Effect of PCC filler on dewatering of fiber suspension

The effect of precipitated calcium carbonate (PCC) paper filler on water removal from pine, eucalyptus, and birch kraft pulps was investigated in the vacuum filtration process by measuring average specific filtration resistances (SFRs). PCC reduced the filtration resistance of beaten pulps, that is, increased water removal, in a lab-scale process. This result, which contradicts previous findings with other fillers, is thought to be related both to the high porosity of scalenohedral PCC and, as proved here, to the cationic surface charge of PCC particles, which promotes particle deposition on anionic fibers and reduces the specific surface area of the stock. The responses of pulps to PCC addition varied, and a correlation between SFR and the zeta potential of the fibers was observed.