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1.
周丽  李和平  徐丽萍 《矿物岩石》2006,26(1):110-115
金属硫化物矿物之间的原电池反应对于酸性矿山排水的形成、硫化物矿床的次生富集作用、地球电化学勘探以及湿法冶金过程等都有很重要的影响。通过改变溶液中氧化剂组分F e3 的浓度、pH值、溶液的流动状况以及溶液的盐度(如N a2SO4的浓度),采用精密的电流计和电位计,对作为阳极的黄铁矿与作为阴极的方铅矿所形成的原电池反应的电流密度和整个原电池的混合电位进行研究,结果表明:溶液中[F e3 ],pH值以及溶液的流动状况对黄铁矿和方铅矿之间原电池反应的影响很大,而溶液的盐度对反应的影响不是很显著。实验还发现,当黄铁矿电极表面存在微小裂纹时,其电极电位可降低至同条件下方铅矿的电极电位以下。这一实验结果在混合电位理论和Bu tler-V o lm er方程中得到了理论上的解释。  相似文献   

2.
When galvanic interactions between pyrite and chalcopyrite occur in solution, pyrite, with the higher rest potential, acts as a cathode and is protected whereas chalcopyrite, with the lower rest potential, acts as an anode and its oxidation is increased. In this work a three-electrode system was used to investigate the corrosion current density and mixed potential of a galvanic cell comprising a pyrite cathode and a chalcopyrite anode in a flowing system. The results showed that with increasing concentration of ferric ion in the solution, with increasing acidity, and with increasing flow rate of the solution, the corrosion current density increased and the mixed potential of the galvanic cell became more positive. These experimental results are of direct significance to the control of environmental pollution in mining activity. By using the galvanic model, mixed potential theory, and the Butler–Volmer equation, the experimental results were explained theoretically.  相似文献   

3.
Managing mine water that has been contaminated with metal sulfide minerals due to galvanic corrosion is becoming an increasingly important environmental problem. Here, galvanic corrosion was investigated by studying galvanic interactions between pyrite–chalcopyrite and pyrite–galena in flowing mediums such as mine discharge water and flowing rainwater. The results showed that the corrosion current density of pyrite–galena is greater than that of pyrite–chalcopyrite under identical conditions. The corrosion current density of the galvanic cell tends to increase with increasing concentrations of strongly oxidizing ions (e.g., Fe3+) in the flowing medium, whereas the existence of non-oxidizing and non-reducing ions (e.g., Na+) have no obvious influence on the galvanic cell. In addition, the corrosion current density increases with increasing flow rate. Using the galvanic model, mixed potential theory and Butler–Volmer equation, the experimental results were explained theoretically. Because these experiments were performed under conditions very similar to those seen in mine discharge water and flowing rainwater, these results have direct implications for the future management and control of environmental pollution from mining operations.  相似文献   

4.
黄铁矿表面的扫描隧道显微镜研究   总被引：3，自引：0，他引：3  
为了探讨硫元素在煤中的赋存，对煤硫元素的主要载体黄铁矿的表面进行了扫描隧道显微镜研究，在硅油保护下得到了黄铁矿表面高分辨率图象。根据黄铁矿晶体结构的几何分析，所观察到的是黄铁矿｛２２０｝表面的原子分布，黄铁矿的能带结构资料及前人在这方面的研究均表明，用扫描隧道显微镜应首先观察到黄铁矿表面的铁原子，但作者首先观察到的却是黄铁矿表面的硫原子，此外，作者根据所获得的实验结果认为。无论是在｛２１０｝文向还  相似文献   

5.
The rate of decomposition of potassium ethyl monothiocarbonate has been determined at pH values between 5 and 10, and its molar absorptivity at 221 nm determined to be 1.24 · 104mol/cm.A novel apparatus for use in the study of reactions between sulphide minerals, oxygen and thiol reagents has been developed, and applied to the reactions of potassium ethyl xanthate with galena and pyrite. It has been shown that both minerals react with ethyl xanthate in the presence of oxygen or oxidation products to form soluble as well as adsorbed xanthate derivatives. The soluble derivative has been identified to be ethyl monothiocarbonate. The adsorbed xanthate at a galena surface, unlike that at a pyrite surface, is gradually converted to a soluble monothiocarbonate under the action of dissolved oxygen. The effect of variables such as pH, the initial xanthate and oxygen concentrations, and the initial state of oxidation of the mineral on the formation of monothiocarbonate has been studied. It is tentatively proposed that an intermediate adsorbed mixed xanthate-hydroxide species is involved in the formation of monothiocarbonate at both galena and pyrite surfaces.The significance of the formation of monothiocarbonate to flotation practice is discussed briefly. The formation of monothiocarbonate represents a wastage of reagent, and could lead to a decrease in flotability of xanthated galena with time of exposure to aerated solutions.  相似文献   

6.
Acid mine drainage (AMD) is a widespread environmental problem associated with working and abandoned mining operations. It results from the microbial oxidation of pyrite in the presence of water and air, affording an acidic solution that contains toxic metal ions. Pyrite microencapsulation, utilizing silica coating, is a novel approach for controlling AMD that has been shown to be very effective in controlling pyrite oxidation. The roles of the solution pH and silica concentration in the formation mechanism for the AMD-preventing coating were investigated. A silica coating can be formed from silica solution at pH 7, at which the amount of Fe eluted from pyrite into the solution is small. No coating was formed at other pH values, and the amounts of eluted Fe were larger than at pH 7, especially at pH 11. The silica coating forms from 2,500 to 5,000 mg/L silica solutions, but not from 0 or 1,000 mg/L silica solutions. The coating formation rate was slower in the 2,500 mg/L silica solution than in the 5,000 mg/L silica solution. The formation of silica coating on pyrite surfaces depends on three main steps: formation of Fe(OH)3 on the surface of pyrite, reaction between Fe(OH)3 and silicate in the solution on the pyrite surface, and growth of the silica layer on the first layer of silica. The best pH condition to enable these steps was around 7, and the silica coating formation rate can be controlled by the concentration of silica.  相似文献   

7.
The galvanic effect between the main associated mineralogical phases in a mineral sphalerite concentrate was evaluated using an alternative methodology. Comparative voltammetric studies were performed between high purity galena mineral (94.65%) and sphalerite concentrate (content of 78.11% sphalerite, ZnS; 13.64% galena, PbS; 0.57% chalcopyrite, CuFeS2; 0.41% cadmium sulfide, CdS; and 0.11% arsenopyrite, FeAsS) using carbon paste electrodes (CPE) in order to identify galvanic interactions that affect their reactivity. The electrolyte was an aqueous solution of 0.1 M NaNO3 (pH 6.5). The results showed that, in sphalerite concentrate, the electrochemical reactivity of the galena was diminished and displaced to more positive potentials with respect to the high purity galena mineral response. This behavior can be attributed to the galvanic protection offered by the sphalerite on the galena, thereby avoiding its free oxidation. On the other hand, sphalerite oxidation was diminished by the formation of a passive products film that is dissolved to more positive potentials which provokes oxidation of other minerals like CuFeS2, (Zn,Cd)S and FeAsS present in a minor proportion in the sphalerite concentrate.  相似文献   

8.
The ability of O-isopropyl-N-ethyl thionocarbamate (IPETC), O-isobutyl-N-ethoxycarbonyl thionocarbamate (IBECTC) and butyl ethoxycarbonyl thiourea (BECTU) collectors to increase the flotation of the sulphide minerals, chalcopyrite, galena and pyrite, has been studied. For each collector, the flotation characteristics of these minerals, flotation rate constant and flotation recovery maximum, have been calculated from the flotation data and compared as a function of pH and collector concentration. Overall, the flotation performance of these collectors is stronger for chalcopyrite than for galena and pyrite. Flotation increases with collector concentration and decreasing pH values. For chalcopyrite, the collector performances of BECTU are slightly better than those of IPETC but far superior to those of IBECTC, especially at high pH values or at low collector concentrations. The flotation performance of these collectors has been shown to be in good agreement with the amount of collector adsorbed at the mineral surface. The affinity of BECTU for the various minerals has been calculated using a multilayer adsorption model.  相似文献   

9.
Several mechanisms have been proposed to explain the interactions between proteins and mineral surfaces, among them a combination of electrostatic, stereochemical interactions and molecular recognition between the protein and the crystal surface. To identify the mechanisms of interaction in the lysozyme-calcium carbonate model system, the effect of this protein on the precipitation kinetics and morphology of calcite crystals was examined. The solution chemistry and morphology of the solid were monitored over time in a set of time-series free-drift experiments in which CaCO3 was precipitated from solution in a closed system at 25°C and 1 atm total pressure, in the presence and absence of lysozyme. The precipitation of calcite was preceded by the precipitation of a metastable phase that later dissolved and gave rise to calcite as the sole phase. With increasing lysozyme concentration, the nucleation of both the metastable phase and calcite occurred at lower Ωcalcite, indicating that lysozyme favored the nucleation of both phases. Calcite growth rate was not affected by the presence of lysozyme, at least at protein concentrations ranging from 0 mg/mL to 10 mg/mL.Lysozyme modified the habit of calcite crystals. The degree of habit modification changed with protein concentration. At lower concentrations of lysozyme, the typical rhombohedral habit of calcite crystals was modified by the expression of {110} faces, which resulted from the preferential adsorption of protein on these faces. With increasing lysozyme concentration, the growth of {110}, {100}, and finally {001} faces was sequentially inhibited. This adsorption sequence may be explained by an electrostatic interaction between lysozyme and calcite, in which the inhibition of the growth of {110}, {100}, and {001} faces could be explained by a combined effect of the density of carbonate groups in the calcite face and the specific orientation (perpendicular) of these carbonate groups with respect to the calcite surface. Overgrowth of calcite in the presence of lysozyme demonstrated that the protein favored and controlled the nucleation on the calcite substrate. Overgrowth crystals nucleated epitaxially in lines which run diagonal to rhombohedral {104} faces.  相似文献   

10.
The Bunker Hill Mine in Idaho's Coeur d'Alene mining district produces approximately 10 m3/minute of acid water containing high concentrations of heavy metals. Field and laboratory studies indicate that much of the acid water is produced in a single ore body in the upper part of the mine. The ore of this body contains mainly sphalerite, galena, and pyrite in a siderite-quartz gangue. Ground water recharges this ore body through a near-vertical zone of high permeability, which is the result of mining by the caving technique. Ore samples from the caving area contained oxidized forms of iron and produced acid in a laboratory leaching test. Leaching experiments with several ore samples from the mine also indicated that the ratio of pyrite to calcite in the samples strongly controlled the resultant pH values. Oxidation of pyrite to sulfuric acid and compounds of iron is apparently responsible for the production of acid water in the mine. In contrast, dissolution of calcite in water results in a basic solution, with pH around 8.3, that can neutralize the acid produced by the oxidation process. Methods for prevention of acid mine drainage in this and other similar mines are noted.  相似文献   

11.
The Lavrion ore district contains carbonate-replacement and vein-type Pb–Zn–Ag deposits as well as low-grade porphyry Mo, Cu–Fe skarn, and minor breccia-hosted Pb–Zn–Cu sulfide mineralization. These ore types are spatially related to a Late Miocene granodiorite intrusion (7 to 10 Ma), and various sills and dikes of mafic to felsic composition. Samples of sphalerite and pyrite from the Ilarion carbonate replacement deposit, and galena from Vein 80 (vein-type mineralization) in the Adami deposit show heterogeneous Re–Os values. These values were partially disturbed by hydrothermal activity associated with the formation of hydrothermal veins (e.g., Vein 80). A plot of initial 187Os/188Os versus 1/Oscommon ratios for pyrite and sphalerite from the Ilarion deposit form a mixing line (r2?=?0.78) between high concentration crustal-like and low concentration mantle-like end-members, or two crustal end-members one of which was more radiogenic than the other. Based on the Re–Os systematics and previously published geological and geochemical evidence, the most plausible explanation for the Re–Os isotope data is that ore-forming components were derived from mixed sources, one of which was a radiogenic crustal source from schists and carbonates probably near intrusion centers and the other, intrusive rocks in the district that are less radiogenic. Although the Re and Os concentrations of galena from Vein 80 are above background values they cannot be used as a chronometer. However, the results of the current study suggest that although pyrite, sphalerite, and galena are poor geochronometers in this ore deposit, due to partial open-system behavior, they still yield valuable information on the origin of the source rocks in the formation of bedded replacement and vein mineralization in the Lavrion district.  相似文献   

12.
《Applied Geochemistry》2006,21(9):1469-1481
The removal of chromate from aqueous solutions, using finely ground pyrite and biotite, was investigated by batch experiments. The kinetics and mechanism of chromate reduction are discussed here. Chromate reduction by pyrite was about 100 times faster than that by biotite, and was also faster at pH 3 than 4. When pyrite was used, more than 90% of the initial chromate was reduced within 4 h at pH 4, and within 40 min. at pH 3. However, with biotite more than 400 h was required for the reduction of 90% of the initial chromate. The results indicate that the rate of chromate reduction was strongly depending on the amount and dissolution rate of the Fe(II) in the minerals. The reduction of chromate at pH 4 resulted in the precipitation of (Cr, Fe)(OH)3(s), which is believed to have limited the concentrations of dissolved Cr(III) and Fe(III) to less than the expected values. When biotite was used, the amounts of decreased Fe(II) and reduced Cr(VI) showed no stoichiometric relationship, which implies that not only was there chromate reduction by Fe(II) ions in the acidic solution, but also heterogeneous reduction of Fe(III) ions by structural Fe(II) in biotite. However, the results from a series of the experiments using pyrite showed that the concentrations of the decreased Fe(II) and the reduced Cr(VI) were close to the stoichiometric ratio of 3:1. This was because the oxidation of pyrite rapidly created Fe(II) ions, even in oxygenated solutions, and the chromate reduction by the Fe(II) ions was significantly faster than the Fe(II) ion oxygenation. When compared with the experimental sets controlled at an initial pH of 3, the pH of the biotite batch, which was not controlled, increased to 3.4. Because of the increase in the pH, Cr(VI) was not completely removed, and 25% (1.2–1.3 mg/L Cr(VI)) of the initial concentration remained for up to 1000 h. The pH increase is, in most cases, caused by the hydrolysis of clay minerals. However, in the pyrite batches, there was no difference in the variations of the chromate reduction in relation to the pH control. There was also no difference in the capacity and rate of Cr(VI) reduction in 0.01 M NaCl or Na2SO4 solutions. In the 0.01 M NaH2PO4 solution pyrite experiment, the Cr(VI) was not completely removed, despite the maintenance of the pH at 3. The dominant Fe species was about 10 mg/L Fe(III) and few Fe(II) ions existed in solution. The Fe phosphate (Fe3(PO4)2 or FePO4) coatings on the surface of pyrite prevented access of O2 or Cr(VI). Therefore, the surface coatings are likely to have caused the deterioration of the Cr(VI) reduction capacity in the NaH2PO4 solution.  相似文献   

13.
The effects of injecting oxic water from the New York city (NYC) drinking-water supply and distribution system into a nearby anoxic coastal plain aquifer for later recovery during periods of water shortage (aquifer storage and recovery, or ASR) were simulated by a 3-dimensional, reactive-solute transport model. The Cretaceous aquifer system in the NYC area of New York and New Jersey, USA contains pyrite, goethite, locally occurring siderite, lignite, and locally varying amounts of dissolved Fe and salinity. Sediment from cores drilled on Staten Island and western Long Island had high extractable concentrations of Fe, Mn, and acid volatile sulfides (AVS) plus chromium-reducible sulfides (CRS) and low concentrations of As, Pb, Cd, Cr, Cu and U. Similarly, water samples from the Lloyd aquifer (Cretaceous) in western Long Island generally contained high concentrations of Fe and Mn and low concentrations of other trace elements such as As, Pb, Cd, Cr, Cu and U, all of which were below US Environmental Protection Agency (USEPA) and NY maximum contaminant levels (MCLs). In such aquifer settings, ASR operations can be complicated by the oxidative dissolution of pyrite, low pH, and high concentrations of dissolved Fe in extracted water.  相似文献   

14.
《Geochimica et cosmochimica acta》1999,63(19-20):3171-3182
The oxidation rate of pyrite at pH 7, 25°C and at constant partial pressure of oxygen (0.21 and 0.177 atm) was measured in the presence of the Fe(III)-chelators NTA, oxalate, leucine, EDTA, citrate, IDA and the Fe(III)-reductant ascorbic acid. With the exception of leucine and EDTA, non-reducing Fe(III)-chelators increased the oxidation rate relative to the reference state of formation of the Fe(OH)2+ complex at pH 7. The rate increase was proportional to the logarithm of the conditional stability constant of the ligands for the complexation of Fe3+. No effect on the oxidation rate was observed in the presence of EDTA, which shifted the redox potential of the redox couple Fe2+/Fe3+ to a value below that in the absence of any ligand at pH 7. Ascorbic acid decreased the pyrite oxidation rate by a factor of 5 at ascorbic acid concentrations between 10−4 and 10−2 mol L−1. Comparison of the rate constants for the oxidation of ascorbic acid by surface bound Fe(III) in the absence and presence of pyrite shows that the pyrite surface accelerates this reaction by a factor of 10. The oxidation of both pyrite and ascorbic acid is of fractional order with respect to ascorbic acid (HAsc): rpy=0.55 c(HAsc)−0.35 rHAsc=3.6 c(HAsc)0.59. Both the results from experiments with Fe(III)-chelating ligands and the Fe(III)-reductant, suggest a very efficient interference in the electron cycling between Fe(II) and Fe(III) at the pyrite surface. The interference seems to be mainly related to the reductive side of the iron cycling. It is therefore concluded that the electron transfer between ferric iron and pyritic sulfur limits the pyrite oxidation rate at pH 7.  相似文献   

15.
Gold deposits at El Sid are confined to hydrothermal quartz veins which contain pyrite, arsenopyrite, sphalerite and galena. These veins occur at the contact between granite and serpentinite and extend into the serpentinite through a thick zone of graphite schist. Gold occurs in the mineralized zone either as free gold in quartz gangue or dissolved in the sulfide minerals. Ore-microscopic study revealed that Au-bearing sulfides were deposited in two successive stages with early pyrite and arsenopyrite followed by sphalerite and galena. Gold was deposited during both stages, largely intergrown with sphalerite and filling microfractures in pyrite and arsenopyrite.Spectrochemical analyses of separated pyrite, arsenopyrite, sphalerite and galena showed that these sulfides have similar average Au contents. Pyrite is relatively depleted in Ag and Te. This suggests that native gold was deposited in the early stage of mineralization. Arsenopyrite and galena show relatively high concentrations of Te. They are also respectively rich in Au and Ag. Tellurides are, thus, expected to be deposited together with arsenopyrite and galena.  相似文献   

16.
The adsorption of ethyl, propyl and butyl xanthates on pyrite has been studied through electrokinetics, batch adsorption tests, and quantification of Fe2+ ions in solution. Adsorption isotherms for the three alkyl xanthates indicate that their adsorption to dixanthogen produces Fe2+ ions in solution and decreases the pyrite zeta potential negatively. It seems that the oxidation reaction of xanthates to dixanthogen on pyrite is coupled with the reduction reaction of surface-ferric hydroxide to ferrous ions, leading to the dissolution of hydrophilic ferric hydroxide and growth of hydrophobic dixanthogen on the surface of pyrite. Flotation of pyrite is presented as a function of pH using various ethyl xanthate concentrations. The floatability results are explained in terms of the surface coverage relationship between ferric hydroxide and dixanthogen, which is pH dependent.  相似文献   

17.
山东烟台南张家金矿黄铁矿的标型特征   总被引：8，自引：1，他引：8  
通过对烟台南张家金矿黄铁矿的形态、成分和热电性标型的分析和测试 ,对金矿的深部成矿远景进行了评价。南张家金矿黄铁矿的形态以 { 1 0 0 } +{ 2 1 0 }为主 ,反映了成矿溶液中硫浓度较高 ,金具有明显的亲硫性。黄铁矿成分贫 Co、Ni,富 As、Hg。热电导型主要为 P型 ,表明所采矿体为浅部矿 ,深部仍有远景。同时 ,黄铁矿 P型导型出现率由上到下变化很小 ,成矿环境稳定 ,显示矿体向下继续延伸。另外 ,矿石中的黄铁矿与磁山二长花岗岩中的副矿物黄铁矿在形态、成分和热电性上具相似性 ,表明二者具有继承关系 ,佐证了金矿的形成与岩体的演化有关。  相似文献   

18.
The role of municipal solid waste (MSW) landfill leachate on the genesis of minor amounts of pyrite associated with gypsum in an otherwise predominantly evaporitic sequence was studied in geological and geochemical terms. The potential association between landfill leachate and the conditions required for bacterial reduction of sulfate and fixation of H2S as pyrite were examined. The lithological column was generally found to contain little or no Fe. The δ34S values for sulfates were consistent with previously reported data; however, the measured δ18O values were slightly higher. Sulfides disseminated in the marl/lutite exhibited higher δ34S values (≈−8‰) than gypsum-coating pyrite crystals (δ34S < −30‰). Dissolution of gypsum to sulfate and the supply of metabolizable organic matter and Fe required for H2S fixation as sulfides may have originated from landfill leachate. Intermittent availability of leachate, a result of the precipitation regime, can facilitate sulfur disproportionation and lead to fractionations as high as   相似文献   

19.
筲箕湾铅锌矿床位于黔西北铅锌成矿区中部,为该区铅锌矿床中的又一典型代表,其金属资源量（Pb＋Zn）超过20万t。本文利用电感耦合等离子体质谱（ICP-MS）分析了不同类型矿石中原生矿石硫化物（黄铁矿、闪锌矿和方铅矿）中分散元素含量,结果显示除Cd含量较高外,Ga、In、Se、Tl和Re的富集程度均较低。不同分散元素在硫化物中表现出不同的富集规律,表现为Ga含量在闪锌矿中最高,黄铁矿次之,方铅矿最低;方铅矿中Tl含量高于闪锌矿,黄铁矿最低;Cd在闪锌矿中含量最高,方铅矿次之,黄铁矿最低;从黄铁矿→方铅矿→闪锌矿In含量依次升高;Re含量表现出在闪锌矿中最高,黄铁矿次之,方铅矿最低;Se富集程度从黄铁矿→方铅矿→闪锌矿依次升高。Ga、In和Re在不同颜色闪锌矿中富集程度相似,而Se、Cd和Tl则相对富集在棕色闪锌矿中。统计发现闪锌矿中Zn含量与Cd、Ga含量不呈类质同象的负相关特征,而其中的Fe含量与Cd、Ga含量间表现出曲线相关或负相关特征,暗示Cd、Ga可能是通过替代先进入闪锌矿中的Fe而占据其晶格,这可能是一种新的机制。闪锌矿Ga、Cd、In含量及Ga/In、Zn/Cd比值等参数,指示筲箕湾铅锌矿床形成于中-高温条件,其矿床成因类型与沉积-改造型相似。  相似文献   

20.
利用XRD和SEM测试方法表征了热活化胶状黄铁矿结构和微观形貌,考察了溶液pH、溶解氧和热活化温度对热活 化胶状黄铁矿去除水中Cd（Ⅱ）的影响,并探讨了除Cd（Ⅱ）反应动力学和作用机理。胶状黄铁矿在N2氛围下650℃热活化 5 min可完全分解生成多孔结构化单斜磁黄铁矿（PMPyr）。在pH 2~6的无氧水溶液中PMPyr除Cd（Ⅱ）效率均达到88%以 上,除Cd（Ⅱ）效率受pH影响较小;PMPyr表面氧化会抑制其与Cd（Ⅱ）的反应。PMPyr除Cd（Ⅱ）动力学可用准二级动力学模型拟合（R2> 0.9992）,结合溶液pH变化趋势、Fe（Ⅱ）和SO42-浓度变化推测,PMPyr除Cd（Ⅱ）机理主要是Fe1-xS和CdS溶度积差异推动了PMPyr与Cd（Ⅱ）交换反应,表面络合属于次要作用。  相似文献   

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