KINETICS OF DEPOSITION OF CALCIUM-CARBONATE PARTICLES ONTO PULP FIBERS

The kinetics of deposition of calcium carbonate particles of about 1 m um in diameter onto pulp fibres has been investigated both with and wi thout a retention aid present. The deposition and detachment process w as shown to follow Langmuir kinetics. The deposition and detachment ra te coefficients have been determined and shown to have a strong depend ence on the rate of shear Polyethylenimine (PEI) added as a retention aid shows no effect on the deposition rates when added as a pretreatme nt to calcium carbonate particles, while it decreases the deposition r ate when added as a pretreatment to pulp fibres. When added to the cal cium carbonate particles, PEI increases the detachment rate implying t hat it decreases the bond strength between the calcium carbonate parti cles and the pulp fibres. The PEI-fibre bond is weaker than the PEI-Ca CO3 bond.