“…This result postulates that the total charge, which is determined by the potentiometric titration using sodium hydroxide, is not always a reliable method applied to cations that can form complexes. The total charge of the pulp was 186.6 meq/kg which was determined using the potentiometric method [17]. If a divalent Fe 2+ ion binds with two negative sites on the fibre, the sorption capacity of the fibre will be 93.3 mmol/kg of Fe 2+ .…”