Bioleaching of chalcopyrite by Acidithiobacillus ferrooxidans

Acidithiobacillus ferrooxidans (A. ferrooxidans) was selected to experimentally study the effects of bacteria on the oxidation of chalcopyrite. The results indicated that A. ferrooxidans remarkably promoted the oxidation of chalcopyrite. The pH of the cell broth medium was observed to increase and then decrease during the bioleaching experiment. The number of suspended bacteria in the bio-oxidation process could be divided into three stages: the initial 4 days, in which the bacteria attached to the chalcopyrite surface and the number of suspended bacteria slightly decreased; day 5 to day 52, in which the suspended bacteria clearly increased with time and reached a maximum of 3.58 × 10⁷ cells/L on day 52; and day 53 to day 80, in which the number of suspended bacteria decreased. Other parameters such as redox potential (Eh) and iron ion concentrations increased with time. SEM micrographs showed that the cells were directly attached to the erosion pits on the smooth surfaces of the chalcopyrite. The erosion pits were similar to the bacteria in shape and size, and thus, the pits were likely products of dissolution by organic acids secreted by the attached cells. Compared to the unoxidized chalcopyrite, the elemental sulfur of the eroded chalcopyrite was clearly reduced, and the elemental oxygen was slightly increased. Moreover, a biofilm was present on the surfaces of the chalcopyrite particles. Therefore, the adherence of the cells to the mineral surfaces played a predominant role in altering the mineral appearance, which is important during the leaching of chalcopyrite.     

较低温度下细菌浸出黄铜矿工艺影响因素研究

以黄铜矿为研究对象,在温度较低的浸出条件下（15℃）采用正交试验的方法考察了矿石粒度、矿浆浓度、酸度、接种量以及起始Fe²⁺浓度对氧化亚铁硫杆菌（T.f菌）摇瓶浸出黄铜矿浸出过程的影响。试验结果表明：初始Fe²⁺浓度对细菌浸铜工艺影响最为显著;在15℃下的最佳浸出工艺条件为初始Fe²⁺浓度为6g/L,酸度控制在pH=2.0,接种量保持在15%,矿浆浓度为15%,矿石粒度为-200目。     

矿物学因素对黄铜矿微生物浸出影响的研究现状

黄铜矿微生物浸出一直是近年来的研究热点,研究者们主要从化学、矿物学及生物化学等角度展开对黄铜矿与细菌相互作用的研究。本文综述了影响黄铜矿微生物浸出的矿物学因素方面的研究,指出晶格能、晶格缺陷和同质多像等是影响微生物浸出黄铜矿的重要因素,并对未来的研究趋势进行了展望,这对日后黄铜矿微生物浸出工作的发展具有重要的意义。     

黄铜矿细菌浸出机理及钝化原因研究进展

细菌冶金技术由于成本低、污染少、流程短等优点,越来越受到人们重视,由于在常温下黄铜矿的细菌浸出速率较慢,有必要研究提高黄铜矿浸出速率的方法。综述了黄铜矿的细菌浸出机理以及黄铜矿的钝化原因。研究结果表明黄钾铁矾、硫层、中间产物层、高的溶液还原电位和黄铜矿稳定的晶体结构可能是黄铜矿细菌浸出过程中的钝化原因。     

中等嗜热菌浸出德兴黄铜矿的试验研究

对中等嗜热菌在45 ℃下浸出德兴黄铜矿的情况进行了试验研究。结果表明,添加适量（4 g/L）的Fe²⁺有利于中等嗜热菌的生长和黄铜矿的浸出;中等嗜热菌活性高有利于提高黄铜矿的浸出率;在试验酸度范围内,pH=1.50时中等嗜热菌的活性最高;矿浆浓度越低、粒度越细,越有利黄铜矿的浸出。在最佳试验条件下,黄铜矿49.2 d的铜浸出率为73.32%。浸出渣的XRD分析结果揭示,在浸出一段时间后,黄铜矿慢慢发生钝化的原因在于硫单质和黄钾铁矾在其表面的附着。     

白银含铜废石常温生物可浸性试验

从白银铜矿矿坑水中筛选分离的BY 1#细菌对黄铁矿有较好的氧化效果,也具有较好的抗剪切性和金属离子抗性。生物浸出综合试验表明该细菌在对黄铜矿的生物氧化溶解过程中,矿物表面可能存在某种钝化膜层,导致铜浸出率偏低,延长浸出时间所获得的效果也较差。在接种浓度10%、矿浆浓度5%、矿样粒度D70=400、摇床转速175rpm的试验条件下,浸出60d可获得的铁浸出率为57.24%,铜浸出率为42.16%。     

Bioleaching of chalcopyrite by Acidianus manzaensis under different constant pH

The bioleaching of pure chalcopyrite by thermophilic Archaea strain Acidianus manzaensis YN-25 under different constant pH was first comparatively investigated. Then the relevant sulfur speciation was analyzed by synchrotron radiation based X-ray diffraction (SR-XRD) and S K-edge X-ray absorption near edge structure (XANES) spectroscopy. The acidity of the leaching solution was monitored at 3-h intervals to make it steady at pH 1.25, 1.50, 1.75, 2.00, 2.25 and 2.50, respectively. Leaching results showed that the copper ion extraction increased during chemical leaching but decreased during bioleaching when pH value decreased from 2.50 to 1.25. SR-XRD analysis showed that, during bioleaching, new elemental sulfur (S⁰) phase was detected at all tested pH cases; new jarosite phase was detected at cases of pH 1.50 to 2.50; and jarosite gradually became a major phase when pH value increased. XANES analysis further showed that covellite was detected during bioleaching at cases of pH 1.25 to 2.00 at higher redox potential (ORP) value, while chalcocite and bornite were detected at cases of pH 2.25 and 2.50 at lower ORP value. These results suggested that the formation of S⁰ was mainly accounting for hindering the dissolution of chalcopyrite while the formation of bornite could accelerate the dissolution of chalcopyrite by A. manzaensis.     

黄铁矿在生物浸矿过程中的电化学氧化行为

自然界中大多数次生硫化铜矿都伴生一定量的黄铁矿，在生物浸出过程中黄铁矿过量溶解，造成浸出体系中铁酸不平衡。根据原子轨道及分子理论，分析了黄铁矿的电化学溶解机理，认为氧化还原电位是影响黄铁矿溶解的关键因素。用黄铁矿纯矿物进行硫酸浸出、硫酸高铁浸出和钩端螺旋菌细菌浸出试验，结果证实，无菌时，体系氧化还原电位基本低于700 mV，黄铁矿很难溶解，铁浸出率低于10%：有菌时，体系氧化还原电位可提高到800 mV以上，从而加速了黄铁矿的溶解，铁浸出率最高可达67%。     

黄铜矿生物浸出机制研究进展

要解决黄铜矿生物浸出效率较低的难题,需要从生物浸出机制入手。回顾了生物浸出机制从“直接作用”和“间接作用”理论到“接触作用”理论,再到“间接作用-直接接触作用-间接接触作用”理论的发展历程,并对这些理论的相关模型和解释进行了详细介绍。最后指出黄铜矿生物浸出机制尚未定论,还有待于继续深入研究。     

Cooperative effect of chalcopyrite and bornite interactions during bioleaching by mixed moderately thermophilic culture

The cooperative interactions between chalcopyrite and bornite during bioleaching by mixed moderately thermophilic culture were investigated mainly by bioleaching experiments and electrochemical experiments. Bioleaching results showed that a cooperative effect existed between chalcopyrite and bornite. When the mass ratio of chalcopyrite to bornite was 3:1, an extremely high copper extraction of more than 88% was achieved after bioleaching for 27 days. One of the major reasons for the cooperative effect was that a certain redox potential range (370–450 mV vs. Ag/AgCl) could be maintained for a long period of time during bioleaching due to the mixture of chalcopyrite and bornite. Electrochemical measurements revealed that chalcopyrite was much easier to be reduced than oxidized, while bornite was prone to be directly oxidized. Hence, galvanic effect between chalcopyrite and bornite enhanced the reduction of chalcopyrite to secondary copper-iron species and promoted the oxidative dissolution of bornite. Therefore, redox potential controlling and galvanic effect both contributed to the cooperative bioleaching of chalcopyrite and bornite.     

含钴矿物的生物提取

本文综述了含钴矿物的细菌浸出研究现状。包括浸出条件、机理和影响因素。指出了这项研究工作存在的问题和应用前景     

微生物浸出难浸黄铜矿的研究

比较详细地介绍了国内外微生物浸出黄铜矿及其多金属的最新成果,以期对我国微生物浸出铜工业的发展有一定的指导作用     

Comparison of the electrochemical mechanism of chalcopyrite dissolution in the absence or presence of Sulfolobus metallicus at 70 °C

The electrochemical mechanisms of chalcopyrite dissolution in the absence and presence of Sulfolobus metallicus at 70 °C were studied using cyclic voltammetry and Tafel methods. The cyclic voltammetry experiments show that S. metallicus does not change the oxidative and reductive mechanisms of chalcopyrite dissolution. The initial oxidation potentials of chalcopyrite dissolution are equal in the absence and presence of S. metallicus. However, the current density of oxidation in the presence of S. metallicus increases significantly. At about 0 V, the products on the surface of chalcopyrite are CuS, elemental S⁰, and Fe²⁺. At about 0.384 V, CuS may be oxidized, and chalcopyrite may be transferred to CuO, Fe₂O₃, and elemental S⁰. The Tafel experiments show that S. metallicus may increase the corrosion potential and corrosion current density of chalcopyrite. S. metallicus may also reduce the polarization resistance of chalcopyrite in bioleaching. These results indicate that S. metallicus may accelerate the oxidation of chalcopyrite.     

黄铜矿和黄铁矿微生物浸出差异性研究

采用搅拌浸出法,搅拌转速350 r/min、搅拌温度45℃,使用相同菌种对黄铜矿与黄铁矿浸出差异性进行了研究。结果表明,在相同生物浸出条件下,黄铁矿较黄铜矿更易浸出。黄铜矿生物浸出后期,浸出速率减慢的决定因素并非黄钾铁矾钝化层的罩盖。两种矿物浸出差异性产生的根本原因在于由其自身晶体结构所决定的生物浸出机理不同。     

The generation of toxic reactive oxygen species (ROS) from mechanically activated sulphide concentrates and its effect on thermophilic bioleaching

Two types of laboratory mills, planetary and vibratory, were used to activate sulphide mineral concentrates mechanically before thermophilic (bio)leaching. These samples were analysed in terms of particle size, surface area, density, SEM, XRD line profile analysis and reactivity. The product particle size distributions indicated different particle breakage mechanisms of the two mills. The surface area for pyrite milled with the planetary mill was three fold that milled in the vibratory mill for the same length of time. Planetary milled samples showed lower densities, up to 4% less for pyrite samples, compared to vibratory milled samples. Particle surface oxidation, observed by SEM, occurred post milling. Surface oxidation products were more prevalent with planetary milled sulphide samples. XRD line profile analysis showed more line broadening effects with the planetary mill. This indicated that more bulk particle-related structural defects were present in the planetary milled samples. The reactivity in acidic solution was measured in terms of the generation of toxic reactive oxygen species (ROS): hydrogen peroxide and hydroxyl radicals. The ROS generation from milled sulphides, normalised to constant surface area loading, increased with increased mechanical activation. The planetary milled samples generated greater ROS per sample surface area than vibratory milled samples, more than 4-fold for pyrite after 60 min of milling. Increased ROS generation was postulated to result from increased surface area defects, solubilisation of iron oxidation products and bulk particle-related defects.The effect of mechanical activation on performance on thermophilic leaching and bioleaching tests was investigated using milled samples at 2% (w/v) pulp density. Short mill times improved leach rates from both mills, up to 7-fold cf. unactivated feed leach rates. Poor bioleaching performance resulted following long periods of mechanical activation (20-60 min). Pyrite and chalcopyrite bioleaching performance decreased dramatically above surface area loadings of 25 and 125 m²/L respectively. Planetary milled samples were less amenable to bioleaching. For pyrite milled for 20 and 60 min and chalcopyrite milled for 40 min, no viable cells were observed following inoculation via fluorescence microscopy, suggesting culture death supported by compromised ferrous iron oxidation. The generation of ROS was postulated to cause poor bioleaching performance under these conditions.     

Bioleaching and recovery of metals from final slag waste of the copper smelting industry

Solid waste from the copper smelting industry may be harmful if disposed of in the environment, but it may be a valuable resource if metals can be recovered. The purpose of this study was to evaluate the acid bioleaching of metals from a sample of final smelter slag and the recovery of metals from the leach liquors. Bioleaching was tested in a continuously stirred tank reactor (CSTR) at 20-25 °C with 5% pulp density (particle size 75% <47 μm). The yields of metal solubilization after 29 days of contact were 41% Fe, 62% Cu, 35% Zn and 44% Ni. Metals were precipitated in a separate CSTR by titrating the leach liquors with sulfide-rich effluent from a sulfate-reducing fluidized-bed reactor (FBR) (25 °C) to desired pH values. Over 98% of the Cu precipitated at pH ? 2.8 and over 99% of the Zn precipitated at pH ? 3.9. The precipitation of Ni and Fe required higher pH values and was less efficient than Cu and Zn recovery. In addition, bulk precipitation of metals was also tested by feeding the leach liquor directly to another sulfate-reducing FBR. In order to reduce its toxicity and maintain stable sulfate reduction performance in the FBR, the leach liquor had to be diluted ten-fold and the pH adjusted from 0.6 to approximately 4.     

Synchrotron X-ray photoelectron spectroscopic study of the chalcopyrite leached by moderate thermophiles and mesophiles

SXPS (Synchrotron X-ray Photoelectron Spectroscopy) and NEXAFS (Near Edge X-ray Absorption Fine Structures) have been applied to study the surface chemical species of chalcopyrite leached by a moderate thermophilic consortia, Leptospirillum ferrooxidans and a mesophilic mixed culture of L. ferrooxidans, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A sulfur-rich layer dominated by S_n²⁻ developed with time, which was found to control the rate of bioleaching. Fe L_2,3-edge NEXAFS and Fe 2p spectra indicate the formation of jarosite during bioleaching. Thermophiles significantly enhanced the leaching efficiency, in which 1.34 g/L copper was dissolved in 25 days, while less than 0.3 g/L copper was released in 30 °C bioleaching. This was mostly caused by the increased abiotic reaction rate. The solution copper concentration in presence of L. ferrooxidans was higher than that with mesophilic mixed culture, which suggests the synergistic effect of mixed microorganisms did not play a comparably important role as temperature under the conditions used in this study. Explicit evidence of elemental sulfur was only found in samples leached by L. ferrooxidans by Raman spectroscopy. However, the formation of elemental sulfur does not significantly hinder the leach rate.     

A new method for testing the self-heating character of sulphide concentrates

A rapid, inexpensive, and quantitative method has been developed to quantify the self-heating potential of sulphide concentrates. The method consists of measuring the sulphur dioxide evolved when a concentrate is heated and oxidized in air at 300 °C. Sulphur dioxide is the reaction product of the oxidation of elemental sulphur present in the concentrate. We found a strong correlation between the output of the sulphur method (i.e. the elemental sulphur grade) and the output of the United Nations self-heating protocol (i.e. the temperature rise). Both methods provide evidence of the extent of prior oxidation of the sulphide concentrate, but do not inform about the rate at which the concentrate was oxidized.     

The effect of redox control on the continuous bioleaching of chalcopyrite concentrate

A continuous bioleaching process was developed for the dissolution of chalcopyrite concentrate with electrochemically redox control. Therefore, using a flotation concentrate containing 46% chalcopyrite and 23% pyrite, bioleaching tests were carried out at 47 °C with 15% pulp density under controlled and uncontrolled redox conditions. To increase the copper recovery in contrast to the conventional bioleaching (∼39.62%), the effect of redox potential on the chalcopyrite bioleaching was investigated by electrochemically controlled bioleaching. The results showed that by controlling the redox potential, faster copper leach kinetics could be achieved. At last, reducing the redox potential from high levels to optimum window (420–440 mV SCE) caused an increase in copper recovery from around 39% to higher than 69% (over 25 g/L Cu²⁺).