Effect of pH and neutral salts upon the swelling of cellulose gels

Abstract

SynopsisThe swelling of cellulose gel is considered to be caused by an osmotic pressure differential resulting from a difference in concentration of mobile ions between the interior of the gel and the exterior solution. The fundamental feature within the gel, bringing about the unequal distribution, is the presence of ionizing acidic groups attached to the macromolecular network. Using the Donnan theory to describe the distribution of ions, it is shown that the experimentally observed decreases in swelling brought about by extremes of pH and by salt addition may be explained in a semiquantitative way. The swelling behavior of superabsorbent gels appears to be almost completely governed by the proposed mechanism. For conventional wood pulps, the mechanism describes the smaller variations in swelling caused by pH and salt addition. For these gels, electrolytic effects are only responsible for a fraction of the total swelling-the remainder being associated with the macromolecular network itself. The unequal distribution of hydrogen ions between a gel and an exterior solution is described briefly, along with the effect that this has on the potentiometric titration of the gel.

Initial wet web strength of paper

“…These phenomena can be explained with DLVO theory, named after Derjaguin, Landau, Vervey and Overbeek (Derjaguin 1954;Derjaguin and Landau 1941;Israelachvili 2006b;Pelton 1993;Vervey and Overbeek 1948). The type and amount of salt added to the solvent water has a negative impact on IWWS, similar to the findings of Grignon for dry paper (Belle et al 2014a;Grignon and Scallan 1980).…”

“…Both parameters, pH and salt content, have a direct influence on the electrostatic potential and swelling behavior of the fibers. Because of that, these parameters have an indirect effect on the strength formation in both, wet and dry paper (Grignon and Scallan 1980;Nelson and Kalkipsakis 1964a, b;Scallan 1983;Scallan and Grignon 1979). These phenomena can be explained with DLVO theory, named after Derjaguin, Landau, Vervey and Overbeek (Derjaguin 1954;Derjaguin and Landau 1941;Israelachvili 2006b;Pelton 1993;Vervey and Overbeek 1948).…”

Enhanced Absorbent Products Incorporating Cellulose and Its Derivatives: A Review

“…This section will consider osmotic pressure and various studies showing how osmotic pressure can account for such swelling, especially when a cellulosic material or a hydrogel is placed in water having few or no salt ions (Grignon and Scallan 1980;Vitta et al 1986;Oppermann 1995;Sannino et al 2003;Buchholz et al 2005;Ganji et al 2010). The same principles also apply to cellulosic fibers, though usually to a lesser extent.…”

“…Part of the justification for considering cellulosic materials in the context of hydrogels involves the presence of ionizable bound groups, mainly carboxyl groups, within their structure (Herrington and Petzold 1992). Such groups contribute to swelling (Grignon and Scallan 1980;Lindström and Carlsson 1982) and ion exchange phenomena (Rudie et al 2006;Hubbe et al 2011) within cellulosic fibers.…”

“…One of the most important principles underlying swelling is that, under equilibrium conditions, there will be a fixed relationship between the concentrations of ions inside and outside of a swellable, gel-like material (Grignon and Scallan 1980). In other words a Donnan equilibrium condition will become established between the ion concentrations inside and outside of the hydrogel.…”