A particulate TiO.sub.2 includes a TiO.sub.2 content of at least 99 wt.-%, an anatase content of at least 98 wt.-%, a primary crystallite size X.sub.50 of at least 200 nm, a numerical fraction of TiO.sub.2 with a primary crystallite size of at most 100 nm of at most 10%, a specific surface area of at most 8 m.sup.2/g as determined by BET measurements, 1200 ppm to 2400 ppm of alkali with respect to the TiO.sub.2 content, an Al content of 1 ppm to 1000 ppm, expressed as Al and with respect to the TiO.sub.2 content, a weight ratio of Al.sub.2O.sub.3 to Nb.sub.2O.sub.5 of from 0.17 to 0.74, and 0.1 wt.-% to 0.3 wt.-% of P, expressed as phosphorus and with respect to the TiO.sub.2 content.

The invention relates to a method for obtaining nanoparticulate titanium dioxide in agglomerate form from a hydrolyzed acidic titanyl compound, the thus obtained titanium dioxide as well as the use thereof as a photocatalyst, process catalyst or adsorbent, especially in aqueous systems.

Titanium oxide particles of the present invention include octahedral-shaped particles, in which each particle of the octahedral-shaped particles has line segments each of which connects two apexes which face each other and has a maximum value of the line segments, an average value of the maximum values is 300 nm or more and 1,000 nm or less, and a value (the average value of the maximum values/BET-converted average particle diameter) obtained by dividing the average value of the maximum values of the line segments by an average particle diameter converted from a BET specific surface area is 1.0 or more and 2.5 or less.

The invention relates to a process for extracting metals and salts from titanium-bearing minerals such as perovskite. More particularly, although not exclusively, the invention relates to extracting titanium dioxide and optionally other compounds from melter slag derived from an iron-making process.

In a coloring ultraviolet protective agent, the average molar absorption coefficient in the wavelength range from 200 nm to 380 nm is increased, and the color characteristics in the visible region are controlled. The coloring ultraviolet protective agent is useful for shielding ultraviolet rays and coloring. The coloring ultraviolet protective agent comprises M2 doped oxide particles in which oxide particles (M1Ox) including at least M1 being a metal element or metalloid element, are doped with at least one M2 selected from metal elements or metalloid elements other than M1, wherein x is an arbitrary positive number, wherein an average molar absorption coefficient in the wavelength range of 200 nm to 380 nm of a dispersion in which the M2 doped oxide particles are dispersed in a dispersion medium, is improved as compared with one of a dispersion in which the oxide particles (M1Ox) are dispersed in a dispersion medium, and wherein a hue or chroma of color characteristics in the visible region of the M2 doped oxide particles is controlled.

The invention relates to a process for extracting metals and salts from titanium-bearing minerals such as perovskite. More particularly, although not exclusively, the invention relates to extracting titanium dioxide and optionally other compounds from melter slag derived from an iron-making process.

The present invention provides titania particles which are formed by providing a titania sol and spray drying the titania sol. A morphology of the dried titania particles is controlled by producing the titania sol from a TiO.sub.2 containing slurry and controlling the pH of the slurry to be 3 pH units or more from the iso-electric point of the titania by adding a peptizing agent to reduce an extent to which the titania sol is flocculated, or by producing the titania sol from a TiO.sub.2 containing slurry and adjusting the iso-electric point to be 3 pH units or more from the pH of the slurry by adding a dispersant to reduce an extent to which the titania sol is flocculated. The titania particles have a continuous exterior convex surface, a diameter of 30 m or less, a BET specific surface area of 50 m.sup.2/g or more, and are porous.

Digestion of impure alumina with sulfuric acid dissolves all constituents except silica. The resulting sulfatesaluminum sulfate, ferric sulfate, titanyl sulfate, and magnesium sulfate for alumina contaminated with iron-, titanium-, and/or magnesium-containing speciesremain in solution at approximately 90 C. Hot filtration separates silica. Solution flow over metallic iron reduces ferric sulfate to ferrous sulfate. Controlled ammonia addition promotes hydrolysis and precipitation of hydrated titania from titanyl sulfate that is removed by filtration. Addition of ammonium sulfate forms ferrous ammonium sulfate and ammonium aluminum sulfate solutions. Alum is preferentially separated by crystallization. Addition of ammonium bicarbonate to an ammonium alum solution precipitates ammonium aluminum carbonate which may be heated to produce alumina, ammonia, and carbon dioxide. The remaining iron rich liquor also contains magnesium sulfate. The addition of oxalic acid generates insoluble ferrous oxalate which is thermally decomposed to ferrous oxide and carbon monoxide which is used to reduce the ferrous oxide to metallic iron. Further oxalic acid addition precipitates magnesium oxalate which is thermally decomposed to magnesium oxide.

The invention relates to processes for the extraction of products from titanium-bearing minerals. In particular embodiments the invention relates to methods of recycling sulphuric acid used in a titanium dioxide extraction process. The invention also relates to methods for minimising chromophore contamination in calcined titanium dioxide. The process may also comprise steps for removing contaminants from recycled acid or desirable products.

The invention provides a process for the production of titania particles with a desired morphology. The process comprises providing a titania sol and then drying the sol to provide dried titania particles. The process is characterized in that the morphology of the dried titania particles is controlled by applying one or more of the following criteria: (a) the titania sol is produced from a TiO.sub.2 containing slurry obtained using a precipitation step in a sulphate process, wherein the size of micelles formed during the precipitation is controlled; (b) the titania sol is produced from a TiO.sub.2 containing slurry and the pH of the slurry is controlled in order to affect the extent to which the titania sol is flocculated; (c) the titania sol is produced from a TiO.sub.2 containing slurry and the iso-electric point of the titania is adjusted in order to affect the extent to which the titania sol is flocculated; (d) the titania sol is dried by application of heat and the temperature used during the drying step is controlled.