Pilot-scale Studies of Different Covers on Unoxidised Sulphide-rich Tailings in Northern Sweden: the Geochemistry of Leachate Waters

Abstract.  Leachate water quality from covered and uncovered unoxidised sulphide-rich tailings in six pilot-scale (5x5x3 m³) test cells was monitored during 2004 and 2005. The covers consisted of a layer of clayey till, sewage sludge, apatite or Trisoplast (a commercial mixture of tailings, bentonite, and a polymer). All layers were protected by an unspecified till except in one reference cell, where the tailings were left open. All leachate waters showed near-neutral pH as a result of neutralization by calcite in the tailings and by Ca(OH)₂ added prior to deposition. Average dissolved sulphur concentrations in the leachates were ≈ 600 mg L^-1, except in the cell with sewage sludge (300 mg L^-1). The source of sulphur was mainly pyrite oxidation, but residual sulphur probably remained from the enrichment process. The near-neutral pH favoured precipitation of metal-(oxy)hydroxides with subsequent removal of trace elements such as Cd, Cu and Pb (< 15 μg L^-1) from the solutions. High concentrations of Co, Mn, Ni, and Zn were found in leachates from the apatite, Trisoplast, and uncovered tailings cells. High As concentrations were found in the leachates in the sewage sludge and clayey till cells. The lowest metal concentrations, redox potential, and highest pH were found in the sewage sludge cell. Decreased elemental metal concentrations during 2004 suggest improved performance over time.     

The use of ion exchange resins for the treatment of cyanidation tailings part 1––process development of selective base metal elution

This work investigates the use of oxidative acid eluents for the elution of base metals from strong base ion exchange resins. Eluents composed of a mixture of H₂O₂ and H₂SO₄ were tested for eluting base metals from resins loaded with mixtures of base and precious metal cyanides. This process removed 100% of Cu and Zn loaded on the resin, without affecting the precious metal loading. It was found that copper could be removed separately from the other base metals. The elution technique was not effective for removing iron from the resin. Cyanide associated with base metals was recovered as NaCN. Some oxidation of cyanide was noticed, subject to the elution conditions.This oxidative acid elution process could be used in commercial operations for the selective elution of base metals from a strong base ion exchange resin bed operating in alternative adsorption/base metal elution cycles. Thus, virtually all metal cyanide species could be recovered from cyanide leached solutions or slurries to give relatively clean tailings without compromising precious metal recovery efficiency. The process also caters for cyanide recovery and recycling.     

Simultaneous Removal of Copper, Zinc, and Sulfate from Coal Mine Waste in a Laboratory SRB Bioreactor Using Lactate or Ethanol as Carbon Sources

The feasibility of inoculating coal mine waste piles with sulfate-reducing bacteria (SRB) to prevent the production of acidic leachates containing sulfate and metal contaminants was evaluated in batch and column bioreactors. The results showed that SRB growth and activity could be attained in the presence of acidic (pH 4.5) coal mine waste using lactate or ethanol as a carbon source, while no obvious growth was found at pH <3.5. Inoculation of coal mine waste in batch reactors with lactate or ethanol as a carbon source resulted in efficient neutralization and high removal of sulfate and metals. Similar results were attained in dynamic-flow columns inoculated with SRB. SEM-EDS analysis of the precipitates showed iron sulfide to be the main component. This study indicates that SRB could possibly be used to prevent or limit acidic drainage from coal mine waste piles.     

Geochemistry of Perched Water in an Abandoned Underground Mine, Butte, Montana

Abstract.  The Lexington tunnel is the last accessible underground mine working in the Butte, Montana mining district. Used as recently as 1993, the tunnel and adjacent workings have been abandoned for over 10 years. Although the Lexington tunnel is over 200 m above the regional water table, perched water is present over much of its extent. Mine water near the portal is moderately acidic (pH 4 to 5), with extremely high concentrations of metals, including Cu (up to 1000 mg/L) and Zn (up to 1400 mg/L). In the middle reaches of the tunnel, the quality of the water is much better, with near-neutral pH, high bicarbonate alkalinity, and lower concentrations of heavy metals. The low acidity and metal content is attributed to a lack of pyrite and other sulfides in this portion of the mine, as well as the presence of carbonate minerals, such as rhodochrosite (MnCO₃), in exposed veins. Sulfide minerals are more widespread further back in the tunnel, and are now oxidizing rapidly, leading to pockets of severe acid drainage (pH< 3, dissolved Zn up to 5000 mg/L). Geochemical modeling suggests that the near-neutral waters—the most voluminous type encountered in the Lexington tunnel—are close to equilibrium saturation with rhodochrosite and hydrous Zn-carbonate (ZnCO₃•H₂O). The Eh of these waters is most likely controlled by redox reactions involving dissolved Mn²⁺ and secondary, Zn-rich, hydrous Mn-oxides. In contrast, the Eh of the acidic waters appears to be controlled by reactions involving Fe²⁺ and Fe³⁺. Most of the acidic waters are saturated with K-jarosite, which forms delicate, straw-like dripstones at several localities. Decaying mine timbers could be an important renewable source of organic carbon for heterotrophic microorganisms, such as iron- and sulfate-reducing bacteria, especially deeper in the mine workings where the ground is saturated with anoxic ground water.     

Tailings Weathering and Arsenic Mobility at the Abandoned Zgounder Silver Mine,Morocco

The abandoned Zgounder Mine (Morocco) was exploited for Ag from 1982 to 1990 and generated nearly 490,000 t of mill tailings before it was closed without being reclaimed. The tailings contain low concentrations of sulfide (mainly as pyrite, sphalerite, and galena) and carbonates (mainly dolomite). Silicates (muscovite, albite, chlorite, labradorite, actinolite, and orthoclase) occur in high concentrations. The most abundant trace elements are As, Ti, Fe, Mn, Zn, and Pb. We studied the geochemical behavior of the mine wastes to identify the main factors controlling drainage water chemistry. Particular emphasis was put on sorption phenomena to explain the low As concentrations in the leachates despite significant As levels in the tailings. Weathering cell tests carried out on various tailings produced two types of contaminated drainage: acidic and neutral. The kinetic test leachates contained high concentrations of some contaminants, including As (0.8 mg L^?1), Co (11 mg L^?1), Cu (34 mg L^?1), Fe (70 mg L^?1), Mn (126 mg L^?1), and Zn (314 mg L^?1). Acidity and contaminants in the leachates were controlled by dissolution of soluble salts and Fe hydrolysis rather than sulfide oxidation. Batch sorption tests quantified the significance of As sorption, and sequential extraction showed that most of the As sorption was associated with the reducible fractions (Fe and Mn oxides and oxyhydroxides).     

粉煤灰防治煤矸石酸性与重金属复合污染

采用柱状淋溶模拟试验,分析添加粉煤灰防治煤矸石酸性和重金属污染的效果及机理.结果表明：煤矸石淋溶液具有典型的酸性矿山废水特征.在粉煤灰处理中,淋溶液的pH值呈中性或微碱性,重金属浓度显著下降.这主要是因为：① 粉煤灰促进了Fe等氢氧化物沉淀和多种重金属的共沉淀;② 生成的Fe沉淀具有包被作用,阻隔黄铁矿的氧化;③ 碱性环境抑制了氧化亚铁硫杆菌的生长和对黄铁矿的微生物催化氧化.研究表明,粉煤灰直接覆盖可以明显地抑制煤矸石中硫化物的氧化并提高煤矸石淋溶液的水质.     

低电位生物浸出黄铜矿研究

在酸性溶液中,高浓度Fe²⁺离子的存在有助于溶解氧对黄铜矿的氧化浸出。试验驯化培养具有单一硫氧化性的高效浸矿细菌,运用其对单体硫的高效氧化性能,结合Fe²⁺离子对黄铜矿氧化浸出的促进作用,开展黄铜矿低电位生物浸出研究。研究发现硫氧化菌可有效利用黄铜矿氧化溶解的产物--单体硫,将其氧化为硫酸并补充溶液H⁺离子消耗。同时,清除黄铜矿表面氧化溶解产物--单体硫后,有助于离子扩散和黄铜矿的进一步氧化溶解。     

化学废水中重金属离子浓度软测量方法研究

为了降低废水重金属离子浓度测量误差,结合现有的研究理论,提出化学废水中重金属离子浓度软测量方法。采用电导率计和密度计组成可用于废水检测现场的检测装置,利用安装金属铁板的电解槽对化学废水进行电化学检测;通过电解液溶解氧化铁离子,生成吸附重金属离子的氢氧化铁,定量描述氢氧化铁絮体吸附能力,建立重金属离子浓度软测量模型;根据装置检测到的废水电导率、密度、温度,计算软测量模型待辨识的变量参数,确定离子浓度软测量值。将某化学废水处理厂作为研究对象,采集不同类型废水水样,把检测装置安装在废水排放出口,现场检测废水中的钴离子、铅离子、钨离子浓度。结果表明,3类重金属离子浓度软测量值和实际值的相对误差都小于14%,软测量精度较高。     

应用高梯度磁选技术处理含铜废水的试验研究

目前,去除水中重金属离子的常用方法存在处理成本较高、易造成二次污染等问题,为此,以浓度为100 mg/L的硫酸铜溶液作为模拟含重金属离子的废水,采用铁氧体沉淀—高梯度磁选分离技术去除水中铜离子。结果表明:在溶液初始pH为10.47,n(FeCl2)∶n(CuSO4)=1.0时,沉淀反应后铜离子沉淀率为99.98%,水中残余铜离子浓度仅0.0127 mg/L;生成的沉淀中按n(Fe3O4)∶n(Cu2+)=0.8加入磁铁矿作为磁种,在背景磁感应强度为1.0 T,采用直径为0.6 mm的网状介质盒,经高梯度强磁选可将93.39%的沉淀物快速分离出来。试验结果为应用高梯度磁选技术处理含重金属离子废水提供了理论依据,为该技术的工业应用提供了技术支撑。     

Potential Release of Metals from Tailings and Soil at the Hamekasi Iron Mine,Hamadan, Iran

This study focused on acid neutralization reactions and the effects of water composition on the release and mobility of metals from mine tailings. The aims of this study were to: investigate leaching of metals from neutral mine tailings, determine the factors responsible for metal leaching, and investigate potential metal filtering by the soil. Tailings and soil samples were collected from an iron mine and analyzed. Equilibrium thermodynamic data and metal fractionation were then used to predict precipitation/dissolution of minerals and ion adsorption/desorption. Three column experiments were designed. The first column was filled with tailings, while the second column contained tailings above a layer of soil; both were leached with distilled water as rainfall. The third column was packed with soil and percolated with synthetic groundwater. The results indicated that iron (Fe) and zinc (Zn) mobility are mainly controlled by precipitation–dissolution mechanisms, while sorption onto oxides and carbonates limit the mobility of copper (Cu) and nickel (Ni). Cadmium (Cd) and manganese (Mn) mobility are affected by both mechanisms. Water discharging from column 3 (soil washed with groundwater) contained high concentrations of dissolved metals, indicating that water composition played an important role in metal mobility. Buffering minerals like carbonates and hornblende, chlorite, and albite decreased acid generation.     

矿山除铁器应用现状及探讨

在矿山破碎工艺中，为防止金属进入设备对其产生损坏，都会使用除铁器将金属物除去。对目前的矿山除铁方式及存在的问题进行了探讨，并对未来除铁器的发展方向进行了展望。目前，非磁性矿山主要通过除铁器除铁，后续金属探测仪探测，如有金属未除去，停机人工捡出。磁性矿主要通过金属探测仪探测，电磁除铁器适时励磁除铁，此种方式在除铁要求较高的矿山应用存在诸多问题，部分磁性矿山对此进行了改进，采用金属探测仪+电动三通阀的除铁方式，以上除铁方式虽在矿山普遍采用，但也存在各种弊端。未来要开发新型智能化的高差异化除铁设备、新原理除铁设备，能满足各种复杂条件下的除铁。     

Solvent extraction of tetravalent hafnium from acidic chloride solutions using 2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (PC-88A)

Solvent extraction of Hf(IV) from acidic chloride solutions has been carried out with PC-88A as an extractant. Increase of acid concentration decreases the percentage extraction of metal indicating the ion exchange type mechanism. The plot of logD vs log[extractant], M is linear with slope 1.8 indicating the association of two moles of extractant with the extracted metal species. Plot of logD vs log[H⁺] gave a straight line with a negative slope of ∼2 indicating the exchange of two moles of hydrogen ions for every mole of Hf(IV). The effect of Cl⁻ ion concentration at constant concentration of [H⁺] did not show any change in D values. Addition of sodium salts enhanced the percentage extraction of metal and follows the order NaSCN > NaCl > NaNO₃ ∼ Na₂SO₄. Stripping of metal from the loaded organic (LO) with different acids indicated sulphuric acid as the best stripping agent. Regeneration and recycling capacity of PC-88A, temperature, extraction behavior of associated elements was studied.     

煤矿综采液压支架系统污染研究

深入分析了煤矿液压支架系统污染源(系统自身污染、现场环境、配液水质、系统运行)及危害,通过对黄玉川煤矿226上工作面液压支架系统高压过滤装置堵塞进行研究,开展了滤芯整体宏观形貌分析、污染物溶解实验、污染物元素分析和配液水水质分析。研究结果表明：滤芯外部污染物为胶状颗粒和煤粉|内部污染物主要为铁锈、金属残渣、金属试件腐蚀物及少量残留泥沙等|铁、铝和钙元素质量含量分别为74.868%、10.218%和4.581%。     

有色金属行业绿色矿山采矿技术现状（增刊）

本文针对有色金属行业112家绿色矿山,通过函调与现场调研相结合的方式,对其中57家绿色矿山建设情况进行了调研。通过对调研矿山资源情况的统计分析,总结出有色金属矿产资源具有构成复杂、品位低、开发利用技术复杂、环保要求高等特点。通过对调研矿山回采率指标的统计分析,总结了有色金属行业绿色矿山建设存在的问题,提出了相关建议。     

Acid Rock Drainage Remediation and Element Removal Using a Peat-Humic Agent with Subsequent Thermal Treatment of the Metal–Organic Residue

A novel, alternative method for acid rock drainage (ARD) remediation and metal recovery has been developed that uses a peat-humic agent (PHA) created by mechanical, chemical, and thermobaric treatment of peat from the Krugloe deposit (Novosibirsk region, Russia). The PHA effectively neutralised moderately acidic ARD and removed potential pollutants (e.g. Fe, Al, Zn, Cu, Pb, Cd, Ni, Co, and Hg), forming metal–organic residues. The organic matter can be removed completely from the metal–organic residues by heating them at 450–500 °C. After this treatment, the metal concentrate residues generally contained aggregates (20–350 μm in size), mainly composed of metal oxides and sulphates. Thermal decomposition of the organic matter in the PHA and metal–organic residues is an exothermic process with significant calorific value (9–15 kJ/g).     

Laboratory Evaluation of the Use of Alkaline Phosphate Wastes for the Control of Acidic Mine Drainage

Pyrrhotite tailings at the abandoned Kettara mine site in Morocco are producing acid mine drainage (AMD). We investigated the use of alkaline phosphate waste (APW) rock from a nearby operating open-pit phosphate mine to control the AMD. The neutralizing potential of the APW, using the Paktunc method, was estimated between 500 and 680 kg CaCO₃/t. In laboratory column tests, the addition of 15 wt% APW to the coarse Kettara tailings produced leachates with significantly lower acidities and metal concentrations than unamended controls. The high calcium concentration in the flushed solutions indicates that calcite was responsible for the neutralization. Dolomite dissolution seems to be negligible and fluorapatite was stable under the testing conditions. It was also observed that when the treated solution comes in contact with unweathered Kettara coarse tailings, the pH becomes acidic, although the metal concentrations remain low.     

Impact of organic carbon on the leachability of vanadium,manganese, iron and molybdenum from shale residues

From 1942 to the 1966, oil was produced by pyrolysis of shale, in Kvarntorp, Sweden. This generated some 40 million m³ of metal rich pyrolyzed shale and discarded fines that were piled on site with its original metal content almost intact. The present study focuses on the leaching of vanadium, manganese, iron and molybdenum from fines after addition of wood chips and steel slag, in outdoor 1 m³ reactor systems at low liquid to solid ratio, in order to evaluate the potential environmental impact and recovery of the elements from the leachates. Seasonal variations were observed, with increased leaching during peak summer. For vanadium and molybdenum, high addition of wood chips decreased the leaching, probably due to adsorption. Manganese showed the opposite behavior while leaching of iron was almost independent of the amount of wood chips. Depending on the systems, up to 2200 μg L⁻¹ vanadium, 90 μg L⁻¹ molybdenum, 25 mg L⁻¹ manganese and 500 mg L⁻¹ iron was found in the aqueous phase. Applied to the 40 million m³ pile, the annual leaching of those elements may reach 14 ton, 0.6 ton, 200 ton and 2400 ton, respectively.     

Novel Two-stage Biochemical Process for Hybrid Passive/Active Treatment of Mine-influenced Water

Current passive treatment systems for metal removal from sulphate-rich mine-influenced water, such as biochemical reactors and permeable reactive barriers, are based on a one-time application of a solid waste organic matrix. These are prone to declining efficiency and reliability as the carbon source is depleted over time. Also, in many of these systems, metal sulphide precipitates are retained in situ, creating a legacy liability on the mine site. A novel hybrid passive/active treatment system was designed to overcome these shortcomings by supplying a liquid nutrient source derived in a separate upstream step through fermentation of waste organic material, and by carrying out sulphidogenesis and chemical metal precipitation in two separate packed-bed column reactors, in which sulphide is fed back from the bioreactor into the upstream metal sulphide precipitation reactor. A separate metal precipitation module will enable eventual removal of the metals from the mine site. Liquid fermentation products from a woodchip/hay-grass mixture were compared with molasses as nutrient sources. The systems were tested for a duration of 96 days, demonstrating that the tested liquid carbon sources reduced sulphate at maximum rates of 41.2 and 28.7 mg-SO₄^2?L^?1 d^?1, respectively, and removed 85% and 90% Zn, respectively, in the chemical precipitation step, making it possible to remove these from the mine site for recycling.

     

铅锌矿选矿废水净化回用工艺的试验研究

为解决某铅锌矿选矿废水循环利用的问题,重点对自然降解、混凝沉降、混凝沉降-活性炭吸附及Na2SO3处理等方法,分别进行了回用方案的试验研究。其中,混凝沉降-活性炭吸附处理,可有效去除废水中的重金属离子及有机污染物,处理后的选矿废水回用作选矿用水,不会对选矿指标造成不利影响,可实现选矿厂废水的零排放。     

我国铁矿资源“劣质能用、优质优用”发展战略研究

针对我国铁矿资源禀赋差、利用效率低、成本高、优质铁精矿匮乏的开发利用现状,提出了我国铁矿资源"劣质能用、优质优用"的发展战略。重点介绍了复杂难选铁矿石预富集—悬浮焙烧—磁选选冶联合新技术研究现状,讨论了悬浮焙烧技术在盘活劣质铁矿资源,提高资源利用率方面的应用前景;针对优质铁矿资源提出了超级铁精矿及洁净钢基料短流程绿色制备技术路线,以期通过多学科交叉融合,推动我国钢铁材料产品从中低端向中高端迈进。最后指出了强化技术创新、加快产业结构调整,提高铁矿资源利用效率和产品质量将是铁矿石选矿重点发展方向。