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.     

Characterization of copper bioreduction and biosorption by a highly copper resistant bacterium isolated from copper-contaminated vineyard soil

Copper is an essential but toxic heavy metal that negatively impacts living systems at high concentration. This study presents factors affecting copper bioremoval (bioreduction and biosorption) by a highly copper resistant monoculture of Pseudomonas sp. NA and copper bioremoval from soil. Seven bacteria resistant to high concentration of Cu(II) were isolated from enrichment cultures of vineyard soils and mining wastes. Culture parameters influencing copper bioreduction and biosorption by one monoculture isolate were studied. The isolate was identified by 16S rRNA gene sequence analysis as a Pseudomonas sp. NA (98% similarity to Pseudomonas putida, Pseudomonas plecoglossicida and other Pseudomonas sp.). The optimal temperature for growth was 30 °C and bioremoval of Cu(II) was maximal at 35 °C. Considerable growth of the isolate was observed between pH 5.0 and 8.0 with the highest growth and biosorption recorded at pH 6.0. Maximal bioreduction was observed at pH 5.0. Cu(II) bioremoval was directly proportional to Cu(II) concentration in media. Pseudomonas sp. NA removed more than 110 mg L^− 1 Cu(II) in water within 24 h through bioreduction and biosorption at initial concentration of 300 mg L^− 1. In cultures amended with 100 mg L^− 1, 20.7 mg L^− 1 of Cu(II) was biologically reduced and more than 23 mg L^− 1 of Cu(II) was biologically removed in 12 h. The isolate strongly promoted copper bioleaching in soil. Results indicate that Pseudomonas sp. NA has good potential as an agent for removing copper from water and soil.     

Bioleaching of metals from sewage sludge: Microorganisms and growth kinetics

Microbial leaching is one of the advantageous methods of removing heavy metals from sewage sludge, however, the microbiological aspects of this technology have not been studied. This study presents the characterization of the naturally occurring microorganisms, responsible for the metal leaching activity, in 21 different sewage sludges. The results obtained indicate that the bioleaching of metals is carried out by successive growth of less-acidophilic and acidophilic thiobacilli. Several species of less-acidophilic thiobacilli participate in the sludge acidification, but Thiobacillus thioparus is the most important species. In contrast, Thiobacillus thiooxidans seems to be the only species involved in the acidophilic group of thiobacilli. The growth kinetics of the two groups of thiobaciili was followed in five different sewage sludges. After 5 days of incubation in shake flasks, the pH of the sludge was decreased to about 2.0 and this pH decrease solubilized the toxic metals (Cd: 83–90%; Cr: 19–41%; Cu: 69–92%; Mn: 88–99%; Ni: 77–88%; Pb: 10–54%; Zn: 88–97%). The maximum specific growth rate (μ_max) for the less-acidophilic thiobacilli varied between 0.079 and 0.104 h⁻¹ and that for the acidophilic thiobacilli varied between 0.067 and 0.079 h⁻¹.     

黄铜矿与斑铜矿在酸性细菌培养基中的电化学溶解对比(英文)

采用电化学测试和X射线光电子能谱(XPS)测试分析黄铜矿与斑铜矿在酸性细菌培养基中的电化学溶解过程。斑铜矿直接氧化反应比还原反应更容易发生,但黄铜矿既难被氧化,又难被还原。斑铜矿具有更高的氧化速率,从而比黄铜矿更容易被溶解。铜蓝(CuS)是黄铜矿与斑铜矿溶解过程的中间产物。因此,斑铜矿的溶解途径主要为直接氧化过程,中间产物铜蓝(CuS)可能限制其进一步溶解。黄铜矿的溶解途径包含了还原-氧化过程,其中,黄铜矿首先被还原为与斑铜矿类似的中间产物,再进一步被氧化,并产生铜蓝(CuS),而黄铜矿的最初还原过程是其溶解过程的主要限制步骤。     

Cooperative bioleaching of chalcopyrite and silver-bearing tailing by mixed moderately thermophilic culture: An emphasis on the chalcopyrite dissolution with XPS and electrochemical analysis

In this work, the interactions between one sample of silver-bearing tailing (223 g/t silver) and chalcopyrite during bioleaching by mixed moderately thermophilic culture were investigated. Bioleaching results showed that copper can be almost totally extracted from chalcopyrite as the result of addition of the silver-bearing tailing, and silver (Ag) extraction can be significantly improved with the addition of chalcopyrite. Hence, cooperative bioleaching process of chalcopyrite and the chosen silver-bearing tailing was feasible. Ag mainly occurred as silver sulfate (Ag₂SO₄), and further work of enhancing the Ag extraction and its recovery is currently in progress. The catalytic effect of the silver-bearing tailing on chalcopyrite dissolution was investigated mainly with X-ray photoelectron spectroscopy (XPS) and electrochemical analysis. Results proved that the presence of the silver-bearing tailing enhanced the oxidation rate of chalcopyrite and also eliminated the passivation effect of polysulfide, thus resulting in an extremely high copper extraction.     

生物冶金ORP与关键工艺参数关联规则的挖掘

针对生物冶金提金率难以提高这一难题,通过深入分析生物冶金工艺,依据工艺现场实测数据库、新型数据分析方法和数据挖掘方法,得到氧化还原电位(ORP)与工艺过程可控因素间的可描述数学关系,为可控工艺参数的优化控制提供指导依据,进而提高生物冶金提金率。     

国内外铀矿石生物浸出机理及工艺应用研究现状

微生物对铀矿的浸出主要以间接作用为主,Fe2+是铀矿氧化反应的电子传递者.生物浸出铀可以减少酸用量,提供硫酸高铁代替双氧水或过氧硫酸(盐)等氧化剂,可用于多种不同的浸出方式中,强化浸出过程,改善铀浸出动力学,提高铀浸出率,有利于环境保护.铀的生物浸出工艺主要有:生物堆浸工艺、生物地浸工艺和生物槽浸工艺.     

生物淋滤技术处理城市垃圾堆肥中重金属的研究进展

阐述了生物淋滤技术的研究现状,着重介绍了生物淋滤技术用于堆肥中重金属去除的研究进展,包括微生物种群、环境条件以及堆肥产品营养组成等。优化运行条件、运用分子生物学技术对机理进行深入探讨以及建立完善的数学模型将是生物淋滤技术的发展方向。     

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。     

Use of mesophilic and thermophilic bacteria for the improvement of copper extraction from a low-grade ore

Bioleaching was examined for copper extraction from a low grade ore using mesophilic and moderate thermophilic bacteria. Five equal size columns were used for the leaching of the ore. Sulfuric acid solution with a flow rate of 3.12 L.m-2.h-1 and pH 1.5 passed through each column continuously for 90 d. In the first and the second column, bioleaching was performed without agglomeration of the ore and on the agglomerated ore, respectively. 28wt% of the copper was extracted in the first column after 40 d, while this figure was 38wt% in the second column. After 90 d, however, the overall extractions were almost the same for both of them. Bioleaching with mesophilic bacteria was performed in the third column without agglomeration of the ore and in the fourth column on the agglomerated ore. After 40 d, copper extractions in the third and the fourth columns were 62wt% and 70wt%, respectively. Copper extractions were 75wt% for both the columns after 90 d. For the last column, bioleaching was performed with moderate thermophilic bacteria and agglomerated ore. Copper extractions were 80wt% and 85wt% after 40 and 90 d, respectively. It was concluded that crushing and agglomeration of the ore using bacteria could enhance the copper extraction considerably.