Downloaded By: [HEAL- Link Consortium] At: 10:18 18 June 2007 SEPARATION SCIENCE AND TECHNOLOGY, 30(2), pp. 263-284, 1995 Recovery of Co2+ Ions from Aqueous Solutions by Froth Flotation. Part 11. CoS Precipitation M. M. KOUTLEMANI, P. MAVROS," and A. I. ZOUBOULIS DEPARTMENT OF CHEMISTRY ARISTOTLE UNIVERSITY GR-540 06 THESSALONIKI. GREECE ABSTRACT Cobalt ions have been recovered from aqueous solutions by dispersed-air flota- tion in acidic conditions. The preliminary step of precipitation as cobalt sulfide using Na2S is kinetically limited, with only approximately 70% of the cobalt ions being recovered. Recoveries increase considerably under alkaline conditions. where CO(OH)~ is also precipitated. Several collectors have been tested: cetyl trimethyl ammonium bromide, sodium dodecyl sulfate, cetyl pyridinium chloride, and dodecylamine; dodecylamine was found to be the most efficient. The gas flow rate was found to affect the process, with a flow rate corresponding to a superficial gas velocity of 0.1 cmis yielding maximum recoveries; any further gas flow rate increase resulted in lower recoveries. An increase in column height was found to have an adverse effect on CoS recovery. Key Words. Dodecylamine; Cobalt sulfide Precipitate flotation; Column flotation; Cobalt ions; INTRODUCTION The recovery and/or removal of metals from wastewaters or aqueous solutions may be achieved by applying avariety of methods, e.g., chemical precipitation, complexation, solvent extraction, cementation, reverse os- * To whom correspondence should be addressed. 263 Copyright 0 1995 by Marcel Dekker, Inc