Influence of the attachment of acidophilic bacteria during the oxidation of mineral sulfides

Acidophilic bacteria found in mining environments are capable of oxidising insoluble sulfide minerals. The use of these bacteria during the oxidation of various mineral sulfides has received significant commercial interest.The attachment of Thiobacillus ferrooxidans and moderately thermophilic bacteria to sulfide minerals was investigated to further understand the mechanism(s) involved in the leaching of sulfide minerals. T.ferrooxidans (DSM 583 and ATCC 23270) and four strains of moderate thermophilic bacteria, Sulfobacillus thermosulfidooxidans, (strain TH1) and Sb.acidophilus (strains THWX, ALV and YTFI) all grown on ferrous iron, sulfur and a chalcopyrite concentrate (termed chalconc) were investigated using 3 sulfide mineral systems; pyrite, a chalcopyrite concentrate (chalconc) and an arsenic containing concentrate (termed arsenoconc). The degree of attachment of all substrate-grown cells along with contact angle measurements of both minerals and cells were determined in order to evaluate the effect of the growth substrate and the hydrophobic interactions on the attachment process. The attachment of both the mesophiles and moderate thermophiles were found to be dependant on the type of growth substrate, the substrate concentration and also the type of mineral studied. Whilst sufur-grown T. ferrooxidans (DSM 583) cells exhibited a higher degree of hydrophobicity, both ferrous iron and chalconc-grown cells showed a greater degree of attachment. This suggests that hydrophobic interactions are not principally responsible for the attachment of T. ferrooxidans to mineral sutfides. However, each moderately thermophilic strain exhibited greater attachment to the mineral sulfides when cultured on either the chalconc sample or elemental sulfur and all showed greater adhesion to the pyrite and arsenoconc samples than to the chalconc sample. Separate shake flask leaching of the sulfide samples T. ferrooxidans and Sb. thermosulfidooxidans (TH1) respectively in conjunction with the results of the attachment studies suggested that the leaching of mineral sulfides was a combination of both the direct and indirect mechanisms.     

A comparative study on thermophilic and mesophilic biooxidation of ferrous iron

High temperature biooxidation of ferrous iron was studied in a batch system, using the acidophilic thermophile Acidianus brierleyi. The effect of ferrous iron initial concentration on the growth and activity of the cells was investigated. A. brierleyi was able to grow on ferrous iron at concentrations below 7.5 kg m⁻³. The values of specific growth rate and yield were 0.043 h⁻¹ and 2.2×10¹⁴ cells/kg iron respectively. At ferrous iron concentrations of 7.5 kg m⁻¹³ and higher the growth of the cells was prohibited, however the non-growing cells were able to oxidise iron. The maximum biooxidation rate of ferrous iron, 0.105 kg m ⁻³ h⁻¹, was achieved in a culture initially containing 7.5 kg m⁻³ Fe²⁺. The mesophilic iron oxidiser Thiobacillus ferrooxidans was capable of growing on ferrous iron at concentrations as high as 30 kg m⁻³. Moreover the rate of mesophilic biooxidation offerrous iron was significantly higher than that observed in the presence of A. brierleyi.     

Investigation of the attachment of Thiobacillus ferrooxidans to mineral sulfides using scanning electron microscopy analysis

Thiobacillus ferrooxidans is a facultatively aerobic bacteria which catalyses the oxidation of inorganic substrates; in particular mineral sulfides.The mechanism(s) for the oxidation of mineral sulfides is not completely understood. The direct oxidation mechanism involves the attachment of bacteria to the mineral surface. Scanning Electron Microscopy (SEM) was used to investigate the surface erosion of three mineral sulfide samples by the attachment of Thiobacillus ferrooxidans (DSM 583). The mineral samples; Pyrite, a chalcopyrite concentrate ('termed Chalconc) and a sample containing arsenopyrite and loellingite (FeAs₂) (termed Arsenoconc) were all mounted in resin blocks and following the addition of T.ferrooxidans the particles exhibited varying degrees of surface erosion. Erosion patterns on the surface of minerals from the chalconc and arsenoconc samples appeared to follow the crystallographic structure of the mineral species. However, no apparent erosion patterns were observed on the pyrite sample. In addition, elemental sulfur was found deposited on the surfaces of each mineral sample. Chalopyrite in the Chalconc sample exhibited preferential erosion compared with the pyrite and indicated the electrochemical nobility of pyrite. In addition, during the oxidation of the Arsenoconc sample, loellingite was seen to be have been significantly more oxidised than the arsenopyrite.The observations from the SEM suggested a greater involvement of the indirect oxidation mechanism which utilises the oxidant ferric iron than direct bacterial attachment.     

Studies on the mechanism and kinetics of bioleaching

The use of off gas analysis and redox potential measurement has shown that bioleaching involves at least three important sub-processes. The primary attack of the sulphide mineral is a chemical ferric leach. The role of the bacteria is to convert the iron from the ferrous to the ferric form, thereby maintaining a high redox potential.The kinetics of bacterial ferrous iron oxidation by Thiobacillus ferrooxidans and a Leptospirillum-like bacterium, and the chemical ferric leach kinetics of pyrite have both been described as functions of the ferric/ferrous-iron ratio. Thus, the chemical ferric leach of the mineral and the bacterial oxidation of the ferrous iron are linked by the redox potential, and are in equilibrium when the rate of iron turnover between the mineral and the bacteria is balanced.These rate equations have been used to predict the steady state redox potential and sulfide mineral conversion in a continuous bioleach reactor. The model successfully predicts laboratory data and is being tested against data from pilot-plant and full-scale bioleach systems. Furthermore, the model predicts which bacterial species will predominate and which mineral will be preferentially leached under specific operating conditions. Enzyme restriction analysis has shown that in pyrite-arsenopyrite bioleach reactors the dominant iron oxidizer is L. ferrooxidans, which is in agreement with the predictions of the model.     

Electrochemical investigation of wettability of sulfide minerals under conditions of flotation. I. Galena and copper sulfides

Conclusions 1. The wettability of sulfide surfaces in the presence of thiol collectors depends not only on the length of the hydrocarbon radical of the collector and the amount of collector used, but also on the nature and redox state of the sulfide mineral; this finding does not support the conclusion of Wark to the effect that the surface wettability is independent of the nature of the mineral when using thiol collectors.2. Without any xanthate, in the case of galena and chalcopyrite, an increase of the electrochemical potential by 50–70 mV from the stationary value leads to a maximum decrease of wettability and increase of natural flotability.3. In the presence of xanthate, for all of the minerals described, an increase of the electrochemical potential by 150–200 mV from the stationary value provides a means for maximizing the force of air bubble detachment.4. For copper and lead sulfides, the potential of electrochemical hydrophobization of the surface increases with increasing length of the hydrocarbon radical of the xanthate: Ethyl < butyl < amyl < hexyl.5. For galena and chalcopyrite in the region of potentials for stable sticking, the force of air bubble detachment increases exponentially with increasing length of the hydrocarbon radical of the xanthate.6. On galena, when using the higher xanthates (amyl and hexyl), a second region of air bubble sticking potentials is observed, at potentials of 0.4-1.2 V.This work was performed with the support of the Russian Fundamental Research Fund as a part of Project No. 95-05-14180, "Theoretical and experimental modeling of formation of hydrophobic coatings on the surface of sulfide minerals under conditions of flotation."Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 73–80, January–February, 1996.     

混合黄药与硫化矿作用对其降解规律的影响

对几种不同的单一/混合黄药在自然条件下及与硫化矿作用后的降解规律进行了分析研究,考察了黄药浓度、不同比例的混合黄药及其与硫化矿作用对黄药降解的影响,并建立了相应的降解动力学方程。结果表明,在自然降解条件下,混合黄药中不论提高乙黄还是戊黄的比例,与单一黄药的自然降解相比,其更难降解;提高混合黄药中戊基黄药的比例,能加快其与硫化矿作用后的自然降解速率。与硫化矿作用后的混合黄药,都明显大于在自然条件下黄药的降解速率,与含硫低的硫化矿作用后的降解速率高于与含硫高的硫化矿作用后的。不同浓度的单一黄药、不同比例的混合黄药自然条件下及与硫化矿作用后的降解过程基本符合一级动力学方程。      

黄铜矿与磁黄铁矿浮选分离行为及机理研究

通过黄铜矿与磁黄铁矿的单矿物浮选试验,研究矿浆pH、捕收剂丁黄药、抑制剂石灰对其浮选行为的影响。利用红外光谱、循环伏安测试技术,研究其浮选分离的机理。单矿物浮选试验结果表明黄铜矿和磁黄铁矿浮选分离的最佳条件为pH=10,丁黄药浓度为20 mg/L,石灰浓度为300 mg/L。红外光谱测试结果表明丁黄药在矿物表面氧化生成双黄药并通过化学吸附吸附在矿物表面,石灰在磁黄铁矿表面生成氢氧化钙和硫酸钙组成的钙膜。循环伏安测试表明在未添加丁黄药时黄铜矿表面氧化生成疏水的硫单质和硫化铜,磁黄铁矿表面会生成亲水的氢氧化物。     

弱碱性介质中提高永平铜矿铜金银回收率的研究

T 2K捕收剂与黄铜矿形成正配键和反馈键的能力很强,而与黄铁矿的作用弱。工业试验结果表明,T 2K捕收剂对硫化铜矿物具有优异的捕收能力和选择性,能在弱碱性介质中实现铜的优先浮选,克服黄药混浮工艺铜硫分离时高碱对部分铜、金、银的抑制。与黄药混浮工艺相比,T 2K全优先浮选工艺使铜精矿品位提高0 42%,铜回收率提高2 54%;硫精矿品位提高1 37%,硫回收率提高4 17%;铜精矿中金银回收率也分别提高3 73%和5 73%。     

某复杂多金属铅锌铁矿石工艺矿物学研究

为更好地开展矿石的选矿工艺研究，对某复杂多金属磁铁矿石进行了工艺矿物学研究。结果表明：矿石铁、锌品位分别为59.94%和2.93%。矿石中的主要矿物为磁铁矿，少量其他铁矿物赤铁矿、褐铁矿（包括针铁矿）为成矿后期的次生氧化物；金属硫化物主要有闪锌矿、黄铁矿、磁黄铁矿，黄铜矿、方铅矿较少；脉石矿物主要为普通角闪石，透闪石少量，此外还有少量绿帘石、绿泥石、云母类矿物等。矿石中的铁主要以磁铁矿的形式存在，占总铁的87.82%，锌、铅氧化程度均较高，硫化锌、氧化锌分别占总锌的55.29%和42.32%，硫化铅、氧化铅分别占总铅的39.39%和43.94%。矿石构造为黑色致密块状构造，多呈自形-半自形粒状连晶结构，各种矿物间形成交代结构、交代残余结构等。矿石中的有用矿物磁铁矿、闪锌矿的嵌布粒度与闪石类矿物相差不大，磁铁矿、闪锌矿及其与其他矿物间的嵌布关系较复杂，单体解离较困难。为了确保铁精矿含硫不超标，在弱磁选回收磁铁矿前需采用浮选工艺尽可能脱除硫化矿物。     

以羟乙基纤维素为抑制剂浮选分离铜硫

为检验铜硫分离新型抑制剂HEC的有效性,并了解HEC作用效果的影响因素,以丁基黄药为捕收剂,对黄铜矿、黄铁矿纯矿物进行了浮选试验,并以HEC为抑制剂进行了实际矿物浮选试验。结果表明：①丁基黄药对黄铜矿的捕收能力强于黄铁矿,且几乎不受矿浆pH值的影响,在无抑制剂的情况下,高碱环境可抑制黄铁矿的上浮。②HEC可用于铜硫分离,用量为200 mg/L时可显著抑制黄铁矿,但对黄铜矿的抑制能力很弱。③抑制剂HEC适宜在pH=7的环境下浮选分离黄铜矿与黄铁矿的人工混合矿。④在分选内蒙古某铜硫矿石时,以HEC为铜硫分离黄铁矿的抑制剂,可获得铜品位为23.21%、铜回收率为81.75%的铜精矿,以及硫品位为13.20%、硫回收率80.83%的硫精矿,较好地实现了铜硫分离。     

In situ investigation and visualisation of microbial attachment and colonisation in a heap bioleach environment: The novel biofilm reactor

In this paper, the development of a novel means of investigating the attachment and subsequent biofilm formation of mineral bioleaching micro-organisms to mineral surfaces in situ is described. The protocol was developed to investigate the interactions of micro-organisms with sulfide minerals and low-grade chalcopyrite ore under conditions resemblant of a bioheap environment. The method makes use of a biofilm reactor in which thin sections of mineral ore are mounted. The reactor is operated as a continuous flow-through system. Attachment of pure and mixed cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum is assessed. The technique allows for the investigation of microbial ecology with special regard to microbe–mineral attachment, site and mineral specific associations of micro-organisms and spatial organisation of microbial communities present through the use of fluorescent microscopy techniques. Preliminary fluorescent in situ hybridisation (FISH) analysis of the attachment of L. ferriphilum and A. ferrooxidans to massive chalcopyrite sections, as well as to low-grade chalcopyrite containing ore sections is presented. In the case of both low-grade and massive sulfide mineral samples, attachment of mixed micro-colonies was observed in regions where surface defects were prevalent. In low-grade samples, preferential attachment was observed in regions where sulfide minerals were present. The density of the attached micro-colonies increased with an increase in contacting time (from 20, 72 and 96 h) and was indicative of an actively growing mono-layered biofilm.     

草分枝杆菌在硫化矿物表面的选择性吸附规律

研究了草分枝杆菌在黄铁矿、方铅矿、黄铜矿和闪锌矿表面的吸附情况。试验结果表明，草分枝杆菌可以在4种硫化矿物表面发生明显的选择性吸附，在黄铁矿表面吸附情况较好，而在其他3种矿物表面则较差；pH值是影响草分枝杆菌在4种硫化矿物表面发生选择性吸附的关键因素，在pH为4～12之间时选择性吸附现象明显；矿浆浓度在6g／L以上和菌液浓度在0．5—4g／L之间有利于选择性吸附；温度对吸附影响不大；扫描电镜结果显示，草分枝杆菌细胞外膜表面的荚膜是重要的吸附位。研究结果表明，可以在浮选分离中利用草分枝杆菌抑制黄铁矿而优先浮选其余3种硫化矿物。     

L-半胱氨酸与NaHS组合抑制剂在铜钼分离浮选中的应用及其机理研究

针对目前铜钼分离中黄铜矿抑制剂用量大、环境污染严重等问题,采用L-半胱氨酸(L-CYS)与NaHS的组合作为抑制剂,对黄铜矿和辉钼矿浮选分离进行了研究.在黄药体系下,分别考察了单一抑制剂L-CYS、NaHS和组合抑制剂对单矿物及人工混合矿浮选效果的影响.结果 表明,在pH=8,药剂配比为1∶30,药剂用量为310 mg...     

云南大红山铜矿化学浸出研究

以云南大红山铜矿的铜精矿为研究对象,分别考查其在稀硫酸、硫酸高铁、硫酸亚铁三种介质中的溶解情况。通过试验研究发现,在pH1.0~2.0、常温常压条件下,该铜精矿基本不溶于稀硫酸溶液和硫酸高铁溶液,而在硫酸亚铁溶液中该铜精矿溶解速率明显加快,但浸出后期有明显的钝化现象。浸渣XRD和SEM分析表明,硫酸亚铁溶液浸出后浸出渣有单体硫物相存在,而且矿物表面有明显的"腐蚀坑",能谱分析也证实矿物表面有硫元素过量的情况。另外,硫酸亚铁溶液浸出过程中体系酸耗明显增加,这一方面是由于Fe2+离子氧化造成的,另一方面矿石的大量溶解也增加了酸耗量。     

巯基乙酸抑制硫化矿物的电化学机理研究

研究了巯基乙酸（TGA）对硫化矿物电极电位和动电位的影响。试验表明巯基乙酸对黄铁矿、方铅矿和黄铜矿有抑制作用,对毒砂和亲锌矿没有抑制作用。电化学测试表明巯基乙酸对表面覆盖有捕收剂膜的硫化矿物动电位影响较小,能够显降低硫化矿物的静电位,它对硫化矿物抑制的电化学机理为当硫化矿物的静电位EMS低于黄药氧化为双黄药的可逆电位EX^-/X2时,硫化矿物表面双黄药不稳定被还原,从而降低了可浮性;反之,双黄药保持稳定,不被抑制。用巯基乙酸实现两种硫化矿物浮选分离的电化学条件为：EMS1＜EX^-X2(EX^-/GPbX2）＜EMS2。     

云南迪庆氧硫混合铜矿选矿试验研究

我国氧硫混合铜矿资源丰富,对这类铜矿进行高效选矿富集具有重要意义.云南迪庆地区有大量氧硫混合铜矿,铜品位0.67％,氧化率17.37％,含铜矿物主要为黄铜矿、斑铜矿和孔雀石.采用硫化—黄药浮选法对该矿石进行选矿,分析了活化剂和捕收剂的作用机理.研究了磨矿细度、药剂制度及粗精矿再磨等对浮选指标的影响.结果表明,以石灰为抑...     

The effect of heavy oxidation upon flotation and potential remedies for Merensky type sulfides

Surface oxidation of sulfide minerals, such as that found in the regions of a sulfide ore body near the water table, can have a significant impact upon flotation. This theme has been explored for Merensky ore type sulfides where an ore containing pyrrhotite, pentlandite and chalcopyrite was thermally oxidised and the role of potential remedies investigated. Back-scattered scanning electron microscope images are presented showing the oxidation layer which formed in the mineral surfaces. These oxidation layers were depleted in both sulfur and iron with incorporated oxygen. Flotation recovery rapidly decreased with increasing oxidation, particularly after 27 days and reached a plateau after 50 days. Up to 27 days, this effect could be partially overcome with higher collector additions. Oxidation had more impact upon the finer size fractions, particularly for pyrrhotite. For more heavily surface oxidised samples, ultrasonic treatment prior to collector conditioning was found to improve flotation recoveries. This treatment had the greatest effect upon chalcopyrite particles. Sulfidisation was successful in restoring the flotation recovery of the heavily oxidised sulfide minerals. Longer sulfidisation conditioning times were not conducive to good flotation recoveries of both oxidised pyrrhotite and pentlandite due to oxidation of the freshly formed sulfide surfaces. For maximum flotation recoveries of oxidised pyrrhotite, pentlandite and chalcopyrite, different sulfidisation conditions are indicated. It appears likely that in a mineral processing operation treating oxidised Merensky type ores, two stages of sulfidisation employing different conditions would be required.     

酸性体系下硫化矿浮选因素的交互影响研究

在酸性体系中,碱性脉石矿物溶解受磨矿细度、酸用量的影响明显,矿物溶解改变了体系pH值,使可溶性离子增加,影响了硫化矿物的浮选。为探究酸性体系下卡林型金矿浮选硫化矿过程中的影响因素及其交互作用,在单因素试验的基础上进行了响应曲面优化试验,并分析了磨矿细度、H₂SO₄用量、丁基黄药用量三因素的交互作用对浮选的影响。研究结果表明：最优的浮选指标的药剂制度为磨矿细度-0.075 mm粒级占比90%,H₂SO₄用量为800 g/t,水玻璃用量为400 g/t, CuSO₄用量为300 g/t,丁基黄药用量为200 g/t,松醇油用量为75 g/t。单因素试验可获得硫回收率为75.28%,品位为10.46%,金品位为6.73%,回收率为58.19%的选矿指标。探究的三种因素对硫精矿回收率的影响大小为：磨矿细度>丁基黄药用量>H₂SO₄用量;对硫精矿品位的影响大小为：丁基黄药用量>磨矿细度>H₂SO     

The effect of temperature and culture history on the attachment of Metallosphaera hakonensis to mineral sulfides with application to heap bioleaching

Temperatures in excess of 60 °C are required for efficient bioleaching of chalcopyrite. Within heaps, colonisation of the mineral with thermophilic archaea is important in reaching and maintaining these high temperatures. The effect of temperature and culture history on the attachment of Metallosphaera hakonensis, an extreme thermophilic acidophile identified as a key player in heap bioleaching, to sulfide concentrates and low-grade ore was investigated in shake flasks and packed beds. Attachment studies were conducted at 25 °C, 45 °C and 65 °C. The results show a clear relationship between increasing temperature and attachment efficiency for both suspended and packed bed systems. Attachment at 25 °C was low. Increasing the temperature to 45 °C improved attachment efficiency by between 50% and 100% while a further increase to 65 °C improved attachment by an additional 20-50%. Cells cultured on elemental sulfur as energy source prior to contacting showed 1.3 times greater affinity for the mineral concentrate than those cultured on sulphide mineral concentrates or ferrous sulphate. In contrast to previous studies using mesophilic organisms the selective attachment of Metallosphaera to sulfide minerals, relative to gangue, was less pronounced. Attachment efficiency was lower in the packed bed system which more closely mimicked flow through a heap. The cell surface properties surface charge and hydrophobicity as well as metabolic activity were investigated to provide insight into the observed phenomena. The data suggest that retention of thermophiles within the heap could be enhanced by a secondary inoculation following elevation of the temperature above 40 °C by the mesophilic pioneer species.     

提高德兴铜矿高氧化率矿石铜金钼回收率的研究

对新型Mac-12 进行了普遍化微扰理论研究, 结果表明,Mac-12中反应中心硫原子给电子的能力较弱, 而接受反馈电子的能力很强, 其对提供反馈电子能力较弱的黄铁矿的捕收能力弱, 而对易提供反馈电子的黄铜矿的捕收能力强。工业试验结果表明,Mac-12对硫化铜矿物和氧化铜矿物具有强亲固能力, 与传统黄药工艺相比, Mac-12与少量丁黄药工艺混用可降低铜硫浮选分离中的石灰用量, 铜精矿中铜品位提高0.93个百分点, 铜回收率提高1.03 个百分点;金品位提高1.29 g/t, 金回收率提高7.16 个百分点;钼品位提高0.0293 个百分点, 钼回收率提高3.90个百分点。Mac-12已工业应用于德兴铜矿, 取得了较好的经济效益。