Abstract: A method for obtaining particulate calcium carbonate having an average particle size less than about 12 microns is provided. The method includes the steps of (1) withdrawing from a pulp mill a mixture containing calcium carbonate; (2) treating the mixture to remove contaminants contained in the mixture to produce a treated mixture containing calcium carbonate and further having a chemical composition and/or purity which substantially inhibits the fusing together of calcium carbonate particulates; (3) recovering from the treated mixture particulate calcium carbonate having an average particle size less than about 12 microns. The calcium carbonate produced has a high surface area to volume ratio and is therefore highly reactive and suitable for numerous applications such as in the treatment of soil, filler paper production, paint production, and contaminant containment in coal stack emission assemblies.

Abstract: A method and apparatus for the production of calcium carbonate and calcium silicate in common superatmospheric reactors. Multiple reactors can be provided for switching production between reactors, and advantageously utilizing process waste heat. On site production of both PCC and Calcium Silicate Hydrates is thus achieved in a paper mill.

Abstract: Calcium carbonate in the form of aragonite crystals suitable for use as a filler for papermaking to give useful properties for bulk, whiteness, opacity, wire abrasion and yield is obtained by taking advantage of the causticization step.

Abstract: A process comprising introducing CO2 into milk of lime, in which the milk of lime is first ground, and then the CO2 is introduced to precipitate the calcium carbonate.

Abstract: A process for continuously producing precipitated calcium carbonate having a controllable particle diameter, in which nucleation and crystal growth are carried out in separate phases or phases. The size of the calcium carbonate particles is determined and/or controlled by the concentration of the calcium hydroxide suspension and by the ratio of CO2 introduced to the volume of Ca(OH)2 suspension as early as in the nucleation phase.

Abstract: The invention concerns a micronized alkaline earth metal carbonate prepared with or without the use of an agent preventing crystal growth, and a process for its preparation and use. The prepared micronized calcium carbonate, barium carbonate with a BET surface area ranging from 3 to 30 m2/g or strontium carbonate with a BET surface area ranging from 3 to 50 m2/g is suitable in particular for preparing capacitors, thermistors and other oxide ceramic electrical components containing calcium oxide, barium oxide or strontium oxide, and high-temperature superconductors. Ammonium salts or alkylammonium salts of carboxylic acids having a total of between 3 and 12 carbon atoms and at least two COOH groups or at least two OH groups, e.g. salts of maleic acid or nitric acid, are used as agents preventing crystal growth.

Abstract: A process for the preparation of precipitated calcium carbonate by introducing CO2 into milk of lime, in which the milk of lime is first ground, and then the CO2 is introduced to precipitate the calcium carbonate.

Abstract: The invention is related to a method for forming calcium carbonate. In the method, calcium oxide is reacted with carbonate ions in the presence of water to produce calcium carbonate. According to the invention, the formation is carried out directly from calcium oxide to calcium carbonate without intermediate stages in a three-phase precipitation, whereby the hydration of the calcium oxide to calcium hydroxide and the carbonation of the hydrated part are carried out immediately after one another under so intensive agitation that the calcium carbonate elements thus created are detached from the surface of the calcium hydroxide. The mixing is preferably carried out in a fluid medium where the amount of gaseous phase is at least 20 parts by volume and the amount of liquid phase is 0.5 to 1 part per one part by volume of the solid matter of the suspension. In the process, the desired end product, PCC, can be prepared in a very short residence time and with a small operational content.

Abstract: A method and an apparatus for controlling a causticizing process, the process comprising slaking, causticizing and white liquor preparation. The slaking is carried out using a slaker into which green liquor and lime is fed to produce lime milk. The causticizing process is controlled by applying a model that describes at least a part of the causticizing process.

Abstract: A process and an apparatus for the preparation of precipitated calcium carbonates calcium hydroxide using gaseous carbon dioxide, whereby the carbonation is performed in a gaseous phase by mixing calcium-hydroxide-containing liquor mist with the carbon dioxide gas in a turbulence having an energy intensity in excess of 1000 kW/m3. The reaction is advantageously carried out in an apparatus, comprising at least two serially arranged pin mills having one or more rotatable vane rings which can be used to impose a great energy intensity on the material which is fed into the apparatus, whereby the first pin mill is provided with at least an inlet for slaked lime and carbon dioxide and an outlet for the reaction product, and the second pin mill is provided with an inlet for the product from the previous mill and an outlet for the reaction product. Carbonating is extremely swift. The residence time of the reaction is even less than 1 second.

Abstract: Processes for making high quality PCC compositions, and the resulting PCC products thereof. A precipitated calcium carbonate (PCC) composition is prepared by a process comprising the step of wet media mill grinding an aqueous slurry of PCC made by carbonation of lime milk, with the grinding being done at a low solids content in a plurality of separate grinding stages, which can done while essentially free of the presence of organic dispersant. After the multi-stage wet grinding step, the ground PCC slurry is partially dewatered in the presence of an organic dispersant in a solid bowl centrifuge. Then, the partially dewatered PCC slurry is subjected, in the presence of an organic dispersant, to fluid shearing forces created in a rotor/stator type mixer. While these three steps are advantageously used together within a single PCC process flow for optimal effect, the individual steps also can be incorporated singly or in lesser combinations thereof into different PCC manufacturing schemes to beneficial effect.

Abstract: A method of preparing a modified cationic layer compound which includes providing a layer compound of the general formula (I): [EeZzDdVv(OH−)x](An−)a.qH2O  (I) wherein E represents one or more monovalent alkali metal cations, e represents a number of from 0 to about 2, Z represents one or more divalent metal cations, z represents a number of from 0 to about 6, D represents one or more trivalent metal cations, d represents a number of from 0 to about 3, V represents one or more tetravalent metal cations, v represents a number of from 0 to about 1, (An−) represents an acid anion wherein n represents an integer of from 1 to 3, q represents a number of from about 1 to about 10, and wherein x>a and e+2z+3d+4v=x+na; subjecting the layer compound to crystallization to provide a resultant material; and subjecting the resultant material to steam drying at a temperature of from about 200° C. to about 260° C.

Abstract: Disclosed is a novel form of particulate precipitated aragonite, a novel process for producing it and compositions containing it.

Abstract: A product and a process for the preparation of discrete calcium carbonate particles that result from preparing an aqueous calcium carbonate slurry containing carbohydrates, carbonating the aqueous calcium carbonate slurry while maintaining the selected starting carbonation temperature. The product of the present invention is discrete particles of calcium carbonate which are especially useful in paints, plastics, paper coating, paper filling, and because of the purity level of the calcium carbonate particle may be used in cosmetics, pharmaceuticals and food applications.

Abstract: A process for stabilizing a halogen-containing plastic against thermal or photochemical degradation by adding to the plastic an additive consisting essentially of cationic layer compounds corresponding to general formula (I): [M(II)xAl(OH)y](An−)z.mH2O  (I) where M(II) represents at least one divalent metal ion and An− represents an acid anion having the charge n−(n=1, 2 or 3) and 1<x<5, y>z, (y+nz)=2x+3 and 0<m<10, and wherein the cationic layer compounds have been prepared by adding alkali metal hydroxide to a water-containing mixture of at least one source of divalent metal ions M(II), one source of the anion An− and crystalline aluminum hydroxide in a quantity of 1 to 20 mole-%, based on aluminum hydroxide, heating the mixture for 10 to 240 minutes at a temperature of 100° C. to 240° C., and drying the mixture to form a powder without previous separation of the solid from the aqueous phase.

Abstract: A process for the production of precipitated calcium carbonate. A slurry of calcium hydroxide is agitated in a pressurized reactor, and carbon dioxide is provided under pressure to the reactor to produce precipitated calcium carbonate at a high reaction rate. Carbon dioxide is utilized at a high efficiency. Solubilized calcium ions and carbonate ions react to produce a calcium carbonate precipitate. Control of process conditions such as temperature, slurry concentration, and pressure, enables production of a desired crystal habit (including sclenohedral, rhombohedral, stacked rombohedral, or aragonite crystal structures), crystal size, or crystal aspect ratio. The precipitated calcium carbonate produced by the process under pressure is useful as either a paper filler or as an ingredient in paper coatings, and provides a paper product with improved preselected properties, which properties include opacity, density, and/or brightness.

Abstract: A method of producing a precipitated calcium carbonate (pcc) product which has a coarse crystalline form which comprises the steps of: (a) preparing a suspension in an aqueous medium of calcium hydroxide particles which partially dissolve as calcium ions in the aqueous medium, the aqueous medium also incorporating an agent which promotes release into solution in the aqueous medium of calcium ions from the calcium hydroxide; (b) adding carbon dioxide to the aqueous medium to react with the calcium ions therein to produce a suspension in the aqueous medium of a precipitate of calcium carbonate crystals; (c) concentrating the suspension of the precipitate by a dewatering process; and (d) adding to the suspension of the precipitate a dispersing agent for the precipitate; wherein in step (a) the calcium hydroxide particles of the suspension of calcium hydroxide particles have a specific surface area measured by the BET nitrogen method of less than 33 m2/g and the said agent comprises a water soluble organic c

Abstract: Inexpensive spindle- or needle-like calcium carbonate giving useful properties for bulk, brightness, opacity, wire abrasion resistance and yield as a paper filler is provided by taking advantage of the causticization step. In a first step, a quick lime having a calcium carbonate content of 10% by weight or less is slaked with a liquor having a pH of 5.5 to 13.5 at a concentration of 20 to 60% to prepare a milk of lime. In a second step, causticization reaction takes place at a green liquor loading rate of 0.02 to 0.5 cc (green liquor)/min/g (quick lime) at a reaction temperature of 20 to 105° C. to afford spindle- or needle-like calcium carbonate.

Abstract: Fine-grained aragonite precipitated calcium carbonate is produced on a commercial scale by seeding with a coarse-grained aragonite precipitated calcium carbonate. The coarse-grained seeding material is produced by interrupting, after the production of 0.1 to 0.6 g/L min. of calcium carbonate, the supply of carbon dioxide to the quicklime slurry early in the reaction to allow subsequent nucleation of the crystals and then continuing the supply of carbon dioxide at reaction rates of 0.1 g/L min. to 0.6 g/L min. This coarse-grained seeding material has a Blaine surface area which may be less than 30,000 cm.sup.2 /g, the solids of which are 35 to 70 weight percent aragonite, and is added to subsequent batches as a slurry at about 1 weight percent, based on the total weight of the slurry of the material to be seeded. For the seeded batches, carbonation is carried out at reaction rates of up to 1.8 g/L min. at the commercial scale resulting in fine-grained aragonite product.

Abstract: A method of significantly improving the brightness and shade properties of a high quality PCC product. The method includes providing a calcium containing feed source that contains discoloring impurities. The calcium containing feed source is formed into an aqueous slurry of calcium carbonate. Thereafter, the slurry is fine screened through a 325 mesh screen in order to yield a slurry of filler grade calcium carbonate. The filler grade calcium carbonate slurry is wet milled in order to liberate the discoloring impurities and reduce the median particle size of the calcium carbonate to less than 2 microns. The discoloring impurities are then magnetically separated from the milled calcium carbonate slurry by subjecting the slurry to a high intensity magnetic filed. After the magnetic separation step, the purified slurry may be de-watered to yield a dry powder; or alternatively, the slurry may be retained in aqueous form.

Abstract: The blooming type, hard surface cleaning concentrate compositions according to the invention comprise the following constituents:0.1-10% wt. of a terpene containing solvent which desirably includes both pine oil and d-limonene;0.1-12% wt. of at least one organic solvent other than a terpene containing solvent constituent;0.1-20% wt. of a nonionic surfactant system which includes both at least one non-ionic surfactant constituent which desirably includes at least one nonionic surfactant having an HLB of greater than or equal to 10, and at least one nonionic surfactant based on a C.sub.8 -C.sub.18 primary alcohol ethoxylate which exhibits a cloud point of about 20.degree. C. or less in water;a bloom enhancing effective amount at least one amphoteric surfactant selected from alkylampho(mono)- and (di)-acetates, as well as alkylampho(mono)- and (di)-propionates, and aminopropionates;and the balance, to 100% wt. of water.

Abstract: A method for producing precipitated calcium carbonate by reacting an aqueous solution of calcium nitrate [Ca(NO.sub.3).sub.2 ] with an aqueous solution of ammonium carbonate [(NH.sub.4).sub.2 CO.sub.3 ] and allowing calcium carbonate to precipitate from the resultant mixture containing nitrate [NH.sub.4 NO.sub.3 ] in the mother liquor, the process being characterized in that: (i) the calcium nitrate [Ca(NO.sub.3).sub.2)] solution utilized in the processes is prepared by slaking lime [CaO] in water in the presence of ammonium nitrate [NH.sub.4 NO.sub.3 ] to form calcium nitrate [Ca(NO.sub.3).sub.2 ] and ammonium hydroxide [NH.sub.4 OH] in solution, filtering the solution to render it solids free, and heating the filtrate to dissociate the ammonium hydroxide [NH.sub.4 OH] and to drive ammonia gas [NH.sub.3 ] from the solution; (ii) the ammonium carbonate (NH.sub.4).sub.2 CO.sub.3 solution utilized is prepared by absorbing ammonia gas [NH.sub.3 ] and carbon dioxide gas [CO.sub.

Abstract: The present invention relates to a calcium carbonate composition having both calcite and aragonite crystalline morphology. More particularly, the present invention relates to an acicular calcite and an acicular aragonite product and a method for the production of the same and the use of such as fillers, additives and modifiers of consumer and commercial products such as toothpaste, paper, plastics and sealants.The acicular calcite/aragonite composition of the present invention provides a balance of properties such as sheet bulk, strength, stiffness, and sizing, when employed as a filler for paper. As a coating pigment, the acicular calcite/aragonite product of the present invention provides gloss characteristics suitable for dull and matte grades of low gloss coated paper. Upon further processing such as milling, grinding, or other means of comminution, the resulting product provides gloss characteristics suitable for high gloss coated paper.

Abstract: A solution process for the purification of calcium hydroxide, particularly from hydrated carbide lime, which is subsequently used as a feed stock for a high-value calcium product, preferably calcium carbonate. Precipitated calcium carbonate is formed by reaction of the purified calcium hydroxide solution with carbon dioxide in a plug-flow reaction system.

Abstract: Process for the coproduction of calcium carbonate and sodium hydroxide, comprisingcausticizing sodium carbonate with milk of lime;separating the calcium carbonate and the sodium hydroxide formed in the causticizing stage; andcarbonating a mixture of milk of lime and of the calcium carbonate resulting from the causticizing stage.

Abstract: A fire suppressant powder with particle sizes less than 5 .mu.m is made by a chemical reaction between a gas or vapour of a first material and a vapour or an aerosol of a second material. For example an aerosol of sodium hydroxide droplets may be reacted with carbon dioxide gas to produce sodium bicarbonate powder; or boron halide vapour may be reacted with steam to form boric acid powder The powder may be used in fire extinguishers either on its own, or combined with other ingredients such as silica and/or alumina, and calcium stearate.

Abstract: A method for the manufacture of precipitated calcium carbonate from impure calcium oxide of improved colour is disclosed. The method comprises admixing impure calcium oxide with an aqueous solution consisting essentially of a salt of at least one compound selected from the group consisting of organic amines of the formula RNH.sub.2 and alkanolamines of the formula NH.sub.2 (R.sup.1 OH), where R and R.sup.1 are alkyl groups of 1-4 carbon atoms, and hydrochloric or nitric acid. The solution obtained is separated from insoluble matter and then treated with carbon dioxide or the carbonate of the amine or alkanolamine. Preferably, the amine of the salt and of the carbonate are the same, and the salt is used in at least the stoichiometric amount to dissolve the lime.

Abstract: A process for producing calcium carbonate particles having an average size of 0.3.+-.0.1 .mu.m, the process comprising the steps of preparing light calcium carbonate particles of 0.6.+-.0.4 .mu.m in average size by carbonating calcium hydroxide suspended in water, drying and pulverizing the light calcium carbonate particles, admixing the dry powders thereof with a dispersing agent, and wet-grinding the slurry. The final product imparts high opacity and brightness to coated papers when it is used as a pigment.

Abstract: A solution process for the purification of calcium hydroxide, particularly from hydrated carbide lime, which is subsequently used as a feed stock for a high-value calcium product, preferably calcium carbonate. Precipitated calcium carbonate is formed by reaction of the purified calcium hydroxide solution with carbon dioxide in a plug-flow reaction system.

Abstract: There is disclosed a method for the preparation of a precipitated calcium carbonate (PCC) for use as a pigment in paper coating compositions, the method comprising the steps of (a) carbonating an aqueous lime-containing medium to produce an aqueous suspension of a PCC predominantly in a selected crystal form, (b) at least partially dewatering the PCC-containing suspension; and (c) subjecting the PCC-containing suspension to comminution by high shear attrition grinding with an attrition grinding medium. Steps (b) and (c) may be applied in either order, ie. (b) followed by (c) or alternatively (c) followed by (b). The dewatering step (b) is preferably carried out using a pressure filter device operating at a pressure of at least 5 MPa, preferably at least 10 MPa. A pH reduction step may be applied after steps (b) and (c). Also disclosed are pigments produced by the method and pigment and paper coating compositions including such pigments.

Abstract: Continuous measurements are made of a characteristic of the individual components of green liquor fed to a slaker and white liquor exiting from the slaker. The liquor component measurements provide a precise characterization of the liquors allowing for a more efficient control of the causticizing reaction in the kraft process. The individual component measurements are provided as inputs, along with certain ambient measurements, to a non-linear controller. The controller produces a causticizing control signal which is used to control the amount of lime introduced to the slaker. The controller is adapted to a particular process installation through the application of data collected from that installation. The controller, for example a neural network or fuzzy logic controller, produces a causticizing control signal according to unique parameters developed for the specific installation.

Abstract: A process for producing calcium carbonate particles having an average size of 0.1 to 1.0 .mu.m, the process comprising the steps of introducing carbon dioxide into a milk of lime containing a first reagent to prepare an aqueous suspension containing calcium carbonate particles of 0.4 .mu.m in average size, adding a milk of lime into the aqueous suspension, and continuously reacting a carbonated solution containing a second reagent with the aqueous suspension. Calcium carbonate powders according to the process show a superior quality as a filler for adhesives, paints, inks, papers and plastics, especially PET films.

Abstract: Flue gases exhausted from a lime kiln containing lime kiln dust are treated to produce a high purity calcium carbonate precipitate. This is accomplished by passing the flue gases from the lime kiln through a kiln dust separator so that lime kiln dust containing calcium oxide is removed from the remaining flue gas. The lime kiln dust is mixed with water so that an aqueous suspension of the lime kiln dust is formed. Quicklime or calcium oxide in the lime kiln dust is thus hydrated to form calcium hydroxide. The solids within the suspension are then allowed to settle so that a clear, saturated solution of calcium hydroxide having a pH of about 12.4 is formed. This solution is then contacted with carbon dioxide gas so that the calcium hydroxide reacts to form a high purity calcium carbonate precipitate. This high purity calcium carbonate precipitate is then allowed to settle from supernatant water of the solution.

Abstract: An improved thermal ink jet recording paper, incorporating heat aged precipitated calcium carbonate ("PCC") and a binder, is disclosed. Heat aging the PCC in the presence of an organophosphonate produces discrete particles of PCC with a surface morphology and chemistry that enhances the ability of the PCC to bind to ink jet ink without binding so strongly that the color of the ink is changed. Ink jet recording papers incorporating the PCC and binders of the present invention have reduced feathering, spreading, and penetration or backside showthrough, as well as improved optical density, dry time, and water fastness.

Abstract: A novel CaCO.sub.3 sorbent with its physical properties tailored for high SO.sub.2 removal is produced in accordance with the present invention. The surface area, porosity and the distribution of pore sizes of the sorbent have been designed and controlled to give rise to the optimum internal structure necessary for high SO.sub.2 removal. The CaCO.sub.3 sorbent possesses 60 m.sup.2 /g surface area and 0.18 cc/g pore volume and exhibits extraordinary reactivity towards SO.sub.2 (70% utilization in 530 milliseconds at 1080.degree. C. and 3900 ppm SO.sub.2 concentration) when compared with other carbonate and hydrate sorbents in our laboratory reactor system. The sorbent may be produced by precipitation in a slurry bubble column reactor system and preferably contains about 2% by weight of a surfactant which is added during its preparation and improves the properties of CaCO.sub.3 in the course of precipitation. The high utilization of this tailored CaCO.sub.

Abstract: A process for producing ultrafine particles of colloidal calcium carbonate which comprises the steps of adding magnesium sulfate into an aqueous suspension of calcium hydroxide, carbonating the aqueous suspension by introducing carbon dioxide into the aqueous suspension, and adding zinc sulfate alone or together with sulfuric acid into the aqueous suspension simultaneously with the carbonation step. Ultrafine particles of colloidal calcium carbonate in a chain-structured configuration which have an average diameter of 0.01 .mu.m or smaller, an average length of 0.05 .mu.m or longer, and a BET surface area of 70 m.sup.2 /g or greater are produced.

Abstract: A process for the precipitation of discrete prismatic calcium carbonate particles by carbonation of aqueous calcium hydroxide containing a saccharide or polysaccharide or a saccaride or polysaccharide and a metal ion at temperatures of from about 8.degree. C. to about 64.degree. C. is disclosed. The resulting product has specific surface areas between about 10 m.sup.2 /g and about 120 m.sup.2 /g and is useful in paints, plastics, paper coating, paper filling, and pharmaceutical applications.

Abstract: Novel precipitated calcium carbonate particles in clustered form, which when used as fillers impart improved strength, opacity and other advantages to paper, are prepared by a process involving adding lime and carbon dioxide to a reaction mixture containing seed material having a scalenohedral morphology, the lime and carbon dioxide being added simultaneously. The flow rates of the lime and carbon dioxide are adjusted to control the solution conductivity of the reaction minute to between about 2.0 and about 4.0 mS to form the clusters of calcite particles, the clusters having an average equivalent spherical diameter of between about 1.5 and 3.5 microns and a specific surface area of between about 2.0 and 9.0 m.sup.2 /g. At least about 25% of the particles of said clusters have a prismatic form.

Abstract: A thermally stable steelmaking slag is produced which is suitable for use in applications requiring dimensional stability, e.g. as aggregate in road construction. Fine particles of slag obtained from a basic oxygen furnace operation or from an arc furnace operation is firstly subjected to a thermal hydration at a temperature in the range of about 100.degree. to 400.degree. C. Thereafter, the hydrated slag particles are carbonated in the presence of carbon dioxide at a temperature in the range of about 500.degree. to 900.degree. C., whereby substantially all free calcium oxide in the slag particles is converted to calcium carbonate. The product obtained is well suited for road construction and cementitious applications.

Abstract: The calcium carbonate is prepared by:(a) slaking quicklime in an aqueous medium;(b) carbonating and neutralising the suspension of slaked lime formed in step (a) using a gas comprising carbon dioxide; and(c) separating the precipitated calcium carbonate formed in step (b) from the aqueous medium in which it is suspended. There is added 0.1% to 2% by weight, based on the weight of dry calcium oxide, of a reagent having one or more active hydrogen atoms (or a salt thereof), to the aqueous medium in which the quicklime is slaked in step (a).

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 monodisperse spherical, ellipsoidal or plate-like vaterite calcium carbonate almost free from secondary aggregation is disclosed. The vaterite type calcium carbonate is prepared by the steps of adding 5-20 times mol equivalent of water with respect to unslaked lime to a methanol suspension of 0.5-12 weight % of unslaked lime and/or slaked lime (in case of slaked, conversion is to be made into unslaked lime of the same mol) to prepare of a mixture of methanol, unslaked lime and/or slaked lime and water, letting carbon dioxide gas through said mixture, adjusting the temperature in the carbonation reaction system to not less than 30.degree. C. before arrival of conductivity within carbonation reaction system at the maximal point on conductivity variation curve in the carbonation reaction system and adjusting the time from start of carbonation reaction to the point where the conductivity is 100 .mu.S/cm to be less than 1,000 minutes.

Abstract: A carbon dioxide absorber is made by separating sludge from exhaust water discharged upon manufacturing fresh mixed concrete or concrete secondary products, then dewatering the separated sludge, and drying and crushing the dewatered sludge into dry fine particles.

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 method of producing relatively pure calcium carbonate from a relatively impure source of calcium oxide, characterized in that the method comprises the steps ofslaking the calcium oxide source in water to produce an aqueous hydrated lime slurry;treating the slurry by the addition thereto of a water soluble source of anions which anions are capable of forming a salt with calcium ions which salt has a dissociation constant greater than the dissociation constant of calcium hydroxide;separating the solid content of the slurry from the liquid fraction content thereof to obtain a substantially solids-free solution of calcium ions and anions;intimately contacting the solids-free liquid fraction with carbon dioxide gas at a selected rate to maintain the temperature of the solution within a specific range and to lower the pH of the solution to a pre-set value conducive for the formation of a precipitate of calcium carbonate in which one of the crystalline forms, selected from the group consisting of calcite, vaterite

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 producing an anion intercalated hydrotalcite without first forming hydrotalcite and then having to activate the hydrotalcite prior to substituting anions in the hydrotalcite structure. The method includes reacting an activated magnesia with an aqueous solution of aluminate, anion, such as bromide, chloride, sulfate, borate and combinations thereof and hydroxyl ions. The method can be carried out at atmospheric pressure to form hydrotalcite in high purity and high yield. In a preferred embodiment of the invention, the aluminate solution is formed from sodium aluminate, sodium bromide and sodium hydroxide and the aqueous solution is substantially carbonate free. Other anion intercalated hydrotalcites can also be produced by the method of the present invention.

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: Compositions and methods which are effective to treat benign gynecological disorders for extended periods of time in women in who the risk of endometrial stimulation is minimized or absent are described, wherein an effective amount of a gonadotropin hormone releasing hormone composition and an effective amount of an estrogenic composition are provided over a period of time, optionally with addition of an androgenic composition.

Abstract: A process for producing rhombic or barrel shaped precipitated calcium carbonate. Quicklime is slaked in an aqueous solution containing about 0.1% to about 2% by weight of a sugar, based upon the weight of the CaCO.sub.3 to be produced. Carbon dioxide is added to the slaked lime slurry at a preferred temperature of about 50.degree. F.-70.degree. F. until the pH drops from about 11-12 to about 7-8.