Removal and characterization of anionic trash in mechanical pulp

The present methodology to measure anionic trash in a bleached chemi thermomechanical pulp (CTMP) was modified. Also, an acid treatment with sulphurous acid, a pressing, and a heat treatment were tested with the objective to improve the removal of anionic trashes from CTMP.; Pressing of the pulp successfully removed anionic trash from the pulp. An increase from 13% to 40% consistency gave an impressive 70% decrease in cationic demand. The acid treatment caused a decrease in the anionic trash of a heat-treated pulp while lignin precipitated out of the pulp, polymerised-silica bonded to the pulp, metals detached from the fibres, and dissolved organics travelled to the pressate. A heat treatment reduced the anionic trash content and dissolved the resin and fatty acid agglomerates of non-acid treated pulps.; The soda ash/NaOH bleaching process is a good compromise between the desired brightness gains and anionic trash concentrations.