Sorption of dissolved galactoglucomannans and galactomannans to bleached kraft pulp

Sorption of mannans onto bleached kraft pulp (BKP) was investigated withreference to other interactions of mannans in mechanical pulping andpapermaking. O-Acetyl galactoglucomannans (GGM) isolated from thermomechanicalpulp (TMP), as well as enzymatically modified guar gum galactomannans (GM) wereused in the study. The results showed that deacetylation of TMP GGMs, alsooccurring during peroxide bleaching of TMP, dramatically increased thesorption.A higher sorption was also achieved after salt addition, while temperature hadno effect. Sorption of guar gum GMs onto BKP fibres was, on the other hand,quite unaffected by external conditions such as temperature, pH and saltaddition. The degree to which the pulp was beaten did not notablyinfluence the sorption either – only unbeaten pulp gave a clearly lower mannansorption. A lower number of galactose side groups, however, strongly affectedsorption – the lower the number of side groups, the higher the sorption.The molar mass did not seem to affect the rate of sorption to any higher extentat ambient temperature. At higher temperatures the rate of sorption of smallerGM polymers was, nevertheless, slightly increased. Low-molar-mass GMs alsosorbed at a higher rate onto unbeaten pulp compared to high-molar-mass mannans.GM sorption appeared to be virtually irreversible.