SURFACE-CHEMISTRY OF FLOTATION DEINKING - EFFECT OF VARIOUS CHEMICAL CONDITIONS ON INK AGGLOMERATE CHARACTER AND FLOATABILITY

Interaction between ink particles and air bubbles during deinking of w aste paper has been determined by contact angle and flotation experime nts. Different parameters have been tested with regard to their effect on these interactions. The contact angles for the ink-soap agglomerat es were between 18 degrees and 63 degrees, which indicates poor intera ctions between the solid surface and the air bubble and indicates an a rea for improvement. The contact angle increased with increasing elect rolyte concentrations, a hydrophobizing agent (AKD), a non-ionic surfa ctant, increasing amounts of calcium soap and surprisingly with CMC. T he contact angle must be greater than 50 degrees (Dalmijn 1995) for hy drodynamic reasons for flotation of large particles, although lower co ntact angles can be accepted for the flotation of smaller particles. T he flotation experiments showed that a high agglomeration efficiency ( right size) is more important for the flotation than a high contact an gle. All chemicals with dispersion properties i.e. CMC, starch and non -ionic surfactants, decreased the flotation efficiency.