Complexation characteristics of sanitary landfill leachates

The complexation of cadmium by organic components of sanitary landfill leachates was investigated using ion-exchange and specific ion electrode methods. Four Southern Ontario leachates were all found to be capable of complexing cadmium, to varying degrees. The complexing ability associated with certain molecular weight fractions was studied. In one leachate, complexation was mainly attributed to low (<500) molecular weight compounds. Their behaviour was consistent with that of simple carboxylic acids. In another leachate, high (> 10,000) molecular weight compounds contributed significantly to complexation. Their behaviour suggested that they might contain phenolic hydroxyl groups having a stability constant towards cadmium of the order of 10⁵. It was concluded that the role of complexation in determining the fate of metals in sanitary landfill leachates depended upon several factors whose importance had not yet been adequately investigated or reported in the literature.