thickening process. "Leaching is the process of extracting a soluble metallic compound from an ore by selectively dissolving it in a solvent such as water, sulfuric or hydrochloric acid, or cyanide solution. The desired metal is then removed from the "pregnant
about by ferric sulphate is termed indirect leaching because it proceeds in the absenc~ of both oxygen and viable bacteria. This mode is responsible for leaching several minerals: CuFeS2 (chalcopyrite) + 2Fe/S0 4)3 --. CuS0 4 + 5FeS0 4 + 2So, V02 + Fe/S0 2
which often referred to as the direct and indirect mechanisms. Both direct leaching (bacteria attached to the sulphide minerals) and indirect leaching (Fe+2 oxidised to Fe4'' by the bacteria followed by metal leaching by the Fe+'') take place. In the presence of
SGS MINERALS SERVICES – T3 SGS 173 09-2013 Bacterial leaching is an established method of treating refractory gold and base metal ores or concentrates. SGS Minerals Services has undertaken testing for numerous projects for flowsheet development and
Process performance of bacterial leaching reactors Therefore, not only does the number balance account for the effect of particle size on the performance of the reactor, but it also yields valuable new insight into the relationship between various competing leaching
leaching tests were initiated by charging the 1.7 litre reactor by an inoculums bacterial stock leach solution and sample plus "9K" nutrient chemicals to promote bacterial growth. Water lost due to evaporation was replaced by the addition of acidified water (pH 1.8) to
There are some bacterial leaching set-ups which in a broader sense can be called in situ leaching. To this belongs the percolating of a worked-out mine with residues of ore as is schematically shown Canadian uranium mines after they were worked-out the walls, roofs and floors were hosed down at intervals of several months.The water was collected and the uranium extracted.
The indirect mechanism of bacterial leaching, which is a combination of these two sub-processes, is able to account for the shape of the reaction curve obtained from bacterial leaching experiments. It is also shown that even at very low concentrations of iron in solution the indirect mechanism may be the dominant pathway in bacterial leaching or sulphidic minerals.
Bioleaching - SlideShare
Bacterial Leaching Biotechnology in the Mining Industry Preston Devasia and K A Natarajan Bacterial leaching is the extraction of metals from their ores using microorganisms. Microbial technology offers an eco nomic alternative for the mining industry, at a time
· 6. Indirect bacterial leaching in this process the microbes are not in direct contact with minerals, but leaching agents are produced by these microbes which oxidize the ores. 7. There are three commercial process used in bioleaching; a.
Autoclave oxidation, bacterial and chemical liberation, roasting, acid oxygen processes, atmospheric oxidation prior to cyanidation are applied to process refractory sulphide concentrates. It is obvious that the processes with the maximum effect regarding
· Indirect bacterial leaching in this process the microbes are not in direct contact with minerals, but leaching agents are produced by these microbes which oxidize the ores. 7. There are three commercial process used in bioleaching; a. Slope leaching b. Heap
In bacterial leaching, certain strains of bacteria are used to liberate gold or base metals from their mineralogical host. They metabolize energy from the oxidation of ferrous iron and/or sulfur compounds and free gold or metals in the process. This can take place in …
· Indirect leaching proceeds via the metal sulfide-oxidizing agent, iron(III) ions, which are generated by iron(II)-oxidizing bacteria either planktonic or attached to the mineral surface. Since a direct electron transfer via enzymes, nanowires, etc., between the metal sulfide and the attached cell has not been demonstrated, a direct mechanism does not seem to exist.
The present invention relates to a process for removing heavy metals and substantially destroying indicator bacteria pres-ent in municipal sludges, which comprises: lowering, under aerobic conditions, the pH of a municipal sludge from about 7 to 8 to about 2.0 to 2.5 ...
In indirect bioleaching, microorganisms are not in direct contact with minerals during the process. However, leaching agents are created by microbes, which still oxidise the ore. Some advantages of bioleaching include: Bioleaching can stabilise sulphate toxins
direct and indirect processes, whereas that of A. thiooxidans only adopts the indirect approach [3–7]. The direct process is a result of direct bacterial attack on sulﬁde minerals, whereas the indirect one involves ferric iron which acts as a chemical leaching agent
· Metals are released from their ores or sulphide minerals and other mineral concentrates by either direct bacterial leaching or indirect bacterial leaching. In direct bacterial leaching, the bioleaching bacteria are in direct physical contact with the surface of the mineral sulphide; and the process is enzymatically catalyzed by bioleaching microbes via oxidation-reduction reaction.
· Although both bacterial oxidation and non-bacterial heap leaching are established in the gold and copper industries, their combined use in nickel extraction is unique. The BioHeap process treats crushed ore, so avoiding the need for fine grinding and concentration steps usually needed for most bacterial oxidation techniques.
During sulphide heap leaching, bacterial activity can be utilised to catalyse the oxidation of iron, which acts as an electron carrier between the mineral and oxygen for the conversion of sulphides. Indirect or direct bacterial attack on sulphur species can
· Electron microscope pictures show the pits as clearly locally etched nanocrystalline areas. The original definition of ''direct'' leaching is a leaching process by which the bacterial membrane directly interacts with the sulfide using enzymatic mechanisms. This is not the situation seen in electron microscope pictures Fig. 5, Fig. 6.
Indirect bacterial leaching •In this process the microbes are not in direct contact with minerals, but bacteria produces strong oxidising agents such as ferric ion and sulfuric acid on oxidation of soluble iron or soluble sulfur respectively. •For indirect bioleaching
· Indirect bacterial leaching: In this indirect method, the bacteria produce strong oxidizing agents such as ferric iron and sulfuric acid on oxidation of soluble iron or soluble sulfur respectively. Ferric iron or sulfuric acid, being powerful oxidizing agents react with metals and extract them.
Paten US3679397 - Bacterial leaching process - Google Paten It is a further object of the present invention to provide a bacterial leaching process and composition therefor in which the leaching solution has . US Patent for Process for leaching copper from copper
The overall leaching process occurs by bacterial oxidation referred to as indirect mechanism (Hansford and Vargas 2001) is: ZnS + 2Fe3+ = Zn2+ + S + 2Fe2+ (3) or as direct interact with the mineral: ZnS +2H+ + 0.5O 2 + bacteria = Zn ...
· YES can recommend labs who have permission to use this novel bisulfide leaching process to perform amenability testing on bio-oxidized ore samples. We are open to negotiating an R&D evaluation license with either a single company or with a consortium of companies, allowing a credit against future royalties for any investment made in process development.
We work with you to develop and test the bacterial leaching process that best meets the needs of your site and the composition of your ore. SGS provides globally respected, independent testing services world-class facilities, equipment and technical expertise to test a variety of oxidation processes including bacteria and other pressure and ambient leaching processes.
· Bacterial Leaching of Metal Sulfides Proceeds by Two Indirect Mechanisms via Thiosulfate or via Polysulfides and Sulfur
It is possible to dissolve iron through direct bacterial leaching as shown in the above reactions. (ii) Indirect Bioleaching: This leaching process takes place without direct involvement of microorganisms but they indirectly support the leaching by producing agents responsible for oxidation of minerals.
bacteria is the control link of the whole bacterial leaching process. Bacterial leaching is sometimes dominated by direct action and sometimes by indirect action. However, in the process of leaching, both functions exist simultaneously and cannot be excluded.
Cyclic leaching process employing iron oxidizing bacteria Download PDF Info Publication number US2829964A US2829964A US542387A US54238755A US2829964A US 2829964 A US2829964 A US 2829964A US 542387 A US542387 A US 542387A Prior art ...
· Adding small amounts of surfactants like Tween 20 to the leaching process increases the rate of biooxidation of minerals from sulfide ores. The surfactants decrease the surface tension of the leach solution, thus, wetting the ore and resulting in increased bacterial contact which ultimately increases the rate of biooxidation.
Bacterial leaching processes will be significant in the treatment of difficult-to-process refractory ores [60–63]. The gold in refractory ores is encapsulated as fine particles in the crystal structure of sulfide matrix such as pyrite (FeS 2 ) and arsenopyrite (FeAsS).