Fremgangsmåte ved behandling av avfallspapir

摘要

A method of treating reject from a plant for de-inking waste paper which reject comprises a mixture of ink particles, inorganic particles and fibres includes the step of forming in an aqueous suspension or slurry comprising said reject a precipitate of a substantially white insoluble salt which entrains or aggregates ink particles, inorganic particles and fibres contained in said reject whereby the darkness of the reject is reduced by formation of the precipitate. The precipitate may comprise calcium carbonate formed by reacting carbon dioxide with calcium hydroxide in the said suspension. The precipitate and entrained or aggregate material therein may be separated for re-use as a particulate coating or filler material. The said product may be separated from water which after separation is clearer than when originally treated and is recycled for re-use. The said reject may be a slurry or sludge produced from a flotation process of a waste paper de-inking plant.