The metal sulfides are first removed by microbial leaching and the precious metals are then recovered from the residue. 7.1 Industrial waste products. The industrial application of microbial leaching is related mainly to the chemolithotrophic iron-oxidizing bacteria T. ferrooxidans and L. ferrooxidans. Mineral industrial waste products which ...

The effect of stirring rate on the mineral dissolution was also investigated.Microbial leaching: 10g of iron ore sample and 1.0g of rusting iron sample were weighed and transferred into a sterilized test tube and 9ml of the thiobacillus medium (prepared according to (Atkinson and Movituna, 1991)) was measured with the aid of 10ml syringe into ...

The energy metabolism structure of microbial community plays an important role in the process of biohydrometallurgy. In this article, an artificial microbial community composed of three strains (Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum and Acidithiobacillus thiooxidans) was used to leach three kinds of chalcopyrites with different iron-sulfur ratios. After 36 d of leaching ...

Iron-rich acidic waters draining from abandoned coal and metal mines as well as from unmined mineralized areas are another evidence of microbial leaching. In fact, history records that mine water problems began at the same time that mining activities began.

Chemical and microbial leaching of base metals from obsolete cell-phone printed circuit boards. ... to be effective parameters to extract higher amount of metals as pH is important for growth and metabolic activity of bacteria, while ferrous iron is converted to ferric iron by the organisms and it solubilise metals. In turn, oxidation of ...

The effects of ferrous and ferric iron as well as redox potential on copper and iron extraction from the copper flotation concentrate of Sarcheshmeh, Kerman, Iran, were evaluated using shake flask leaching examinations. Experiments were carried out in the presence and absence of a mixed culture of moderately thermophile microorganisms at 50?C. Chemical leaching experiments were performed in ...

Microbial Leaching of Iron from Hematite: Direct or Indirect Elution. Apichaya Aneksampant, ... the possible mechanism for bacterial reduction of hematite in seawater is still unclear. The present work has investigated the reductive dissolution of iron by the bacteria in two elution systems, namely direct and indirect elution systems. ...

ferric-to-ferrous iron ratio and an increase in the copper leaching rate. However, the increased leaching rate was not sustained, and 120 days after inoculation the bacterial activity declined, the ferrous iron content increased, and the copper leaching rate decreased.

As will be shown later, owing to its ability to oxidize ferrous iron, T. ferrooxidans is the principal agent of bacterial ore leaching at moderate temperatures. Thiobacilli and sulfidic minerals . Some Thiobacilli, especially T. ferrooxidans, are able to oxidize sulfide and some heavy metals -mainly iron but also copper, zinc, molybdenum and presumable some other metals - in the form of ...

Although the inhibition by 0.1M NaCl (~6 g/L) of bacterial growth and iron oxidation activity was not evident at the beginning of the experiment, over extended leaching duration NaCl was likely to ...

leaching has been use as an alternative approach to conventional hydrometallurgical methods of uranium's extraction. In the microbiological leaching process, iron-oxidizing bacteria oxidize pyretic phase to ferric iron an d sulfuric acid, and uranium is dissolved from the ore due to sulfuric acid attack.

These are naturally occurring, harmless bacteria that gain energy by breaking down iron available in the soil. In addition to the oily film, side effects of iron-oxidizing bacteria can include a swampy odor, a reddish filament, or red chunks of iron. In large amounts, these byproducts can clog wells if present in pipes.

atmospheres were maintained during leaching periods). Leachates were analyzed for sulfate. Periodically, a three‐tube, most probable number (MPN) bacterial enumeration (23) using the media described by Cobley and Haddock (24) was performed to estimate the number of iron‐ oxidizing bacteria.

A process of extracting metals from a material containing at least 10% by weight of pyrite and selected from the group consisting of ores containing sulphide, concentrates of such ores and mixtures of such ores and/or concentrates by microbial leaching which comprises roasting the material before the microbial leaching to convert part of the pyrite to pyrrhotite and thus remove part of the ...

is further confirmed by the leaching of synthetic sulphides free of iron, where only the direct attack of the bacteria can lead to leaching: CuS (covellite) + 202 --.CuS04, ZnS (sphalerite) + 20z -+ ZnS04 • Bacterial Leaching Techniques The two major techniques used in leaching are percolation and agitation leaching.

The fundamental reaction for indirect leaching then involves the microbial oxidation of ferrous iron to ferric sulphate and elemental sulphur to sulphuric-acid as shown in equations 3 and 4 respectively. Thiohacillus ferrooxidans are able to oxidise ferrous iron at a rate 500.000 times as fast as would occur in their absence (Brierly, 1978). (3 ...

Microbial Leaching (Bioleaching, Biomining) Microbial leaching is the process by which metals are dissolved from ore bearing rocks using microorganisms. For the last 10 centuries, microorganisms have assisted in the recovery of copper dissolved in drainage from water. Thus biomining has emerge as an important branch of biotechnology in recent ...

Key Terms. ore leaching: The process of recovering metals from ores by using a number of different techniques.; Microbial ore leaching (bioleaching) is the process of extracting metals from ores with the use of microorganisms. This method is …

microorganisms is called microbial leaching, bioleaching or bacterial leaching. At present bacterial leaching is widely used commercially to produce copper from low-grade mine wastes. Although microbial leaching seems to be restricted to metal sulfides, metals such as uranium, silver or gold can be solubilized when they occur in association ...

This study was undertaken to determine the leaching of Cu and Zn from a smelter slag in acidic, sulfate-rich solutions with, and without, mesophilic Fe- and S-oxidizing bacteria. Cu in the slag ...

Abstract. It is in its infancy to use bacteria as a novel biotechnology for leaching precious and heavy metals from raw materials. The objective of this study was to investigate biogeochemical processes of iron leaching from magnetite reduction by iron-reducing bacteria isolated from intertidal flat sediments, southwestern part of Korea.

Leaching of iron, either as an impurity to be removed or as a metal to be recovered, requires a different approach than the oxidative leaching that dominates biohydrometallurgy of other metals.

E-waste is an important secondary source of precious metals. Especially discarded printed circuit boards (PCBs) contain high concentrations of precious metals. In recent years, the bacterial leaching was more widely preferred due to its low environmental impact and cost in the recovery of these precious metals. In this study, a PCBs-adapted pure culture of A. ferrooxidans, A. thiooxidans and ...

Bacteria. Seven strains of iron-oxidizing heterotrophic bacteria were used in the leaching experiments. Three strains (strains T-21, T-23, and T-24) were isolated either directly or indirectly (via enrichment cultures) from AMD from inside an abandoned pyrite mine (Cae Coch) in the Conwy Valley, North Wales (); strain T-25 was isolated from an AMD stream at the derelict Parys …

Bacterial leaching is the extraction of metals from their ores using microorganisms. … is further confirmed by the leaching of synthetic sulphides free of iron, … » More detailed Microbial Leaching (Bioleaching, Biomining) – Environmental …

In all the flasks where high metal leaching rates were observed, concomitantly biomass production rates were also high indicating high growth rates. It showed that the metal bioleaching capability of the bacteria was associated with their growth. Pyrite contained 42% iron. (author)

iron oxyhydroxides and mica. The experimental results showed that these bacteria are able to remove 43 % of free Fe occurring in kaolin in amorphous form of oxyhydroxides (KS1 sample) and approximately 15 % of Fe bound in mica (KS2 sample) after 1 month of bioleaching. The amorphous form of Fe is extractable by bacterial leaching easier than Fe ...

The leaching of iron pyrite by Thiobacillus ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.012–0.22 h −1), pyrite surface areas (18–194 m 2 /L), and inlet soluble substrate (Fe 2+) concentrations (0–3000 ppm).The bacterial leaching rate was found to increase with increasing pyrite surface area, dilution rate, and inlet Fe 2+ concentration.

The critical reaction is the oxidation of sulfide by ferric iron. The main role of the bacterial step is the regeneration of this reactant. Copper leaching has a very similar mechanism. Microorganisms Capable of Ore Leaching. Bioleaching reactions industrially are performed by many bacterial species that can oxidize ferrous iron and sulfur.

Mixed microbial consortia of iron and sulfur-oxidizing microorganisms were used for batch bioleaching at varying pulp density of 7%, 10% and 15% (w/v). The copper content in the feed material was 26.3% (w/w) and the prime focus was to recover maximum copper along with other minor metals, such as zinc, aluminum, and nickel.

Bacterial leaching is the extraction of metals from their ores using microorganisms. … is further confirmed by the leaching of synthetic sulphides free of iron, … » More detailed Microbial Leaching …

In this study the effects of initial concentration of Fe(II) and Fe(III) ions as well as initial pH on the bioleaching of a low-grade sphalerite ore in a leaching column over a period of 120 days with and without bacteria were investigated. Four different modifications of medium were used as column …

the medium during the first instant of leaching. 2.4. Bacterial Leaching Experiments . In order to determine the influence of ferrous and ferric iron addition on the bioleaching of the copper concen-trate, shake flasks experiments were carried out in the presence and absence of …

Microbial Leaching of Iron from Hematite: Direct or Indirect Elution 397. four systems. The total iron concentration was almost zero at the beginning of incubation and increased up to 30.6mgL¹1 at the end of incubation in direct elution (Fig. 2(a)).

Microbial leaching: 10g of iron ore sample and 1.0g of rusting iron sample were weighed and transferred into a sterilized test tube and 9ml of the thiobacillus medium (prepared according to (Atkinson and Movituna, 1991)) was measured with the aid of 10ml syringe into the test tube containing the samples, and was covered with aluminium foil.