Conclusions AcknowledgmentsThis research was supported by Mid career Research Program

4. Conclusions
AcknowledgmentsThis research was supported by Mid-career Research Program through HOBt National Research Foundation of Korea (NRF) founded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A2A1A11049950) and was also supported by the 2015 Research Fund (1.150033.01) of UNIST (Ulsan National Institute of Science & Technology). This work was also supported by In-house Research and Development Program of the Korea Institute of Energy Research (KIER) (B5-2435).
Acid mine drainage; Ferrite; Ferrite sludge; Magnetic nanoparticle; Trace metal
1. Introduction
Minerals containing iron, copper, gold, lead, silver, mercury and zinc are manly found underground as sulphide ores deposit in enormous quantities [30]. During mining time, these minerals are exposed to atmospheric conditions and then sulphide is oxidized to sulphate and easily forms sulphuric acid of low pH, which is commonly called AMD. Composition of AMD varies widely from site to site [31]. However, high concentration of dissolved iron (II) and sulphate are the most common. Moreover, metals such as arsenic, manganese, aluminium, nickel, zinc, cobalt, and copper are commonly found in AMD [13] and [32].