The disclosure features methods that include obtaining a first plurality of particles that include calcium carbonate, where the particles have a distribution of sizes between 8 mm and 12 mm, and heating the first plurality of particles to a temperature of between 900 C. and 1200 C. for a time period of at least 1 hour to generate a second plurality of particles that include calcium oxide.

The disclosure features methods that include obtaining a first calcium hydroxide solution that includes a first concentration of calcium ions and a second calcium hydroxide solution that includes a second concentration of calcium ions, adding a phosphoric acid solution to the first calcium hydroxide solution to generate a combined solution featuring an aqueous suspension of calcium dihydrogen phosphate particles, and adding the second calcium hydroxide solution to the combined solution to form a product solution that includes an aqueous suspension of particles of a calcium phosphate composition.

The disclosure features compositions that include a material featuring three calcium phosphate phases that form one or more integral units of a solid, where a first one of the three phases includes one or more regions formed of hydroxyapatite, a second one of the three phases includes one or more regions formed of -tricalcium phosphate, a third one of the three phases includes one or more regions formed of amorphous calcium phosphate, and where at least some of the regions corresponding to the first, second, and third phases contact one another in the one or more integral units of the solid.

The present invention provides that powder is mainly constituted from secondary particles of hydroxyapatite. The secondary particles are obtained by drying a slurry containing primary particles of hydroxyapatite and aggregates thereof and granulating the primary particles and the aggregates. A bulk density of the powder is 0.65 g/mL or more and a specific surface area of the secondary particles is 70 m.sup.2/g or more. The powder of the present invention has high strength and is capable of exhibiting superior adsorption capability when it is used for an adsorbent an adsorption apparatus has.

The disclosure features compositions that include a material featuring three calcium phosphate phases that form one or more integral units of a solid, where a first one of the three phases includes one or more regions formed of hydroxyapatite, a second one of the three phases includes one or more regions formed of -tricalcium phosphate, a third one of the three phases includes one or more regions formed of amorphous calcium phosphate, and where at least some of the regions corresponding to the first, second, and third phases contact one another in the one or more integral units of the solid.

The disclosure features methods that include obtaining a first calcium hydroxide solution that includes a first concentration of calcium ions and a second calcium hydroxide solution that includes a second concentration of calcium ions, adding a phosphoric acid solution to the first calcium hydroxide solution to generate a combined solution featuring an aqueous suspension of calcium dihydrogen phosphate particles, and adding the second calcium hydroxide solution to the combined solution to form a product solution that includes an aqueous suspension of particles of a calcium phosphate composition.

The disclosure features methods that include obtaining a first plurality of particles that include calcium carbonate, where the particles have a distribution of sizes between 8 mm and 12 mm, and heating the first plurality of particles to a temperature of between 900 C. and 1200 C. for a time period of at least 1 hour to generate a second plurality of particles that include calcium oxide.

A process for producing a calcium phosphate reactant, according to which: in a first step, use is made of a source of calcium and a source of phosphate ions in water, in a molar ratio that is adjusted so as to obtain a Ca/P molar ratio of between 0.5 and 1.6, and the source of calcium is reacted with the phosphate ions at a pH of between 2 and 8, in order to obtain a suspension (A) of calcium phosphate, and in a second step, added to the suspension (A) are an alkaline compound comprising hydroxide ions in order to set a pH of more than 8 and an additional source of calcium in order to obtain a suspension (B) of calcium phosphate reactant having a Ca/P molar ratio of more than 1.6.

A calcium phosphate reactant obtainable by such a process.

The invention relates to an ultralong hydroxyapatite nanowire/microwire, a method of preparing the same, a hydroxyapatite paper comprising the same and a preparation method thereof, and provides an ultralong hydroxyapatite nanowire/microwire having a length of tens to hundreds of micrometers and a diameter of tens to hundreds of nanometers. There is also provided a method of preparing the ultralong hydroxyapatite nanowire/microwire, a hydroxyapatite paper comprising the ultralong hydroxyapatite nanowire/microwire, and a method of preparing the hydroxyapatite paper.

The present invention provides that powder is mainly constituted from secondary particles of hydroxyapatite. The secondary particles are obtained by drying a slurry containing primary particles of hydroxyapatite and aggregates thereof and granulating the primary particles and the aggregates. A bulk density of the powder is 0.65 g/mL or more and a specific surface area of the secondary particles is 70 m.sup.2/g or more. The powder of the present invention has high strength and is capable of exhibiting superior adsorption capability when it is used for an adsorbent an adsorption apparatus has.