Removing metals form leachate: When is sorption the solution?

Three potential filter materials, granular activated carbon, bone meal and iron fines, were evaluated for treatment of heavy metal contaminated landfill leachate. All materials could sorb some metals to a high extent; more than 90 % of some metals were removed. However, all filters suffered from the drawback of releasing unwanted substances. Geochemical modelling was used to elucidate sorption mechanisms since the mechanisms are important for predicting long-term behaviour of the filter and for choosing option for disposal of the spent filters. It was not possible to draw any certain conclusions about sorption mechanisms. However, the results indicate that that ion exchange with H+ was important in the case of activated carbon, hydroxyapatite precipitation might have been important in the case of bone meal and sorption to and precipitation with iron corrosion products should have been important in iron fines filtration.