Abstract: The invention relates to a method for coating the surface of inorganic particles in an aqueous phase, particularly of titanium dioxide pigment particles, with a dense skin of silicon dioxide and at least one further inorganic compound, particularly with aluminum oxide, where the coating largely consists of separate layers. Titanium dioxide pigment particles, treated with SiO2 and Al2O3 according to the invention, are characterized by improved tinting strength, reduced acid solubility and an isoelectric point shifted towards higher pH values.

Abstract: A method for coating the surface of inorganic solid particles in an aqueous suspension, particularly for coating titanium dioxide with SiO2 includes: a) disagglomeration of the solid particles contained in aqueous suspension, b) addition of a water-soluble precursor of the coating substance to the suspension, c) immediately following step b) homogenization of the suspension, where the temperature and pH value of the suspension do not change significantly in steps a) to c), d) feeding the slurry into a tank and precipitation of the coating substance onto the particle surface and, optionally, application of further coatings, and e) separation of the solid particles from the suspension. The method produces to a highly homogeneous and continuous skin on the particle surface, and to less separately precipitated coating substance.

Abstract: The invention relates to a method for coating the surface of inorganic solid particles in an aqueous suspension. The untreated particles, particularly TiO2 base material, are made into an aqueous suspension and subsequently disagglomerated. According to the invention, a disagglomerated suspension of untreated particles is fed (recirculated) from an intermediate vessel (vessel) in a cyclic process. The intermediate vessel contains a high-speed agitator preferably having a minimum peripheral speed of 15 m/s or a specific agitator capacity P/V of at least 30 W/m3. A pipeline mixer (e.g. inline disperser) based on the rotor/stator principle is furthermore installed in the circuit. The water-soluble precursor compounds of the coating substances, and equally any necessary pH-controlling substances, are metered into the pipeline mixer.

Abstract: The invention relates to a method for coating the surface of inorganic particles in an aqueous phase, particularly of titanium dioxide pigment particles, with a dense skin of silicon dioxide and at least one further inorganic compound, particularly with aluminium oxide, where the coating largely consists of separate layers. Titanium dioxide pigment particles, treated with SiO2 and Al2O3 according to the invention, are characterised by improved tinting strength, reduced acid solubility and an isoelectric point shifted towards higher pH values.

Abstract: The invention relates to a method for coating the surface of inorganic solid particles in an aqueous suspension. The untreated particles, particularly TiO2 base material, are made into an aqueous suspension and subsequently disagglomerated. According to the invention, a disagglomerated suspension of untreated particles is fed (recirculated) from an intermediate vessel (vessel) in a cyclic process. The intermediate vessel contains a high-speed agitator preferably having a minimum peripheral speed of 15 m/s or a specific agitator capacity P/V of at least 30 W/m3. A pipeline mixer (e.g. inline disperser) based on the rotor/stator principle is furthermore installed in the circuit. The water-soluble precursor compounds of the coating substances, and equally any necessary pH-controlling substances, are metered into the pipeline mixer.

Abstract: A method for coating the surface of inorganic solid particles in an aqueous suspension, particularly for coating titanium dioxide with SiO2 includes: a) disagglomeration of the solid particles contained in aqueous suspension, b) addition of a water-soluble precursor of the coating substance to the suspension, c) immediately following step b) homogenization of the suspension, where the temperature and pH value of the suspension do not change significantly in steps a) to c), d) feeding the slurry into a tank and precipitation of the coating substance onto the particle surface and, optionally, application of further coatings, and e) separation of the solid particles from the suspension. The method produces to a highly homogeneous and continuous skin on the particle surface, and to less separately precipitated coating substance.

Abstract: A method for reprocessing cyclone dust occurring during the carbochlorination of titaniferous raw materials, which essentially consists of titanium dioxide, coke and other inert metal oxides, such as silicon dioxide, and for returning a coke-rich and/or a TiO2-rich fraction to the chlorination reactor includes: preparing an aqueous suspension of the cyclone dust; separating a coke-rich fraction (1) from the aqueous suspension by flotation; adding hydrofluoric acid to the remaining suspension; and separating a TiO2-rich fraction (2) by flotation from the remaining suspension.