Synthesis of magnetite nanoparticles with ferric iron recovered from acid mine drainage: Implications for environmental engineering

The synthesis of magnetite nanoparticles has been the focus of numerous recent research efforts, with emerging focus on environmental applications. In previous research, reagent-grade chemicals have been used as the iron source in magnetite nanoparticle synthesis, which presents an economic challenge to the application of this technology in areas such as water and wastewater treatment. It is known that acid mine drainage (AMD) from the Mid Appalachian coal fields is low in pH and high in dissolved metals, of which iron is most abundant. In this study, ferric iron recovered from AMD via an oxidation-selective precipitation process was used as feed stock to synthesize magnetite nanoparticles by coprecipitation of ferric and ferrous iron at the pH 9.5 under an inert atmosphere. Based on X-ray diffraction analysis, the iron oxide phase in the black precipitate was magnetite. Through scanning and transmission electron microscopic studies, it was demonstrated that most of the magnetite particles ranged from 10 to 15 nm and were spheroidical or cubic in shape. Thus, the synthesis of magnetite nanoparticles with the iron recovered from AMD was technically feasible. Consequently, the need for low-cost raw feed stocks for nanoparticle manufacturing was addressed, providing additional opportunities for future application of magnetite nanoparticles in environmental engineering.