The most frequently used
salt in the papermaking industry is aluminumsulphate. Below
pH 9, the cations are primarily adsorbed to the pulp fibres
by electrostatic interactions with the carboxyl groups in the
lignocellulose material. The electrostatic interactions result
in adsorption of small species or colloids on the fibre surface,
altering the surface properties of the fibres (Ohman and
Wågberg, 1997; Kato et al., 2000).