wt / wt of vaterite; or 30% wt / wt of vaterite; or 40% wt / wt of vaterite; or 50% wt / wt of vaterite; or 60% wt / wt of vaterite; or 70% wt / wt of vaterite; or 75% wt / wt of vaterite; or 80% wt / wt of vaterite; or 85% wt / wt of vaterite; or 90% wt / wt of vaterite;or 95% wt / wt vaterite; or 99% wt / wt vaterite. The vaterite can be stable vaterite, reactive vaterite, or PCC. In some embodiments of the above aspects and embodiments, the precipitate material comprising vaterite after combination with water, fixation and hardening (i.e., transformation to aragonite) or the stable vaterite mixed with cement and water and after fixation and hardening, has a compressive strength of at least 3 MPa; at least 7 MPa; at least 14 MPa; or at least 16 MPa; or at least 18 MPa; or at least 20 MPa; or at least 25 MPa; or at least 30 MPa; or at least 35 MPa; or at least 40 MPa; or at least 45 MPa; or at least 50 MPa; or at least 55 MPa; or at least 60 MPa; or at least 65 MPa; or at least 70 MPa; or at least 75 MPa; or at least 80 MPa; or at least 85 MPa; or at least 90 MPa; or at least 95 MPa;or at least 100 MPa; or from 3 to 50 MPa; or from 3 to 25 MPa; or from 3 to 15 MPa; or from 3 to 10 MPa; or from 14 to 25 MPa; or from 14 to 100 MPa; or from 14 to 80 MPa;or from 14 to 75 MPa; or from 14 to 50 MPa; or from 14 to 25 MPa; or from 17 to 35 MPa; or from 17 to 25 MPa; or from 20 to 100 MPa; or from 20 to 75 MPa; or from 20 to 50 MPa; or from 20 to 40 MPa; or from 30 to 90 MPa; or from 30 to 75 MPa; or from 30 to 60 MPa; or from 40 to 90 MPa; or from 40 to 75 MPa; or from 50 to 90 MPa; or from 50 to 75 MPa; or from 60 to 90 MPa; or from 60 to 75 MPa; or from 70 to 90 MPa; or from 70 to 80 MPa; or from 70 to 75 MPa; or from 80 to 100 MPa; or from 90 to 100 MPa; or from 90 to 95 MPa; or 14 MPa; or 3 MPa; or 7 MPa; or 16 MPa; or 18 MPa; or 20 MPa; or 25 MPa; or 30 MPa; or 35 MPa; or 40 MPa; or 45 MPa. For example, in some of the above aspects and the above modalities, the composition after fixing and hardening has a compressive strength of 3 MPa to 25 MPa; or 14 MPa to 40 MPa; or 17 MPa to 40 MPa; or 20 MPa to 40 MPa; or 30 MPa to 40 MPa;or 35 MPa to 40 MPa. In some modalities, the compressive strengths described herein are the compressive strengths after 1 day, or 3 days, or 7 days, or 28 days, or 56 days or longer. In some embodiments, the precipitate material comprising vaterite is a composition of particles with an average particle size of 0.1 to 100 microns. The average particle size (or average particle diameter) can be determined using any conventional particle size determination method, such as, but not limited to, multi-detector laser scattering, laser diffraction, or sieving. In certain embodiments, unimodal or multimodal distributions are present, for example, bimodal or others. Bimodal distributions can allow the surface area to be minimized, thus allowing a lower liquid-to-solids mass ratio when the composition is mixed with water while still providing smaller reactive particles through early reaction. In some embodiments, the composition or precipitate material provided herein is a composition of particles with an average particle size of 0.1 to 1000 myeras; or from 0.1 to 500 myeras; or from 0.1 to 100 myeras; or from 0.1 to 50 myeras; or from 0.1 to 20 myeras; or from 0.1 to 10 myeras; or from 0.1 to 5 myeras; or from 1 to 50 myeras; or from 1 to 25 myeras; or from 1 to 20 myeras; or from 1 to 10 myeras; or from 1 to 5 myeras; or from 5 to 70 myeras; or from 5 to 50 myeras; or from 5 to 20 myeras; or from 5 to 10 myeras; or from 10 to 100 myeras; or from 10 to 50 myeras; or from up to 20 myeras; or from 10 to 15 myeras; or from 15 to 50 myeras; or from 15 to 30 mieras; or from 15 to 20 mieras; or from 20 to 50 mieras; or from 20 to 30 mieras; or from 30 to 50 mieras; or from 40 to 50 mieras; or from 50 to 100 mieras; or from 50 to 60 mieras; or from 60 to 100 mieras; or from 60 to 70 mieras; or from 70 to 100 mieras; or from 70 to 80 mieras; or from 80 to 100 mieras; or from 80 to 90 mieras; or 0.1 mieras; or 0.5 mieras; or 1 mieras; or 2 mieras; or 3 mieras; or 4 mieras; or 5 mieras; or 8 mieras; or 10 mieras; or 15 mieras; or 20 mieras; or 30 mieras; or 40 mieras;. or 50 microns; or 60 microns; or 70 microns; or 80 microns; or 100 microns. For example, in some embodiments, the composition or precipitation material provided herein is a composition of particles with an average particle size of 0.1 to 20 microns; or 0.1 to 15 microns; or 0.1 to 10 microns; or 0.1 to 8 microns; or 0.1 to 5 microns; or 1 to 25 microns; or 1 to 20 microns; or 1 to 15 microns; or 1 to 10 microns; or 1 to 5 microns; or 5 to 20 microns; or 5 to 10 microns. In some forms, the composition or precipitation material includes two or more, three or more, four or more, five or more, ten or more, twenty or more, three to twenty, or four to ten different particle sizes. For example, the composition or precipitation material may include two or more, three or more, or between three and twenty particles ranging from 0.1 to 10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200 to 500 microns, 500 to 1000 microns, and / or sub-micron particle sizes. In some embodiments, the PCC in the precipitated material may have an average particle size between 0.1 microns, such as between 0.001 microns and 1 micron or more. In some embodiments, the PCC may be in the nanometer particle size range. In some formulations, the composition or precipitation material may also include Ordinary Portland Cement (OPC) or Portland cement clinker. The amount of Portland cement component may vary and range from 10 to 95% w / w; or 10 to 90% w / w; or 10 to 80% w / w; or 10 to 70% w / w; or 10 to 60% w / w; or 10 to 50% w / w; or 10 to 40% w / w; or 10 to 30% w / w; or 10 to 20% w / w; or 20 to 90% w / w; or 20 to 80% w / w; or 20 to 70% w / w; or 20 to 60% w / w; or 20 to 50% w / w; or 20 to 40% w / w. or 20 to 30% weight / weight; or 30 to 90% weight / weight; or 30 to 80% weight / weight; or 30 to 70% weight / weight; or 30 to 60% weight / weight; or 30 to 50% weight / weight; or 30 to 40% weight / weight; or 40 to 90% weight / weight; or 40 to 80% weight / weight; or 40 to 70% weight / weight; or 40 to 60% weight / weight; or 40 to 50% weight / weight; or 50 to 90% weight / weight; or 50 to 80% weight / weight;or 50 to 70% w / w; or 50 to 60% w / w; or 60 to 90% w / w; or 60 to 80% w / w; or 60 to 70% w / w; or 70 to 90% w / w; or 70 to 80% w / w. For example, the composition or precipitation material may include a mixture of 75% OPC and 25% composition; or 80% OPC and 20% composition; or 85% OPC and 15% composition; or 90% OPC and 10% composition; or 95% OPC and 5% composition. In certain applications, the composition or precipitation material may also include aggregate. Aggregate may be included in the composition or precipitation material to supply mortars, which include fine aggregate, and concretes, which also include coarse aggregate. Fine aggregates are materials that pass almost completely through a No. 4 sieve (ASTM C 125 and ASTM C 33), such as silica sand. Coarse aggregates are materials that are retained predominantly on a No. 4 sieve (ASTM C 125 and ASTM C 33), such as silica, quartz, crushed rounded marble, glass spheres, granite, limestone, calcite, feldspar, alluvial sands, sands, or any other durable aggregate or mixtures thereof. As such, the term aggregate is broadly used to refer to several different types of both fine and coarse particulate material, including, but not limited to, sand, gravel, crushed stone, slag, and recycled concrete.The quantity and nature of the aggregate can vary widely. In some forms, the amount of aggregate can range from 25 to 80%, such as 40 to 70%, and including 50 to 70% weight / weight of the total composition made up of both the composition and the aggregate. In some embodiments, the composition or precipitate material, as prepared by the methods described above, is fixed and hardened after treatment with the aqueous medium under one or more appropriate conditions. The aqueous medium includes, but is not limited to, fresh water optionally containing additives or brine. In some embodiments, the one or more conditions include, but are not limited to, temperature, pressure, time to fixation, an aqueous medium-to-composition ratio, and combinations thereof. The temperature may be related to the temperature of the aqueous medium. In some embodiments, the temperature is in the range of 0 to 110°C; or 0 to 80°C; or 0 to 60°C; or 0 to 40°C; or 25 to 100°C; or 25 to 75°C; or 25 to 50°C; or 37 to 100°C; or 37 to 60°C. or 40 to 100°C; or 40 to 60°C; or 50 to 100°C; or 50 to 80°C; or 60 to 100°C; or 60 to 80°C; or 80 to 100°C. In some modes, the pressure is atmospheric pressure or above atmospheric pressure.In some forms, the time period for fixing the cement product is 30 min. to 48 h; or 30 min. to 24 h; or 30 min. to 12 h; or 30 min. to 8 h; or 30 min. to 4 h; or 30 min. to 2 h; 2 to 48 h; or 2 to 24 h; or 2 to 12 h; or 2 to 8 h; or 2 to 4 h; 5 to 48 h; or 5 to 24 h; or 5 to 12 h; or 5 to 8 h; or 5 to 4 h; or 5 to 2 h; 10 to 48 h; or 10 to 24 h; or 24 to 48 h. During mixing of the composition or precipitate material with the aqueous medium, the precipitate may be subjected to high shear mixing. After mixing, the precipitate may be dewatered again and placed in pre-formed molds to manufacture building materials, or it may be used to manufacture shaped building materials using processes well known in the art or as described herein. Alternatively, the precipitate may be mixed with water and allowed to set. The precipitate may be set over a period of days and then placed in an oven for drying. For example, at 40°C, or from 40°C to 60°C, or from 40°C to 50°C, or from 40°C to 100°C, or from 50°C to 60°C, or from 50°C to 80°C, or from 50°C to 100°C, or from 60°C to 80°C, or from 60°C to 100°C.The precipitate can be cured at high temperature, such as from 50°C to 60°C, or from 50°C to 80°C, or from 50°C to 100°C, or from 60°C to 80°C, or from 60°C to 100°C, or 60°C, or 80°C to 100°C, in high humidity, such as 30%, or 40%, or 50%, or 60% humidity. The product produced by the methods described herein may be an aggregate or construction material, a precast material, or a formed construction material. In some embodiments, the product produced by the methods described herein includes non-cementitious materials such as paper, paint, PVC, etc. In some embodiments, the product produced by the methods described herein includes artificial reefs. These products are described herein. In some embodiments, the precipitate material, in wet or dry form, may be mixed with one or more additives to impart one or more properties to the product, including, but not limited to, strength, flexural strength, compressive strength, porosity, thermal conductivity, etc. The amount of additive used may vary depending on the nature of the additive. In some embodiments, the amount of one or more additives ranges from 1 to 50% w / w, such as 1 to 30% w / w, or 1 to 25% w / w, or 1 to 20% w / w, or 2 to 10% w / w.Examples of additives include, but are not limited to, accelerator assemblies, retarder assemblies, air-entraining agents, foaming agents, defoamers, alkali-reactivity reducers, bonding agents, dispersants, coloring agents, corrosion inhibitors, moisture-proofing agents, gas formers, permeability reducers, pumping aids, shrinkage-compensating additives, fungicidal additives, germicidal additives, insecticidal additives, rheology-modifying agents, finely divided mineral additives, pozzolans, aggregates, wetting agents, strength-enhancing agents, water repellents, reinforcing material such as fibers, and any other additive.When an additive is used, the composition or precipitation material, into which the additive raw materials are introduced, is mixed for a sufficient time to cause the additive raw material to disperse relatively uniformly throughout the composition. Establishing accelerators can be used to speed up the early setting and strength development of cement. Examples of established accelerators that can be used include, but are not limited to, POZZOLITH® NC534, a non-chloride type established accelerator, and / or the calcium nitrite-based corrosion inhibitor RHEOCRETE® CNI, both sold under the above trademarks by BASF Admixtures Inc. of Cleveland, Ohio. Establishing retarders, also known as retarded setting or hydration control, are admixtures used to retard, slow down, or encourage the rate of cement setting. Most established retarders also act as low-level water reducers and can also be used to trap some air within the product. An example of a retarder is DELVO® by BASF Admixtures Inc. of Cleveland, Ohio. An air-entrainer includes any substance that allows air to enter the composition.Air-entraining agents also reduce the surface tension of a composition at low concentrations. Air-entraining agent mixtures are used to intentionally introduce microscopic air bubbles into the cement. An air-entraining agent can increase the workability of the mixture while eliminating or reducing segregation and bleeding. Materials used to achieve these desired effects can be selected from wood resin, natural resin, synthetic resin, sulfonated lignin, petroleum acids, proteinaceous material, fatty acids, resinous acids, alkylbenzene sulfonates, sulfonated hydrocarbons, vinsol resin, anionic surfactants, formerly cationic surfactants, nonionic surfactants, natural rosin, synthetic rosin, an inorganic air-entraining agent, synthetic detergents and their corresponding salts, and mixtures thereof.Air-entraining agents are incorporated in a quantity to produce the desired level of air in a cementitious composition. Examples of air-entraining agents that can be used in the admixture system include, but are not limited to, MB AE 90, MB VR, and MICRO AIR®, all available from BASF Admixtures Inc. of Cleveland, Ohio. In some formulations, the precipitate material is mixed with a foaming agent. Foaming agents incorporate large amounts of void space / air porosity and facilitate the reduction of material density. Examples of foaming agents include, but are not limited to, soap, detergent (alkyl ether sulfate), Millifoam™ (alkyl ether sulfate), Cedepal™ (ethoxyalkyl ammonium sulfate), Witcolate™ 12760, and similar products. Also of interest as additives are defoamers. Defoamers are used to reduce the air content in cementitious compositions. Dispersants are also of interest as additives. Dispersants include, but are not limited to, polycarboxylate dispersants, with or without polyether units. The term dispersant also means that it includes those chemicals that also function as a plasticizer, water reducer such as a high-range water reducer, fluidizer, anti-flocculant, or superplasticizer for compositions, such as lignosulfates, sulfonated naphthalene sulfonate salts or condensates, sulfonated melamine sulfonate salts or condensates, beta-naphthalene sulfonates, sulfonated melamine formaldehyde condensates, sulfonated naphthalene formaldehyde condensate resins, for example, the dispersant LOMAR D® (Cognis Inc., Cincinnati, Ohio), polyaspartates, or oligomeric dispersants.Polycarboxylate dispersants can be used, which is understood to be a dispersant having a carbon skeleton with hanging side chains, wherein at least a portion of the side chains are attached to the skeleton through a carboxyl group or an ether group. Synthetic and natural additives may be used to color the product for aesthetic and safety reasons. These coloring additives may consist of pigments and include carbon black, iron oxide, phthalocyanine, dark ochre, chromium oxide, titanium oxide, and blue. MA / a / zuzz / uuuo r 4 cobalt and organic coloring agents. Also of interest as additives are corrosion inhibitors. Corrosion inhibitors can serve to protect integrated reinforcing steel from corrosion. Materials commonly used to inhibit corrosion are calcium nitrite, sodium nitrite, sodium benzoate, certain phosphates or fluorosilicates, fluoroaluminites, amines, and related chemicals. Also of interest are moisture-proofing additives. Moisture-proofing additives reduce the permeability of products with low cement content, high water-cement ratios, or a deficiency of fine particles in the aggregate. These additives retard moisture penetration in dry products and include soaps, stearates, and petroleum products. Also of interest are gas-forming additives.Gas formers, or gas-forming agents, are sometimes incorporated into the mix to cause slight expansion before hardening. The amount of expansion depends on the quantity of gas-forming material used and the temperature of the fresh mix. Aluminum powder, resin soap, and vegetable or animal glue, saponin, or hydrolyzed protein can be used as gas formers. Permeability reducers are also of interest. Permeability reducers can also be used to reduce the rate at which water under pressure is transmitted through the matrix. Silica vapor, fly ash, soil slag, natural pozzolans, water reducers, and latex can be employed to decrease the permeability of the mix. Also of interest are rheology-modifying agent additives. Rheology-modifying agents can be used to increase the viscosity of compositions. Appropriate examples of rheology modifiers include silica vapor, colloidal silica, hydroxyethylcellulose, starch, hydroxypropylcellulose, fly ash (as defined in ASTM C618), mineral oils (such as light naphthenic acid), clay such as hectorite clay, polyoxyalkylenes, polysaccharides, natural gums, or mixtures thereof. Some mineral extenders, such as, but not limited to, sepiolite sand, are rheology-modifying agents. Also of interest are shrinkage-compensating additives. TETRAGUARD® is an example of a shrinkage-reducing agent and is available from BASF Admixtures Inc. of Cleveland, Ohio. Bacterial and fungal growth on or in the hardened product can be partially controlled through the use of fungicidal or germicidal additives. Materials for these purposes include, but are not limited to, polyhalogenated phenols, dialdrin emulsions, and copper compounds. Also of interest in some applications are workability-enhancing additives. Introduced air, which acts as a lubricant, can be used as a workability-enhancing agent. Other workability-enhancing agents include water reducers and certain finely divided additives. In some forms, the precipitation composition or material is used with reinforcing material such as fibers, for example, where the fiber-reinforced product is desirable. The fibers may be manufactured from materials containing zirconium, aluminum, glass, steel, carbon, ceramic, bronze, bamboo, wood, fiberglass, or synthetic materials, for example, polypropylene, polycarbonate, polyvinyl chloride, polyvinyl alcohol, nylon, polyethylene, polyester, rayon, high-strength aramid (i.e., Kevlar®), or mixtures thereof. The reinforcing material is described in U.S. Patent Application Serial No. 13 / 560,246, filed July 27, 2012, which is incorporated herein by reference in its entirety. The components of the precipitation material can be combined using any appropriate protocol. Each material can be mixed during the work process, or some or all of the materials can be mixed beforehand. Alternatively, some of the materials can be mixed with water, with or without additives such as high-range water-reducing additives, and then the remaining materials can be mixed in. Any conventional mixing apparatus can be used. For example, a Hobart mixer, inclined drum mixer, Omni mixer, Henschel mixer, V-type mixer, and Nauta mixer can be employed. In one aspect, a system is provided comprising a processor configured to process or solvate calcium compounds with nitrogen-containing salts and optionally ammonia to produce an aqueous solution comprising calcium salts and nitrogen-containing salts; a reactor configured to treat the aqueous solution comprising calcium salts and optionally solids with carbon dioxide from the cement plant to produce a precipitate comprising vaterite or PCC and a supernatant comprising the aqueous solution of residual nitrogen-containing salts; and a recovery system for recovering the residual nitrogen-containing salts from the aqueous solution for recycling back to the processor. The recovery system is configured to carry out thermal decomposition, reverse osmosis, multi-stage scintillation, multi-effect distillation, vapor recompression, distillation, and combinations thereof. The methods and systems provided herein can be implemented on land (e.g., at a location where a limestone calcining cement plant is present or easily and economically transportable), at sea, or in the ocean. In some embodiments, limestone calcining cement plants can be retrofitted with the systems described herein to form the precipitate material and further to form products from the precipitate material. Aspects include systems, including processing plants or factories, for practicing the methods as described herein. The systems may have some configuration that enables the practice of the particular production method of interest. In certain embodiments, the system includes a source of calcium compound or the calcium compound containing the aqueous solution from the cement plant and a structure with an inlet for the aqueous solution. For example, the systems may include a pipeline or analogous feed of aqueous calcium compound solution, where the aqueous solution is brine, seawater, or freshwater. The system additionally includes a CO2 inlet from the cement plant as well as components for combining these sources with water (optionally an aqueous solution such as water, brine, or seawater) before or within the precipitation reactor. In some embodiments, the gas-liquid contactor is configured to contact sufficient CO2 to produce excess precipitate material of 1, 10, 100, 1,000, or 10,000 tons per day. The systems also include a precipitation reactor that subjects the water introduced into the reactor to one or more precipitation conditions (as described herein) and produces the precipitate and supernatant. In some embodiments, the precipitation reactor is configured to hold enough water to produce precipitate in excess of 1, 10, 100, 1,000, or 10,000 tons per day. The precipitation reactor can also be configured to include any of several different elements, such as temperature modulation elements (e.g., configured to heat the water to a desired temperature), chemical additive elements (e.g., configured to introduce additives, etc., into the precipitation reaction mixture), computer automation, and the like. A waste stream of CO2 gas can be supplied from the cement plant to the precipitation site in some convenient manner. In some embodiments, the waste stream is supplied by a gas carrier (e.g., a pipeline) running from a location at the cement plant to one or more locations at the precipitation site. The source of the waste stream can be located at a distance from the precipitation site, such that it is 1.61 km (1 mile) or more, such as 16.1 km (10 miles) or more, including 161 km (100 miles) or more, from the precipitation location. For example, the waste stream may have been transported to the precipitation site from a remote cement plant by a CO2 gas transport system (e.g., a pipeline).The CO2-containing gas generated from the cement plant may or may not be processed (e.g., other compounds are removed) before reaching the precipitation site (i.e., the site where precipitation and / or product production occurs). In other instances, the source of the gaseous waste stream is close to the precipitation site. For example, the precipitation site is integrated with the source of the gaseous waste stream, such that the cement plant incorporates a precipitation reactor for the precipitation of material that can be used to produce the products. Where the source of saline water that is processed by the system to produce the carbonate compound composition is seawater, for example, such as where the input is a pipe or feed from ocean water into a land-based system or an inlet port on the ship's hull, for example, where the system is part of a ship, for example, in an ocean-based system. The methods and systems may also include one or more detectors configured to monitor the aqueous medium source or the carbon dioxide source (not illustrated in the figures). Monitoring may include, but is not limited to, collecting data on the pressure, temperature, and composition of the water or carbon dioxide gas. The detectors may be any convenient device configured for monitoring, for example, pressure sensors (e.g., electromagnetic pressure sensors, potentiometric pressure sensors, etc.), temperature sensors (resistance temperature detectors, thermocouples, gas thermometers, thermistors, pyrometers, infrared radiation sensors, etc.), and volume sensors (e.g., geophysical diffraction tomography, X-ray tomography, hydroacoustic surveyors, etc.).) and devices for determining the chemical composition of water or carbon dioxide gas (e.g., IR electrochemical, NMR electrochemical, UV-vis electrochemical, high-performance liquid chromatographs, inductively coupled plasma emission spectrometers, inductively coupled plasma mass spectrometers, ion chromatographs, X-ray diffractometers, gas chromatographs, gas chromatography mass spectrometers, flow injection analysis, flash counters, acidimetric titration and flame emission spectrometers, etc.). In some models, the detectors may also include a computer interface configured to provide a user with the collected data about the aqueous medium, composed of calcium, and / or carbon dioxide gas. In some models, the summary can be stored as a computer-readable data file or printed as a user-readable document. In some configurations, the detector may be a monitoring device capable of collecting real-time data (e.g., internal pressure, temperature, etc.). In other configurations, the detector may consist of one or more detectors configured to determine the parameters of the aqueous medium and / or carbon dioxide gas at regular intervals, such as every 1 minute, every 5 minutes, every 10 minutes, every 30 minutes, every 60 minutes, every 100 minutes, every 200 minutes, every 500 minutes, or some other interval. In certain configurations, the system may also include a station for preparing a construction material, such as cement or aggregate, from the precipitate. Other materials, such as building materials and / or non-cementitious materials, may also be formed from the precipitate, and the appropriate station may be used to prepare them. As previously stated, the system can be located on land or at sea. For example, it can be a land-based system in a coastal region, such as near a seawater source, or even an inland location where water is piped into the system from a saltwater source, such as the ocean. Alternatively, the system can be a water-based system; that is, a system located on or in water. Such a system could be on a boat, an ocean-based platform, or any other suitable location. The calcium carbonate slurry is pumped to the drying system, which in some versions includes a spray-drying filtration step. The water separated from the drying system is discharged or recirculated to the reactor. The resulting solid or powder from the drying system is used as cement or aggregate to produce construction materials, effectively sequestering CO2. The solid or powder can also be used as a PCC filler in non-cementitious products such as paper, plastic, paint, etc. It can also be used in forming construction materials such as drywall, cement board, etc. In some configurations, the systems may include a control station, configured to control the amount of carbon dioxide, the amount of nitrogen-containing salt, and / or the amount of calcium compound conveyed to the precipitator or loader; the amount of precipitate conveyed to the separator; the amount of precipitate conveyed to the drying station; and / or the amount of precipitate conveyed to the refining station. A control station may include a set of valves or a multi-valve system that is manually, mechanically, or digitally controlled, or it may employ any other convenient flow regulation protocol.In some cases, the control station may include a computer interface (where regulation is computer-assisted or fully computer-controlled) configured to provide a user with input and output parameters to control the quantity, as described above. II. PRODUCTS Methods and systems are provided herein for utilizing the gaseous waste stream of CO2 and calcium compounds from a cement plant to produce precipitation material comprising calcium carbonate in vaterite and / or polymorphic forms of aragonite, which transform vaterite into aragonite and form cement. Environmentally friendly methods are provided herein for removing or separating CO2 from a gaseous waste stream from a cement plant and fixing the CO2 in a stable, non-gaseous storage form (e.g., materials for constructing structures such as buildings and infrastructure, as well as the structures themselves or formed construction materials such as drywall, or non-cementitious materials such as paper, paint, plastic, etc., or artificial reefs) in such a way that the CO2 does not escape into the atmosphere. Building material! The construction material used herein includes material used in construction. In one aspect, a structure or construction material is provided comprising the fixed and hardened form of the precipitate material, for example, where reactive vaterite has been converted to aragonite or PCC, which is then fixed and hardened. The product containing the aragonite form of the precipitate exhibits one or more unexpected properties, including but not limited to high compressive strength, high porosity (low density or light weight), neutral pH (e.g., useful as an artificial reef), a microstructure network, etc. Examples of such structures or building materials include, but are not limited to, construction, driveway, foundation, cooktop, furniture, paving, roads, bridges, highways, overpass, parking structure, brick, block, wall, foundation for a gate, fence or post and combinations thereof. Building material formed The formed construction material used herein includes materials molded (e.g., cast, cut, or otherwise produced) into structures with a defined physical shape. The formed construction material may be a precast construction material, such as a precast cement or concrete product. Formed construction materials and methods for producing them using formed construction materials are described in U.S. Patent Application Serial No. 12 / 571,398, filed September 30, 2009, which is incorporated herein by reference in its entirety. Formed construction materials can vary greatly and include materials molded (e.g., cast, cut, or otherwise produced) into structures with a defined physical shape, i.e., configuration.Formed building materials differ from amorphous building materials (e.g., powder, paste, grout, etc.) that do not have a defined and stable shape but instead conform to the container in which they are held, such as a bag or other container. Formed building materials also differ from irregularly or imprecisely formed materials (e.g., aggregate, mass forms for placement, etc.) in that formed building materials are produced according to specifications that permit their use in, for example, buildings. Formed building materials can be prepared according to traditional manufacturing protocols for such structures, except that the composition of the invention is used to produce such materials. In some embodiments, the methods provided herein further include fixing and hardening the precipitation material comprising reactive vaterite where the reactive vaterite has been converted to aragonite or PCC which has been fixed and hardened and formed into a building material. In some forms, the formed building materials made from the precipitation material have a compressive strength or flexural strength of at least 3 MPa, at least 10 MPa, or at least 14 MPa, or between 3 to 30 MPa, or between approximately 14 to 100 MPa, or between approximately 14 to 45 MPa; or the compressive strength of the precipitation material after fixation and hardening is written herein. Examples of formed building materials that can be produced by the methods described above include, but are not limited to, masonry units, for example, bricks, blocks, and roof tiles; building panels, for example, cement board (boards traditionally made of cement, such as fiber cement board) and / or drywall (boards traditionally made of gypsum); ducts; troughs; beams; columns; slabs; sound barriers; insulation material; or combinations thereof. Building panels are formed building materials used in a broad sense to refer to any non-load-bearing structural element characterized by having a length and width substantially greater than its thickness. As such, a panel may be a sheet, board, shingle, and / or tile.Examples of construction panels made from precipitation material include cement boards and / or drywall. Construction panels are polygonal structures with dimensions that vary greatly depending on their intended use. The dimensions of construction panels can range from 50 to 500 cm in length, including 100 to 300 cm, such as 250 cm; the width from 25 to 200 cm, including 75 to 150 cm, such as 100 cm; and the thickness from 5 to 25 mm, including 7 to 20 mm, and 10 to 15 mm. In some applications, cement board and / or drywall can be used to manufacture different types of panels, such as, but not limited to, paper-faced board (e.g., surface reinforced with cellulose fiber), fiberglass or fiberglass-faced board (e.g., surface reinforced with cellulose fiber), fiberglass mesh-reinforced board (e.g., surface reinforced with glass mesh), and / or fiber-reinforced board (e.g., cement reinforced with cellulose, glass, fiber, etc.). These panels can be used in various applications, including, but not limited to, sheathing such as fiber-cement sheathing, roofing, ceilings, molding, cladding, roofing, column sheathing, partition board, backing, trim, wainscoting, shingles, facades, and / or subflooring. Traditional cement boards are made from cement, just like cement. Ordinary Portland cement (OPC), magnesium oxide cement, and / or calcium silicate cement. Cement boards may be manufactured by the methods provided herein from the precipitation of material that partially or completely replaces traditional cement in the board. In some embodiments, cement boards may comprise panels prepared as a combination of aragonitic cement (setting and hardening when vaterite transforms to aragonite) and fiber and / or fiberglass and may have additional fiber and / or fiberglass reinforcement on both faces of the board. Cement boards are formed building materials which, in some forms, are used as backing boards for ceramic tiles. They can be used behind bathroom tiles, kitchen counters, kitchen worktops, etc. Lengths range from 100 to 200 cm. Cement boards can vary in physical and mechanical properties. In some forms, flexural strength can range from 1 to 7.5 MPa, including 2 to 6 MPa, such as 5 MPa. Compressive strength can also vary, ranging from 5 to 50 MPa, including 10 to 30 MPa, such as 15 to 20 MPa. In some forms, cement boards can be used in environments with extensive exposure to moisture (e.g., commercial saunas). The composition or precipitation material described herein can be used to produce the desired shape and size for forming a cement board.In addition, a variety of other components can be incorporated into cement boards, including, but not limited to, plasticizers, clay, foaming agents, accelerators, retarders, and air-entraining agents. The mixture is then poured into sheet molds or a roller can be used to form sheets of the desired thickness. The molded mixture can then be compacted by roller compaction, hydraulic pressure, vibratory compaction, or resonant shock compaction. The sheets are then cut to the desired dimensions of the cement boards. Another type of construction panel made from the precipitation material described herein is the reinforcing board. Reinforcing board can be used for constructing interior and / or exterior floors, walls, and ceilings. In some versions, the reinforcing board is manufactured partially or entirely from the precipitation material. Another type of construction panel made from precipitated or gypsum-based materials is drywall. Drywall, as used herein, includes boards used for the construction of interior and / or exterior floors, walls, and ceilings. Traditionally, drywall is made of gypsum (referred to as paper-faced board). In some forms, drywall is manufactured partially or entirely from gypsum-based carbonate-based materials, thus replacing the gypsum in the drywall product. In some forms, drywall may comprise construction panels prepared as a combination of aragonitic cement (setting and hardening when vaterite transforms to aragonite) and cellulose, fiber, and / or fiberglass, and may have paper, fiber, fiberglass mesh, and / or fiberglass mat reinforcement on both sides of the board.Several processes for manufacturing drywall products are well known in the art and are well within the scope of the invention. Some examples include, but are not limited to, wet processes, semi-wet processes, extrusion processes, Wonderboard® processes, etc., which have been described herein. In some embodiments, drywall is made of a paper facing wrapped around an inner core. For example, in some embodiments, during the process of manufacturing drywall from precipitate material, the precipitate slurry comprising vaterite is poured onto a sheet of paper. Another sheet of paper is then placed on top of the precipitate material so that the precipitate material is flanked by paper on both sides (the resulting composition trapped between two sheets of outer material, e.g., heavy paper or fiberglass mats). The vaterite in the precipitate material is then transformed into aragonite (using additives and / or heat), which is then set and hardened. When the core is set and dried in a large drying chamber, the sandwich becomes rigid and strong enough for use as a building material.The drywall sheets are then cut and separated. The flexural and compressive strengths of drywall formed from precipitation material are equal to or greater than those of conventional drywall prepared with gypsum plaster, which is known to be a soft building material. In some embodiments, flexural strengths can range from 0.1 to 3 MPa, including 0.5 to 2 MPa and 1.5 MPa. Compressive strengths can also vary, in some cases ranging from 1 to 20 MPa, including 5 to 15 MPa and 8 to 10 MPa. In some embodiments, the resulting building materials, such as construction panels including, but not limited to, cement board and drywall produced by the methods described herein, have low density and high porosity, making them suitable for lightweight insulation applications.The high porosity and light weight of the resulting building materials, such as construction panels, can be attributed to the development of the aragonic microstructure when vaterite transforms into aragonite. The transformation of vaterite during the dissolution / re-precipitation process can lead to the generation of microporosity, while simultaneously, the voids created between the formed aragonitic crystals can provide nanoporosity, thus resulting in a highly porous and lightweight structure. Certain mixtures can be incorporated during the transformation process, including, but not limited to, foaming agents, rheology modifiers, and mineral extenders such as clay, starch, etc.These can incorporate porosity into the product since the foaming agent can draw air into the mixture and decrease the overall density, and the mineral extender such as sepiolite clay can increase the viscosity of the mixture, thus preventing segregation of the precipitate material and water. One application of cement board or drywall is fiber cement sheathing. Fiber cement sheathing formed by the methods provided herein comprises construction panels prepared as a combination of aragon cement, aggregate, cross-linked cellulose and / or polymer fibers and may possess a texture and flexibility similar to wood. In some applications, the finished building materials are masonry units. Masonry units are finished building materials used in the construction of load-bearing and non-load-bearing structures, typically assembled using mortar, grout, and similar materials. Examples of masonry units include bricks, blocks, and tiles. Another construction material formed from the precipitation material described herein is a conduit. Conduits are pipes or analogous structures configured to transport a gas or liquid from one location to another. Conduits may include any of several different structures used in the transport of a liquid or gas, including, but not limited to, pipes, culverts, square culverts, drainage channels and portals, inlet structures, intake towers, sluice boxes, outlet structures, and the like. Another building material made from the precipitation material described herein is a reservoir. The term reservoir can include any configured container used to hold a liquid, such as water. As such, a reservoir may include, but is not limited to, structures such as wells, collection boxes, sanitary manholes, septic tanks, sumps, grease traps / separators, storm drain collection tanks, etc. Another building material formed from the precipitation material described herein is a beam, which, broadly speaking, refers to a horizontal load-bearing structure possessing high flexural and compressive strength. Beams can be rectangular in cross-section, C-channel, L-section edge beams, I-beams, parapet beams, H-beams, inverted T-shaped, etc. The beams of the invention can also be horizontal load-bearing units, which include, but are not limited to, joists, lintels, arches, and cantilevers. Another building material formed from the precipitation material described herein is a column, which, in a broad sense, refers to a vertical load-bearing structure and includes structural elements such as compression elements. Other vertical compression elements of the invention may include, but are not limited to, columns, pillars, pedestals, or posts. Another building material formed from the precipitation material described herein is a concrete slab. Concrete slabs are building materials used in the construction of prefabricated foundations, floors, and wall panels. In some cases, a concrete slab can be used as a floor unit (e.g., hollow plate unit or double-T design). Another building material formed from the precipitation material described herein is an acoustic barrier, which refers to a structure used as a barrier for sound attenuation or absorption. As such, an acoustic barrier may include, but is not limited to, structures such as acoustic panels, reflective barriers, absorption barriers, reactive barriers, etc. Another building material formed from the precipitation material described herein is an insulating material, which refers to a material used to attenuate or inhibit heat conduction. Insulation can also include materials that reduce or inhibit radiant heat transmission. In some forms, other formed construction materials such as precast concrete products include, but are not limited to, bunker silo; livestock feed trough; livestock fencing; agricultural fencing; H-bunker, J-bunker; livestock slats; livestock watering troughs; architectural panel walls; cladding (brick); trim (brick); building moldings; foundations; floors; including barrier over-plates; walls; precast double-wall sandwich panel; aqueducts; mechanically stabilized earth panels; box culverts; 3-sided culverts; bridge systems; RR crossings; RR sleepers; sound walls / barriers; Jersey barriers; tunnel segments; reinforced concrete box; utility protection structure; handholes; hollow core product; light pole base; meter box; vault panel; alarm box; telephone structure; transformer pad;transformer vault; trench; utility vault; utility pole; climate-controlled vaults; underground vaults; mausoleum; tombstone, urn, beam mat storage container; detention vaults; concrete storm drain box; manhole; aeration system; distribution box; dosing tank; dry well; grease interceptor; leaching pit, sand-oil / oil-water interceptor; septic tank; water / wastewater storage tank; wet walls; fire cisterns; floating docks; underwater infrastructure; terraces; railings; sea walls; roof tiles; paving stone; community retaining wall; residential retaining walls; modular block systems; and sectorial retaining walls. Non-cementitious compositions In some embodiments, the methods described herein include the manufacture of other products from the precipitate material described herein, but not limited to, non-cementitious compositions including paper, polymer products, lubricants, adhesives, rubber products, chalk, asphalt products, paint, paint remover abrasives, personal care products, cosmetics, cleaning products, personal hygiene products, edible products, agricultural products, soil amendment products, pesticides, environmental sanitation products, and combinations thereof. Such compounds are described in U.S. Patent No. 7,829,053, filed November 9, 2010, which is incorporated herein by reference in its entirety. Artificial marine structures In some embodiments, the methods described herein include, but are not limited to, the fabrication of artificial marine structures from the precipitated material described herein, including artificial corals and reefs. In some embodiments, the artificial structures may be used in aquariums or the sea. In some embodiments, these products are manufactured from the precipitated material comprising reactive vaterite, which transforms into aragonite after setting and hardening. The aragonite cement provides a neutral or near-neutral pH, which can be conducive to the maintenance and growth of marine life. Aragonite reefs can provide suitable habitat for marine species. The following examples are presented to provide those of ordinary experience in the art with a full disclosure and description of how to make and use the invention, and are not intended to limit the scope of what the inventors consider to be their invention, nor are they meant to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to the numbers used (e.g., quantities, temperature, etc.), but some experimental errors and deviations should be taken into account. Unless otherwise stated, parts are parts by weight, molecular weight is weight-average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric pressure. EXAMPLES EXAMPLE 1 Formation and transformation of calcined limestone precipitate material NH4Cl is dissolved in water. Limestone was calcined at 950°C for 4 hours, cooled to room temperature, and incorporated into the aqueous NH4Cl solution and mixed for a few hours. The resulting mixture was decanted to remove heavy impurities. The unfiltered solution was transferred to a sealed vessel. The solution was fed through a heat exchanger, which preheated it to 40°C. The carbonation reactor was an acrylic cylinder equipped with baffles, a gas diffuser, a pH electrode, a thermocouple, a turbine impeller, and inlet and outlet ports for liquids, gases, and slurry. Mass flow controllers provided a CO2 inlet gas. During startup, the solution in the vessel was pumped into the reactor through the heat exchanger. The mixer was agitated while CO2 gas was introduced through the gas diffuser. The continuous inlet flow of fresh reactant solution was controlled by maintaining the reactor pH at 8.The resulting reactive vaterite slurry is continuously collected in a support container. The slurry is vacuum filtered. The reactive vaterite filter cake is oven-dried at 100°C. The cake shows 100% vaterite with a 9. The clear filtrate containing regenerated NH4Cl is recycled in subsequent experiments. EXAMPLE 2 Formation and transformation of precipitate material from lime and CO2 NH4Cl is dissolved in water. Calcium oxide is added to the aqueous solution and mixed for a few hours. The resulting mixture is vacuum-filtered to remove insoluble impurities. The clear filtrate is transferred to a sealed, collapsible bag. The bag is immersed in a water bath, which preheats the solution to 35°C. The carbonation reactor is an acrylic cylinder, equipped with baffles, a gas diffuser, a pH electrode, a thermocouple, a turbine impeller, and inlet and outlet ports for liquids, gases, and slurry. Mass flow controllers provide a CO2 inlet gas. During startup, the solution in the bag is pumped into the reactor. The mixer is agitated while CO2 gas is introduced through the gas diffuser. An automated computer control loop controls the continuous inlet flow of fresh reagent solution, maintaining the pH at 7.5.The resulting reactive vaterite slurry is continuously collected in a support container. The slurry is vacuum filtered. The reactive vaterite filter cake is oven-dried at 100°C. The cake shows 100% vaterite with an average PSA. The clear filtrate containing NH4CI is recycled in subsequent experiments. The dried reactive vaterite solid is mixed into a paste. XRD of the paste after 1 day shows 99.9% aragonite (vaterite completely converted to aragonite). The pastes are cast into 2x2x2 cubes, which are set and hardened in a humidity chamber set at 60°C and 80% relative humidity for 7 days. The cemented cubes are dried in a 100°C oven. Destructive testing determines the compressive strength of the cubes to be ~31 MPa (4600 psi). Although the prior invention has been described in some detail by way of illustration and example to facilitate understanding, it will be readily apparent to those skilled in the art, in light of the teaching of this invention, that certain changes and modifications may be made to it without departing from the spirit or scope of the appended claims. As appropriate, the foregoing merely illustrates the principles of the invention. Those skilled in the art will appreciate that they will be able to conceptualize several arrangements which, although not explicitly described or shown herein, represent the principles of the invention and are included within its spirit and scope.Furthermore, all examples and conditional language cited herein are intended primarily to assist the reader in understanding the principles of the invention and the concepts contributed by the inventors to advance the art and should be considered as being without limitation to such specifically cited examples and conditions. In addition, all statements herein that cite the principles, aspects, and embodiments of the invention, as well as examples thereof, are intended to encompass both structural and functional equivalents thereof. Furthermore, such equivalents are intended to include both currently known equivalents and future developed equivalents, that is, any developed elements that perform the same function, regardless of structure. The scope of the invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein.The following claims are intended to define the scope of the invention and to cover the methods and structures within the scope of these claims and their equivalents.

Claims

1. A method 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.

2. The method according to claim 1, further characterized in that the calcium oxide is an incomplete calcination lime, low reactivity lime, high reactivity lime or combinations thereof.

3. The method according to claim 1 or 2, further characterized in that the calcination step is carried out in a shaft kiln or a rotary kiln. 4 - The method in accordance with any of the preceding claims, further characterized in that the cement plant is a wet process plant or a dry process plant.

5. The method in accordance with any of the preceding claims, further characterized in that the treatment step additionally comprises incorporating anhydrous ammonia or an aqueous ammonia solution. 6 - The method in accordance with any of the preceding claims, further characterized in that the N-containing salt is an inorganic N-containing salt, an organic N-containing salt, or combinations thereof.

7. The method according to claim 6, further characterized in that the salt containing N is an inorganic salt containing N.

8. The method according to claim 7, further characterized in that the inorganic salt containing N is selected from the group consisting of ammonium halide, ammonium acetate, ammonium sulfate, ammonium sulfite, ammonium nitrate, ammonium nitrite and combinations thereof.

9. The method according to claim 8, further characterized in that the ammonium halide is ammonium chloride.

10. The method in accordance with any of the preceding claims, further characterized in that the N-containing salt is ammonium chloride.

11. The method according to claim 6, further characterized in that the N-containing salt is an N-containing organic salt having an N-containing organic compound selected from the group consisting of aliphatic amine, alicyclic amine, heterocyclic amine and combinations thereof.

12. The method in accordance with any of the preceding claims, further characterized in that the molar ratio of the salt containing N: calcium compound is from approximately 0.5:1 to 2:1 by weight.

13. The method according to any of the preceding claims, further characterized in that it additionally comprises removing and optionally recovering ammonia and / or N-containing salt using one or more steps of (i) recovering an exhaust gas stream comprising ammonia during the treatment and / or contact step; (ii) wherein the supernatant aqueous solution comprises residual N-containing salt and further comprises recovering the residual N-containing salt from the supernatant aqueous solution; and (iii) wherein the precipitation material comprises residual N-containing salt and further comprises removing and optionally recovering the residual N-containing salt from the precipitation material. 14.- The method according to claim 13, further characterized in that it additionally comprises recovering the salt containing residual N from the supernatant aqueous solution using the recovery process selected from the group consisting of thermal decomposition, pH adjustment, reverse osmosis, multi-stage flash, multi-effect distillation, vapor recompression, distillation and combinations thereof.

15. The method according to claim 14, further characterized in that it additionally comprises recycling the recovered residual N-containing salt back to the process treatment step, the process contact step, or combinations thereof.

16. The method according to claim 13, further characterized in that the step of recovering the exhaust gas stream comprising ammonia comprises subjecting the exhaust gas stream comprising ammonia to a purification process wherein the purification process comprises purifying the exhaust gas stream comprising ammonia with carbon dioxide from the industrial process and water to produce an ammonia solution. 17.- The method according to claim 13, further characterized in that the step of recovering the exhaust gas stream comprising ammonia comprises subjecting the exhaust gas stream comprising ammonia to a purification process wherein the purification process comprises purifying the exhaust gas stream comprising ammonia with hydrochloric acid and water to produce an ammonium chloride solution.

18. The method according to claim 16, further characterized in that the ammonia solution comprises carbamate which is optionally recycled back to the contact step.

19. The method according to claim 13, further characterized in that step (ii) of removing and optionally recovering the residual N-containing salt from the precipitation material comprises heating the precipitation material to approximately 150 to 360°C to evaporate the N-containing salt from the precipitation material with optional recovery by condensation of the N-containing salt.

20. The method in accordance with any of the preceding claims, further characterized in that the calcium carbonate comprises reactive vaterite.

21. The method according to claim 19, further characterized in that the calcium carbonate comprises reactive vaterite which remains in the precipitation material as reactive vaterite after heating in step (iii).

22. The method according to claim 21, further characterized in that the heating of the precipitation material between approximately 150 to 360°C is for more than approximately 10 minutes or between approximately 10 to 60 minutes. 23.- The method according to claim 19, further characterized in that the N-containing salt is evaporated from the precipitation material in a manner comprising ammonia gas, hydrogen chloride gas, chloride gas, or combinations thereof.

24. The method according to claim 20 or 21, further characterized in that it additionally comprises incorporating water into the precipitation material comprising reactive vaterite and transforming the vaterite into aragonite wherein the aragonite is fixed and hardened to form cement or cementitious product.

25. The method according to claim 24, further characterized in that the cementitious product is a construction material formed from selected masonry unit, construction panel, duct, trough, beam, column, block, acoustic barrier, insulation material and combinations thereof.

26. The method in accordance with any of the preceding claims, further characterized in that the aqueous solution also comprises solids.

27. The method according to claim 26, further characterized in that it additionally comprises separating the solids from the aqueous solution before the contact step by filtration and / or centrifugation.

28. The method according to claim 27, further characterized in that the separated solids are incorporated into the precipitation material as a filler.

29. The method according to claim 27, further characterized in that it additionally comprises recovering the salt containing residual N from the solids using a recovery process selected from the group consisting of rinsing, thermal decomposition, pH adjustment and combinations thereof.

30. The method according to claim 26, further characterized in that the solids are not separated from the aqueous solution and the aqueous solution is in contact with carbon dioxide to produce the precipitate material which further comprises the solids.

31. The method in accordance with any of claims 26 to 30, further characterized in that the solids comprise carbon, silica, iron oxide, aluminum oxide or combinations thereof.

32. The method according to any of claims 26 to 31, further characterized in that the solids are between 1 and 40% by weight in the aqueous solution, in the precipitation material or combinations thereof.

33. The method in accordance with any of the preceding claims, further characterized in that the one or more precipitation conditions are selected from temperature, pH, pressure, ion ratio, precipitation index, presence of additive, presence of ionic species, concentration of additive and ionic species, agitation, residence time, mixing index, forms of agitation, presence of seed crystal, catalyst, membrane, or substrate, dewatering, drying, ball mill crushing, and combinations thereof. 34.- The method in accordance with any of the preceding claims, further characterized in that the one or more precipitation conditions that favor the formation of calcium carbonate or that favor the formation of reactive vaterite comprise a pH of between 7 and 8.5 of the aqueous solution, a temperature of the solution between 20 and 80°C, a residence time of between 15 and 60 minutes, or combinations thereof. 35.- A product formed by the method of claim 1.