Reactive liquid-liquid extraction of heavy metals from leachate with oil-soluble complexing surfactants

Reactive liquid-liquid extraction is a well-known technology for the selective winning of metals. However, the application of this method in environmental processing, such as the non-selective separation of heavy metals from waste water (e.g. leachate from landfills), is new. It is shown that technical oil-soluble surfactants with complexing properties are able to lower,the content of simultaneously present heavy metals by about two or three orders of magnitude, starting at 10-100 mg l(-1). By applying commercially available quinolines (such as LIX26(R)) and oximes (such as LIX84(R)), it is possible to extract the heavy metals Cu, Cr, Cd, Ni, Zn and Pb in one step, keeping within the limits set by the German authorities. Bulk metals such as Ca remain in the waste water. Besides fundamental investigations on the stoichiometry of the extracting reaction, the extraction selectivity and the phase separation, experiments concerning the extraction and re-extraction speed using a continuously operating mixer-settler were performed.