Halophilic bacteria could recover metals from mine waste

In a process called bioleaching, microorganisms like bacteria catalyze the extraction of metals and metalloids from ores or waste materials, helping to recover the metals for reuse and reducing their negative impact on the environment. At ACS Spring 2022, Chiamaka Belsonia Opara of Helmholtz Institute Freiberg for Resource Technology reported that two halophilic bacteria, Thioclava electrotropha and Thioclava pacifica, can extract some metal from mine waste without losing effectiveness in seawater and without acidifying the environment. Bioleaching often relies on acidophilic bacteria, which face both issues. To leach metals from waste, acidophilic bacteria require an environment of pH 2 or below, and this high acidity can be harmful to the surrounding ecosystem, Opara said. T. electrotropha and T. pacifica can operate at a pH of 4, posing less of a risk. These halophilic bacteria work in seawater, which could also make them useful in areas where freshwater is scarce. While the halophilic bacteria extracted up to 30% of the cobalt and up to 20% of other metals, like lead and silver, from mine waste samples, these species are still not as effective as acidophilic bacteria, which can extract around 80% of metals from mine waste. Researchers plan to investigate whether the bioleached mine waste residues could be recycled into construction materials like green cement, ceramics, and inorganic polymers.