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Prediction of Acid Mine Drainage Formation
Published in Geoffrey S. Simate, Sehliselo Ndlovu, Acid Mine Drainage, 2021
James Manchisi, Sehliselo Ndlovu
The biokinetic test, as presented by the work of Hesketh et al (2010), is an improvement to the existing shake flask tests. The objective of this test is to determine the potential and likelihood of acid formation by mine wastes in the presence of bacteria and to determine the rates of acid formation and neutralisation reactions. In the test, the mine waste materials are milled to form an acidic slurry at pH 2 through sulphuric acid addition in flasks and inoculated with more than one bacterial species. The bacteria is a mixed culture of Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum, Acidithiobacillus caldus and Sulfobacillus benefaciens that simulate typical microbial environments found at actual mine sites with AMD. The biokinetic test data (e.g., final pH, acid consumption) are able to validate the NAG pH, ANC and waste classification criteria under the static ABA methods. However, the timing is different between ACM and acid-generating reactions. The ANC of the waste material is depleted rapidly and controlled by the more reactive carbonate phases. The sulphides oxidise and form more acid over long term than that predicted by static tests. Thus, the biokinetic shake flask test is seen to be relatively simple, fast and of low-cost. However, there is still no practical use of this test to predict AMD formation (Parbhakar-Fox and Lottermoser, 2015).
Recycling of Metal Production Wastes
Published in Hong Hocheng, Mital Chakankar, Umesh Jadhav, Biohydrometallurgical Recycling of Metals from Industrial Wastes, 2017
Hong Hocheng, Mital Chakankar, Umesh Jadhav
Lead/zinc smelting slag contains not only high doses of lead and zinc, but also many minor and trace heavy metals, such as Cd, As, Cr, Hg, In, Ag, Cu, Ni, and Co (Liu et al. 2008, Cheng et al. 2009, Guo et al. 2010). The acidophilic sulfur-oxidizing bacteria (SOB) Acidithiobacillus thiooxidans and iron-oxidizing bacteria (IOB) Leptospirillum ferriphilum were used as pure cultures or mixed culture for the experiments. Sulfur and pyrite were supplemented as respective energy sources alone or in combination for pure and mixed cultures referred to as S-SOB, P-IOB, and MS-MC. Noncontact bioleaching was performed by using the slag encapsulated with a dialysis bag.
Biotechnological Avenues in Mineral Processing: Fundamentals, Applications and Advances in Bioleaching and Bio-beneficiation
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Srabani Mishra, Sandeep Panda, Ata Akcil, Seydou Dembele
Mesophilic acidophiles can grow at optimum conditions of temperature ranging 20–40ºC and at a pH range of 1.5–2.5. This group of microorganisms include (to name a few) Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans and Leptospirillum ferriphilum, that have been widely used in bioleaching studies (Mishra et al. 2018c; Panda et al. 2013; Sukla et al. 2014). The genus Acidithiobacillus is comprised of gram-negative, rod-shaped, autotrophic bacteria with a size of about 0.4 × 2 µm. The most studied and applied microbe for bioleaching is Acidithiobacillus ferrooxidans. It is a Gram-negative, chemoautotrophic, aerobic bacterium that obtains energy and electrons by the oxidation of reduced sulfur compounds to sulfate or by the oxidation of Fe2+ to Fe3+ iron. It thrives in extremely acidic conditions (pH 1–2), utilizes CO2 as carbon source and has an optimum growth temperature of about 28°C. This microbe has been used industrially to recover copper, gold, and uranium from their sulfidic ores or concentrates (Abhilash and Pandey 2013; Sukla et al. 2014). In addition, Acidithiobacillus thiooxidans is also one of the most widely known bacteria in bioleaching that oxidizes only reduced sulfur compounds (H2S, S0 and S2O2−2) to produce sulfuric acid (H2SO4) by metabolism (Miranda-Arroyave, Márquez-Godoy and Ocampo-Carmona 2019; Quatrini, Jedlicki and Holmes 2005). Although Acidithiobacillus ferrooxidans is the most studied and known bacteria, many investigations have confirmed that the most abundant genus among mesophilic microorganism is Leptospirillum species in some specific environmental conditions (Brandl 2001). Leptospirillum ferriphilum has been found to be abundant in many continuous biooxidation tanks (Tzvetkova, Selenska-Pobell and Groudeva 2002). In general, Leptospirillum species are gram-negative, spiral-shaped bacteria with 0.3–0.5 microns width and 0.9–3.0 microns in length that obtain energy from the oxidation of ferrous (Fe2+) iron. This genus include microorganism namely L. ferrooxidans, L. ferriphilum, L. ferrodiazotrophum and can grow in extremely low pH, below 1.3 (Issotta et al. 2016; Tzvetkova, Selenska-Pobell and Groudeva 2002).