嗜酸氧化亚铁硫杆菌和嗜酸氧化硫硫杆菌联合浸出高锡多金属硫化矿

高锡多金属硫化矿选冶过程中,硫化矿的存在严重影响了锡的回收率,目前国内外对锡矿生物法脱硫的报道极少,针对上述问题,研究采用嗜酸氧化亚铁硫杆菌和嗜酸氧化硫硫杆菌联合浸出高锡硫化矿.通过摇瓶实验考察嗜酸氧化亚铁硫杆菌、嗜酸氧化硫硫杆菌纯菌及混合菌对锡矿脱硫的影响,并采用实时定量PCR技术(qRT-PCR)对生物浸出过程中2种菌的动态变化进行了分析.结果表明:混合菌浸出优于纯、菌浸出,能够有效地提高脱硫率,当pH为2.0,转速170 r/min,温度30 ℃,矿浆密度为10 %时,混合菌在18天内可使锡矿中的硫脱除率达到97 %.混合菌浸矿初期(第6天),嗜酸氧化亚铁硫杆菌是优势菌种,所占比例为69.4 %, 浸矿中后期,嗜酸氧化硫硫杆菌含量逐渐上升,并成为优势菌种,在稳定期(第24天)比例达到58.3 %.以上结果为锡矿生物法脱硫技术的开发提供了一条新的思路.      

Adhesion to metal sulfide surfaces by cells of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans

Attachment of four strains of Acidithiobacillus ferrooxidans to pyrite, chalcopyrite, galena, sphalerite or quartz was found to be mineral-selective. The bacterial extracellular polymeric substances (EPS) are responsible for mediating this process. Attachment of cells of A. ferrooxidans as well as of Acidithiobacillus thiooxidans was diminished, when depleted of their EPS. After 5 days of cultivation cells of A. ferrooxidans cover mineral surfaces with a dense biofilm, as visualised by fluorescence microscopy and AFM. Primary attachment was restricted to surface sites with visible defects.Chemical analyses of EPS of A. ferrooxidans, A. thiooxidans and Leptospirillum ferrooxidans indicated neutral sugars, fatty acids and uronic acids. The composition differed with the strain and the growth substrate. IronIII ions were only detectable in EPS of ironII ion- and pyrite-grown cells, but not in EPS of sulfur grown cells. Pyrite oxidation rates correlated with the amount of EPS-complexed ironIII ions in the case of A. ferrooxidans and L. ferrooxidans. Furthermore, pyrite oxidation rates of L. ferrooxidans were correlated with the genetic affiliation of the strains. The data for A. ferrooxidans seem to indicate a similar correlation, however, the results were not as clear-cut as those obtained for L. ferrooxidans. Sulfur oxidation rates of A. thiooxidans did not require EPS complexed ironIII ions.     

Rapid and specific detection of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans by PCR

Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans are two of the most important bacteria in heap bioleaching processes of copper sulphide at common operating temperatures (18–24 °C). In this paper, both microorganisms were detected in solutions and ores coming from processes in 2 days, using specific amplification of 16S rDNA sequences by PCR. The technique was first validated using template DNA from pure cultures of the microorganisms. Then it was applied to samples of solutions and ores from bioleaching processes. Results were confirmed using tRFLP (terminal Restriction Fragment Length Polymorphism) with universal primers and by identification of isolated bacteria by means of culture. This methodology is more rapid and specific than the identification by tRFLP or by culture, which require from 1 to three weeks to positively detect the bacteria. The detection limit of this technique is 10⁵ cells per ml.     

Microbial extraction of nickel from Sukinda chromite overburden by Acidithiobacillus ferrooxidans and Aspergillus strains

In this study, the recovery of nickel from a low-grade chromite overburden was attempted by employing two fungal strains, Aspergillus niger and Aspergillus fumigatus, and a mixed culture of mesophilic acidophiles (predominantly Acidithiobacillus ferrooxidans). Various factors were studied for bioleaching of chromite overburden such as, temperature, pH and pulp density. It was found that the At. ferrooxidans culture solubilized nickel effectively at temperatures ranging from 30 °C to 37 °C, whereas the organism was not able to solubilize nickel at higher temperatures, such as 45 °C. The use of higher pulp density resulted in a decrease of the percent nickel recovery whereas lower pulp density resulted in higher recovery values. Besides, increased supplemental ferrous iron increased the leaching efficiency of the At. ferrooxidans culture. The maximum nickel solubilization was 40%, at 2% pulp density, and 24%, at 10% pulp density, at 30 °C after 28 days leaching at 150 rpm.In the case of fungal strains, a comparison of leach ability of chromite overburden and roasted overburden was made. The factors studied were pulp density and reaction time. The adapted fungal strain showed better leaching results as compared to the unadapted strains. The in situ nickel leaching efficiency of a laboratory stock culture of A. niger showed maximum recovery of 34% nickel with roasted chromite overburden, at 2% pulp density, while 32% nickel was solubilized by A. fumigatus, under the same conditions at 30 °C and 150 rpm, after 28 days incubation.     

Direct oxidation of copper sulfide by a biofilm of Acidithiobacillus ferrooxidans

The direct oxidation of synthetic copper sulfide by Acidithiobacillus ferrooxidans was studied under iron-free conditions in two different types of biofilm reactors. It was shown that copper was oxidized biologically in the absence of intermediate oxidants such as ferric ions, but at rates much lower than these due to the indirect mechanism within the iron reduction–oxidation cycle. The effect of temperature on the rate of copper sulfide biooxidation was studied and the results show that the optimal temperature for the direct copper sulfide oxidation by A. ferrooxidans was close to 35 °C. The variation of acidity of the liquid medium between pH 1.5 and 3.5 did not affect the oxidation rate significantly.     

氧气对嗜酸氧化亚铁硫杆菌磁性颗粒形成的影响

生活在高酸高浓度铁环境的嗜酸氧化亚铁硫杆菌其生物矿化作用可以形成胞内致密电子颗粒-磁性颗粒,其是一种具有极广应用潜能的生物纳米材料.为了探究氧气对嗜酸氧化亚铁硫杆菌生物矿化的影响,运用Real-time PCR技术,研究嗜酸氧化亚铁硫杆菌中2个与磁性颗粒形成相关的二价铁转运基因feoB、mpsA和三价铁转运基因tonB、ABC在不同转速下的差异表达,以及利用透射电子显微镜检测不同转速下磁性颗粒形成情况,结果发现氧气对基因的表达以及磁性颗粒的形成有一定影响,这为深入研究嗜酸氧化亚铁硫杆菌中磁性颗粒形成机理打下了基础.      

Ferrous iron oxidation and uranium extraction by Thiobacillus ferrooxidans

The microbiological oxidation of ferrous iron in batch and continuous systems has been investigated in relation to uranium extraction from a low-grade ore by Thiobacillus ferrooxidans. The influence of the parameters, agitation, and aeration on oxygen saturation concentration, rate of oxygen mass transfer, and rate of ferrous iron oxidation was demonstrated. The kinetic values, Vmax and K were determined using an adapted Monod equation for different dilution rates and initial concentrations of ferrous iron. The power requirements for initial leaching conditions were also calculated. Uranium extraction as high as 68% has been realized during nine days of treatment. Regrinding the leach residue and its subsequent leaching yielded 87% uranium solubilization.     

Resin-in-pulp method for uranium recovery from leached pulp of low grade uranium ore

An improved process for the separation of uranium from the leached pulp of low grade uranium ore is reported using the resin-in-pulp method. For this study, four small pachucas were designed and calibrated. A series of tests were conducted batch-wise to determine the optimum conditions for uranium adsorption on a strong base anion exchange resin. The particle size of resin was 0.6–1.6 mm and the particle size of pulp was − 0.1 mm. Flow rates of resin and pulp were adjusted on 10 ml/h and 1 ml/h, respectively. The redox potential of pulp was 500 mV and the pH of pulp was 1.8. A McCabe Thiele diagram was constructed for the process and the experimental results confirmed the theoretical predictions. It is concluded that four stage counter-current resin-in-pulp operation under optimum conditions is sufficient to recover about 99% of the uranium from the leached ore.     

Microbial depyritisation of three different coals by Acidithiobacillus ferrooxidans in a batch stirred tank reactor

Abstract

The present study aimed to investigate the depyritisation potential of Acidithiobacillus ferrooxidans on two different types of coals, namely lignite and anthracite collected from three different countries (Korea, China and Indonesia). The experimental work was conducted on a batch mode in a stirred tank reactor. All the batch biooxidation of pyrite in the different coal samples were conducted in a pH controlled condition (pH?=?1·5). The growth medium employed for the batch biooxidation of pyritic coal was free from iron supplement. At. ferrooxidans oxidised mineral pyrite of Korean anthracite at a greater rate (98%) compared to 96 and 92% of pyrite oxidation for Indonesian and Chinese lignite respectively. The ratio of bioleach residue to the feed was reasonably good with range of 8·56–9·06 stating the net mass loss of 9–14. Coal depyritisation was carried out by the available Fe³⁺ ion in the inoculum producing Fe²⁺ ion as a product and this Fe²⁺ ion was further oxidised to Fe³⁺ ion by At. ferrooxidans. This Fe³⁺ ion produced by At. ferrooxidans continued the oxidation of the residual pyrite in the coal until all pyrite content was oxidised completely. The three different coals were found to be feasible for biological depyritisation of the coal could be scaled up for further studies in a continuous stirred tank bioreactor.

L’étude présente avait pour but d’examiner le potentiel d’enlèvement de la pyrite par Acidithiobacillus ferrooxidans dans deux types de charbons, soit le lignite et l’anthracite, récoltés dans trois pays, soit la Corée, la Chine et l’Indonésie. On a effectué le travail expérimental dans un mode en vrac, dans un réacteur agité. On a effectué toute la bio-oxydation en vrac de la pyrite des échantillons de charbon à un pH contrôlé de 1·5. Le médium de croissance utilisé pour la bio-oxydation en vrac du charbon pyritique ne contenait pas de supplément de fer. At. ferrooxydans oxydait le minerai de pyrite de l’anthracite coréen en plus grande proportion (98%) que l’oxydation de la pyrite du lignite indonésien (96%) ou chinois (92%), respectivement. Le rapport de résidu de biolixiviation à l’alimentation était raisonnablement bon, avec une gamme de 8·56 à 9·06, établissant la perte de masse nette de 9 à 14. L’enlèvement de la pyrite du charbon était effectué par l’ion Fe³⁺ disponible dans l’inoculum, donnant lieu à l’ion Fe²⁺ comme produit et cet ion Fe²⁺ était davantage oxydé en ion Fe³⁺ par At. ferrooxidans. Cet ion Fe³⁺ produit par At. ferrooxidans continuait l’oxydation de la pyrite résiduelle dans le charbon jusqu’à ce que toute la pyrite soit complètement oxydée. On a trouvé qu’il était possible d’effectuer l’enlèvement biologique de la pyrite des trois charbons et d’augmenter l’échelle pour des études futures dans un bioréacteur en continu agité.     

Liquid scintillation counting as a means of measuring uranium leached from low-grade ores by Thiobacillus ferrooxidans

Studies of U₃O₈ leaching by Thiobacillus ferrooxidans in pulverized uranium ore samples usually involve fluorimetry or X-ray fluorescence to determine the concentration of U₃O₈. As these analyses could not be performed routinely in our laboratory, we sought an alternative means of estimating the U₃O₈ generated in our leach experiments. Initial experiments indicated that liquid scintillation counting could be used to measure U₃O₈, for a given batch of pulverized ore, in conjunction with a standard curve relating counts per minute to U₃O₈ concentration measured fluorimetrically or by X-ray fluorescence. This relationship (U₃O₈ concentration vs. counts per minute) was shown to be true for a number of pulverized ore samples of different uranium grades. Moreover, the results indicated that a single standard curve consisting of the data from all of the different ores could be used, in spite of the ores containing different proportions of uranium and other radioactive emitters. An examination of a linear and two non-linear regression models showed that a power function gave the best fit to the data.     

Mechanism of enhanced bioleaching efficiency of Acidithiobacillus ferrooxidans after adaptation with chalcopyrite

To clarify the role and mechanism of bacterial adaptation in bioleaching, the leaching of chalcopyrite by adapted and unadapted Acidithiobacillus ferrooxidans was compared. Three extrinsic factors (adsorption, tolerance to shearing stress and copper tolerance) in relation to bioleaching were investigated. The results showed that there were significant differences in bacterial attachment and tolerance to shearing stress of unadapted and adapted cells due to the variation of cellular wall component and structure. Consequently, there was significant difference in bioleaching rate between unadapted and adapted bacteria. In addition, some differences of copper accumulation and distribution in adapted and unadapted cells also existed, but this was not one of the key factors that affected their bioleaching rates.     

Electrochemical noise analysis of bioleaching of bornite (Cu5FeS4) by Acidithiobacillus ferrooxidans

Electrochemical noise (EN) is a generic term describing the phenomenon of spontaneous fluctuations of potential or current noise of electrochemical systems. Since this technique provides a non-destructive condition for investigating corrosion processes, it can be useful to study the electrochemical oxidation of mineral sulfides by microorganisms, a process known as bacterial leaching of metals. This technique was utilized to investigate the dissolution of a bornite electrode in the absence (first 79 h) and after the addition of Acidithiobacillus ferrooxidans (next 113 h) in salts mineral medium at pH 1.8, without addition of the energy source (Fe²⁺ ions) for this chemolithotrophic bacterium. Potential and current noise data have been determined simultaneously with two identical working bornite electrodes which were linked by a zero resistance ammeter (ZRA). The mean potential, E_coup, coupling current, I_coup, standard deviations of potential and current noise fluctuations and noise resistance, R_n, have been obtained for coupled bornite electrodes. Noise measurements were recorded twice a day in an unstirred solution at 30 °C. Significant changes in these parameters were observed when the A. ferrooxidans suspension was added, related with bacterial activity on reduced species present in the sulfide moisture (Fe²⁺, S²⁻). ENA was a suitable tool for monitoring the changes of the corrosion behavior of bornite due to the presence of bacterium.     

Raman characterization of secondary minerals formed during chalcopyrite leaching with Acidithiobacillus ferrooxidans

Chalcopyrite passivation greatly reduces the yields from leaching and bioleaching but the problem has not been successfully resolved. Passivation involves the formation of a layer of secondary minerals on chalcopyrite surface, which becomes a diffusion barrier to fluxes of reactants and products. This study aims to identify secondary minerals formed during chalcopyrite passivation in the presence of iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) in mineral salts solution. The minerals were characterized with X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. Potassium jarosite was the initial product covering chalcopyrite grains, followed by the formation of ammonio-jarosite. Covellite and elemental sulfur were also detected in the passivation layer. The results suggest that passivation may be reduced by controlling jarosite precipitation and prior acclimatization of bacteria to oxidize CuS and elemental S in the presence of ferrous and ferric iron.     

Problems in the separation of radium from uranium ore tailings

The radium content of a representative sandstone type of uranium ore was found to be distributed uniformly according to particle size before leaching, but in sulfuric acid-leached tailings was found predominantly in the ?325 mesh fraction. The radium leaching characteristics from both ore and sulfate-leached tailings were investigated. Several 1 M salt solutions showed poor to moderate RaSO₄ dissolution from “slimes solids” tailings, while 3 M HNO₃ or HCl solutions dissolved approximately 95% of the radium content of either ore or tailings. Tests are reported in which ?325 mesh sand particles were coated with alkaline-earth sulfates by a special technique to simulate slime solids tailings. The dissolution of RaSO₄ from these coated sands was decreased by the presence of BaSO₄, but increased by the presence of CaSO₄. The interrelationships in the dissolution of mixtures of CaSO₄, SrSO₄, BaSO₄, and RASO₄ are shown, and a generalized equation for the estimation of the dissolution of a minor component is presented.     

Coextraction of uranium and radium from ore with ferric chloride

Ferric chloride leaching, at temperatures around 74°C, is found to remove up to remove up to 97% of the uranium from ores occurring in the Elliot Lake area of Canada. Radium removal is poor due to the formation of sulphates from the sulphides present in the ore. However, if the sulphides are removed initially by flotation, then ferric chloride can extract as much as 92% of the radium, giving tailings which are sulphide-free and with radium levels approaching 24 pCi/g. The main steps in a ferric chloride leaching process have been tested at the bench scale. Radium may be removed by adsorption on manganese dioxide and uranium is removed by liquid extraction with D2EHPA (DAPEX process). The ferric chloride may be recirculated for further leaching and the net usage is expected to be in the order of 5 kg/Mg of solids treated. Because of the recycle, it is possible to keep chloride ion levels in the effluent below the prescribed level of 750 mg/L.     

嗜酸氧化亚铁硫杆菌的分离鉴定及对废胎面胶的脱硫再生

从河北兴隆某硫铁矿筛选到一株硫杆菌YT-1,经理化性能和16S rDNA序列分析鉴定为嗜酸氧化亚铁硫杆菌(At.ferrooxidans YT-1),研究了该菌对废胎面胶(GTR)的脱硫再生作用.研究结果表明,三元共混物丁苯橡胶(SBR)/炭黑(CB)/再生GTR比SBR/CB/未再生GTR拉伸强度和断裂伸长率分别提高了5.3%和11.1%;X射线光电能谱检测表明SBR/CB/再生GTR表面硫元素质量分数降低13.92%,且峰位往高氧化态偏移0.2 eV,说明再生GTR表面硫元素被氧化;共混胶断裂面扫描电子显微镜显示再生GTR与SBR/CB基体粘合性能显著提高,说明再生GTR表面硫交联键被打断.     

Leaching of molybdenum and arsenic from uranium ore and mill tailings

A sequential, selective extraction procedure was used to assess the effects of sulfuric acid milling on the geochemical associations of molybdenum and arsenic in a uranium ore blend, and the tailings derived therefrom. The milling process removed about 21% of the molybdenum and 53% of the arsenic initially present in the ore. While about one-half of the molybdenum in the ore was water soluble, only about 14% existed in this form in the tailings. The major portion of the extractable molybdenum in the tailings appears to be associated with hydrous oxides of iron, and with alkaline earth sulfate precipitates. In contrast with the pattern seen for molybdenum, the partitioning of arsenic into the various extractable fractions differs little between the ore and the tailings.     

A kriging interpolation strategy for the optimization of Acidithiobacillus ferrooxidans biomass production using fed-batch bioreactors

In this work, a procedure for the optimization of Acidithiobacillus ferrooxidans biomass production in fed-batch reactors using a model based on optimal spatial interpolation of experimental data is proposed. The approach is useful in those cases where specific growth and substrate consumption rates are unknown. Based on interpolation, the optimal values of biomass and substrate concentrations set points are obtained at the minimum of 2-dimensional cost function. In the fed-batch reactor biomass and substrate concentrations are controlled at their set points by changing the input flow and its concentration. We propose a minimum variance control strategy which improves the classical proportional plus integral control. Since the interpolation is optimal, the proposed linear control strategy allows obtaining a tight minimized upper bound of the variance error in the controlled variables.     

Redox and precipitation reactions of iron and uranium solubilized from ore materials

Uranium are samples were leached with acidic ferric sulfate for 25 h. Changes in concentrations of FeOH²⁺ and Fe²⁺ were opposite, both reflecting the ferric iron reduction by the ore material. The total soluble iron concentrations first increased because of the solubilization of iron sulfides and then decreased because of the precipitation of Fe(III). Loss of soluble uranium occurred towards the end of the contact time with the leach liquor. Uranium was shown to co-precipitate with Fe(III) in a bacterially produced ferric sulfate solution.