A method for releasing impurities from a calcium-based mineral is described. The method comprises reacting a calcium-based mineral containing impurities with an aqueous solution of one or more ionic salts at a temperature of approximately 85 C. or above, wherein at least one of the calcium-based mineral and the one or more ionic salts comprises sulphate and at least one of the calcium-based mineral and the one or more ionic salts comprises ammonium, and wherein the concentration of the solution is approximately 25% or higher mass fraction, such that double salt crystals are formed and impurities are released. The method further comprises separating the double salt crystals from the impurities. Various products of the process are also described.

Provided are a calcium carbonate having a small particle diameter and easily dispersible in polymers and a production method therefor. A calcium carbonate has a magnesium content of 12000 to 120000 ppm, a BET specific surface area of 60 to 120 m.sup.2/g, and a crystallite size of (104) plane of 20 to 50 nm, and particles of the calcium carbonate are concatenated.

The present invention relates to the use of zinc treated precipitated calcium carbonate (PCC), which is obtained by slaking calcium oxide with water to obtain a calcium hydroxide slurry, carbonating the calcium hydroxide slurry, and adding a Zn.sup.2+ ion provider before and/or during the carbonation, in hygienic products, to the hygienic products comprising said zinc treated precipitated calcium carbonate as well as to a process for the preparation of such hygienic products.

The present invention refers to a process for making a calcium carbonate containing material, wherein the process includes a specific drying procedure and allows for the provision of calcium carbonate materials with reduced moisture pick-up and low porosity.

The present invention concerns a process for the preparation of fragmented natural calcium carbonate with a reduced content of impurities by use of a high voltage 5 fragmentation apparatus, as well as products obtained thereof and their use. Furthermore, the present invention refers to the use of a high voltage fragmentation apparatus and a separation step for reducing impurities in at least one natural calcium carbonate and impurities containing material.

Methods for reducing moisture content of alkaline earth metal carbonate may include introducing alkaline earth metal carbonate having a moisture content ranging from about 0.1% by mass to about 10% by mass into a primary crusher and operating the primary crusher to obtain alkaline earth metal carbonate particles having a top cut particle size d.sub.90 of 90 microns or less. The method may also include introducing the particles into a primary grinder and operating the primary grinder to obtain reduced-size alkaline earth metal carbonate particles having a median particle size d.sub.50 of about 60 microns or less. The method may further include introducing the reduced-size particles into a classifier mill and operating the classifier mill to obtain further-reduced-size alkaline earth metal carbonate particles having a median particle size d.sub.50 of about 12 microns or less, and a moisture content of about 0.15% by mass or less.

Disclosed herein are systems and methods from processing flue gas desulfurization (FGD) gypsum feedstock and ash feedstocks, either separately or together. FGD gypsum conversion comprises reacting FGD gypsum (calcium sulfate) feedstock or phosphogypsum, in either batch or continuous mode, with ammonium carbonate reagent to produce commercial products comprising ammonium sulfate and calcium carbonate. A process to separate the impurities and convert the calcium carbonate to a pure precipitated calcium carbonate is disclosed. These impurities include a concentrate of valuable Rare Earth Elements, and radioactive thorium and uranium. A process to convert calcium sulfite to calcium sulfate using oxygen and a catalyst is also disclosed. Ash conversion comprises a leach process followed by a sequential precipitation process to selectively precipitate products at predetermined pHs resulting in metal hydroxides which may be converted to oxides or carbonates. The processes may be controlled by use of one or more processors.

The present invention relates to a method for performing a condensation reaction by heterogeneous catalysis using a surface-reacted calcium carbonate catalyst and the use of a dry surface-reacted calcium carbonate as a catalyst. The condensation reaction involves reacting a first substrate comprising a CO double bond and a second substrate comprising an activated hydrogen to obtain a reaction mixture comprising one or more condensation products and one or more condensation byproducts.

A process is described for manufacturing white pigment containing products. The white pigment containing products are obtained from at least one white pigment and impurities containing material via froth flotation.

A high-purity calcium carbonate sintered body containing less impurities and available for biological and like applications, a production method, a high-purity calcium carbonate porous sintered body containing less impurities and available for biological and like applications, and a production method. A method for producing a high-purity calcium carbonate sintered body includes the steps of: compaction molding calcium carbonate with a purity of 99.7% by mass or more to make a green body; and sintering the green body to produce a calcium carbonate sintered body. A method for producing a high-purity calcium carbonate porous sintered body according to the present invention includes the steps of: preparing a dispersion liquid containing calcium carbonate with a purity of 99.7% by mass or more; adding a foaming agent to the dispersion liquid, followed by stirring until foamy to make a foam; and sintering the foam to produce a calcium carbonate porous sintered body.