Adsorption behaviour of cationic starch on bleached Eucalyptus globulus kraft pulp

This paper deals with the adsorption kinetics of cationic starch (CS) onto the surface of bleached Eucalyptus globulus kraft pulp fibres. Six cationic starches (CSs), with different degrees of substitution (DSs), namely: 0.01 7, 0.022, 0.034, 0.047, 0.06 and 0.09, were investigated. Adsorption for al l starches studied was found to occur mainly within the first few seconds. The influence of electrical conductivity of the furnishes on the adsorption of CS was also investigated and showed that for all starches studied, adso rption decreased drastically for electrical conductivities between 1 and 10 mS/cm. CS retention decreased from 90 to 40% at these high conductivity lev els. The adsorption of CS, as a function of starch addition, showed high re tention of CS for levels of addition less than 30 mg CS per gram of fibres; above this level the retention efficiency was greatly reduced.