Calcium-Resistant Clay-Polymer Liner for Containment of Aggressive Leachates

There is a need for soil-based liner systems in containment facilities as an alternative to compacted clay liners to control groundwater contamination from leaches.  Geosynthetic Clay Liners (GCL’s) made with bentonite have been widely used in these applications.  However, bentonite only GCL’s are not effective for calcium-rich leachates such as waste from energy power plants, leachates from coal-ash by-products, and leachates from mining operations.

The industry has developed “Polymer-Modified” GCL’s containing bentonite and water-soluble polymers.  Some of these new products seem to work only when the ionic strength of the leachates is below a certain value.  These polymers also elute from the GCL (leave the GCL) when permeated with harsher leachates.  This can lead to even higher permeabilities.

We have developed a mix of granular bentonite and a specific super-absorbent polymer that can be used to manufacture a new generation of Geosynthetic Clay Liners.  The polymer is resistant to aggressive leachates that are rich in divalent cations.  The polymer used in the new mix design does not elute from the GCL substrate.  Therefore, it maintains low permeability in the long-term.  There is no product currently on the market that can achieve the performance of our new design with this new polymer at its base.

Advantages

• The polymer is resistant to aggressive leachates that are rich in divalent cations.
• The polymer used in the new mix design does not elute from the GCL substrate.
• Therefore, it maintains low permeability in the long-term.