Interpretation of breakthrough curves and percolation factors from sub-tropical smectite, Fe-chlorite and kaolinite clayey soil-AMD interactions

Climate change, growth in population and rising pressures on natural recourses triggered by mining and similar activities have led to enormous environmental challenges. Acid mine drainage (AMD) from mining operations in South Africa causes severe environmental issues in need of drastic and lasting solutions. Contamination from AMD requires prevention and mitigation measures to address the various significant impacts on human and environmental health. This pressing challenge permitted the study to investigate and analyze the breakthrough curves and permeation parameters of a subtropical kaolinite clay mineral soil interacted with AMD towards determining its buffering efficacy as a natural contaminant barrier for use in sites prone to AMD contamination. Series of AMD permeation through the soil medium was conducted. The results of the study revealed that when the soil was percolated with 0.01N CaS0₄, a baseline hydraulic conductivity of 8.2 ^∗ 10^-12 m/s was reached which increased to about 9.1 x 10^-12 m/s after percolation with 2 pore volumes of AMD. Nevertheless, after passing 23 pore volumes of AMD, the hydraulic conductivity was seen to increase by nearly half an order of magnitude (8.2 x 10^-12 m/s to 1.5 ^∗ 10^-11 m/s). The value was found to be below the accepted criterion of 1 ^∗ 10^-9 m/s specified for clay liner construction in South Africa as such may not be used solely in the construction of containment barriers for acid-forming waste.