Process for protecting magnetic particles with chromium oxide
AssigneesICI Australia Limited, Commonwealth Scientific and Industrial Research Organization
InventorFrancis D. Whillans
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Abstract
A method for the preparation of magnetic particulate matter coated with a protective layer of chromium(III) hydroxide, oxyhydroxide or oxide, optionally crosslinked with polyacrylic acid, which process comprises a first step of depositing a hydrogel of chromium(III) hydroxide onto magnetic material in a desired particulate form, a second step of heating to form chromium(III) hydroxide, oxyhydroxide or oxide, and a third optional step, which may precede or follow the said second step, of crosslinking with polyacrylic acid. The coated protected magnetic particles are useful for the preparation of composite magnetic polymeric particles for use in processes involving ion exchange, filtration and adsorption.
Claims19
A process for preparing protected magnetic particulate matter which process comprises coating particles of magnetic material with at least one coating compound selected from the group consisting of chromium (III) hydroxide, chromium (III) oxyhydroxide and chromium (III) oxide by a first step of depositing chromium (III) hydroxide hydrogel on the said particles by the addition of a basic reagent to an aqueous solution of a chromium (III) salt containing the said particles wherein the said basic reagent is generated in situ by the hydrolysis of urea precursor, and a second step of heating the hydrogel-coated magnetic material to a temperature above 100.degree. C.
A process for preparing protected magnetic particulate matter which process comprises coating particles of magnetic material with at least one coating compound selected from the group consisting of chromium (III) hydroxide, chromium (III) oxyhydroxide and chromium (III) oxide by a first step of depositing chromium (III) hydroxide hydrogel on the said particles by the addition of a basic reagent to an aqueous solution of chromium (III) nitrate containing the said particles wherein the said basic reagent is generated in situ by the hydrolysis of a basic reagent precursor, and a second step of heating the hydrogel-coated magnetic material to a temperature above 100.degree. C.
A process for preparing protected magnetic particulate matter which process comprises coating particles of magnetic material with at least one coating compound selected from the group consisting of chromium (III) oxyhydroxide and chromium (III) oxide by a first step of depositing chromium (III) hydroxide hydrogel on the said particles by the addition of a basic reagent to an aqueous solution of a chromium (III) salt containing the said particles wherein the said basic reagent is generated in situ by the hydrolysis of a basic reagent precursor, and a second step of heating the hydrogel-coated magnetic material to a temperature in the range 240.degree. to 360.degree. C.
A process for preparing protected magnetic particulate matter which process comprises coating particles of magnetic material with at least one coating compound selected from the group consisting of chromium (III) hydroxide, chromium (III) oxyhydroxide and chromium (III) oxide by a first step of depositing chromium (III) hydroxide hydrogel on the said particles by the addition of a basic reagent to an aqueous solution of a chromium (III) salt containing the said particles wherein the said basic reagent is generated in situ by the hydrolysis of a basic reagent precursor, and a second step of crosslinking the coating with polyacrylic acid and heating the hydrogel-coated magnetic material to a temperature in the range 100.degree. to 275.degree. C.
A process according to any one of claims 9 and 10 wherein oxygen is excluded.
Dependencies are inferred from the claim text.