ABSTRACT
The base liners known, that is, conventional sealing materials such as plastic foil and mineral liner, both show a very low permeability. For a mineral liner of a swelling clay mineral mixture there is, in addition to the very low permeability, also a very high sorption capacity. An upper, highly reactive, 'active' layer, which is oriented towards the waste should extract as much pollutant as possible from the leachate. These noxious substances will then be fixed either on the surfaces inside the crystal or as new mineral phases. The solute transport in the inactive layer can be kept very small, given an adequate granular grading, an appropriate compaction and a low hydraulic gradient. The upper, active layer is composed of minerals having a very large specific surface and thus a high sorption capacity and/or very reactive mineral phases, which rapidly form stable compounds with the noxious substances or act as reaction-accelerating catalysers.
