Process for Deinking Recycled Fibers and Use of an Acid Deinking

摘要

The present invention relates to a process for deinking recycled fibers wherein an aqueous pulp suspension with recycled fibers, printing ink and calcium carbonate is provided. The hardness of the suspension is stabilized by causing dissolution of calcium carbonate contained in the suspension or in an aqueous fluid added to the suspension. The increased hardness suspension is subjected to flotation to separate said printing ink from the suspension. The present invention also relates to use of a weak acid for dissolving calcium carbonate and for stabilizing the hardness in a flotation process for the deinking of an aqueous pulp suspension containing said recycled fibers, printing ink and calcium carbonate.