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Adsorption of cationic starch on fibres from mechanical pulps

1996; Volume: 100; Issue: 6 Linguagem: Inglês

10.1002/bbpc.19961000647

0005-9021

Lars Wågberg, Kat Kolar,

Lignin and Wood Chemistry

Abstract The present investigation, in which the adsorption of cationic potato and corn starch on fibres from Thermo Mechanical Pulps (TMP) has been studied, has been divided into two parts. In the first part, the adsorption of differently charged cationic potato starches onto the fibre fraction of a peroxide‐bleached TMP was investigated. The results show that the adsorption can be viewed as an ion‐exchange process in which the anionic charges on the fibres are neutralised by cationic charges on the starch. Experiments with different electrolyte concentrations show that the starch adsorption on this kind of fibre follows theories for polyelectrolyte adsorption. When Dissolved and Colloidal Substances (DCS) from the TMP is introduced into the experiments these conclusions are no longer valid since the complexation between the starch and the DCS becomes the dominating process. the results from the second part show the large influence of cellulosic fines and DCS on the amount of starch that can be adsorbed on the fibres. Since both fines and DCS have a higher charge density and a higher specific surface area than the fibres, they can adsorb significantly larger amounts of starch and may hence increase the total amount of starch adsorbed on the fibres, provided the fines and DSC can be retained to the fibres. The fines fraction is retained to the fibres by a bridging type of mechanism whereas the DCS‐fraction is retained through charge neutralisation of the charges on the DCS‐fraction by the charges on the starch. Potato starch was somewhat more efficient than corn starch in neutralising the effect of the DCS‐fraction.