Bauxite residue recovery includes mixing a solution of hydrochloric acid (HCL) according to a predetermined concentration, and adding the HCL solution to a quantity of raw red mud recovered from industrial operations as waste material. The highly alkaline property of the bauxite residue, commonly known as red mud is at least partially neutralized from the HCL, and makes the resulting washed red mud more amenable to subsequent uses in various applications in fields such as construction, wastewater treatment, and metal recovery processes. The process recovers washed red mud from the red mud and HCL solution by filtering the raw red mud and HCL solution for generating a stream of leach liquor from the filtrate and the recovered washed red mud from the residue. The neutralized red mud is further treated to extract metals such as calcium, iron, aluminum, silicon, and titanium.

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.

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.

The present invention disclosed use of lactam as a solvent in the preparation of nanomaterials by precipitation method, sol-gel method or high temperature pyrolysis. These methods are able to recycle lactam solvent, which meet requirements of environmental protection.

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.

The present disclosure discloses a method for co-producing synthetical rutile and polymeric ferric sulfate with waste sulfuric acid, which includes the following steps of: S1, performing deep reduction on ilmenite to obtain reduced ilmenite with a metallization rate of 85% or more; S2, leaching the reduced ilmenite with waste sulfuric acid; S3, performing solid-liquid separation on a mixed solution after the leaching in step S2, and drying a solid to obtain synthetical rutile, wherein a filtrate is a ferrous sulfate solution; and then performing step S4 or S5 to obtain a polymeric ferric sulfate finished product. The waste sulfuric acid is adopted in the present disclosure to leach the reduced ilmenite to prepare the synthetical rutile, a novel waste acid recycling mode is formed

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.

Processes to solubilize the titanium and, later, hydrolyze it as titanium dioxide, in part based on the mineral ogical complexity of the anatase ore. The process described is capable of sufficiently solubilizing titanium in anatase using H.sub.2SO.sub.4, while overcoming the low reactivity of the ore to this acid. Moreover, the process does not require a reduction step prior to anatase digestion.

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.

Provided is a titanium dioxide paste that can form a porous semiconductor layer having excellent close adherence with a conductive substrate. The titanium dioxide paste contains titanium dioxide nanoparticles and water, and has a pH of not lower than 2.6 and not higher than 3.5.