Study of the adsorption of polyethylenimine on cellulosic fibres in an aqueous suspension

The adsorption of commercial polyelectrolytes, based on polyethylenimine (P EI) polymers, on cellulosic fibres in a pulp suspension of bleached long fi bre kraft pulp is presented in this paper. The amount of polyethylenimine a dsorbed per unit mass of pulp has been determined under different operating conditions: i) initial concentration of polyethylenimine (50, 75 and 100mg /L); ii) pH (4.5 and 6.5); iii) pulp treatment (unrefined, refined, classif ied refined and classified refined with fillers). The results showed that t he amount of adsorbed polyethylenimine depends notably on the process varia bles. The adsorption levels have been theoretically explained by considerin g the concentration gradient between the solution and the fibre surfaces an d the influence of pH on the ionic character of cellulose and polyethylenim ine. Furthermore, the influence of the specific surface of cellulose, accor ding to the freeness and the presence of fines and fillers, has also been c onsidered.