THE EFFECT OF FROTH STABILITY AND WETTABILITY ON THE FLOTATION OF A XEROGRAPHIC TONER

The Separation of ink and pulp fibers in recycled paper is primarily a chieved by flotation methods. Xerographic toners from photocopiers and laser printers are known to cause problems in flotation deinking. Wet tability and froth stability are two important factors which determine the floatability of xerographic toners. The floatability is investiga ted for a selected toner using a cationic, a nonionic, and an anionic surfactant. At low surfactant concentrations the froth is too unstable to support flotation, whereas at high surfactant concentrations the t oner is rendered hydrophilic by adsorbed surfactant molecules and does not stick to air bubbles. Consequently, a maximum in flotation respon se is found at an intermediate surfactant concentration near the criti cal micelle concentration. Cationic, nonionic, and anionic surfactants all adsorb with their hydrocarbon tails on the toner surface. By choo sing appropriate froth-stabilizing additives it is possible to enhance the flotation performance.