Treating effluent from paper pulp bleaching - by decolourising and ultrafiltering to remove chloride ions

摘要

A process for the treatment of bleaching effluents from the mfr. to chemical pulps, esp. kraft pulp, contg. coloured organic materials arising particularly from lignin and its degradation products, and also mineral chlorides is provided. The effluent is given a decolouration treatment enabling the coloured organic materials to be sepd. in a concentrated state in a small volume. The concentrate is diluted with an aq. diluent but not below the concn. required for effective ultrafiltration. The liquid is then ultrafiltered to obtain a retentate with a reduced mineral content such that the retentate may be recycled in the manufacturing circuits without risk of corrosion. The organic material is recovered with a low mineral content so that it may be used e.g. combusted in the recovery heater, or in a lime oven etc., without causing corrosion.