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Abstract

In the preparation of a suspension with a high content of titanium dioxide, which has been produced according to the chloride process, a finely divided titanium dioxide is slurried, in unflocculated condition without use of a dispersing agent, dechlorinated and then filtered. The content of multivalent anions can be controlled in the slurry before the filtration through suitable dechlorinating agents, particularly hydrogen peroxide and/or sodium hydrogen sulfite, and thereby the solid content in the filter cake and the consistency of the filter cake are advantageously influenced. If, on one hand, no or only few multivalent anions are present, a thixotropic filter cake with a high solids content is obtained in a pressure filtration. The filter cake is converted into a titanium dioxide suspension with a high solids content through feeding into a titanium dioxide suspension to which a dispersing agent has been added. If, on the other hand, a rigid filter cake is desired by, for example, a vacuum filtration, a minimum quantity of multivalent anions is necessary for the formation of the rigid filter cake. The solids content is, however, lowered in comparison to the thixotropic filter pastes. Where this minimum quantity of multivalent anions is exceeded, the solids content declines further. The rigid filter cakes can be rendered flowable through the direct admixing of dispersing agent. Hydrogen peroxide is particularly preferred as a dechlorinating agent.

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