Factors influencing retention behavior of aluminum compounds on handsheets

Abstract

Handsheets were prepared with aluminum sulfate under various conditions of pulp suspension, and factors influencing retention behavior of aluminum components on the handsheets were studied on the basis of their aluminum contents. When deionized water was used in the handsheet-making process, aluminum contents in the handsheets had a plateau level of 0.7 mg/g in the range of 1%-8% Al2(SO4)3 addition levels on dry weight of pulp. On the other hand, when tap water was used aluminum contents increased up to 5.6 mg/g, increasing the Al2(SO4)3 addition levels to 8%. The high aluminum contents in the handsheets are explained in terms of pH and the presence of calcium ions from the tap water used. Cationic aluminum species, which are formed from aluminum sulfate added to pulp suspensions, are primarily adsorbed on pulp fibers by electrostatic interactions with carboxyl groups in the pulp, competing with OH- ions in water. These aluminum components, once adsorbed on pulp fibers by ionic interactions, are not removed from the fibers by extending the stirring time of the pulp suspensions. © The Japan Wood Research Society 1999.