In this study, the flotation behaviour and surface adsorption of smithsonite were investigated using various concentration ratios of potassium amyl xanthate (KAX) and dodecylamine (DDA) in a surfactant mixture. The use of either KAX or DDA during flotation resulted in an increase in smithsonite recovery as the collector concentration increased. Further, the smithsonite recoveries were for the most part less than 40% irrespective of collector concentration However, when a mixture of KAX and DDA was used, smithsonite recovery increased dramatically. The FT-IR spectra show co-adsorption of the amine-xanthate complex using a collector mixture. The presence of KAX in the mixture decreases the electrostatic head-head repulsion between the surface and ammonium ions and increases the lateral tail-tail hydrophobic bonds. (C) 2007 Elsevier Ltd. All rights reserved.