THE INFLUENCE OF SOME METALLIC CATIONS ON DEINKING FLOTATION

This paper presents some aspects of the fundamentals of ink flotation with sodium stearate, oleic acid and sodium dodecyl sulphate collector s as well as the influence of metallic cations such as Ca2+, Mg2+ and Al3+ on floatability. Zeta potential studies showed that the isoelectr ic point (IEP) of ink reached a pH of about 2.3. The presence of calci um, magnesium and aluminum cations modified the zeta potential curves of ink particles in relation to the indifferent electrolyte. The resul ts of microflotation tests indicated that, with sodium stearate, an in crease in floatability was probably associated with the precipitation of stearate species on the ink surface. It was suggested that a non-sp ecific adsorption mechanism had occurred with sodium dodecyl sulphate, whilst a specific adsorption mechanism was associated with oleic acid . In the presence of calcium cation, an increase in floatability at pH 8.0 was verified, probably due to calcium/collector salt precipitatio n on the ink particle surface. In the presence of magnesium and alumin um species, an increase in floatability was noted for pH ranges relate d to the maximum concentration of their hydroxy complexes and to the p redominance of metallic hydroxides at pH values below their IEPs. Scan ning electron microscope studies suggested that ink particles formed a ggregates with a rough surface in the absence of metallic cations. In contrast, aggregates had a more homogeneous surface in the presence of metallic cations.