Abstract
The application of acidophilic sulfate-reducing bacteria (SRB) for the treatment of acidic mine water has been recently developed to integrate mine water remediation and selective biomineralization. The use of biogenic hydrogen sulfide (H2S) produced from the dissimilatory reduction of sulfate to fabricate valuable products such as metallic sulfide nanoparticles has potential applications in green chemistry. Here we report on the operation of a low-pH sulfidogenic bioreactor, inoculated with an anaerobic sediment obtained from an acid river in northern Chile, to recover copper via the production of copper sulfide nanoparticles using biogenic H2S. The laboratory-scale system was operated as a continuous flow mode for up to 100 days and the bioreactor pH was maintained by the automatic addition of a pH 2.2 influent liquor to compensate for protons consumed by biosulfidogenesis. The “clean” copper sulfide nanoparticles, produced in a two-step process using bacterially generated sulfide, were examined using transmission electron microscopy, dynamic light scattering, energy dispersive (X-ray) spectroscopy and UV-Vis spectroscopy. The results demonstrated a uniform nanoparticle size distribution with an average diameter of less than 50 nm. Overall, we demonstrated the production of biogenic H2S using a system designed for the treatment of acid mine water that holds potential for large-scale abiotic synthesis of copper sulfide nanoparticles.
Highlights
Dissimilatory sulfur-reducing bacteria (SRB) generate hydrogen sulfide (H2 S) as result of a reductive metabolic process, using sulfate as a terminal electron acceptor
We describe the operation of a low-pH, sulfate-reducing biofilm-bioreactor populated with novel acidophilic sulfate-reducing bacteria (SRB) designed to produce enough H2 S to remediate a synthetic acidic mine water for the removal of copper and to synthesize copper sulfide nanoparticles
A continuous stream of oxygen-free nitrogen (OFN) was used to remove H2 S produced by the bioreactor vessel which was delivered to an off-line vessel to mediate selective precipitation of copper from synthetic acidic mine water based on the chemical composition of a stream draining from a Chilean copper mine (Table 1)
Summary
Dissimilatory sulfur-reducing bacteria (SRB) generate hydrogen sulfide (H2 S) as result of a reductive metabolic process, using sulfate as a terminal electron acceptor. The Biosulfide and Thiopaq processes are successful industrial applications for the treatment of mine impacted water, and employ offline systems based on a second vessel where sulfide pumped from the bioreactors is in contact with an acidic metal solution [2]. In both systems, the oxidation of organic carbon (e.g., acetic acid) or hydrogen is coupled to the reduction of an oxidized source of Minerals 2018, 8, 35; doi:10.3390/min8020035 www.mdpi.com/journal/minerals
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