嗜酸氧化亚铁硫杆菌浸出黄铜矿中氧化还原电位、黄铁钾钒和胞外聚合物的关系和影响(英文)

在合成的胞外聚合物(EPS)溶液中,研究不同起始总铁量、不同Fe(III)与Fe(II)摩尔比条件下嗜酸氧化亚铁硫杆菌浸出黄铜矿过程中pH、电位、可溶性铁离子和Cu2+浓度随浸出时间的变化。结果表明:当溶液电位低于650mV(vsSHE)时,因细菌产生的EPS可通过絮凝黄铁钾钒延缓污染,即使铁离子浓度达到20g/L,黄铁钾钒对细菌浸出黄铜矿的阻碍作用也不是致命的,但随着铁离子浓度的增加而增加;细菌氧化的铁离子容易吸附在黄铜矿表面的EPS表层,有黄铁钾钒的EPS层是弱离子扩散壁垒,细菌通过把EPS空间内外的Fe2+氧化成Fe3+,进一步创造高于650mV的电位,导致EPS层离子扩散性能的快速恶化,严重地和不可逆地阻碍生物浸出黄铜矿。     

Cu2+、Fe2+和Fe3+对中等嗜热混合菌浸出黄铜矿的影响

在50℃、pH 1.6的条件下,研究了Fe2+、Fe3+和Cu2+对中等嗜热混合菌浸出黄铜矿的影响.结果表明:添加低质量浓度Fe2+时,在浸出前期能够促进黄铜矿的浸出;而添加较高质量浓度Fe2+时,铜的浸出率反而降低;当添加不同质量浓度Fe3+时,由于形成黄钾铁矾而导致总铁质量浓度降低,但铜的浸出率并没有明显变化;添加...     

铁闪锌矿的Sulfobacillus thermosulfidooxidans菌浸出及电化学性能（英文）

采用纯种Sulfobacillus thermosulfidooxidans菌进行铁闪锌矿的生物浸出及电化学实验,研究颗粒大小、p H值控制和外加Fe3+离子对锌浸出的影响。结果表明:在生物浸出过程中铁闪锌矿生物浸出的最佳粒度范围为0.043~0.074 mm;定期调整p H值至初始值对获得较高的浸出率有重要影响;外加Fe3+离子能加速铁闪锌矿的生物浸出,但当外加Fe3+离子浓度超过2.5 g/L时,促进作用变弱,甚至阻碍铁闪锌矿的溶解。SEM和XRD分析浸渣发现,在矿物表面形成一层由单质硫和黄钾铁矾组成的产物层,并导致后期的浸出速度低。电化学测试实验结果表明,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。     

利用光生空穴清除剂强化光催化黄铜矿生物浸出（英文）

通过嗜酸氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)研究光生空穴清除剂(抗坏血酸、草酸、腐质酸和柠檬酸)对光催化黄铜矿生物浸出的影响。设置4组生物浸出实验:(1)可见光+0 g/L光生空穴清除剂;(2)可见光+0.1 g/L不同光生空穴清除剂(抗坏血酸、草酸、腐植酸和柠檬酸);(3)黑暗+0.1 g/L不同光生空穴清除剂(抗坏血酸、草酸、腐植酸和柠檬酸);(4)黑暗+0 g/L光生空穴清除剂(对照组)。结果表明,光照条件下,抗坏血酸和草酸作为光生空穴清除剂时,能够显著促进黄铜矿生物浸出。可见光+0 g/L光生空穴清除剂组的铜离子溶出率比对照组高18.7%;可见光+0.1 g/L草酸组和可见光+0.1 g/L抗坏血酸组的黄铜矿溶出率分别比对照组高30.1%和32.5%。SEM,XRD和FT-IR分析表明,抗坏血酸和草酸作为光生空穴清除剂能够捕获光生空穴和抑制黄钾铁矾在黄铜矿表面形成,从而促进光催化黄铜矿的生物浸出。     

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。     

聚乙二醇对氧化亚铁硫杆菌浸出黄铜矿的影响

为提高黄铜矿生物浸出率,研究聚乙二醇(PEG)对Acidithiobacillus ferrooxidans strain XZ11 Fe2+氧化活性和黄铜矿生物浸出过程的影响,并采用SEM和EDS对浸出后矿物表面形貌和相组成进行表征。结果表明:相对分子质量大于200的PEG对Acidithiobacillus ferrooxidans Fe2+氧化活性具有一定的促进作用,添加30 mg/L PEG 2000时,浸出20 d后,铜浸出量高达451.70 mg/L,较不添加FEG时提高了1.11倍;添加PEG时,黄铜矿表面的侵蚀面呈沟壑状,出现溶蚀坑,并生成Fe3+的羟基化多聚物Fe(Ⅲ)—O—OH。PEG的添加提高了浸出体系中细菌浓度和Fe3+浓度,加速了黄铜矿的溶解。     

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。     

黄铜矿生物浸出过程中Fe(Ⅱ)和Fe(Ⅲ)的行为

采用Fe(Ⅱ)和Fe(Ⅲ)对黄铜矿进行生物浸出,主要研究浸出过程中体系的pH值、铁离子浓度、细菌吸附率及铜浸出率变化规律。结果表明:介质中Fe(Ⅲ)含量不同,生成黄钾铁矾的形态不同。在Fe(Ⅲ)生物浸出体系中,絮状的黄钾铁矾逐渐生成并全部覆盖在黄铜矿表面,阻碍黄铜矿的浸出过程。在Fe(Ⅱ)生物浸出体系中,生成皮壳状、结核状的黄钾铁矾分散于浸出液中,不覆盖在黄铜矿表面,对黄铜矿的浸出没有阻碍作用。     

氧化硫硫杆菌作用下黄铜矿-MnO2同时发电浸出的机制

采用双电池体系研究发电浸出过程和生物发电浸出过程中放电量、Fe2+和Mn2+浸出率与时间的关系.结果表明:生物发电浸出的Cu2+和Fe2+浸出率比单纯发电浸出提高近2倍,发电量和Mn2+浸出率提高近3倍.对发电浸出产物进行XRD和SEM分析表明,经历发电浸出过程,晶体的形貌与反应前相似,发电浸出产物单质硫和杂质PbS大量存在;经历生物发电浸出过程,杂质PbS被氧化成PbSO4,沉积在残渣表面.对氧化硫硫杆菌作用下CuFeS2-MnO2发电浸出机制研究表明,黄铜矿的发电浸出和生物发电浸出都存在表层的黄铜矿离解产生Cu2+、Fe2+和单质硫的过程,而生物发电浸出中还进行了单质硫部分被A.t菌氧化的后续过程,且生物氧化过程为控制步骤.MnO2的浸出在本研究的系统中是被动的,如果黄铜矿的浸出还能进行,MnO2的浸出就能持续.     

不同成矿成因黄铜矿化学浸出的差异性

采用XRD、XPS和MLA等检测研究海相火山岩型黄铜矿及斑岩型黄铜矿化学浸出的差异性。结果表明:在化学浸出过程中,海相火山岩型黄铜矿与斑岩型黄铜矿浸出特性有很大的差异,这是由于两种黄铜矿表面形成中间产物的性质不同。两种黄铜矿化学浸出的产物除单质硫S8之外,还有非化学计量的中间产物Cu3.5Fe4S2.5、Cu5Fe4S及Cu3.5Fe1.5S5生成。海相火山岩型黄铜矿的中间产物以Cu3.5Fe4S2.5为主,斑岩型黄铜矿的中间产物以Cu3.5Fe1.5S5为主。海相火山岩型黄铜矿与斑岩型黄铜矿具有不同的溶解途径:海相火山岩型黄铜矿受到H+的腐蚀后矿物中的Cu—S断裂,Cu2+与Fe2+同时溶解,而斑岩型黄铜矿受到H+腐蚀后Fe2+优先溶解。     

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.     

Catalytic effect of visible light and Cd2+ on chalcopyrite bioleaching

The effects of visible light and Cd²⁺ ion on chalcopyrite bioleaching in the presence of Acidithiobacillus ferrooxidans (A. ferrooxidans) were studied by scanning electron microscopy (SEM), synchrotron radiation X-ray diffraction (SR-XRD), and X-ray photoelectron spectroscopy (XPS). The results of bioleaching after 28 days showed that the copper dissolution increased by 4.96% with only visible light, the presence of Cd²⁺ alone exerted slight inhibition effect on chalcopyrite dissolution and the concentration of dissolved copper increased by 14.70% with visible light and 50 mg/L Cd²⁺. The results of chemical leaching showed that visible light can promote the circulation of iron. SEM results showed that Cd²⁺ promoted the attachment of A. ferrooxidans on chalcopyrite surface under visible light. SR-XRD and XPS results indicated that visible light and Cd²⁺ promoted chalcopyrite dissolution, but did not inhibit the formation of passivation. Finally, a model of synergistic catalysis mechanism of visible light and Cd²⁺ on chalcopyrite bioleaching was proposed.     

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%.     

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

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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 iron- and sulphur-oxidizing bacteria (A.ferrooxidans) was studied.The bacterial number,pH,redox potential,and the concentrations of Fe2+and Cu2+ 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 Fe3+ 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 Fe3+ 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.     

Sorption of Hg2+, Nd3+, Dy3+, and Uo 22+ ions at polysiloxane xerogels functionalized with phosphonic acid derivatives

The sorption properties of silicas with mono- and bifunctional surface layers containing the complexing fragment ≡Si(CH₂)₃NHP(S)(OC₂H₅)₂ were studied. It was found that xerogels synthesized by the solgel method (like mesoporous silicas obtained by the template method) can extract mercury(II) ions from acidified solutions (SSC up to 450 mg/g). In a nonporous xerogel with a bifunctional surface layer (≡P=S/-SH), thiol groups proved to be primary sorption sites for Hg²⁺ ions; part of the ligand groups were inaccessible to metal ions. Xerogels containing the phosphonic acid residues ≡Si(CH₂)₂P(O)(OH)₂ sorbed uranyl and lanthanide ions from their nitrate solutions. The resulting surface complexes contained two (for the UO₂²⁺ ion) or three innersphere ligand groups (for the Nd³⁺ and Dy³⁺ ions). The maximum SSCs were 340 mg/g for the uranyl ion and 120 mg/g for the lanthanide ions. Original Russian Text ? O.A. Dudarko, V.P. Goncharik, V.Ya. Semenii, Yu.L. Zub, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 207–212.     

X-ray photoelectron spectrum of Fe2+ state in iron oxides

As a standard for identification of iron oxides by X-ray photoelectron spectroscopy, Fe²⁺ spectra are extracted from mixed Fe 2p_3/2 spectra of Fe³⁺, Fe³⁺ and metallic states. The peaks of Fe²⁺ spectra are all located at binding energy of 708·5 eV. The width of Fe²⁺ spectrum seems to be dependent on crystallinity, and is 2·2 eV for a bulk crystalline oxide and 2·9 eV for an amorphous thin film under instrumental condition with FWHM of 1·3 eV for Au 4f_7/2.     

Mechanism of electro-generating leaching of chalcopyrite-MnO2 in presence of Acidithiobacillus thiooxidans

A dual cell system with chalcopyrite anode and MnO2 cathode was used to study the relations between time and such data as the electric quantity and the dissolution rates of the two minerals in the electro-generating leaching（EGL） and the bio-electro-generating leaching（BEGL）, respectively. The results showed that the dissolution rates for Cu^2＋ and Fe^2＋ in BEGL were almost 2 times faster than those in EGL, and nearly 3 times for Mn^2＋; the electric output increased nearly by 3 times. The oxidation residue of chalcopyrite was represented by TEM and XRD, whose pattern was similar to that of the raw ore in EGL. The mechanism for leaching of CuFeS2-MnO2 in the presence of Acidithiobacillus thiooxidans was proposed as a successive reaction of two independent sub-processes for the anode. The first stage, common to both processes, is dissolution of chalcopyrite to produce Cu^2＋, Fe^2＋ and sulfur. The second stage is subsequent oxidization of sulfur only in BEGL, which is the controlling step of the process. However, the dissolution of MnO2 lasts until the reaction of chalcopyrite stops or the ores exhaust in two types of leaching.