Bioleaching of copper sulphide concentrate using extreme thermophilic bacteria

An extreme thermophilic, iron-sulphur oxidising bacterial culture was isolated and adapted to tolerate high metal and solids concentrations at 70°C Following isolation and adaptation, the culture was used in a continuous multi-stage pilot plant employing standard mechanically agitated and aerated tanks, for the bioleaching of a mixed secondary copper sulphide-chalcopyrite concentrate. The culture exhibited stable leach performance over the period of pilot plant operation and overall copper extractions of higher than 97% were maintained. It was shown, however, that solids concentration had a significant effect on the copper bioleach kinetics. Increased solids concentrations resulted in a drop in redox potential and copper extractions in the first stage reactor. Batch chemical ferric leaches, performed at controlled redox potentials, indicated that reduced residence times may be possible in bioleach processes, using thermophiles, if high redox potential levels can be maintained.     

The cell attachment and oxygen consumption of two strains of Thiobacillus ferrooxidans

Thiobacillus ferrooxidans is a chemolithoautotropic aerobic bacteria which derives energy for its metabolic functions through the oxidation of ferrous iron, sulfur and insoluble sulfides minerals.The attachment of Thiobacillus ferrooxidans cells to sulfide mineral surfaces was investigated to further understand the mechanism involved in the leaching of sulfide minerals. Two strains of Thiobacillus ferrooxidans (DSM 583 and ATCC 23270) grown on ferrous iron, sulfur and a chalcopyrite concentrate were investigated on three sulfide mineral surfaces; pyrite, chalcopyrite and arsenopyrite. The degree of attachment of all substrate grown cells along with contact angle measurements of both minerals and cells were determined to evaluate the effect of growth substrate and hydrophobic interactions on the attachment process. In addition, concentrations of both ferrous iron and the flotation collector potassium amyl xanthate were also studied. Whilst sulfur grown cells exhibited a higher degree of hydrophobicity, both ferrous iron and chalcopyrite grown cells showed a greater degree of attachment. This suggests hydrophobic interactions at the mineral/cell interface are not principally responsible for the attachment process. Differences in the adhesion of the two strains were also observed and suggests alternative interaction(s) between the cell and mineral surface is/are principally responsible for attachment. Increasing the concentration of ferrous iron as a growth substrate resulted in an increase in the degree of cell attachment. Correspondingly, increasing the concenrration of amyl xanthate decreased the adhesion of Thiobacillus ferrooxidans.Growth substrate, solution pH, ferrous iron, copper and cobalt ion concentrations were also investigated with respect to the oxygen consumption of the two strains of Thiobacillus ferrooxidans. Enzyme reaction kinetics were also studied allowing for determination of Km values for ferrous iron similar to those previously reported. Whilst cells grown on ferrous iron were able to oxidise the iron substrate over the range 1–200mM, cells grown on 1% sulfur were unable to oxidise similar concentrations of the iron substrate. However, following a single subculture onto ferrous iron, sulfur grown cells were able to utilise the ferrous iron substrate all be it at a decreased rate. Investigation of solution pH suggested both cultures had different optimum pH values for ferrous iron oxidation. Increasing concentrations of copper and cobalt (1–100mM) proved to decrease the rate of iron oxidation.     

硫化矿细菌浸出过程的电化学(Ⅰ)

系统阐述了硫化矿细菌浸出体系细菌生长及细菌存在时硫化矿氧化的电化学理论。文中分析了硫化矿浸矿主导菌种Thiobacillusferrooxidans氧化Fe2 +而代谢的电化学机理 ,给出了Fe2 +氧化响应Thiobacillusferrooxidans生长细胞外的电化学反应标度式 ,分析了细菌的存在对溶液电位的影响 ,给出了应用Fe2 +氧化速率标度的细菌生长速率方程。应用电化学基本原理分析了硫化矿浸出的反应特征 ,提出了只考虑细菌间接作用时硫化矿细菌浸出反应的混合电位模型。分析认为 ,细菌氧化Fe2 +至Fe3 +,使混合电位上升 ,这是细菌强化硫化矿浸出的重要因素之一。     

氧化亚铁硫杆菌浸出废弃线路板中金属铜的研究

利用从硫化矿山分离得到氧化亚铁硫杆菌GZY-1菌株,进行了废弃线路板粉末中金属铜的浸出实验,并对浸出机理进行了分析,同时对浸出体系的pH值、氧化还原电位和细菌数量的变化进行了研究.结果表明:细菌具有将Fe2+不间断地氧化成为Fe3+的生物学特性;在浸出温度30℃及pH值1.32、液固比10∶1、搅拌速率500 r/mi...     

Influence of the attachment of acidophilic bacteria during the oxidation of mineral sulfides

Acidophilic bacteria found in mining environments are capable of oxidising insoluble sulfide minerals. The use of these bacteria during the oxidation of various mineral sulfides has received significant commercial interest.The attachment of Thiobacillus ferrooxidans and moderately thermophilic bacteria to sulfide minerals was investigated to further understand the mechanism(s) involved in the leaching of sulfide minerals. T.ferrooxidans (DSM 583 and ATCC 23270) and four strains of moderate thermophilic bacteria, Sulfobacillus thermosulfidooxidans, (strain TH1) and Sb.acidophilus (strains THWX, ALV and YTFI) all grown on ferrous iron, sulfur and a chalcopyrite concentrate (termed chalconc) were investigated using 3 sulfide mineral systems; pyrite, a chalcopyrite concentrate (chalconc) and an arsenic containing concentrate (termed arsenoconc). The degree of attachment of all substrate-grown cells along with contact angle measurements of both minerals and cells were determined in order to evaluate the effect of the growth substrate and the hydrophobic interactions on the attachment process. The attachment of both the mesophiles and moderate thermophiles were found to be dependant on the type of growth substrate, the substrate concentration and also the type of mineral studied. Whilst sufur-grown T. ferrooxidans (DSM 583) cells exhibited a higher degree of hydrophobicity, both ferrous iron and chalconc-grown cells showed a greater degree of attachment. This suggests that hydrophobic interactions are not principally responsible for the attachment of T. ferrooxidans to mineral sutfides. However, each moderately thermophilic strain exhibited greater attachment to the mineral sulfides when cultured on either the chalconc sample or elemental sulfur and all showed greater adhesion to the pyrite and arsenoconc samples than to the chalconc sample. Separate shake flask leaching of the sulfide samples T. ferrooxidans and Sb. thermosulfidooxidans (TH1) respectively in conjunction with the results of the attachment studies suggested that the leaching of mineral sulfides was a combination of both the direct and indirect mechanisms.     

闪锌矿的生物氧化与化学氧化对比

研究了氧化亚铁硫杆菌对闪锌矿的生物氧化作用,并与Fe³⁺氧化过程进行了对比。研究表明Fe³⁺比细菌具有更高的氧化效率,但生物氧化的效率更稳定。闪锌矿生物氧化过程中氧化亚铁硫杆菌的生长经历了延迟期、指数期、稳定期和衰退期,有部分细菌吸附到了矿物表面,未发现中间物质单质硫沉淀。而闪锌矿的化学氧化过程中有大量的单质硫沉淀到了矿物表面,说明生物氧化更彻底。     

细菌浸出硫化锌矿氧化动力学研究进展

综述近年来氧化铁硫杆菌浸出硫化锌矿的反应机理及其氧化动力学的研究进展概况。对氧化铁微螺菌和氧化铁硫杆菌混合菌种浸出硫化锌矿物的机理做了分析。并对开展混合菌浸出硫化锌矿的动力学模型研究提出建议。     

Investigating heap bioleaching: Effect of feed iron concentration on bioleaching performance

This paper describes an investigation into the effect of iron concentration in the leach solution on the bioleaching of a low grade copper ore, where chalcopyrite was the dominant copper sulphide. The concentration of dissolved iron is primarily controlled by pH and the relative proportion of ferric to ferrous iron, with significant jarosite precipitation occurring above pH ≈ 1.8 in a highly oxidised system. The solution pH may be increased by the dissolution of acid soluble gangue and when iron oxidation is significantly higher than sulphur oxidation. The study was approached using two experimental systems. In the former, the leach solution was recycled through an ore bed of low aspect (reactor height divided by diameter) ratio for a portion of the experiment. During the recycle phase, no acid was added to the system and acid consumption by gangue material led to a pH increase (1.6–2.2). The resulting jarosite precipitation reduced soluble iron from 2.5 g/l to less than 250 mg/l. Copper recovery decreased, but not in proportion to the decrease in iron. This was partly attributed to adsorption on, or entrainment within, the jarosites. To study the effect of reduced iron concentration on leach performance under more controlled conditions, bioleaching was performed in packed bed column reactors with feed iron concentrations ranging from 5 g/l to 200 mg/l. Observations indicated an initial decreased rate of copper liberation with reduced iron concentration in the feed. The relationship between available Fe³⁺ concentration and copper liberation was not proportional. However, with time, the liberation of copper became independent of iron concentration in the percolation liquor. Further, the specific rate of copper liberation was consistently below the theoretical value on a basis of ferric iron concentration. The highest values of copper liberation were reported at the lowest iron concentrations. In summary, while increased iron concentration in solution may enhance the initial rate of leaching, mineral availability appears to dominate CuFeS₂ leach kinetics through the majority of the leach. Furthermore, high iron concentrations in solution aggravate jarosite formation with concomitant retention of copper in the ore bed.     

Biooxidation as pre-treatment for a telluride-rich refractory gold concentrate

Biooxidation is an attractive alternative pre-treatment to roasting for refractory gold concentrates because it eliminates toxic gaseous emissions. Biooxidation utilises the ability of acidophilic chemolithotrophic bacteria to oxidise pyrite and arsenopyrite and release the gold or gold telluride trapped within their grains. The gold can be extracted by cyanidation and recovered using CIl/CIP technologies. Gold telluride may require further oxidation to render it amenable to cyanidation.In this study chemical and bio-oxidative treatments of a refractory, telluride-rich gold concentrate have been compared. It was shown that mesophilic iron- and sulphur-oxidising bacteria enhanced the dissolution of pyrite and arsenopyrite significantly, compared with chemical (ferric ion) oxidation. The gold telluride (calaverite) trapped within the pyrite grains was exposed during the pretreatment and underwent rapid oxidation by ferric ions in solution. Bacteria did not oxidise the telluride directly but contributed to the process by oxidising ferrous ions to ferric ions, the so-called “indirect mechanism” of bacterial oxidation.     

Continuous ferrous iron biooxidation in flooded packed bed reactors

In this paper the biological ferrous iron oxidation in flooded packed bed reactors is studied. Bacterial oxidation of ferrous iron is a potential industrial process for the treatment of acid mine drainage and in the regeneration of ferric iron as a leaching agent in hydrometallurgical processes.The aim of this work is the development of a reactor capable of attaining the oxidation rates demanded by industrial processes, which are higher than those shown in the literature. The bioreactor consists of a polymethylmetacrylate column randomly packed with siliceous stone particles with inlets for fresh medium and air at the bottom from where they flood the reactor.The performance of ferrous iron biooxidation reactors is strongly improved by applying this bioreactor design.     

氧化亚铁硫杆菌氧化Fe~(2+)的动力学研究

氧化亚铁硫杆菌(Thiobacillus ferrooxidans,简称T.f菌)氧化Fe2+为Fe3+,可从中获得能量得以生长,Fe2+的氧化速度表征其代谢活性。文章设计了不同初始Fe2+浓度、pH值、接种量等条件培养T.f菌,测定培养过程中Fe2+浓度,通过对试验数据进行非线性拟合,得出了适合T.f菌生长过程的氧化Fe2+动力学模型,该模型拟合效果较好。研究中还对该模型进行了理论预示,得出了初始Fe2+浓度对T.f菌氧化动力学影响较大的结论。     

云南大红山铜矿化学浸出研究

以云南大红山铜矿的铜精矿为研究对象,分别考查其在稀硫酸、硫酸高铁、硫酸亚铁三种介质中的溶解情况。通过试验研究发现,在pH1.0~2.0、常温常压条件下,该铜精矿基本不溶于稀硫酸溶液和硫酸高铁溶液,而在硫酸亚铁溶液中该铜精矿溶解速率明显加快,但浸出后期有明显的钝化现象。浸渣XRD和SEM分析表明,硫酸亚铁溶液浸出后浸出渣有单体硫物相存在,而且矿物表面有明显的"腐蚀坑",能谱分析也证实矿物表面有硫元素过量的情况。另外,硫酸亚铁溶液浸出过程中体系酸耗明显增加,这一方面是由于Fe2+离子氧化造成的,另一方面矿石的大量溶解也增加了酸耗量。     

金精矿生物氧化过程中菌体吸附的重要性研究

利用改进装置探索了无菌以及嗜酸性氧化亚铁硫杆菌分别吸附于矿石表面、游离于培养基中等条件下,矿石氧化过程的基本工程学特征。结果表明,菌体吸附氧化时,溶液中的Eh值和矿石的氧化率高于游离菌氧化和无菌氧化;电镜观察可见矿石表面菌体吸附留下的蚀坑;A.ferrooxidans游离氧化时的矿石氧化率大于无菌氧化过程。六偏磷酸钠的加入能改变矿石表面的电性,提高菌体在矿石表面的吸附率。     

闪锌矿精矿加压酸浸过程探讨

探索闪锌矿精矿高压酸浸的反应机理,制备一种相对纯净的闪锌矿,并在添加铁离子和不添加铁离子两种情况下对其进行高压酸浸试验.在浸出体系中没有铁元素时,闪锌矿浸出速度很慢.如在氧分压0.3MPa,温度160℃下浸出180min,锌的浸出率也仪有11.06%.在浸出体系中加人铁元素后,闪锌矿浸出速度加快了.在上述例子的条件下,锌的浸出率达到62.55%.然而,温度低于150℃,铁元素并没表现出对闪锌矿浸出的促进作用.锌的浸出速度曲线和亚铁离子氧化速度曲线的趋向是一致的,尽管两者不按比例变化.闪锌矿的浸出速度随着浸出体系中铁元素浓度的增大而不断增大,但当铁离子达到一定浓度后,闪锌矿的浸出速度不再有明显的增大.在一定的反应条件下,铁(或其他变价金属元素)的氧化是高压酸浸过程不可或缺的步骤,并且在一定范围内,铁离子的浓度决定了浸出的速度,对浸出机理进行了阐述.     

Co-processing of sulfidic mining wastes and metal-rich post-consumer wastes by biohydrometallurgy

The consequence of a strong economic growth in emerging countries combined with the rise of the world population is an increase in the demand for raw materials, leading to growing concern regarding their availability and the global efficiency of the supply chain. These tensions reinforce the need to associate the development of the recycling industry to the identification of new resources which could be used for the recovery of valuable materials. The purpose of this study is to develop a novel biological co-processing approach for the recovery of strategic metals in both sulfidic mining wastes and post-consumer wastes (WEEE). The principle of this treatment is based on two steps: mine wastes are biologically oxidized, resulting in the production of a ferric iron-sulfuric acid lixiviant solution which is used to leach base and other soluble metals contained in e-scraps. Batch tests were carried out using flotation tailings wastes containing 60% of pyrite and grinded Printed Circuit Boards (PCB < 750 μm) with a solid load of 2.5%. Two series of tests were conducted in order to study the influence of the ferric iron concentration and of the bacterial activity on metals dissolution. Results showed that a higher ferric iron concentration led to an increase in the dissolution rate of copper which is the main metal contained in the PCBs. Moreover, a dissolution yield of 98.3% was reached for copper after 2 days when bacterial activity was observed, corresponding to an increase of about 20% compared to the tests without bacterial activity. Finally, this study highlights the importance of the availability of ferric iron and of the bacterial oxidation of ferrous iron for the feasibility of this bioleaching process dealing with the recycling of PCBs.     

Electrochemical passivation of sphalerite during bacterial oxidation in the presence of galena

Sphalerite (ZnS), a mineral of particular hydrometallurgical interest, is generally found associated with galena (PbS). As such, the effect of galena on the leaching of sphalerite is of importance, and has been studied here for bacterial and ferric sulphate leaching. During both leaching processes galena was selectively oxidised to anglesite in favour of the dissolution of sphalerite. It is believed that this selective behaviour is due to galvanic interactions between the two minerals, whereby galena is sacrificed and sphalerite is passivated. This theory is consistent with the order of measured rest potential values of both minerals in solution, being 325 mV for galena and 375 mV for sphalerite (versus a standard hydrogen electrode). During bacterial oxidation, sphalerite passivation was observed across a range of mixed sphalerite/galena samples, including a mineral species and four ore specimens of varying grades. From the bacterial oxidation of a mixed mineral species, sphalerite was found to leach in the presence of lead sulphate precipitate, though the presence of this precipitate is believed to have caused diffusion limitation.     

微生物氧化硫铁矿烧渣脱硫的研究

在硫铁矿烧渣生物脱硫的实验室试验中，研究矿浆浓度，Fe^3 浓度及pH值对游离T.f.菌浓度和脱硫率的影响。结果表明硫铁矿烧渣脱硫是T.f.菌直接作用和由细菌而产生的Fe^3 间接作用的联合结果。脱硫速率和菌种氧化活性受吸附在固相上和液相中细菌生长浓度，矿浆浓度，pH值和Fe^3 的影响。三价铁离子的添加可影响菌种活性，抑制浸出，且易在矿物表面产生沉淀，降低氧化率，经生物氧化脱硫后，硫含量降至0.33%。可达到铁精矿标准。     

The role of micro-organisms in the formation of acid mine drainage in the North Eastern Coalfield of India

The paper deals with the nature of mine drainage in the North Eastern Coalfield, Margarita, Assam (India). The drainages from the Margerita group of mines are found to be acidic with high sulphate ranging up to 1500 ppm and iron content rising up to 40 ppm. The total sulphur in coals is up to 7% out of which 50–80% is non-reactive organically found sulphur. The acidity mainly arises from the oxidation of pyrites of coal. Microscopic studies reveal that both the reactive (size 0–5 micron) as well as stable (50 micron) pyrites are present in coal samples studied. Leaching studies indicate that oxidation of reactive pyrites followed by dissolution of sulphate sulphur is sufficient to produce the observed acidity and organic sulphur does not seem to play any significant role in acid production in mine drainages. The presence and chemical activity of iron oxidising; sulphur oxidising; and iron sulphur oxidising bacteria in mine water was ascertained by the chemical oxidation of ferrous iron to ferric iron; decrease in pH and production of acid. Iron and sulphur oxidising bacteria which are having maximum activity were examined under electromicroscope for morphological study. The rod shaped bacteria with rounded ends, size varying from 1.20–3.20 micron in length and 0.51–1.25 micron in breadth are identified asThiobacillus ferrooxidans. This bacteria is found to accelerate the sulphur leaching rate from coal and is indigenous to mine drainages.     

Investigating the effect of acid stress on selected mesophilic micro-organisms implicated in bioleaching

During start-up of heap bioleaching, low grade ores may be treated with acid for agglomeration and to combat the acid neutralising capacity of the gangue minerals. This may stress the bioleaching inocula, particularly upon inoculation during ore agglomeration. Acid addition for agglomeration varies across operations, ore types and their neutralising capacity, with limited information published on recommended concentrations. The initial pH in the agglomeration mix is typically below pH 1.0 and may be as low as pH 0.5.This paper investigates the effect of acid stress in terms of initial acid concentration and duration of exposure in submerged culture on mesophilic micro-organisms typically implicated in mineral sulphide bioleaching and critical for heap colonisation at start-up. Following acid stress, cultures were returned to standard operating conditions in batch stirred slurry reactors and their performance assessed in terms of mineral leach rates, ferrous oxidation and the rate of microbial growth. Increasing acid stress resulted in an increase in the lag period before onset of microbial growth and iron oxidation due to decreased viable cell numbers, specific metabolic activity or both. Following adaptation, typical growth and ferrous iron oxidation rates were observed under low stress conditions while reduction in the rate and extent of microbial growth and ferrous iron oxidation persisted at extreme conditions. A reduction in yield (microbial cells produced per kg iron oxidised) was observed with increased acid concentration over comparative times. Microbial speciation analysis indicated a substantial decrease in the diversity of the microbial species surviving.     

影响Sulfobacillus thermosulfidooxidans生长及亚铁氧化的因素研究

在测定 Sulfobacillus thermosulfidooxidans生长曲线的基础上 ,以 Fe2 +的氧化表征细菌的生长规律 ,考察了初始 p H、接种量、初始 Fe2 +浓度对细菌生长及亚铁氧化的影响。实验结果表明 ,在混合营养条件下 ,初始 p H1 .6、接种量 1 0 %、初始 Fe2 +浓度 50～ 1 0 0 m mol/ L适宜细菌的生长及亚铁的氧化。