Mechanism of Retention of Metal Cations in Linerboard and Never Dried Pulps
Even trace amounts of metal cations, which are naturally present in wood, can affect paper properties. We examined the effect of barium, sodium, and calcium on paper made from linerboard and virgin kraft fibers. Soaking the fibers in a caustic solution improved tensile and stiffness properties of the paper. Caustic soaking seems to minimize the effects of hornification by improving the fibers’ capability to swell and bond. However, strength was not improved when the pulp was treated with barium cations. When the cation levels were compared on the basis of parts per million, barium showed a much higher concentration in the pulp than did calcium and sodium, possibly indicating the formation of a complex; on a milliquivalents per kilogram basis, the cations were retained in similar fashion. The cations appear to be retained by an ion-exchange mechanism.
Mechanism of Retention of Metal Cations in Linerboard and Never Dried Pulps