Screening and characterization of Acidiphilium sp. PJH and its role in bioleaching

A Gram-negative, facultative autotrophic bacterium strain PJH was isolated from the acidic mine drainages sampled in Dexing Mine, Jiangxi Province, China. The isolate grew in a pH range of 1.0 6.0, with pH and temperature optima of 3.5 and 40 ℃, respectively. Spectroscopic experiments show that strain PJH can synthesize polyhydroxybutyrate （PHB）. A phylogenetic analysis based on 16S rRNA sequences shows that the isolate belongs to the genus Acidiphilium. Strain PJH has the capability of leaching chalcopyrite. Bioleaching experiments show that it can improve the leaching rate of chalcopyrite by 10.3% when mixed with L. ferriphilium YTW315 after 35 d. Strain PJH has the potential in application to bioleach chalcopyrite with other mesophilic leaching microbes.     

Surface characterization of chalcopyrite interacting with Leptospirillum ferriphilum

The alteration of surface properties of chalcopyrite after biological conditioning with Leptospirillum ferriphilum was studied by adsorption, zeta-potential, contact angle and bioleaching tests. The strains of L. ferriphilum cultured using different energy sources (either soluble ferrous ion or chalcopyrite) were used. The adhesion of bacteria to the chalcopyrite surface was a fast process. Additionally, the adsorption of substrate-grown bacteria was greater and faster than that of liquid-grown ones. The isoelectric point (IEP) of chalcopyrite moved toward that of pure L. ferriphilum after conditioning with bacteria. The chalcopyrite contact angle curves motioned diversely in the culture with or without energy source. The results of X-ray diffraction patterns (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis indicate that the surface of chalcopyrite is covered with sulfur and jarosite during the bioleaching process by L. ferriphilum. Furthermore, EDS results imply that iron phase dissolves preferentially from chalcopyrite surface during bioleaching. The copper extraction is low, resulting from the formation of a passivation layer on the surface of chalcopyrite. The major component of the passivation layer that blocked continuous copper extraction is sulfur instead of jarosite.     

Screening and characterization of Acidiphilium sp. PJH and its role in bioleaching

A Gram-negative,facultative autotrophic bacterium strain PJH was isolated from the acidic mine drainages sampled in Dexing Mine,Jiangxi Province,China.The isolate grew in a pH range of 1.0-6.0,with pH and temperature optima of 3.5 and 40 ℃,respectively.Spectroscopic experiments show that strain PJH can synthesize polyhydroxybutyrate (PHB).A phylogenetic analysis based on 16S rRNA sequences shows that the isolate belongs to the genus Acidiphilium.Strain PJH has the capability of leaching chalcopyrite.Bioleaching experiments show that it can improve the leaching rate of chalcopyrite by 10.3% when mixed with L.ferriphilium YTW315 after 35 d.Strain PJH has the potential in application to bioleach chalcopyrite with other mesophilic leaching microbes.     

Comparative genome analysis on intraspecific evolution and nitrogen fixation of Leptospirillum ferriphilum isolates

To reveal the intraspecific evolution of Leptospirillum ferriphilum isolates which thrived in industrial bioleaching ecosystems and acid mine drainages, genome sequences of L. ferriphilum YSK, L. ferriphilum DX and L. ferriphilum ZJ were determined to compare with complete genome of L. ferriphilum ML-04. The genome comparisons reveal that extensive intraspecific variation occurs in their genomes, and that the loss and insertion of novel gene blocks of probable phage origin may mostly contribute to heterogeneity of gene content among L. ferriphilum genomes. Surprisingly, a nif gene cluster is identified in L. ferriphilum YSK and L. ferriphilum ZJ genomes. Intensive analysis and further experiments indicate that the nif gene cluster in L. ferriphilum YSK inherits from ancestor rather than lateral gene transfer. Overall, results suggest that the population of L. ferriphilum undergoes frequent genetic recombination, resulting in many closely related genome types in recent evolution. The combinatorial processes profoundly shape their physiologies and provide the basis for adaptation to different niches.     

Transformation of iron in pure culture process of extremely acidophilic microorganisms

Jarosite and extracellular polymer substance generated during pure culture and bioleaching process have been widely accepted the main transformation of decreasing iron in the medium. In the present work, acidophilus bioleaching organisms Ferroplasma thermophilum, Leptospirillum ferriphilum and Acidithioobacillus ferrooxidans were cultured. It was found that they can live in low pH environment, and more than 10 particles in each cell intracellular nano-particles are synthesized in the cells. By analyzing the morphology and chemical composition of nano-particles, they were found to contain iron, and the three microorganisms belonged to high-yielding strains. The results show that the transformation of the decreasing iron ions is not only generating jarosite, but also taken into cells and synthesizing ferruginous nano-particles.     

Bioleaching of pyrite by A. ferrooxidans and L. ferriphilum

Pyrite oxidation rates were examined under various conditions in the presence of A. ferrooxidans and L. ferriphilum, in which different pulp concentration, inoculation amount, external addition of Fe^3＋ and initial pH value were performed. It is found that A. ferrooxidans and L. ferriphilum show similar behaviors in the bioleaching process. The increasing pulp concentration decreases the leaching rate of iron, and external addition of high concentration Fe^3＋ is also adverse to leaching pyrite. The increased inoculation amount and high initial pH value are beneficial to leaching pyrite, and these changed conditions bring more obvious effects on leaching pyrite by L. ferriphilum than by A. ferrooxidans. The results also show that adjusting the pH values in leaching process baffles leaching pyrite due to the formed jarosite. Jarosite formed in leaching process was observed using XRD, SEM and energy spectrum analysis, and a considerable amount of debris with a crystalline morphology is present on the surface of pyrite. The results imply that the indirect action is more important for bioleaching pyrite.     

多金属硫化精矿中铜、锌和铁的生物浸出(英文)

利用嗜温混合菌Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans和Leptospirillum ferrooxidans对低品位复杂Cu-Zn-Pb-Fe-Ag-Au硫化精矿在曝气生物浸出反应器中进行生物浸出。该菌种为从塞尔维亚Bor地下铜矿的酸性溶液中筛选出一种嗜热嗜酸菌。营养液为p H 1.6的9K营养液。87%的矿物粒度大于10μm,矿浆密度为8%(w/v)。在测试条件下,锌、铜和铁的浸出率分别达到89%、83%和68%。动力学分析表明,浸出过程与Spencer-Topley模型相符,受局部反应扩散控制。     

Bio-dissolution of pyrite by Phanerochaete chrysosporium

The dissolution of pyrite was studied with Phanerochaete chrysosporium (P. chrysosporium). This fungus resulted in the dissolution of 18% iron and 33% sulfur. The oxidization layer was formed on the pyrite surface, which probably consisted of iron oxide, iron oxy-hydroxide, iron sulfate, elemental sulfur and mycelia. The electrochemical characteristics of pyrite were studied in the systems without and with P. chrysosporium. P. chrysosporium could accelerate the dissolution of pyrite by decreasing pitting potential and polarization resistance plus improving polarization current, corrosion potential and corrosion current density. The dissolution of pyrite is the combined effect of enzymes, hydrogen peroxide, ferric iron and organic acids. Enzymes attack the chemical bonds by free radicals. Organic acids dissolve pyrite by acidolysis and complexolysis. Enzymes and hydrogen peroxide play an essential role in this process.     

Acidithiobacillus ferrooxidans enhanced heavy metals immobilization efficiency in acidic aqueous system through bio-mediated coprecipitation

This study investigated the promotion effect of A. ferrooxidans on complex heavy metals coprecipitation process. A. ferrooxidans significantly enhanced the ferrous oxidation, which also promoted the formation of iron-oxyhydroxysulphate. Cu(II) concentration reduced to 0.058 mmol/L in A. ferrooxidans inoculated system, and Cd also reduced to the lowest concentration (0.085 mmol/L). Pb was mainly immobilized as anglesite and iron-oxyhydroxysulphate promoted the removal of remanent Pb in solution. The precipitates are characterized by XRD, SEM, and FTIR analysis. The main component of the iron-oxyhydroxysulphate was well crystallized jarosite. A. ferrooxidans contributed to the formation of schwertmannite in later monovalent cation lack stage. Higher ferrous iron oxidation rate and Fe(III) supply rate in A. ferrooxidans inoculated system facilitated polyhedron crystal formation and the increase of particle diameter. Complex heavy metals could be incorporated into iron oxyhydroxysulphate crystal, and efficiently removed from acidic wastewater through A. ferrooxidans mediated coprecipitation.     

Reversible reactions between pyrite and pyrrhotite in SO2

Differential thermal analysis (DTA) of iron sulfides in inert atmospheres containing varying amounts of SO₂ indicates temperature-dependent reversible reactions between pyrite and pyrrhotite in the range from 350°C to 520°C. Hexagonal pyrrhotite (troilite) and sulfur dioxide interact above 350°C to form pyrite and magnetite. Pyrite decomposes endothermically to pyrrhotite and sulfur above 520°C in the same atmosphere. The sulfurization of hexagonal pyrrhotite to pyrite has been investigated kinetically by DTA and confirmed by x-ray diffraction and wet chemical analyses. The reversibility of this pyrrhotite-pyrite reaction in a sulfur dioxide atmosphere merits further metallurgical consideration.     

Bioleaching of pyrite by A. ferrooxidans and L. ferriphilum

Pyrite oxidation rates were examined under various conditions in the presence of A.ferrooxidans and L.ferriphilum,in which different pulp concentration,inoculation amount,external addition of Fe3+ and initial pH value were performed.It is found that A.ferrooxidans and L.ferriphilum show similar behaviors in the bioleaching process.The increasing pulp concentration decreases the leaching rate of iron,and external addition of high concentration Fe3+ is also adverse to leaching pyrite.The increased inoculation amount and high initial pH value are beneficial to leaching pyrite,and these changed conditions bring more obvious effects on leaching pyrite by L.ferriphilum than by A.ferrooxidans.The results also show that adjusting the pH values in leaching process baffles leaching pyrite due to the formed jarosite.Jarosite formed in leaching process was observed using XRD,SEM and energy spectrum analysis,and a considerable amount of debris with a crystalline morphology is present on the surface of pyrite.The results imply that the indirect action is more important for bioleaching pyrite.     

Extraction and purification of magnetic nanoparticles from strain of Leptospirillum ferriphilum

1Introduction From1975,there is much interest in finding magne-totactic bacteria[1],because bacterial magnetosome particles,unlike those produced chemically,have a consistent shape,a unique crystallography,a narrow size distribution within the single magn…     

Discriminating bacterial from electrochemical corrosion using Fe isotopes

Metal corrosion is microbially induced (MIC) and/or electrochemical (ECC) in origin. Here we provide a novel approach to distinguish MIC from ECC, using iron isotope fingerprinting technique. In laboratory experiments, MIC products of Fe in the presence of a pure strain of Thiomonas sp. WJ68 exhibit a major shift in Fe isotope ratios (δ^56/54Fe and δ^57/54Fe, by 1.26 and 1.95‰, respectively) compared to ECC products formed under identical but sterile conditions. The methodology has applications in a broad range of industrial environments, particularly in the petrochemicals sector.     

氧分子在黄铁矿和方铅矿表面的吸附

采用密度泛函理论对氧分子在黄铁矿和方铅矿表面的吸附进行研究。计算结果表明:黄铁矿和方铅矿表面经历了较小的弛豫;氧分子在黄铁矿和方铅矿表面都呈解离吸附状态,且在黄铁矿表面的吸附能远低于在方铅矿表面的吸附能;在黄铁矿表面上,氧原子分别与铁原子和硫原子键合,电子由铁原子和硫原子转移到氧原子上,主要由硫的3p态、氧的2p态和铁的3d态参与反应,铁与氧之间形成d→p反馈键,而在方铅矿表面上,氧原子只与硫原子键合,主要由硫的3p态、氧的2p态和铅的6p态参与反应,未形成反馈键;氧吸附后黄铁矿表面产生键合的铁原子和氧原子都产生自旋现象,而方铅矿表面原子及吸附的氧原子仍然是低自旋态的。     

元素硫对黄铜矿生物浸出行为及群落结构的影响(英文)

研究3种典型铁/硫代谢菌—Acidithiobacillus ferrooxidans,Leptospirillum ferriphilum及Acidithiobacillus thiooxidans混合浸出黄铜矿过程中铁/硫氧化活性、群落结构(PCR-RFLP)的变化,以及不同浓度的元素硫对其影响。结果发现,加入3.193g/L元素硫能促进细菌的表观硫氧化活性,改变浸矿体系的群落结构,并进一步影响钝化层的形成、金属离子的溶出,其浸出率(71%)较未添加硫的(67%)有一定程度的提高。而过量的元素硫会抑制铜的浸出(浸出率44%)。     

Isolation and identification of moderately thermophilic acidophilic iron-oxidizing bacterium and its bioleaching characterization

A moderately thermophilic acidophilic iron-oxidizing bacterium ZW-1 was isolated from Dexing mine, Jiangxi Province, China. The morphological, biochemical and physiological characteristics, 16S rRNA sequence and bioleaching characterization of strain ZW-1 were studied. The optimum growth temperature is 48 ℃, and the optimum initial pH is 1.9. The strain can grow autotrophically by using ferrous iron or elemental sulfur as sole energy sources. The strain is also able to grow heterotrophically by using peptone and yeast extract powder, but not glucose. The cell density of strain ZW-1 can reach up to 1.02×108 /mL with addition of 0.4 g/L peptone. A phylogenetic tree was constructed by comparing with the published 16S rRNA sequences of the relative bacteria species. In the phylogenetic tree, strain ZW-1 is closely relative to Sulfobacilus acidophilus with more than 99% sequence similarity. The results of bioleaching experiments indicate that the strain could oxidize Fe2+ efficiently, and the maximum oxidizing rate is 0.295 g/(L·h). It could tolerate high concentration of Fe3+ and Cu2+ (35 g/L and 25 g/L, respectively). After 20 d, 44.6% of copper is extracted from chalcopyrite by using strain ZW-1 as inocula.     

Effects of Acidiphilium cryptum on biosolubilization of rock phosphate in the presence of Acidithiobacillus ferrooxidans

The bioleaching of pyrite and biosolubilization of rock phosphate (RP) in 9K basal salts medium were compared by the following strains of an autotrophic acidophilic bacterium, Acidithiobacillus ferrooxidans, a heterotrophic acidophilic bacterium, Acidiphilium cryptum, and mixed culture of At. ferrooxidans and A. cryptum. The results show that A. cryptum is effective in enhancing the bioleaching of pyrite and biosolubilization of RP in the presence of At. ferrooxidans, although it could not oxidize pyrite and solubilize RP by itself. This effect is demonstrated experimentally that A. cryptum enhances a decrease in pH and an increase in redox potential, concentration of total soluble iron and planktonic part bacterial number in the broth during pyrite bioleaching processes by At. ferrooxidans. The mixed culture of At. ferrooxidans and A. cryptum leads to the most extensive soluble phosphate released at 30 °C. Pulp density exceeding 3% is shown to adversely influence the release of soluble phosphate by the consortium of At. ferrooxidans and A. cryptum. It is essential to add pyrite to the 9K basal salts medium for the biosolubilization of RP by the mixed culture of At. ferrooxidans and A. cryptum, and the percentage of soluble phosphate released is the greatest when the mass ratio of RP to pyrite is 1:2 or 1:3.     

诱变对新菌株Leptospirillum ferriphilum YXW及浸出金矿的影响

通过稀释分离方法从江西德兴铜矿矿山废水中富集而来的混合菌中分离得到菌株 Leptospirillum ferriphilum YXW,再利用超声波、紫外线和微波对其进行诱变,筛选出更高效的细菌用于金矿的浸出。生理生化特性实验显示,菌株YXW为极端化能自养型细菌,最佳的生长条件为温度40°C,pH=1.5。诱变后,细菌浓度分别可达到9×109(超声波)、8.4×109(紫外线)和4.3×108 mL?1(微波),与原始菌相比,分别提高了291%、265%和87%。微波和紫外诱变后,细菌总蛋白活性升高,而超声诱变后,细菌总蛋白活性降低。诱变对细菌浸出金矿的影响由大到小的排列顺序是微波、紫外线、超声波。在金矿浸出过程中,微波诱变后的细菌具有最好的浸出效果。浸出10 d后,As和Fe的浸出率分别高出原始菌19.6%和17.7%。结果表明,诱变对细菌浸出金矿效果的提高,可能不在于细菌浓度的增大,而是取决于细菌总蛋白活性的提高。     

Coking and Dusting of Fe–Ni Alloys in CO–H2–H2O Gas Mixtures

Metal dusting of Fe–Ni alloys was investigated in a CO–H₂–H₂O–Ar gas corresponding to a _C = 19.6 at 650 °C. Thermogravimetric analysis showed that increasing the nickel content in the alloy decreased the initial rate of carbon uptake. A uniform Fe₃C scale formed on pure iron, a layer with mixed structures of Fe₃C, γ and α-Fe developed on ferritic Fe–5Ni, and small amounts of Fe₃C developed at the surface of an austenite layer grown on two-phase (α + γ) Fe–10Ni. At nickel levels above 10%, no carbide appeared. These observations are shown to be broadly consistent with local equilibrium according to the Fe–Ni–C phase diagram. However, the failure of higher nickel austenitic alloys to form the (Fe,Ni)₃C expected at high carbon activities indicates a barrier to nucleation and growth of this phase. Graphite deposition was catalysed by (Fe,Ni)₃C on ferritics and by the metal itself on austenitics. The rates of carbon deposition on Fe–60Ni corresponded to the existence of three parallel and independent paths: the synthesis gas, the Boudouard and the carbon methanation reactions.     

Leptosririllum ferrooxidans-sulfide mineral interactions with reference to bioflotation nad bioflocculation

The adhesion of ferrous ions grown Leptospirillumferrooxidans cells on pyrite and chalcopyrite minerals was investigated through adsorption, Zeta-potential and diffuse reflectance FT-IR measurements. The influence of bacterial species on minerals floatability was determined by Hallimond flotation tests while the flocculation behaviour was examined by Turbiscan measurements. The minerals iso-electric point （pH 6.5-7.5） after interaction with bacterial cells shifted towards cells iso-electric point （pH 3.3）, indicating the chemical nature of cells adsorption on mineral surfaces. The FT-IR spectra of minerals treated with bacterial cells showed the presence of all the cell functional groups signifying cells adsorption. The bacterial cells adsorption on chalcopyrite was higher compared with pyrite, which agreed with cells greater depression effect on chalcopyrite flotation and pronounced flocculation behaviour in comparison with pyrite.