THE APPLICATION OF COLLOIDAL GAS APHRONS IN THE RECOVERY OF FINE CELLULOSE FIBERS FROM PAPER-MILL WASTE-WATER

Colloidal gas aphrons (CGAs) are micron-sized gas bubbles of 25-30 mu m in diameter produced by a highspeed stirrer in a vessel containing d ilute surfactant solution. These bubbles, because of their small size, exhibit some colloidal properties. In this work, CGAs were used to se parate fine fibres from a lean slurry of cellulosic pulp in a flotatio n column. The pulp fibres were recovered as foamate from the top. Sodi um dodecyl sulphate at a concentration of 2.0 kg/m(3) was used as a su rfactant to generate the CGAs in a spinning disc apparatus. The result s indicated that up to 70% flotation efficiency could be obtained with in a short column height of 0.3-0.35 m. This technique can be applied to recover fine cellulosic pulp from paper-machine backwater. (C) 1998 Elsevier Science Ltd. All rights reserved.