Metal–Organic Interactions in Landfill Leachates and Associated Groundwaters

Abstract

Landfills are important facilities for proper waste disposal in modern societies, but they can also be the potential source of environmental problems. These are mostly due to leachate spilling and releasing through surface and groundwaters. Because organic compounds are the most abundant constituents of these leachates and have a wealth of reactive functional groups, their interaction with metals is of utmost importance to understand the mobility and bioavailability of these metals in the environment. Metal–organic interaction is mostly characterized by complex formation and stability. Predicting metal–organic complex stability is, however, a difficult task, but the electronic configuration of metal cations may provide some insight on that problem based on the classification into hard‐ and soft‐sphere cations. On the other hand, landfill leachates are complex solutions where these interactions are likely to occur with a wide range of organic compounds, rendering individual interactions almost irrelevant. Besides, the number of cations experimentally studied in this particular environment is limited to Cu, Ni, Zn, Cd, Pb, and Cr. What has been shown is that, depending on the cation, they may be predominantly associated with colloidal and/or dissolved organic matter, in particular, forming chelates with the organic compounds, or forming inorganic complexes as well as insoluble solid phases.