Abstract: An improved form of calcium carbonate which is acid resistant to enable its use as a filler material in the making of neutral to weakly acid paper, and a process for producing this acid-resistant calcium carbonate is provided. This acid-resistant calcium carbonate comprises calcium carbonate in admixture with at least about 0.5 to about 10 percent, based on the dry weight of the calcium carbonate, of a cationic salt, together with at least about 0.5 to about 10 percent, based on the dry weight of the calcium carbonate, of an anionic salt.

Abstract: The present invention is a novel process for producing low cost energy, hydrogen, hydrocarbons, carbon monoxide, and oxygen by reacting carbon dioxide and water over a catalyst complex to form low cost energy, various weight hydrocarbons, carbon monoxide and hydrogen which may be used as fuels or for other purposes. The low cost energy results from the heat generated by the exothermic nature of the reaction and is evidenced by the increased temperature of the reactor during the reaction. Said catalyst complex is made from a hydrated magnesium carbonate/hydroxide complex and a catalyst support. The reactants are carbon dioxide and water. This reaction is intended to be used at sites where excess steam, heat or carbon dioxide are produced and are readily available. The recycle of these otherwise excess "waste" products can be economically advantageous by producing useful products and be environmentally advantageous by reducing both greenhouse gas emissions and thermal exhaust.

Abstract: A method of producing a compound oxide of elements including at least one of thallium, bismuth, lead, antimony, yttrium, each of rare earth elements, each of transition metal elements, each of alkali metal elements and each of alkaline earth metal elements. The method is comprised of the steps of (i) reacting at least one of carbonate, basic carbonate, hydroxide and co-precipitates of each of the above-mentioned elements with an amount of citric acid that is less than the weight equivalent of citric acid needed to form a completely citrated compound, and (ii) calcining the partly citrated compound. The co-precipitate can be one of a carbonate, a basic carbonate and a hydroxide of each of the above-mentioned elements.

Abstract: An aggregated synthetic hydrotalcite having a substantially spheroidal shape and an average diameter of up to about 60 .mu.m is disclosed. The aggregates are composed of individual platy particles having plate diameters of from about 0.05 to about 10 .mu.m. The material has a low tapped density, a high pore volume and a high specific surface area. A process for producing the product is also disclosed. Product particle size is determined by controlling process parameters including reaction temperature and pH, stirring speed of the reaction mixture, and reactant addition rates and concentrations, including aqueous solutions of soluble magnesium and aluminum salts, which are mixed in a molar ratio of from about 2.5:1 to 4:1, and a basic solution containing excess carbonate and base to maintain the reaction mixture at a pH of from about 8.5 to about 9.5.

Abstract: Disclosed is a method and an apparatus for the heat treatment of lime sludge (CaCO.sub.3) to form burnt lime (CaO). In the method of the present invention a lime sludge feed is entrained in and thereafter dried in a gas flash dryer means to produce a dried lime sludge. The dried lime sludge is separated from the gases and thereafter is fed to a rotary kiln in which the dried lime sludge is converted to active burnt lime. In order to maintain the flow of gas in the flash dryer means at a predetermined velocity in order to entrain all the lime sludge feed in the gas flow, an adjustable portion of the separated gases are recycled through the flash dryer means.

Abstract: A synthetic hydrotalcite-like material having a sheet-like morphology and a sheet broadness to thickness ratio of at least 50 and a formula Mg.sub.1-x Al.sub.x (OH).sub.2.xA.mH.sub.2 O where A is a mono carboxylic anion of the form RCOO.sup.- where R is C.sub.n H.sub.2n+1 and n=0-5, and x and m are numbers satisfying the following conditions:0.2<=x<=0.40.0<=m<=4It is made by starting with a synthesis mixture having magnesium (divalent cation) to aluminum (trivalent cation) molar ratio between 1:1 and 10:1, mono carboxylic anion to aluminum (trivalent cation) molar ratio between 0.1:1 to 1.2:1 and optionally added other anions. The process comprises of reacting a mixture comprising magnesium and aluminum cations and mono carboxylic anions in an aqueous slurry at a temperature of at least 40.degree. C. and a pH of at least 7.

Abstract: A novel alkaline earth metal carbonate product for use as a raw material in the glass manufacturing process is disclosed. The alkaline earth metal carbonate becomes a part of the liquid phase in the glass furnace more readily and at a lower temperature; it decomposes to release carbon dioxide gas more rapidly so that all of the gas can escape from the molten glass more easily. Using these alkaline earth metal carbonate compositions, the production capacity of a glass furnace is increased.

Abstract: A method for forming monotungsten carbide, comprising heating a solid, non-elemental tungsten-containing material in a flowing atmosphere containing molecular hydrogen and molecular methane for a time sufficient to convert substantially all of the tungsten-containing material to monotungsten carbide, The heating brings the temperature of the tungsten-containing material to a first elevated temperature of from about 520 to about 550.degree. C. and, subsequently, at a rate of from about 3 to about 10.degree. C. per minute, the heating brings the temperature from the first elevated temperature to a second elevated temperature of about 800 to about 900.degree. C. Thereafter the temperature is held at the second elevated temperature for at least about 15 minutes. At least about 50 weight percent of the monotungsten carbide formed is formed while holding the temperature at the second elevated temperature.

Abstract: A method for preparing granulated alkaline earth metal carbonate, particularly barium carbonate or strontium carbonate, by adding a binding agent and optionally water; granulating the resulting mixture, preferably in the presence of water; drying the granular product; and optionally subjecting the granular product to a high-temperature treatment, in which the material to be granulated and the granulated material do not contact any inorganic refractory material during the granulation, during subsequent drying, and during any high-temperature treatment.

Abstract: In the process for making calcium carbonate by the double decomposition reaction of sodium carbonate and calcium hydroxide in aqueous reaction medium the improvement of producing calcium carbonate having a scalenohedral particle shape and a rosette aggregate structure comprising adding said sodium carbonate in more than one stream to said calcium hydroxide over a period of 1 to 8 hours and maintaining said reaction medium in the range of 80.degree. to 140.degree. F.

Abstract: A method for preparing granulated alkaline earth metal carbonate, especially barium carbonate and strontium carbonate, by adding a binding agent and optionally water, and granulating the carbonate material by the action of mechanical forces or by accretional granulation in, for example, a flash reactor, with simultaneous drying, and thereafter optionally subjecting the granules to a high-temperature treatment, in which method the material to be granulated and the granulated material do not come in contact with inorganic refractory material either during the granulation or during any subsequent high-temperature treatment.

Abstract: A stabilizer for a rigid chlorinated resin comprising a hydrotalcite compound and an inorganic copper compound and a stabilized rigid chlorinated resin composition obtained by adding said stabilizer to a chlorinated resin.

Abstract: A method of preparing precipitated calcium carbonate which comprises slaking quicklime in an aqueous medium, passing the suspension of calcium hydroxide through a sieve having an aperture size in the range of 40 to 70 microns, carbonating the calcium hydroxide and separating the calcium carbonate from the aqueous medium in which it is suspended. The sieved calcium hydroxide is subjected to high energy, high shear agitation which is terminated prior to carbonation. During the carbonation, the suspension of calcium hydroxide is subjected to relatively lower energy and shear agitation compared to the previous high energy, high shear agitation.

Abstract: In a process for the stabilization of a solution of ethylmagnesium carbonate in ethanol, which has been prepared by the reaction of a suspension of magnesium ethylate in ethanol with carbon dioxide, 0.2 to 1.0% by weight of water, based on the ethylmagnesium carbonate solution, is added to the solution or its starting materials.

Abstract: The invention relates to a process for producing polyacrylic acids and copolymers of acrylic acid with up to 50 mol-% of comonomers. These compounds have a molecular weight of less than 100,000, measured at a pH-value of 8, and 10 to 60 mol-% are neutralized with calcium hydroxide. The invention also relates to the use of these products as grinding and dispersing aids for calcium carbonate.

Abstract: A form of calcium carbonate having a blocky rhombohedral crystal structure and properties including a surface area of from about 3 to about 15 m.sup.2 g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than about, 2:1 and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed. An accelerated heat-aging process, including embodiments thereof which utilize hydrothermal techniques, for rapidly producing this form of calcium carbonate, and a related form of calcium carbonate having a hexagonal prismatic crystal structure and the same properties, in large quantities to meet the demand of the papermaking industry, as well as a method for using these materials in papermaking, are also disclosed.

Abstract: Mineral fillers, pigments and similar materials containing carbonate are described which are characterized in that they havea) a rhombohedral or primarily round particle formb) a steepness factor of between 1.1 and 1.4c) ##EQU1## and d) an average statistical particle diameter of between 0.4 and 1.5 .mu.m.These materials may be used in the paper industry both as paper fillers and as coating pigments.

Abstract: The present invention relates to a process for the preparation of substantially spherical monocrystalline vaterite, in particular, of vaterite having a determined size.

Abstract: A form of calcium carbonate having a blocky[-six-sided] rhombohedral crystal [habit ] structure and [a morphology, with] properties including a surface area of from about 3 to about 15 m.sup.2 /g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than 2, and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed.

Abstract: Disclosed is a novel basic magnesium carbonate represented by the following general formula:nMgCO.sub.3.Mg(OH).sub.2.mH.sub.2 Owherein n is a number of from 3 to 5 and m is a number of from 3 to 5,which consists of porous particles composed of an aggregate of plate crystals having an average particle size of 1 to 50 .mu.m and a specific surface area of 10 to 70 m.sup.2 /g, wherein in the fine pore size distribution of the particles, the volume of fine pores having a radius smaller than 100 .ANG. is at least 0.02 cc/g and the volume of fine pores having a radius smaller than 75,000 .ANG. is at least 0.8 cc/g.This novel basic magnesium carbonate is highly improved over conventional basic magnesium carbonate in such properties as filling property, dispersibility and flowability.

Abstract: A form of calcium carbonate having a blocky rhombohedral crystal structure and properties including a surface area of from about 3 to about 15 m.sup.2 /g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than about 2:1, and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed. An accelerated heat-aging process, including embodiments thereof which utilize hydrothermal techniques, for rapidly producing this form of calcium carbonate, and a related form of calcium carbonate having a hexagonal prismatic crystal structure and the same properties, in large quantities to meet the demand of the papermaking industry, as well as a method for using these materials in papermaking, are also disclosed.

Abstract: A form of calcium carbonate having a blocky rhombohedral crystal structure and properties including a surface area of from about 3 to about 15 m.sup.2 /g, an average discrete particle size of from about 0.2 to about 0.9 micron, wherein the discrete particles have an aspect ratio less than about 2:1, and a particle size distribution such that at least about 60 weight percent of the particles have a size within 50 percent of the equivalent discrete particle spherical diameter, suitable for use as a filler material in papermaking to improve the optical properties of the resulting paper, is disclosed. An accelerated heat-aging process, including embodiments thereof which utilize hydrothermal techniques, for rapidly producing this form of calcium carbonate, and a related form of calcium carbonate having a hexagonal prismatic crystal structure and the same properties, in large quantities to meet the demand of the papermaking industry, as well as a method for using these materials in papermaking, are also disclosed.

Abstract: The processing of leaching residues from barium sulfide leaching is described. Sodium sulfide as well as a solid which is useful as an additive for fired clay products, particularly bricks, are obtained as valuable reaction products.

Abstract: The invention concerns a method of bleaching particles containing calcium carbonate by keeping them in contact with an aqueous solution containing hydrogen peroxide and having a pH-value below 8.

Abstract: The invention relates to a process for producing a sintered body of calcium carbonate without permitting thermal decomposition of calcium carbonate during sintering, and to the sintered body. A powder material primarily comprising calcium carbonate is subjected to a cold powder pressing process to prepare a green compact, which is then heated in a high-pressure gas atmosphere consisting essentially of an inert gas at a temperature t.degree. C. of900.ltoreq.t<1200and at a high gas pressure P kgf/cm.sup.

Abstract: In the manufacture of ammonium paratungstate, sulfide is added to a tungsten-containing solution in order to precipitate molybdenum sulfide. Volatiles, including sulfides, evolved during this process are collected in a caustic scrubbing solution. The sulfide values in the caustic scrubbing solution may be reused to precipitate molybdenum sulfide by first treating the caustic scrubbing solution with alkaline earth chloride or sulfate to precipitate out alkaline earth carbonate.

Abstract: Disclosed is a process for producing aragonite crystal form calcium carbonate with an acicular shape characterized by premixing aragonite crystal calcium carbonate and Ca(OH).sub.2 to prepare an aqueous slurry, adding a water-soluble phosphoric acid compound into the aqueous slurry, and introducing CO.sub.2 gas into the aqueous slurry to cause the carbonation reaction to take place. According to the present invention, aragonite crystal form calcium carbonate in an acicular shape with a large particle size is produced.

Abstract: Fermentors, reactors and processes for preparing magnesium enriched calcium magnesium acetate (CMA) (Mg:Ca mole ratios of 1:1 to 20:1) by reacting a dolomitic lime product with a Mg:Ca mole ratio less than one with dilute acetic acid, such as in fermentation broths. A process to prepare a mildly aklaline mineral product by calcining the dolomite under conditions to convert only the MgCO.sub.3 to MgO and treating the selectively calcined dolomite with acidic solutions to dissolve largely the MgO, leaving the original CaCO.sub.3 matrix intact. The mildly alkaline mineral product includes a highly porous structure derived from dolomite, consisting of a matrix of CaCO.sub.3 with smaller amounts of MgO and interspersed with a regular array of voids on a molecular scale.

Abstract: There is disclosed a process for purifying a calcium carbonate-containing mineral which process comprises the following steps:a) mixing the calcium carbonate-containing mineral with water and a dispersing agent to form a suspension containing from 60% to 80% by weight of the dry mineral;b) comminuting the suspension of calcium carbonate-containing mineral prepared in step a) to give a product containing not more than 5% by weight of particles which are retained on a sieve having a nominal aperture of 53 microns and not more than 50% by weight of particles which are smaller than 2 microns e.s.d.

Abstract: The present invention is directed to an improved method for carrying out a exothermic chemical reaction with carbon dioxide in an aqueous environment. In the method, a fluid solution containing at least one chemical reactant which is exothermically reactive with carbon dioxide is provided. Liquid carbon dioxide is then injected into the solution of the chemical reactant at a pressure above the triple point of at least about 60 psig. The injection of the liquid carbon dioxide takes place under turbulent conditions wherein the liquid carbon dioxide expands to provide carbon dioxide vapor. The carbon dioxide vapor superheats to approach the exothermic reaction temperature which occurs between the carbon dioxide vapor and the chemical reactant. The chemical reactant and the carbon dioxide react in the dispersion exothermically to produce a chemical reaction product.

Abstract: An extremely pure oxide containing two or more metals, homogeneous at the atomic level, is prepared by (1) reacting in water, soluble salts of two or more metals with quaternary ammonium carbonate; the metals being those that form water-insoluble carbonates, thereby to precipitate mixed carbonates of the metals; (2) recovering and drying the precipitate; (3) calcining the precipitate to provide an oxide of mixed metals homogeneous at the atomic level and substantially free from extraneous contaminants. The calcined oxide can be shaped and compressed as greenware and sintered to form useful ceramic products.

Abstract: Disclosed is a calcium carbonate which is 25 to 55 m.sup.2 /g in BET specific surface area, 5 to 110 in the ratio of BET specific surface area (m.sup.2 /g)/mean particle size (.mu.m), at least 120 ml/100 g in oil absorption as determined by the Ogura method and at least 1.8 g/g in water absorption, and process for preparing the same. The calcium carbonate is formulated into a coating composition for forming a heat-sensitive recording layer or intermediate layer of a heat-sensitive recording paper or for forming an ink-jet recording paper.

Abstract: A starting material composed of calcium carbonate is dissolved in a nitrate aqueous solution containing either Ca(NO.sub.3).sub.2 or NH.sub.4 NO.sub.3 under application of heat and pressure. The starting material is hydrothermally synthesized within the nitrate aqueous solution to effect the rapid growth of calcium carbonate single crystal.

Abstract: This invention concerns a process for the preparation of large surface area, finely divided precipitated calcium carbonate which comprises introducing carbon dioxide into an aqueous slurry of greater than about five weight percent calcium hydroxide containing an anionic organopolyphosphonate polyelectrolyte, starting the introduction at a temperature above about 7.degree. C. and below about 18.degree. C., continuing the introduction until calcite precipitation is substantially complete and adding a quantity of polybasic acid to the slurry in an amount greater than about 0.3% by weight of the precipitated calcium carbonate. This invention also concerns said large surface area, finely divided precipitated calcium carbonate which has been coated with a fatty acid derivative and polymeric compositions which contain such coated calcium carbonate.

Abstract: Disclosed is a method for producing hydrotalcite in high yield including reacting activated magnesia with an aqueous solution containing aluminate, carbonate, and hydroxyl ions. The method further includes a first step of heating magnesium carbonate or magnesium hydroxide to a temperature between about 500.degree.-900.degree. C. to form activated magnesia or magnesium oxide. The method is suited to producing synthetic hydrotalcite from industrial Bayer liquor.

Abstract: A precipitated alkaline earth metal carbonate is produced by calcining raw alkaline earth metal carbonate, for example a calcium carbonate, under conditions such that substantially all the chemically combined carbon dioxide is driven off to form an oxide, slaking the oxide in water to form a suspension of the corresponding alkaline earth metal hydroxide, allowing the suspension to cool to 45.degree. C. or below, and then carbonating the hydroxide in suspension in water with substantially pure carbon dioxide in the presence of a dithionite bleaching reagent to form a precipitate of an alkaline earth metal carbonate of increased brightness and purity. The precipitate may then be separated from the aqueous medium by, for example, filtration.

Abstract: Process for causticizing a water solution containing alkali carbonate with calcium oxide and hydroxide by bringing the water solution containing alkali carbonate into contact with the calcium oxide or hydroxide and by separating the alkali hydroxide solution arisen in the causticizing from the calcium carbonate precipitate. The water solution containing alkali carbonate is conducted through a bed which has been formed by mixing calcium oxide and calcium carbonate in the causticized alkali solution and by removing the excess alkali solution.

Abstract: A process for producing calcium carbonate from calcium hydroxide derived from, for example, limestone, comprises injecting a gas containing carbon dioxide into a recirculating stream flowing in a recycle piping system in communication with a reaction vessel. The carbon dioxide containing gas is injected at a turbulent area located in the recycle piping system. By controlling reaction parameters including pH and temperature, novel calcium carbonate products are formed by the process.

Abstract: A method of converting fine particle size alkaline earth metal carbonate, e.g., barium or strontium carbonate, into a free-flowing granular form with relatively high bulk density, without sintering, grinding, or briquetting, is disclosed. It involves the following steps:(a) forming a suspension of the carbonate in water with enough deflocculating agent, e.g., sodium polyacrylate or sodium hexametaphosphate, to substantially completely deflocculate the carbonate;(b) drying the resultant suspension at a temperature that is elevated, but without heating the carbonate to its sintering point, for example by spray drying in a spray drier operating at an inlet temperature in the range of about 400.degree. to 600.degree. C., to obtain a granular material primarily passing 10 mesh and held on a 150 mesh screen (Tyler); and(c) heating the granular material to about 600.degree. to 700.degree. C., which causes it to shrink, thereby increasing its bulk density by at least about 5%, preferably at least 10 or 20 percent.

Abstract: A glass manufacturing process using a granular, free-flowing form of alkaline earth metal carbonate, e.g., barium or strontium carbonate, is disclosed. The alkaline earth metal carbonate has a relatively high bulk density and is made without sintering, grinding, or briquetting. The carbonate is prepared from a fine particle size material by the following steps:(a) forming a suspension of the carbonate in water with enough deflocculating agent, e.g., sodium polyacrylate or sodium hexametaphosphate, to substantially completely deflocculate the carbonate;(b) drying the resulting suspension, at a temperature that is elevated, but without heating the carbonate to its sintering point, for example, by spray drying in a spray drier operating at an inlet temperature in the range of about 400.degree. to 600.degree. C., to obtain a granular material primarily passing 10 mesh and held on a 150 mesh screen (Tyler); and(c) heating the granular material to about 600.degree. to 700.degree. C.

Abstract: Superior homogeneity in ceramic materials is achieved by forming an aqueous solution of trichloroacetates of certain metals, heating the solution to decompose the trichloroacetates to form carbonate precipitates, and recovering the carbonate precipitates. The latter can be calcined to form superconductors. For example, oxides, or carbonates of Y, Ba, and Cu are dissolved in aqueous trichloroacetic acid and the solution is heated to decompose trichloroacetate ions and to form mixed carbonates, which precipitate. The precipitate is recovered and calcined to form a superconducting material.

Abstract: Disclosed is a novel process of producing plate-shaped calcium carbonate particles. The process comprises the steps of adding aqueous calcium hydrogen carbonate solution with a temperature of less than 50.degree. C. into an aqueous medium bath held at a temperature of not less than 50.degree. C. to generate plate-shaped calcium carbonate particles in the bath, the temperature of the bath being kept not less than 50.degree. C. during the addition of the aqueous calcium hydrogen carbonate solution; and recovering the generated plate-shape calcium carbonate particles.

Abstract: An agent for increasing the pH value of dental plaque, which contains at least one highly disperse, poorly soluble oxide, hydroxide or pure salt of one or more alkaline earth metal elements and a weak acid, having a specific surface area greater than 6 m.sup.2 /g and a concentration of lattice defects which corresponds to a half width of the X-ray peaks for Cu-K.alpha. radiation at glancing angles from 20.degree. to 23.degree. of more than 0.25 degrees, and a process for its preparation.

Abstract: Purified barium salts essentially devoid of strontium impurities, e.g., highly pure barium carbonate, are produced by liquid/liquid extracting an aqueous solution of impure barium values with an organic solvent medium which comprises at least one water-insoluble carboxylic acid, phosphonic acid monoester, or substituted 8-hydroxyquinoline extractant. The mixture of extraction is separated into a purified aqueous phase containing the desired barium salt values and an organic phase containing the impurity values sought to be removed.

Abstract: A method for improving the brightness of limestone utilizing a chelating agent and a bleaching agent in a limestone slurry in which the pH of the slurry is normally between 9.0 and 9.6.

Abstract: A strontium or barium carbonate product that is better suited for use as a glass ingredient is obtained by sintering the powdered carbonate in a kiln lined with fused amorphous silica. The carbonate picks up fewer harmful contaminants from the amorphous silica lining than it does from, say, a refractory silica-alumina brick lining or a kiln having a metallic inner surface.

Abstract: A process for producing ultrafine ground calcium carbonate is disclosed in which a dry feed stone is slurried to a 15 to 60% by weight solids slurry and dispersed with an organic dispersant. The dispersed slurry is fed to an attrition mill where it is bead ground to 50-70% less than 2 microns. The ground calcium carbonate is classified in a centrifuge into a product stream having from 70-99% of its particles less than 2 microns and an underflow stream of larger particles. The product stream is treated with ozone which serves not only to increase the brightness of the product but to return the slurry to a non-dispersed state. The calcium carbonate slurry is then dewatered to produce a 58-69% solids product suitable for preparing a higher solids slurry or for spray drying.

Abstract: Dry, stable carbonating agents comprised of a carbohydrate/metal bicarbonate complex are disclosed. The complex is prepared by reacting a carbohydrate with a metal hydroxide or oxide at a temperature not exceeding 25.degree. C. to form a carbohydrate/metal hydroxide adduct to which carbon dioxide is then introduced to form the complex. The complex is then immediately dried, preferably by freeze drying. The carbonating agents are particularly useful as components of dehydrated beverage powders. Upon rehydration, the complex releases carbon dioxide and carbonates the beverage. Additionally, upon rehydration the complex promotes the solubilization of the carbohydrate components in the beverage.

Abstract: A process is provided for preparing concentrated aqueous solutions of byproduct nitrate compounds from dilute aqueous streams containing said byproduct nitrate compounds, calcium ions and anionic species capable of reaction therewith at elevated temperatures. The process provides for the removal of the calcium ions by the addition of a source of carbonate ions to said stream to form solid, particulated calcium carbonate therein, the separation of the solid particulate from the stream, the neutralization of the stream and concentration of the stream to provide a concentrated aqueous solution containing the byproduct nitrate compound.

Abstract: Disclosed is a method for producing hydrotalcite in high yield including reacting activated magnesia with an aqueous solution containing aluminate, carbonate, and hydroxyl ions. The .[.method further includes a first step of.]. .Iadd.activated magnesia is produced by .Iaddend.heating magnesium carbonate or magnesium hydroxide to a temperature between about 500.degree.-900.degree. C. .[.to form activated magnesia or magnesium oxide..]. The method is suited to producing synthetic hydrotalcite from industrial Bayer liquor.