Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation–reduction reactions in the bioleaching system.     

Effect of L-cysteine on bioleaching of Ni-Cu sulphide by A.manzaensis

The effect of L-cysteine in different concentrations on the bioleaching of Ni-Cu sulfide was studied with an extremely thermophilic archaea, Acidianus manzaensis. It is found that adding certain amounts of L-cysteine to the bioleaching system of Ni-Cu sulfide largely enhances the leaching rate. X-ray diffraction (XRD) patterns show the change of bioleached solid residues and the effect of L-cysteine on the surface charges of minerals. Zeta potential and IR spectra of mineral surface show that the interaction between L-cysteine and mineral leads to the formation of metal complex, which is propitious to the bioleaching of Ni-Cu sulfide by Acidianus manzaensis.     

Homology modeling and evolutionary trace analysis of superoxide dismutase from extremophile Acidithiobacillus ferrooxidans

The gene sod in Acidithiobacillus ferrooxidans may play a crucial role in its tolerance to the extremely acidic, toxic and oxidative environment of bioleaching. For insight into the anti-toxic mechanism of the bacteria, a three-dimensional (3D) molecular structure of the protein encoded by this gene was built by homology modeling techniques, refined by molecular dynamics simulations, assessed by PROFILE-3D and PROSTAT programs and its key residues were further detected by evolutionary trace analysis. Through these procedures, some trace residues were identified and spatially clustered. Among them, the residues of Asn38, Gly103 and Glu161 are randomly scattered throughout the mapped structure; interestingly, the other residues are all distinctly clustered in a subgroup near Fe atom. From these results, this gene can be confirmed at 3D level to encode the Fe-depending superoxide dismutase and subsequently play an anti-toxic role. Furthermore, the detected key residues around Fe binding site can be conjectured to be directly responsible for Fe binding and catalytic function. Foundation item: Project(2004CB619201) supported by the National Basic Research Program of China; Project (50321402) supported by the National Natural Science Foundation of China     

堆浸尾渣的回填技术探讨

铀矿的溶液浸矿技术具有能耗低，原材料消耗少，流程简单，劳动生产率高等特点，但在浸矿过程中产笺废渣等物质将对环境造成污染，葳将其用于井下充填，则不失为一种化害为利的有效途径，文章以堆浸尾渣为例，阐述了用其作井下充填料的技术要点，即堆浸尾渣的中和处理，浸渣的输送，堆浸尾渣的放射性防护等，文章指出，堆浸尾渣作井下充填料是可行的。     

有关原地爆破浸出工艺矿堆质量问题的研究

围绕原地爆破浸出了工艺的技术和持征,对直接影响浸出效果的矿玫主要的影响因素,综合研究与实践现状作了论述。在阐述了一般规律性技术的基础上,着重从爆破筑堆这一控制矿堆质量最为重要的手段上,较为全面地进行了探讨,并提出了实现矿堆质量参数的优化控制和发展的方向。     

Bacterial oxidation activity in heap leaching

Bioleaching of sulfide minerals by bacteria, mainly Thiobacillus ferrooxidans (T. f. ) and Thiobacillus thiooxidans, plays an important role in hydrometallurgy because of its economic and environmental attractions. The surveys of production process and the bacterial oxidation activity in the heap bioleaching were investigated. The results show that pH value is high, bacteria biomass and ferric concentration are low, generation time (above 7.13 h)is long in leachate, and less bacteria are adsorbed on the ores. The bacteria in the leachate exposing on the surface and connecting with mineral, have much faster oxidation rate of Fe(Ⅱ) and shorter generation time, compared with those which are in the reservoir for a long time. There is diversity for oxidation activity of Fe(Ⅱ), while there is no diversity for oxidation of sulfur. So it is advisable to add sulfuric acid to degrade pH value to 2.0, add nutrients and shorten recycling time of leachate, so as to enhance bacteria concentration of leachate and the leaching efficiency.     

浮选尾砂不经制粒直接堆浸问题探讨

本文就千吨级尾矿直接堆浸的问题进行了探讨,取得了较好的技术经济指标。对较高品位的含金尾矿的利用有很大的现实意义。     

Comparison of microbial communities in three different mine drainages and their bioleaching efficiencies to low grade of chalcopyrite

Microbial community diversities in the drainage from three mines(Dexing Copper Mine,Qibaoshan Copper Mine and Yaogangxian Tungsten Mine,China)were analyzed using 16S rDNA PCR-RFLP approach.The efficiencies of chalcopyrite bioleaching were compared using enrichment of the three cultures.Phylogenetic analysis indicates that the dominant microorganisms are clustered with the Proteobacteria,the remaining is affiliated with Nitrospira,Acidobacteria and Actinobacteria.At the genus level,Acidithiobacillus is the dominant group in both YTW and QBS samples,while Spingomonas is dominant in YGX sample.Moreover,the principal component analysis(PCA)reveals that QBS and YTW have similar geochemical character and microbial communities.The results also show that pH value and tungsten concentration play a key role in microbial community distribution and relative abundance.The bioleaching efficiency of the enrichment cultures from YTW and QBS is similar.After 15 d,the bioleaching rates of low grade chalcopyrite(0.99%)are both up to 99.5% when using 10 g/L pulp density due to the similar microbial composition of YTW and QBS.Moreover,the leaching efficiencies of enrichment cultures containing multiple bioleaching microorganisms are higher than that of pure culture Acidithiobacillus ferrooxidans.     

Bioleaching of chalcopyrite by. mixed culture of moderately thermophilic microorganisms

A mixed culture of moderately thermophilic microorganisms was enriched from acid mine drainages(AMDs)samples collected from several sulphide mines in China,and the bioleaching of chalcopyrite was conducted both in shake flask and bioreactor.The results show that in the shake flask,the mixture can tolerate 50 g/L chalcopyrite after being acclimated to gradually increased concentrations of chalcopyrite.The copper extraction increases obviously in bioleaching of chalcopyrite with moderately thermophilic microorganisms supplemented with 0.4 g/L yeast extract at 180 r/min,74% copper can be extracted in the pulp of 50 g/L chalcopyrite after 20 d.Compared with copper extractions of mesophilic culture,unacclimated culture and acclimated culture without addition of yeast extract,that of accliniated culture with addition of yeast extract is increased by 53%,44% and 16%,respectively.In a completely stirred tank reactor,the mass fraction of copper and total iron extraction reach up to 81% and 56%,respectively.The results also indicate that it is necessary to add a large amount of acid to the pulp to extract copper from chalcopyrite effectively.     

蓝辉铜矿的细菌氧化浸出研究

研究了紫金山铜矿中主要目的矿物之一的蓝辉铜矿细菌浸出的过程和影响因素,考察了蓝辉铜矿纯矿物的浸出特性。实验室条件下细菌浸出蓝辉铜矿纯矿物的适宜参数为：接种量50%;培养基中Fe^2＋氧化量为60%。20 d浸出周期内蓝辉铜矿浸出率可达80%以上。通过向纯矿物浸出体系中添加黄铁矿探讨其强化浸出效果。结果表明：以1∶2或1∶1重量比添加黄铁矿能明显加快蓝辉铜矿的细菌浸出速率。通过对蓝辉铜矿和黄铁矿在浸出介质中静电位的测定表明,添加黄铁矿后能在浸出体系中形成较强的原电池效应,促进目的矿物的溶解。