Geosynthetic Clay Liner Permeated with Acid Rock Drainage:The Role of Iron in Arsenic Immobilization

=Geosynthetic Clay Liners(GCLs) have the potential to immobilize cations present in solution. Due to this, GCLs have been considered suitable materials not only in landfill bottom liners, but also in rock containments eith the potential of acid rock drainage(ARD) generation.However,the bentonite inside GCLs dose not have affinity towards anions such as aresenic, which is one of the toxic components present in ARDs. Based on the authors' previous research on swelling, sorption, and hydraulic conductivity of GCL against ARD, through discussion on the role of Fe in As immobiliation was done in this paper.Swelling test showed that the presence of metals, especially a high concentration of Fe(4500 mg/L approximately) due to its high concentration, negatively impact the swelling of bentonite by increaing the hydraulic conductivity value. The hydraulic conductivity remained low during the test duration but was one order of magnitude higher in the ARD permeation case(5.0×10-10 m/s)than in the water permeation case(1.4×10-11 m/s)。Single metal sorption tests showed that Fe was sorbed by the betonite while As was As sorption.Considering that GCLs do not retain As, but Fe does, an additional Fe layer could be placed in the bottom liner system in order to immobilize it. However, if the ARD contains high Fe concentration, this additional layer would not be neccessary as the Fe in solution will prevent As mitigation.