Multimodal zeta potential distributions in chemical pulp bleaching filtrates

As a contribution to a better understanding of colloidal systems in the treatment of recirculating waters in closed mill cycles, multimodal zeta potential distributions in chemical birch (Betula verrucosa) pulp bleaching filtrates were studied by electrophoretic light scattering measurements at four detection angles. The effects of pff and cationic polyelectrolyte addition on the distribution were investigated. At low pH levels, just one zeta potential was observed. The number of populations of various zeta potentials increased with pH. At low levels of polyelectrolyte addition, two to three populations remained in the supernatant whereas, at higher dosages, only one population was left. Comparison of the multi-angle with the single-angle technique showed the simple arithmetic mean of the values measured by the multi-angle technique to be similar to the zeta potential measured by the single-angle technique. In the case of an oxygen-bleached pulp filtrate, 81% of the total organic carbon was identified.