A Review of Static Tests and Recent Studies (Report‪)‬

INTRODUCTION Mining industries are associated with Acid Mine Drainage (AMD), which is formed when sulfide minerals are oxidized on exposure to air and water in mine areas. The resultant acidification of the water from sulfur oxidation, coupled with oxidation itself, can lead to both chemical and microbial release of other pollutants and so mining areas can contain relatively high levels of toxic substances, such as cyanide, sulfate and potentially toxic heavy metals (i.e., Pb, Zn, Cu, Cd, Fe, Mn and Al), which can pose adverse long-term impacts on animals, human health and ecosystem degradation (Ardejani et al., 2010; Liang-qi et al., 2010; Perez-Lopez et al., 2007; Silvia and Zanetti, 2009; Unruh et al., 2009). Under an AMD situation, the release of such toxic substances can severely pollute the soil, surface and ground water systems (Alligui and Boutaleb, 2010; Mossad and Aral, 2010; Oprea et al., 2010; Ouangrawa et al., 2010; Rani and Chen, 2010). Although this process occurs naturally, mining industries may significantly accelerate AMD through disturbing the sulfide mineral and promoting their expose to water and oxygen. Moreover, some bacteria can naturally promote AMD generation, such as Thiobacillus, which is capable of catalyzing iron oxidation at pH levels of 3.5-4.5 (Liang-qi et al., 2010; Jennings et al., 2008). The reactions of acid generation from the oxidation of pyrite (FeS2), which is one of the most common sulfide minerals and precipitation of Fe hydroxides are shown in Eq. 1-4 below: