Consequences of the nanoporosity of cellulosic fibers on their streaming potential and their interactions with cationic polyelectrolytes |
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Authors: | Martin A Hubbe Orlando J Rojas Lucian A Lucia Tae Min Jung |
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Institution: | (1) Department of Wood and Paper Science, North Carolina State University, Box 8005, Raleigh, NC 27695-8005, USA;(2) Hansol Paper Co. Ltd., 481-8 Whachon-Ri, Changhang-Up, Seochun-Kun, Choongnam, Korea |
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Abstract: | Electrokinetic tests, based on the streaming potential method, were used to elucidate interactions between cationic polyelectrolytes
and cellulosic fibers and to reveal aspects of fibers’ nanoporosity. The fibrillated and nanoporous nature of bleached kraft
fibers gave rise to time-dependent changes in streaming potential, following treatment of the wetted fibers with poly-diallyldimethylammonium
chloride. Electrokinetic test results were consistent with an expected longer time required for higher-mass polyelectrolytes
to diffuse into pore spaces, compared to lower-mass polyelectrolytes. Further evidence of the relative inability of polyelectrolyte
molecules to diffuse into the pores of cellulose was obtained by switching back and forth between high and low ionic strength
conditions during repeated measurement of streaming potential, after the fibers had been treated with a moderate amount of
cationic polymer. By changing the concentration of sodium sulfate it was possible to switch the sign of streaming potential
repeatedly from positive to negative and back again. Such results imply that a continuous path for liquid flow exists either
in a fibrillar layer or within the cell walls. The same concepts also helped to explain the dosages of high-charge cationic
polymer needed to achieve maximum dewatering rates, as well as the results of retention experiments using positively and negatively
charged microcrystalline cellulose particles. |
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Keywords: | Adsorption Cellulose Polyelectrolytes Porosity Streaming potential |
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