Effect of cationic polymers on the stability and the electrokinetic characteristics of dissolved and colloidal substances from deinked wastepaper pulp

In recent years dissolved and colloidal substances (DCS) present in pulp have tended to accumulate more. and more seriously, coincident with the increasing of use wastepaper and the recycling degree of white water. In general these DCS have an anionic charge, and they often disturb the papermaking process by interfering with cationic chemicals added. In this paper, the effect of cationic polymers on the stability and the electrokinetic characteristics of DCS from deinked wastepaper pulp were investigated. The results showed that polyamine (PA) with high charge density and low molecular weight destabilized the DCS mainly by a charged patch mechanism. The high cationic starch (HCS) with medium charge density and molecular weight. destabilized the DCS by charged patch mechanism and bridging flocculation mechanism, wherein the action of the former was greater than the latter. The cationic polyacrylamide (CPAM) with low charge density and high molecular weight destabilized the DCS mainly by bridging flocculation mechanism. The Zeta potential of DCS increased with increasing dosage of cationic polymer. The electrokinetic characteristic of DCS was changed when it was closed to the theoretical point of neutralization.