A process for producing a particulate TiO.sub.2 includes supplementing metatitanic acid with an alkali compound in a quantity of 1200 ppm to 2400 ppm of alkali, with a phosphorus compound in a quantity of 0.1 wt.-% to 0.3 wt.-% by weight of P, expressed as phosphorus, and with an aluminum compound in a quantity of 1 ppm to 1000 ppm of Al, expressed as Al, to obtain a mixture. The quantity of the alkali compound, of the phosphorus compound, and of the aluminum compound are with respect to the TiO.sub.2 content. The mixture is calcined at a constant temperature of 940° C. to 1020° C. until a numerical fraction X.sub.50 of TiO.sub.2 has a primary crystallite size of at least 200 nm, to obtain a calcined mixture. The calcined mixture is cooled to obtain a cooled calcined mixture. The cooled calcined mixture is grinded to obtain the particulate TiO.sub.2.

A process for producing a particulate TiO.sub.2 includes supplementing metatitanic acid with an alkali compound in a quantity of 1200 ppm to 2400 ppm of alkali, with a phosphorus compound in a quantity of 0.1 wt.-% to 0.3 wt.-% by weight of P, expressed as phosphorus, and with an aluminum compound in a quantity of 1 ppm to 1000 ppm of Al, expressed as Al, to obtain a mixture. The quantity of the alkali compound, of the phosphorus compound, and of the aluminum compound are with respect to the TiO.sub.2 content. The mixture is calcined at a constant temperature of 940° C. to 1020° C. until a numerical fraction X.sub.50 of TiO.sub.2 has a primary crystallite size of at least 200 nm, to obtain a calcined mixture. The calcined mixture is cooled to obtain a cooled calcined mixture. The cooled calcined mixture is grinded to obtain the particulate TiO.sub.2.

There is provided a titanyl sulfate hydrate powder comprising 25 to 40% by mass of titanium element in terms of TiO.sub.2, 40 to 60% by mass of sulfur element in terms of H.sub.2SO.sub.4, and niobium element in such an amount that a molar ratio of niobium element to titanium element (Nb/Ti) is 0.00005 to 0.012, with a molar ratio of the sulfur element content to the titanium element content (S/Ti) being 1.1 to 1.5, and comprising crystalline titanyl sulfate dihydrate (TiOSO.sub.4.Math.2H.sub.2O). Thus, the present invention can provide a titanyl sulfate hydrate powder with a high dissolution rate in water and a production method therefor, as well as a method for producing an aqueous titanyl sulfate solution, a method for producing an electrolyte and a method for producing a redox flow battery, using the titanyl sulfate hydrate powder.

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.

There is provided a titanyl sulfate hydrate powder comprising 25 to 40% by mass of titanium element in terms of TiO.sub.2, 40 to 60% by mass of sulfur element in terms of H.sub.2SO.sub.4, and niobium element in such an amount that a molar ratio of niobium element to titanium element (Nb/Ti) is 0.00005 to 0.012, with a molar ratio of the sulfur element content to the titanium element content (S/Ti) being 1.1 to 1.5, and comprising crystalline titanyl sulfate dihydrate (TiOSO.sub.4.2H.sub.2O). Thus, the present invention can provide a titanyl sulfate hydrate powder with a high dissolution rate in water and a production method therefor, as well as a method for producing an aqueous titanyl sulfate solution, a method for producing an electrolyte and a method for producing a redox flow battery, using the titanyl sulfate hydrate powder.

A process for improving the grade and optical quality of zircon, comprising: baking a mixture of a zircon feed and concentrated sulphuric acid at a baking temperature in the range of from 200 up to 400° C., and for a time to form water leachable sulphates with impurities therein including at least iron and titanium; leaching the baked mixture to dissolve the leachable sulphates; and separating the zircon from the leachate containing the leached sulphates, which separated zircon is thereby of improved grade and optical quality.

The present disclosure broadly relates to a process for recovering vanadium, iron, titanium and silica values from vanadiferous feedstocks. More specifically, but not exclusively, the present disclosure relates to a metallurgical process in which vanadium, iron, titanium and silica values are recovered from vanadiferous feedstocks such as vanadiferous titanomagnetite, iron ores, vanadium slags and industrial wastes and by-products containing vanadium. The process broadly comprises digesting the vanadiferous feedstocks into sulfuric acid thereby producing a sulfation cake; dissolving the sulfation cake and separating insoluble solids thereby producing a pregnant solution; reducing the pregnant solution thereby producing a reduced pregnant solution; and crystallizing ferrous sulfate hydrates from the reduced pregnant solution, producing an iron depleted reduced solution. The process further comprises removing titanium compounds from the iron depleted reduced solution thereby producing a vanadium-rich pregnant solution; concentrating vanadium and recovering vanadium products and/or a vanadium electrolyte.

The present disclosure broadly relates to a process for recovering vanadium, iron, titanium and silica values from vanadiferous feedstocks. More specifically, but not exclusively, the present disclosure relates to a metallurgical process in which vanadium, iron, titanium and silica values are recovered from vanadiferous feedstocks such as vanadiferous titanomagnetite, iron ores, vanadium slags and industrial wastes and by-products containing vanadium. The process broadly comprises digesting the vanadiferous feedstocks into sulfuric acid thereby producing a sulfation cake; dissolving the sulfation cake and separating insoluble solids thereby producing a pregnant solution; reducing the pregnant solution thereby producing a reduced pregnant solution; and crystallizing ferrous sulfate hydrates from the reduced pregnant solution, producing an iron depleted reduced solution. The process further comprises removing titanium compounds from the iron depleted reduced solution thereby producing a vanadium-rich pregnant solution; concentrating vanadium and recovering vanadium products and/or a vanadium electrolyte.

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.

Preparing a metal-containing solution or gel includes combining a metal oxide and a liquid comprising a polar organic solvent to yield a mixture, wherein the metal oxide comprises hydrogen-bonded molecular chains, and each molecular chain comprises: a metal from Groups 4-6; at least one oxyanion of a main group element from Groups 15 and 16 bound to the metal through a polar covalent bond, wherein the at least one oxyanion is optionally protonated; and at least one water molecule bound to the metal through a polar covalent bond; and heating the mixture to yield a solution or gel comprising the polar organic solvent and the metal. The solution or gel can be acidic.