Abstract:
The invention provides colloidal dispersions of calcium phosphate platelets comprising at least one polymer which complexes the calcium and in which the length of the platelets, L, is between 5 and 500 nm and in which the thickness of the platelets is between 0.5 and 20 nm.Another subject-matter of the invention is the calcium phosphate platelets obtained by drying the colloidal dispersion according to the invention.The invention also provides a process for preparing these colloidal dispersions of calcium phosphate platelets according to the invention.Finally, another subject-matter of the invention is the use of the abovementioned colloidal dispersions of platelets as food additive, reinforcing filler, thermal insulation filler, pharmaceutical excipient, polishing agent, building materials, additive for oral formulations, in particular dentifrices, or encapsulating agent.
Abstract:
The invention concerns an aqueous colloidal dispersion of isotropic particles of a phosphate of at least one rare earth and is characterized in that it comprises either a complexing agent with a pK (cologarithm of the dissociation constant of the complex formed by the complexing agent and said rare earth) of more than 2.5; or an anion of a monobasic acid, soluble in water and with a pKa in the range 2.5 to 5; or said complexing agent and/or said anion of a monobasic acid. In the case of cerium and lanthanum, the mean particle size is at most 20 nm. The dispersions can have a degree of colloid agglomeration of less than 40%.This dispersion can be prepared by forming an aqueous mixture comprising at least one rare earth salt and the complexing agent or monobasic acid anion; by adding a base then phosphate ions to the mixture formed; and heating the mixture obtained. A precipitate is obtained that is re-dispersed in water.
Abstract:
An agent for recovering heavy metal cations from an aqueous effluent, including a silicate or aluminosilicate type compound, e.g. an alkali metal silicate or aluminosilicate, and a carbonate type compound, e.g. an alkali metal carbonate, and preferably a carrier such as a lay. The agent may also form a cation stabilizer. Said agent is useful for removing or stabilizing heavy metal cations in the water used for cleaning flue gases from waste incineration, particularly household refuse and industrial waste incineration.
Abstract:
The invention relates to the use of barium sulphide or strontium sulphide for the removal of heavy metals in industrial acidic solutions. The invention is applicable to the purification of contaminated acids, in particular of spent battery acid, or of industrial solutions of titanyl sulphate.
Abstract:
In a first embodiment, the present invention concerns a colloidal dispersion of a cerium compound, characterised in that it has a CeO.sub.2 concentration of between 500 and 700 g/l and a conductivity of at most 50 mS/cm. In a second embodiment, the colloidal dispersion is characterised in that it has a CeO.sub.2 concentration of more than 700 g/l. A process for the preparation of the dispersion of the invention is characterised in that a starting suspension or dispersion is treated by dialysis or with a cationic resin and an anionic resin. Colloidal dispersions of the invention can be used in automobile post combustion catalysis, in cosmetics, in lubrication, in ceramics or as an anticorrosion agent.
Abstract:
The invention provides colloidal dispersions of calcium phosphate platelets comprising at least one polymer which complexes the calcium and in which the length of the platelets, L, is between 5 and 500 nm and in which the thickness of the platelets is between 0.5 and 20 nm.Another subject-matter of the invention is the calcium phosphate platelets obtained by drying the colloidal dispersion according to the invention.The invention also provides a process for preparing these colloidal dispersions of calcium phosphate platelets according to the invention.Finally, another subject-matter of the invention is the use of the abovementioned colloidal dispersions of platelets as food additive, reinforcing filler, thermal insulation filler, pharmaceutical excipient, polishing agent, building materials, additive for oral formulations, in particular dentifrices, or encapsulating agent.
Abstract:
The invention relates to a colloidal dispersion comprising rhabdophane-structured rare-earth phosphate particles (Ln) and a polyphosphate. Said dispersion is prepared by a method consisting in forming a medium comprising at least one type of rare-earth salt and a poly phosphate in such quantities that the P/Ln ratio is equal to or higher than 3, in heating the thus obtained medium and in removing residual salts, thereby obtaining said dispersion. Said invention also relates to a transparent luminescent material which is obtainable from said dispersion and based on the rare-earth phosphate particles and a polyphosphate and whose P/Ln ratio is higher than 1, to a luminescent system comprising said material and to an excitation source.
Abstract:
The invention concerns a colloidal dispersion of a phosphate of a rare earth and a process for its preparation. The dispersion is characterized in that it comprises anisotropic and disaggregated or disaggregatable particles of a phosphate of at least one rare earth and an anion of a monobasic acid, soluble in water and with a pKa of at least 2.5. It is prepared by a process in which a solution of a salt of at least one rare earth is mixed with phosphate ions while controlling the pH of the reaction medium to a value in the range 4 to 9 and in the presence of a monobasic acid, soluble in water and with a pKa of at least 2.5; the mixture obtained optionally undergoes a maturing step; the precipitate is then separated from the reaction medium; and said precipitate is then dispersed in water.
Abstract:
The invention concerns a heat-stable ordered mesoporous or mesostructured material comprising a mineral phase wherein are dispersed particles of nanometric dimension at least partly crystaline, the global crystallinity index of said mesostructured or ordered mesoporous material being less than 10% in volume. The invention also concern a method for obtaining such a material.
Abstract:
An organic sol is disclosed comprising titanium oxide particles; an organic liquid phase and at least am amphiphilic compound selected among polyethylene phosphate alkyl ethers. In a first embodiment, the method for preparing said sol mixes said amphiphilic compound and the organic liquid phase, and disperses the titanium oxide particles in the resulting mixture. In a second embodiment, the method forms a mixture of titanium oxide and at least said amphiphilic compound, then disperses said mixture in said liquid phase. A solid compound comprising a mixture of titanium oxide particles and at least an amphiphilic compound selected among these mentioned above is also disclosed.