Colloidal gas aphrons (CGAs) were first proposed by Sebba (1971) as micro bubbles (10-100 mum), composed of a gaseous inner core surrounded by a thin surfactant film. CGAs are created by intense stirring (usually over 5000 r(.)min(-1)) of a surfactant solution. Flotation of Cu(II) by colloidal gas aphrons has been conducted in order to explore a new method for separating heavy metal ions from dilute solution. The effects of CGA flow rate, amounts of CGA introduced to the system, surfactant concentration on the flotation efficiency have been investigated. The results show that the flotation efficiency at pH = 5-6 has an optimum value to CGA flow rate and amount. When pH is greater than 7, the flotation efficiency can be as high as 99% at the optimum condition.