ROLE OF SURFACE-CHARGE IN DEPOSITION OF FILLER PARTICLES ONTO PULP FIBERS

The effect of cationic polyethylenimine (PEI) on colloidal stability o f ground calcium carbonate and its deposition on pulp fibres suspended in water was investigated. The adsorption of PEI on negatively charge d CaCO3 particles causes destabilization due to the elimination of cha rge. With increasing additions of PEI, restabilization of positively c harged CaCO3 takes place. Based upon these results the filler was pret reated with PEI in order to encourage its deposition on negatively cha rged fibres. Two levels of PEI addition were used to produce either Ca CO3 aggregates or dispersed particles. The extent of deposition, the d eposition time I, and the capture efficiency alpha(0) were established . The results indicate that positively charged filler aggregates depos it faster than dispersed particles. Alternatively, the fibres were tre ated with two levels of PEI, the same as that used for CaCO3 treatment , and the deposition of CaCO3 was observed. The deposition efficiency in this case was lower. (C) 1998 Elsevier Science B.V. All rights rese rved.