Efficient recovery of nano-sized iron oxide particles from synthetic acid-mine drainage (AMD) water using fuel cell technologies

Acid mine drainage (AMD) is an important contributor to surface water pollution due to the release of acid and metals. Fe(II) in AMD reacts with dissolved oxygen to produce iron oxide precipitates, resulting in further acidification, discoloration of stream beds, and sludge deposits in receiving waters. It has recently been shown that new fuel cell technologies, based on microbial fuel cells, can be used to treat AMD and generate electricity. Here we show that this approach can also be used as a technique to generate spherical nano-particles of iron oxide that, upon drying, are transformed to goethite (α-FeOOH). This approach therefore provides a relatively straightforward way to generate a product that has commercial value. Particle diameters ranged from 120 to 700 nm, with sizes that could be controlled by varying the conditions in the fuel cell, especially current density (0.04-0.12 mA/cm²), pH (4-7.5), and initial Fe(II) concentration (50-1000 mg/L). The most efficient production of goethite and power occurred with pH = 6.3 and Fe(II) concentrations above 200 mg/L. These results show that fuel cell technologies can not only be used for simultaneous AMD treatment and power generation, but that they can generate useful products such as iron oxide particles having sizes appropriate for used as pigments and other applications.