Tailings

Summary

In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed. The extraction of minerals from ore can be done two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires comminution, i.e., grinding the ore into fine particles to facilitate extraction of the target element(s). Because of this comminution, tailings consist of a slurry of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are usually produced from th

Official source

https://en.wikipedia.org/wiki/Tailings

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (7)

Related publications

Related people

Related units

Related concepts (16)

Related concepts

Related courses (6)

Related courses

Related lectures (9)

Related lectures

Sulfide oxidation and acid mine drainage formation within two active tailings impoundments in the Golden Quadrangle of the Apuseni Mountains, Romania

Linda Frei

Sulfidic mine tailings have to be classified as one of the major source of hazardous materials leading to water contamination. This study highlights the processes leading to sulfide oxidation and acid mine drainage (AMD) formation in the active stage of two tailings impoundments located in the southern part of the Apuseni Mountains, in Romania, a well-known region for its long-term gold-silver and metal mining activity. Sampling was undertaken when both impoundments were still in operation in order to assess their actual stage of oxidation and long-term behavior in terms of the potential for acid mine drainage generation. Both tailings have high potential for AMD formation (2.5 and 3.7 wt.% of pyrite equivalent, respectively) with lesser amount of carbonates (5.6 and 3.6 wt.% of calcite equivalent) as neutralization potential (ABA = -55.6 and -85.1 tCaCO(3)/1000 t) and showed clear signs of sulfide oxidation yet during operation. Sequential extraction results indicate a stronger enrichment and mobility of elements in the oxidized tailings: Fe as Fe(III)oxy-hydroxides and oxides (transformation from sulfide minerals, leaching in oxidation zone), Ca mainly in water soluble and exchangeable form where gypsum and calcite are dissolved and higher mobility of Cu for Ribita and Pb for Mialu. Two processes leading to the formation of mine drainage at this stage could be highlighted (1) a neutral Fe(II) plume forming in the impoundment with ferrihydrite precipitation at its outcrop and (2) acid mine drainage seeping in the unsaturated zone of the active dam, leading to the formation of schwertmannite at its outcrop. (C) 2011 Elsevier B.V. All rights reserved.

2011

, ,

Background Two porphyry copper mines located in southern Peru initiated the discharge of mine wastes (tailings) for a final shore deposition in the Bay of Ite (Pacific Ocean). 780 millions metric tons of tailings were deposited, which formed a delta with a surface of ca. 16 km2. A low-pH oxidation zone characterized by the presence of iron hydroxides developed on the surface, along with a strong build-up of efflorescent salts rich in heavy metals. Objectives A 3 years investigation was carried out in order to understand the biogeochemical processes resulting from the remediation of the oxidizing tailings by the implementation of a wetland cover1. Methods Analysis of the bacterial communities was carried out by molecular techniques (T-RFLP and cloning-sequencing). A combination of physical, chemical and mineralogical methods was applied for the characterization of solid tailings and water samples. Results The non-remediated tailings was characterized by a low-pH oxidation zone (pH 3 – 4), in which the oxidative dissolution of sulphide was identified as the dominant process, carried out mainly by Leptospirillum spp, Acidithiobacillus spp and Sulfobacillus spp. This dissolution led to an increase in metal concentrations in the pore water. Below the oxidation zone, the neutrophilic primary zone was characterized by SO42- and Fe reductions induced by sulphate- and iron-reducing bacteria (SRB and FeRB). Drastic changes were observed along the remediation process, as the heavy metal concentrations decreased progressively close or below the detection limits together with the gradual installation of a near neutral pH and more reducing conditions. SO42- and Fe reductions were still observed in the deep section of the remediated tailings. Close to the surface, the presence of lithoautotrophic neutrophilic iron oxidizing bacteria such as Mariprofundus ferroxidans, Galionella spp, Leptotrix mobilis suggested that iron oxidation played an important role in the iron cycle. Other ubiquitous bacteria related to fresh water and marine environment were also detected in the wetland. Conclusions The implementation of a wetland promoted neutralization of the acid mine drainage and induced favourable geochemical conditions for the development of both SRB and FeRB, which lead to the metal removal from solution. References Diaby, N. 2009. Biogeochemical evolution of a marine shore tailings deposit during bioremediation. Ph. D. Thesis, University of Lausanne, Switzerland. 217 pp.

2009

Temporal evolution of bacterial communities associated with the in situ wetland-based remediation of a marine shore porphyry copper tailings deposit

Nouhou Diaby, Christof Holliger, Emmanuelle Rohrbach, Pierre Rossi

Mine tailings are a serious threat to the environment and public health. Remediation of these residues can be carried out effectively by the activation of specific microbial processes. This article presents detailed information about temporal changes in bacterial community composition during the remediation of a section of porphyry copper tailings deposited on the Bahía de Ite shoreline (Peru). An experimental remediation cell was flooded and transformed into a wetland in order to prevent oxidation processes, immobilizing metals. Initially, the top oxidation zone of the tailings deposit displayed a low pH (3.1) and high concentrations of metals, sulfate, and chloride, in a sandy grain size geological matrix. This habitatwas dominated by sulfur- and iron-oxidizing bacteria, such as Leptospirillumspp., Acidithiobacillus spp., and Sulfobacillus spp., in a microbial community which structure resembled acid mine drainage environments. After wetland implementation, the cell was water-saturated, the acidity was consumed and metals dropped to a fraction of their initial respective concentrations. Bacterial communities analyzed by massive sequencing showed time-dependent changes both in composition and cell numbers. The final remediation stage was characterized by the highest bacterial diversity and evenness. Aside from classical sulfate reducers from the phyla δ-Proteobacteria and Firmicutes, community structure comprised taxa derived fromvery diverse habitats. The community was also characterized by an elevated proportion of rare phyla and unaffiliated sequences. Numerical ecology analysis confirmed that the temporal population evolution was driven by pH, redox, and K. Results of this study demonstrated the usefulness of a detailed follow-up of the remediation process, not only for the elucidation of the communities gradually switching from autotrophic, oxidizing to heterotrophic and reducing living conditions, but also for the long term management of the remediation wetlands.

Elsevier2015

, ,

2009

Temporal evolution of bacterial communities associated with the in situ wetland-based remediation of a marine shore porphyry copper tailings deposit

Nouhou Diaby, Christof Holliger, Emmanuelle Rohrbach, Pierre Rossi

Elsevier2015