Photogenerated-hole scavenger for enhancing photocatalytic chalcopyrite bioleaching

The effects of photogenerated-hole scavengers (ascorbic acid, oxalic acid, humic acid and citric acid) on chalcopyrite bioleaching in the presence of visible light were studied using Acidithiobacillus ferrooxidans (A. ferrooxidans). Four sets of bioleaching experiments were performed: (1) visible light + 0 g/L scavenger, (2) visible light + 0.1 g/L of different scavenger (ascorbic acid, oxalic acid, humic acid and citric acid), (3) dark + 0.1 g/L of different scavenger (ascorbic acid, oxalic acid, humic acid and citric acid), and (4) dark + 0 g/L scavenger (control group). The results showed that ascorbic acid and oxalic acid could act as photogenerated-hole scavengers and significantly enhance chalcopyrite bioleaching under visible light. The dissolved copper in the light group without scavenger was only 18.7% higher than that of the control group. The copper extraction rates of the light groups with oxalic acid and ascorbic acid were respectively 30.1% and 32.5% higher than those of the control group. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that ascorbic acid and oxalic acid as photogenerated-hole scavenger could capture photo-generated holes and inhibit jarosite formation on the chalcopyrite surface, thereby enhancing bioleaching of chalcopyrite under visible light.     

Relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture at 65 °C

The relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture (Acidianus brierleyi, Metallosphaera sedula, Acidianus manzaensis and Sulfolobus metallicus) at 65 °C was studied. Leaching experiments showed that the addition of activated carbon could significantly promote the dissolution of chalcopyrite for both bioleaching and chemical leaching. The results of synchrotron-based X-ray diffraction, iron L-edge and sulfur K-edge X-ray absorption near edge structure spectroscopy indicated that activated carbon could change the transition path of electrons through galvanic interactions to form more readily dissolved secondary mineral chalcocite at a low redox potential (<400 mV) and then enhanced the copper dissolution. Jarosite accumulated immediately in the initial stage of bioleaching with activated carbon but copper dissolution was not hindered. However, much jarosite precipitated on the surface of chalcopyrite in the late stage of bioleaching, which might account for the decrease of copper dissolution rate. More elemental sulfur (S⁰) was also detected with additional activated carbon but the mixed thermophilic Archaea culture had a great sulfur oxidation activity, thus S⁰ was eliminated and seemed to have no significant influence on the dissolution of chalcopyrite.     

EPS-contact-leaching mechanism of chalcopyrite concentrates by A. ferrooxidans

The effect of extracelluar polymeric substances（EPS） on the bioleaching chalcopyrite concentrates in the presence of ironand sulphur-oxidizing bacteria （A. ferrooxidans） was studied. The bacterial number, pH, redox potential, and the concentrations of Fe^2＋ and Cu^2＋ ions were investigated. The leached residues were analyzed by the X-ray diffraction and FT-IR. The results indicate that the EPS makes the bacteria adhere to the chalcopyrite surface easily and it is helpful for bacteria in disadvantageous environment At the same time, EPS film layer with Fe^3＋ deposits on the surface of chalcopyrite and becomes a barrier of oxygen transfer to chalcopyrite to passivate chalcopyrite, and creates the high redox potential space through concentrating Fe^3＋ ions to accelerate bioleaching pyrite in chalcopyrite concentrates. The results suggest that EPS formation promotes bioleaching pyrite and inhibits bioleaching chalcopyrite, especially under high potential condition.     

嗜酸氧化亚铁硫杆菌（ATCC 23270）浸出黄铜矿过程中的EPS、Cu2+和Fe3+的相互作用机制（英文）

采用超声-离心方法提取嗜酸氧化亚铁硫杆菌(ATCC 23270)胞外多聚物(EPS)、EPS中的Cu2+、Fe3+离子,研究生物浸出黄铜矿过程中Cu2+、Fe3+和EPS的相互作用机制。结果表明:与Fe3+离子相比,Cu2+离子可刺激细菌产生更多的EPS;当Cu2+离子浓度从0.01mol/L增加到0.04mol/L时,EPS中Fe3+/Cu2+质量比从4:1降低到2:1;从1%黄铜矿的无铁9K介质中提取的EPS中铜铁含量是从含0.04mol/LCu2+离子的9K介质中提取的量的2倍。在生物浸出黄铜矿过程中,黄铜矿表面结合黄铁钾钒的EPS层减弱了Cu2+、Fe3+离子的迁移,逐渐成为离子扩散壁垒。     

Cu-state evolution during leaching of bornite at 50 °C

The bioleaching of bornite with mixed moderately thermophilic culture at 50 °C was investigated. The intermediary species formed during the leaching of bornite were characterized by XRD and XPS. In addition, the evolution of Cu-state during leaching of bornite was further studied by applying φ_h-pH diagram and cyclic voltammetry. The results showed that the bornite was more likely to be leached at high redox potential. Furthermore, the intermediary sulfides, such as isocubanite, covellite, chalcopyrite, disulfide, and polysulfide, were formed in the course of bornite dissolution. The Cu 2p photoelectron spectrum revealed that the valence of copper in bornite and intermediary sulfide formed in the dissolution of bornite is +1. The bornite and chalcopyrite can be converted into each other, and both can be further converted to covellite and/or chalcocite.     

铁闪锌矿的Leptospirillum ferrooxidans菌浸出及电化学性能(英文)

采用纯种L.ferrooxidans菌研究矿浆浓度、pH及外加Fe3+离子对铁闪锌矿生物浸出的影响。结果表明,锌的浸出率随着矿浆浓度的降低而增加。在生物浸出过程中调节pH值到1.6对铁闪锌矿的溶解有促进作用。外加Fe3+离子加速了铁闪锌矿的生物浸出,但当外加Fe3+离子浓度超过2.5g/L时,促进作用变弱。这是因为高浓度的Fe3+离子会对细菌生长产生抑制作用且促进黄钾铁矾的生成。在L.ferrooxidans菌存在条件下,利用电化学测试方法进一步了解有、无外加Fe3+离子时铁闪锌矿的溶解过程。实验数据表明,外加Fe3+离子可以增加腐蚀电流密度,有利于锌的提取。交流阻抗谱表明,添加Fe3+离子后没有改变反应过程的控制步骤。     

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.     

Comparative study on bioleaching of two different types of low-grade copper tailings by mixed moderate thermophiles

The bioleaching of two different types of low-grade copper tailings, acid-leaching tailings (ALT) and copper flotation tailings (CFT) by mixed moderate thermophiles, and the variation of mineralogical and microbiological characteristics during their dissolution processes were comparatively investigated. Results showed that bioleaching behaviors of the two types of tailings were significantly different. In ALT bioleaching, lower redox potential, higher [Fe³⁺]/[Fe²⁺] ratio and higher cell density in solution were obtained. These resulted in higher total copper, primary copper sulfide and secondary copper sulfide extractions, compared with CFT bioleaching. X-ray diffraction analysis suggested that gypsum and some metal organic complexes were detected in CFT bioleaching, which could cause the sluggish oxidation of sulphide minerals. The shifts of microbial community in the leachates and leaching residues varied greatly between ALT and CFT bioleaching. The percentage of iron-oxidizing bacteria in ALT bioleaching was higher than that of CFT, but the sulfur-oxidizing bacteria percentage was the opposite. The archaeon F. thermophilum L1 was detected in ALT but not in CFT.     

Interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution

The interfacial reactions of chalcopyrite in ammonia–ammonium chloride solution were investigated. The chalcopyrite surface was examined by scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) techniques. It was found that interfacial passivation layers of chalcopyrite were formed from an iron oxide layer on top of a copper sulfide layer overlaying the bulk chalcopyrite, whereas CuFe_1–xS₂ or copper sulfides were formed via the preferential dissolution of Fe. The copper sulfide layer formed a new passivation layer, whereas the iron oxide layer peeled off spontaneously and partially from the chalcopyrite surface. The state of the copper sulfide layer was discussed after being deduced from the appearance of S^2–, S^2?₂, S^2?_n, S⁰ and SO^2?₄. A mechanism for the oxidation and passivation of chalcopyrite under different pH values and redox potentials was proposed. Accordingly, a model of the interfacial reaction on the chalcopyrite surface was constructed using a three-step reaction pathway, which demonstrated the formation and transformation of passivation layers under the present experimental conditions.     

Bioleaching of chalcopyrite by UV-induced mutagenized Acidiphilium cryptum and Acidithiobacillus ferrooxidans

The original strains Acidithiobacillus ferrooxidans GF and Acidiphilium cryptum DX1-1 were isolated from the drainage of some caves riched in chalcopyrite in Dexing Mine in Jiangxi Province of China.The optimum temperature and pH for growth were 30℃and 3.5 for Ac.cryptum DX1-1,and 30℃and 2.0 for At.ferrooxidans GF,respectively.For Ac.cryptum DX1-1,the optimum UV radiating time was 60 s and the positive mutation rate was 22.5%.The growth curves show that Ac.cryptum after mutagenesis reached stationary phase ...     

Effect of Cu ions on bioleaching of marmatite

The effect of Cu^2＋ ions on bioleaching of marmatite was investigated through shake leaching experiments. The bacteria inoculated are a mixed culture ofAcidithiobacillusferrooxidans, Acidithiobacillus thiooxidans and Lepthospirillumferrooxidans. The results show that zinc is selectively leached, and the addition of appropriate content of Cu^2＋ ions has positive effect on the bioleaching of marmatite. SEM and EDX analyses of the leaching residue reveal that a product layer composed of iron sulfide, elemental sulfur and jarosite forms on the mineral surface. The biooxidation of elemental sulfur is catalyzed by the Cu^2＋ ions, which eliminate the barrier to bioleaching of marmatite and keep low pH value. With the addition of 0.5 g/L Cu^2＋ ions, the maximum zinc extraction rate reaches 73% after 23 d at the temperature of 30 ℃ with the pulp density of 10%, while that of iron is only about 10%.     

Effect of initial pH on chalcopyrite oxidation dissolution in the presence of extreme thermophile Acidianus manzaensis

The influence of initial pH on the chalcopyrite oxidation dissolution at 65 °C was investigated by bioleaching and cyclic voltammetry experiments, and the oxidation products were investigated by XRD and Raman spectroscopy. Bioleaching results show that chalcopyrite dissolution rate increases with the decrease of the initial pH in chemical leaching, while the influence of initial pH on bioleaching is on the contrary. The presence of Acidianus manzaensis does not promote chalcopyrite dissolution under initial pH 1.0, which mainly results from serious inhibition of high acidity to the growth of Acidianus manzaensis. Electrochemical experiments results show that anodic oxidation currents of electrolyte with or without Acidianus manzaensis both increase with the increase of initial pH, and covellite and sulfur are detected on the electrode surface. The results confirm that chalcopyrite dissolution in chemical leaching is under the combined action of oxidation and non-oxidation of proton, with conversion of chalcopyrite to covellite and elemental sulfur.     

生物浸出过程中黄铜矿钝化的控制方法(英文)

在细菌浸出黄铜矿的过程中,黄铜矿表面钝化是普遍现象,成为生物浸铜技术的瓶颈问题。对比研究了普通浸出与强化浸出(加入玻璃圆珠)对铜浸出的影响。结果表明,玻璃圆珠的加入改善了浸出条件,削弱了黄铜矿的钝化效应,使黄铜矿的Cu浸出率从50%提升至 89.8%。扫描电镜(SEM)和X射线衍射(XRD)分析发现,添加玻璃圆珠的黄铜矿表面没有黄钾铁矾沉淀,钝化作用不明显;而不加玻璃圆珠的黄铜矿表面附着厚厚的结构致密的黄钾铁矾,钝化严重,从而阻碍了黄铜矿的溶解和浸出。     

Enhancing recovery of uranium column bioleaching by process optimization and kinetic modeling

This research aimed to enhance the column bioleaching recovery of uranium ore by Acidithiobacillus ferrooxidans. Seven factors were examined for their significance on bioleaching using a Plackett–Burman factorial design. Four significant variables ([Fe²⁺]_initial, pH, aeration rate and inoculation percent) were selected for the optimization studies. The effect of these variables on uranium bioleaching was studied using a central composite design (CCD). The optimal values of the variables for the maximum uranium bioleaching recovery (90.27±0.98)% were as follows: [Fe²⁺]_initial=2.89 g/L, aeration rate 420 mL/min, pH 1.45 and inoculation 6% (v/v). [Fe²⁺]_initial was found to be the most effective parameter. The maximum uranium recovery from the predicted models was 92.01%. This value was in agreement with the actual experimental value. The analysis of bioleaching residue of uranium ore under optimum conditions confirmed the formation of K-jarosite on the surface of minerals. By using optimal conditions, uranium bioleaching recovery is increased at column and jarosite precipitation is minimized. The kinetic model showed that uranium recovery has a direct relation with ferric ion concentration.     

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.     

Mechanism of silver-influenced bacterial leaching of chalcopyrite, pyrite and a copper ore

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｈａｌｃｏｐｙｒｉｔｅｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｃｏｐｐｅｒｍｉｎｅｒａｌｓ.Ｂｉｏｈｙｄｒｏｍｅｔａｌｌｕｒｇｙｈａｓｇｒａｄｕａｌｌｙｂｅｃｏｍｅａｎｉｍｐｏｒｔａｎｔｔｅｃｈｎｏｌｏｇｙｉｎｔｒｅａｔｉｎｇｌｏｗ ｇｒａｄｅｃｏｐｐｅｒｏｒｅｓ,ｅｓｐｅｃｉａｌｌｙｗｈｅｎｔｈｅｍｉｎｉｎｇｉｎｄｕｓｔｒｙｈａｓｔｏｂｅｆａｃｅｄｕｐｔｏｉｎｃｒｅａｓｉｎｇｌｙｓｅｒｉｏｕｓｐｒｏｂｌｅｍｓｓｕｃｈａｓｔｈｅｐｒｏｇｒｅｓｓｉｎｇｅｘｈａｕｓｔ…     

转鼓和搅拌槽反应器中氧化亚铁硫杆菌氧化Fe2+的比较（英文）

研究转鼓和搅拌槽反应器中氧化亚铁硫杆菌在不同Al2O3粉末含量下对Fe2+的氧化。结果表明:未添加Al2O3粉末时,氧化亚铁硫杆菌在搅拌槽中的生物活性比在转鼓中的生物活性高。当Al2O3粉末含量从0增加到50%(质量分数)时,Fe2+的生物氧化速率从0.23g/(L·h)显著降低到0.025g/(L·h),可能是搅拌槽中的固体颗粒碰撞和研磨作用导致氧化亚铁硫杆菌失活。转鼓中Al2O3的含量增加对氧化亚铁硫杆菌的生物活性仅有较小的负面影响,这是由于两个反应器不同的混合机制所致。在相同的Al2O3含量下,Fe2+在转鼓反应器中的生物氧化速率比在搅拌槽中的生物氧化速率更高,尤其在较高的固体含量下,表明转鼓反应器能允许较高的固体含量和维持较高的生物活性。由于Al2O3粉末与真实硫化矿具有不同的物理化学性质,因此转鼓反应器用于硫化矿生物浸出的可行性还需进一步验证。     

Effect of Cd as a stabilizer in the electroless nickel plating system

Bath decomposition is a major problem in the electroless nickel (EN) plating system. Although the stabilization mechanism is far from being fully understood, bath stabilizers are normally added to extend the bath life in a viable EN plating solution. In this study, the effects of Cd²⁺ as a stabilizer on the plating rate, bath stability, and phosphorus content, corrosion resistance and microstructure of the deposits were investigated. The deposited films were examined using a scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy and the X-ray photo spectroscopy (XPS). The electronic tunneling mechanism was used to elucidate the effect of the Cd²⁺ stabilizer on the plating system theoretically. The results calculated from theoretical method agreed well with the experimental data.     

Electrochemical behavior of chalcopyrite in presence of Thiobacillus ferrooxidans

1 Introduction The bioleaching research has a great progress in metallurgy industry. A significant number of commercial applications have emerged and are able to compete with conventional processing, especially the application for the copper recovery. Fur…     

绢云母对黄铜矿微生物浸出的影响

采用以Acidithiobacillus ferrooxidans为主的混合菌,研究绢云母对微生物浸出黄铜矿的影响。结果表明,铜的浸出率随着绢云母粒度的减小而增加,随着绢云母质量分数的增加而呈先升高后降低的趋势。在添加粒度为-33μm、质量分数为5.0%的绢云母时,铜的最高浸出率为54.88%,比不添加绢云母时的铜浸出率提高了约12%,表明绢云母能促进黄铜矿的微生物浸出。绢云母的加入可使浸出体系pH值降低,最终pH值低于1.22。在浸出过程中,新生成的物质主要是铵黄铁矾,它覆盖于黄铜矿的表面,对微生物浸出铜有一定的阻碍作用。