Recent Developments for Remediating Acidic Mine Waters Using Sulfidogenic Bacteria

Abstract

Acidic mine drainage (AMD) is regarded as a pollutant and considered as potential source of valuable metals. With diminishing metal resources and ever-increasing demand on industry, recovering AMD metals is a sustainable initiative, despite facing major challenges. AMD refers to effluents draining from abandoned mines and mine wastes usually highly acidic that contain a variety of dissolved metals (Fe, Mn, Cu, Ni, and Zn) in much greater concentration than what is found in natural water bodies. There are numerous remediation treatments including chemical (lime treatment) or biological methods (aerobic wetlands and compost bioreactors) used for metal precipitation and removal from AMD. However, controlled biomineralization and selective recovering of metals using sulfidogenic bacteria are advantageous, reducing costs and environmental risks of sludge disposal. The increased understanding of the microbiology of acid-tolerant sulfidogenic bacteria will lead to the development of novel approaches to AMD treatment. We present and discuss several important recent approaches using low sulfidogenic bioreactors to both remediate and selectively recover metal sulfides from AMD. This work also highlights the efficiency and drawbacks of these types of treatments for metal recovery and points to future research for enhancing the use of novel acidophilic and acid-tolerant sulfidogenic microorganisms in AMD treatment.

Covellite (CuS) Production from a Real Acid Mine Drainage Treated with Biogenic H2S

“…Chemical AMD remediation by the addition of alkaline substances is the most common approach adopted for pH neutralization and metals/metalloids precipitation. However, new biological strategies using acidophilic sulfate reducing bacteria (SRB) are gaining force due to the possibility of valuable metal recovery [3]. Despite its simplicity, limestone (CaCO 3 ) application generates high amounts of Metals 2019, 9,206 2 of 9 toxic slurry composed by metal hydroxides and carbonate precipitates that must be safely removed and stored to avoid environmental contamination, thereby raising treatment costs [4].…”

Synthesis of Copper Sulfide Nanoparticles Using Biogenic H2S Produced by a Low-pH Sulfidogenic Bioreactor

“…In contrast, as no pH adjustment is required to precipitate copper as a sulfide phase, off-line low pH sulfidogenic bioreactors developed to over-produce H2S hold potential as a technology to recover copper from AMD and mine process waters [2]. By implementing this strategy, copper contained in a Chilean synthetic mine water was readily precipitated upon contact with biogenic H2S producing copper sulfide using a single bioreactor.…”

“…Therefore, it becomes necessary to avoid direct "contact" between acidic mine waters and the bacteria, which is normally achieved by using "off-line" systems. 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 sulfur, producing biogenic H 2 S that is passed to an anaerobic agitated contactor in which metals can be precipitated.…”

Bioleaching for Copper Extraction of Marginal Ores from the Brazilian Amazon Region

“…The concept behind bioleaching is the microbial production of primary products responsible to the oxidation/solubilization of mineral sulfides, releasing the metals of interest in the leaching solution before a further recuperation by electrochemical/biosulfidation methods [5,6]. The most studied microorganism involved in sulfide ores bioleaching is the aerobic, mesophilic and extremophile acidic bacteria Acidithiobacillus ferrooxidans (A. ferrooxidans) [5].…”