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.
Highlights
Metal mining provides everyday goods and services essential to society
Acidic mine drainage (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
Ethanol or hydrogen is utilized by the sulfate reducing bacteria (SRB) as electron donor, producing sulfide for the precipitation of metal sulfides, and (II) an aerobic submerged fixed film (SFF) reactor where the excess sulfide is oxidized to elemental sulfur, using sulfide-oxidizing bacteria
Summary
Metal mining provides everyday goods and services essential to society. This activity has at times caused extensive and sometimes severe pollution of air, vegetation, and water bodies [1]. As higher-grade ores are diminishing, the primary ores that are processed by mining companies are of increasingly lower grade (metal content) and the growing amount of waste material produced by mining operations is significant. As a result of selective flotation, about 95 to 99% of the ground primary ores end up as fine-grain tailings, in the case of copper ores. Pyritic mine tailings have the potential to become extremely acidic when in contact with surface water. The acidic water further dissolves other metals contained in mine waste, resulting in low pH water enriched with soluble sulfate, Fe, Al, and other transition metals, known as acid mine drainage (AMD) (Figure 1) [7, 8]
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