The use of cationic organic polyelectrolytes as drainage and retention aids in the papermaking process and as flocculants in sewage treatment is steadily increasing. Therefore, there has been a growing interest in a better understanding of the mode of action of these additives.
There are two basic concepts discussed in the current literature which can be briefly described in terms of bridging and of charge neutralisation, respectively.⁽¹⁻⁶⁾ Of particular interest is a variety of the latter, the ‘patch charge model’, which was introduced recently.⁽⁷⁾ In general the discussions are based on the data of electrophoretic mobility and of flocculation, drainage, or retention.⁽⁸⁻¹⁴⁾
Clearly, in all cases the adsorption of the polymers from the bulk of the solution onto the dispersed particles is of prime importance for the discussion of the mechanism of action. There have been, however, only a few attempts to study the adsorption and the adsorption kinetics of cationic polymers in cellulose systems.⁽¹⁵⁻¹⁸⁾
The object of this investigation was to study the influence of molecular weight and of charge density on the adsorption of polyethyleneimines (PEI) and of cationic polyacrylamides (PAA) in cellulose systems, in conjunction with electrokinetic and flocculation measurements.