Abstract: Simplified and improved processes are provided for manufacturing titanium dioxide pigments including a surface treatment whereby a plurality of inorganic oxides or a combination of one or more inorganic oxides with one or more inorganic phosphates are applied to a titanium dioxide base pigment. Aqueous acid-soluble sources of the desired inorganic oxides and/or phosphates are predissolved in an aqueous acid, and these can be added on a batch wise or more preferably on a continuous basis to an alkaline slurry containing the titanium dioxide base pigment and to which aqueous alkaline-soluble sources of the desired inorganic oxides are being or have been added previously. Co-precipitation of the oxides and/or oxides and phosphates is then accomplished by an adjustment of the pH, to provide a surface treated pigment with excellent homogeneity of the deposited mixed oxides and/or oxides and phosphates.

Abstract: The present invention provides for a process for handling carbonyl sulfide waste and waste metal halides produced in industrial processes and, more particularly chlorination processes. The process includes the steps of hydrolyzing the carbonyl sulfide to produce a waste stream containing hydrogen sulfide and sulfidizing the resulting hydrogen sulfide containing stream with a solution of the waste metal halides. The resulting metal sulfide and metal halide-containing stream can be neutralized before disposal of the produced waste solids.

Abstract: The current invention provides improved methods and filter stacks for concentrating a slurry of titanium dioxide. The improved filter stack comprises a series of filter disks and diverter trays arranged in parallel. The present invention provides an improvement over prior art filter stacks by using a substantially complete weld to attach a diverter plate to the diverter trays. The current invention also provides an improved method for pre-conditioning a filter stack. The improved method is designed to pre-condition and gradually prepare the filter stack for production of the desired slurry of titanium dioxide. Further, the current invention provides an improved process for preparing and transporting a slurry of titanium dioxide. Finally, the current invention provides a method for enhancing the lifespan of a filter stack.

Abstract: Novel gas separation apparatus and methods are provided that help reduce the amount of process gas lost through the discharge outlet of either a cyclone separating gas/solid mixtures or a hydroclone separating gas/liquid mixtures. Significant savings are realized by minimizing losses and neutralization costs. A cyclone or hydroclone is placed within a containment vessel that creates a contained atmosphere common to both the gas outlet and the discharge outlet of the cyclone or hydroclone. Process gas mixed with the solids or mixed with the liquids in the discharge underflow are displaced from the discharge underflow and contained within the containment vessel. The displacement of the process gas is facilitated by an introduction of a small amount of purge gas to the discharge underflow exiting the cyclone or hydroclone via the discharge outlet.