Removal of trace elements from acid mine drainage

The mine drainages in some coal mines of North Eastern India, are found to be highly acidic and contain trace elements which are highly undesirable for drinking purposes. This water requires neutralization together with trace metal removal prior to its supply to the public. This paper describes the results of a study conducted to determine the ability of lime neutralization to remove inorganic trace elements from acid mine drainage under different operating conditions. The specified trace elements were arsenic, cadmium, chromium, copper, mercury, lead, zinc, manganese, aluminium, iron and nickel etc. Results of this study indicate that treatment by lime neutralization was very effective in removing these trace metals from acid mine drainage.     

Prevention of acid drainage from gold mining in the western United States and impacts on water quality

Water quality regulations recently adopted by states in the western USA have increasingly stringent limitations on allowable changes in the quality of surface water and groundwater. The “nondegradation of water” provisions in state regulations require accurate predictions and control of the quantity and quality of acid mine water and strictly limit the entry of acid water into natural water systems. Long-term water quality impacts from mine waste rock, spent ore from heap leaching, tailings and open pits must be considered in design, operation and reclamation of proposed or expanded mining operations. Acid-base testing, humidity cells, column testing and shake flask tests have been used with mixed success to predict the extent of acid water production. The types and forms of sulfide minerals present, bacterial catalysis of the sulfide oxidation reaction and configuration of the reclaimed facilities are all important elements in accurately predicting acid mine drainage. A critical factor in prediction of acid mine impacts is a pathway and fate analysis which includes geochemical reactions with aquifer materials and dilution and dispersion of parameters in the leachate plume. Of particular concern is the production and transport of arsenic, metals and residual cyanide from mined areas. Evaluation of three major operating gold mines in the northwestern United States shows the relationship between production of acidic water, movement of this water in aquifers and impacts on groundwater and surface water. Column testing showed reduction in concentrations of most metals by 50 to over 90 percent during travel through aquifers. Clays and silt zones were very effective in adsorbing metals. Operational control of water/rock reactions and reclamation design can significantly reduce or eliminate acid drainage. Soil cover, revegetation and slope are the major components that limit long-term acid drainage and metal contamination of surface water and groundwater. Compliance with water quality limits can be achieved only by design and operation of mining facilities to minimize the formation of acidic waters.     

Discrete mine system simulation in the United States

ABSTRACT

The history of mine system simulation in the United States is traced from the earliest work in the 1950's until the present. The software used and types of mining problems are discussed. The current state of affairs is discussed with emphasis on the current software being used.     

At-source control of acid mine drainage

At present, there is no general solution to the problem of acid drainage from mined lands. There are, however, many options to diminish acid discharges, especially where the oxidizing pyrite is located at or near the land surface. These techniques include barrier methods that isolate the pyrite from oxygen or water, chemical additives and inhibition of iron-oxidizing bacteria. This paper emphasizes technology developed during the last decade that includes the addition of high volumes of alkalinity and/or phosphate, the use of surface geophysics to identify problem source areas, the sealing of fractured streambeds using polyurethane grout and the use of anionic surfactants to inhibit the activity of iron-oxidizing bacteria.     

尾矿库酸性矿山废水的源头控制方法

有色金属矿的尾矿库会产生酸性矿山废水,给矿区周围的土壤和地下水带来严重威胁。通过源头控制技术可以降低尾矿内硫化矿物的氧化速率,从而在源头上减少酸性矿山废水的产生。本文系统介绍了干式覆盖法(无机矿物覆盖层和有机覆盖层)、湿式覆盖法、掺碱混合填埋法以及细菌活性抑制法等几种源头控制方法的工作原理、实施方法以及工程应用实例。另外,论文还对各种源头控制方法存在的问题进行了分析和总结,并指出该领域未来需要在以下方面进行重点研究:对于无机矿物覆盖层,要注意研究其长期性能的劣化问题;对于有机覆盖层,需要对其可能存在的负面效应问题进行探讨;分析环境条件对作用效果的影响是湿式覆盖法在未来需要着重研究的问题;克服包裹效应是掺碱混合填埋法需要首先解决的问题;而对于细菌活性抑制法,则应重点考虑新型抑菌剂的研制及投放方式开发问题。     

开滦矿区瓦斯综合治理的经验做法

总结了开滦(集团)有限责任公司在落实"十二字方针"过程中,依靠科技进步,通过优化通风系统、加强瓦斯抽放、完善安全监测系统和安全管理制度综合治理瓦斯的技术经验。     

Valorization of acid mine drainage treatment sludge as remediation component to control acid generation from mine wastes,part 2: Field experimentation

The possibility of using acid mine drainage (AMD) treatment sludge as a cover component to control AMD generation from mine wastes was investigated through laboratory characterization and kinetic column testing (companion paper). The results showed that mixtures of sludge and waste rock, and sludge and tailings, may be integrated in an AMD prevention and control strategy at Doyon mine site (northwestern Quebec, Canada). In order to further investigate these scenarios in realistic climatic conditions, instrumented field test cells were installed on site to evaluate the performance of the mixtures to control AMD generation from tailings and waste rock under natural field conditions. The main findings from two seasons of monitoring are presented in the paper. The waste rock-sludge mixture placed over waste rock was able to reduce the generation of AMD from the waste rock, therefore confirming lab results, and was able to produce a neutral effluent with low concentrations of dissolved metals. The tailings-sludge mixture placed over tailings, with an evaporation protection layer, maintained a high volumetric water content and reduced sulphide oxidation from the tailings as exhibited by a neutral effluent. Monitoring of the field cells will continue to provide valuable information on the possible sludge valorization options.     

Inhibition of bacterial activity in acid mine drainage

Acid mine drainage water give rise to rapid growth and activity of an iron- and sulphur- oxidizing bacteriumThiobacillus ferrooxidians which greatly accelerate acid producing reactions by oxidation of pyrite material associated with coal and adjoining strata. The role of this bacterium in production of acid mine drainage is described. This study presents the data which demonstrate the inhibitory effect of certain organic acids, sodium benzoate, sodium lauryl sulphate, quarternary ammonium compounds on the growth of the acidophilic aerobic autotroph Thiobacillusferrooxidians. In each experiment, 10 milli-litres of laboratory developed culture ofThiobacillus ferrooxidians was added to 250 milli-litres Erlenmeyer flask containing 90 milli-litres of 9-k media supplemented with FeSO₄ 7H₂O and organic compounds at various concentrations. Control experiments were also carried out. The treated and untreated (control) samples analysed at various time intervals for Ferrous Iron and pH levels. Results from this investigation showed that some organic acids, sodium benzoate, sodium lauryl sulphate and quarternary ammonium compounds at low concentration (10-2 M, 10–50 ppm concentration levels) are effective bactericides and able to inhibit and reduce the Ferrous Iron oxidation and acidity formation by inhibiting the growth ofThiobacillus ferrooxidians is also discussed and presented     

Iron precipitation kinetics in synthetic acid mine drainage

To evaluate the design and operation of a new active treatment system for acid mine drainage (AMD), the behavior of ferric iron solutions after the addition of bicarbonate ions was investigated. The effects of various other factors common to AMD on the precipitation rate of iron were also studied. It was found that the rate of Fe III precipitation in synthetic AMD was not affected by the presence of Al or Mn, within the concentration ranges investigated (for Al, 0-0.01 M, for Mn, 0-0.002 M). Our experiments showed that the induction time (t_md),i.e., the time elapsed between the addition of base ions and the detection of iron precipitation, decreased with increasing iron concentration and pH but increased with increasing sulfate concentration: log t_ind=6.7(±0.30)?1.29 (±0.10) pH+0.94(±0.07) log [SO₄]?0.36 (±0.05) log [Fe] Our results suggested that sulfate sorbed to the surface of growing iron oxyhydroxides, inhibiting their growth. This effect offers an important tool that can be used to control the precipitation of iron in AMD treatment facilities.     

The control of acid mine drainage with Wetlands

The recent increases in environmental legislation, especially in the USA have meant that there is a need on behalf of the mining companies for more judicious operational planning and more thorough restoration techniques in order to reduce costs and prevent violation of the strictly enforced regulations. Water pollution is probably the greatest problem and many less enlightened operators, especially for example, in surface coal milling in Pennsylvania, have been forced into liquidation after having been unable to meet the severe restrictions on Acid Mine Drainage (AMD). The problems of AMD are also inherent in most forms of metalliferous and coal mining and also in some types of aggregate quarrying. As excavations go deeper in search of ever diminishing reserves then they are more likely to encounter groundwater which can become polluted if insufficient care is not taken. It is to be expected that the laws will also become more severe than they are at present in Europe and methods of treatment of AMD will need to be developed that are more efficient than the costly chemical methods currently used. Research by the author and others into the source of AMD pollution and its treatment with engineered wetlands and other operational methods are discussed in the paper. The methods have- the distinct benefit that they are cheap to install, are cost effective over a long period with the minimum of supervision and are environmentally acceptable to the planning and regulatory authorities.     

Remediation of acid mine drainage using metallurgical slags

In this study basic oxygen and stainless steel slag were both assessed for potential use in treating acid mine drainage. The stainless steel slag was able to effect some pH change but was found to not be suitable. Basic oxygen slag was found to have a significant potential as a remediating agent. For a model acid mine water with a pH of 2.5, sulfate concentration of 5000 mg/L and iron concentration of 1000 mg/L, the slag was able to increase pH to 12.1, reduce the soluble iron by 99.7% and reduce sulfate by 75% in batch experiments. In these batch reactors most reaction was completed within 30 min indicating that this is a rapid process. Additional experiments were conducted with continuous flow reactors to assess the maximum treatment capacity of the slag. These experiments indicated that slag replacement strategies are wholly dependent on the strength of the acid mine drainage, the required residence time and the specified residual concentrations of iron or sulfate and the pH. The data indicate that in particular, basic oxygen furnace slag has significant potential as a replacement reagent for lime in treating acid mine drainage.     

准格尔矿区水土流失的综合治理

准格尔矿区在开发建设及生产过程中 ,以保护和改善生态环境为目标 ,坚持在保护水土资源的基础上开发 ,在规划的指导下建设的原则 ,针对所处地区水土流失严重 ,生态环境脆弱的特点 ,采取工程措施与生物措施相结合的办法 ,综合治理水土流失 ,恢复与保护生态环境 ,取得了初步成效     

矿山酸性废水治理的研究综述

矿山废水成分复杂,危害性大,其中以酸性废水的污染最为严重.本文总结了国内外治理酸性废水的方法与研究现状,详细介绍了中和法、人工湿地和微生物法的治理方法.     

富煤一矿西采区瓦斯抽采技术实践

富煤一矿西采区瓦斯涌出量大,对采掘影响大,采用穿层预抽、顺层预抽、卸压抽采、采空区抽采等多种方式结合的瓦斯抽采技术,增加瓦斯抽采量,减少瓦斯涌出量。通过瓦斯预抽后,西采区M7煤层在采掘前瓦斯含量从11.3m3/t降到8.0m3/t以下,抽采率达63.34%,保证了采掘的安全。     

Effect of loess for preventing contamination of acid mine drainage from coal waste

Acid mine drainage (AMD) that releases highly acidic, sulfate and metals-rich drainage is a serious environmental problem in coal mining areas in China. In order to study the effect of using loess for preventing AMD and controlling heavy metals contamination from coal waste, the column leaching tests were conducted. The results come from experiment data analyses show that the loess can effectively immobilize cadmium, copper, iron, lead and zinc in AMD from coal waste, increase pH value, and decrease Eh, EC, and SO ₄ ^2? concentrations of AMD from coal waste. The oxidation of sulfide in coal waste is prevented by addition of the loess, which favors the generation and adsorption of the alkalinity, the decrease of the population of Thiobacillus ferrooxidans, the heavy metals immobilization by precipitation of sulfide and carbonate through biological sulfate reduction inside the column, and the halt of the oxidation process of sulfide through iron coating on the surface of sulfide in coal waste. The loess can effectively prevent AMD and heavy metals contamination from coal waste in in-situ treatment systems.     

Use of organic covers for acid mine drainage control

Organic covers may be used to prevent diffusion of oxygen into reactive sulphide wastes and subsequently to eliminate sulphide compounds oxidation and generation of acidic waters. The main advantages over other types of covers are related with their low hydraulic permeability, high cation exchange capacity and high alkalinity. In addition, the establishment of organic covers, which is considered as a low cost solution for the prevention of acid mine drainage generation, does not disturb the natural environment, since they consist of industrial wastes rather than natural materials and allow the development of vegetation, which improves the aesthetics of the reclaimed areas. However, treatment of municipal sewage sludge is necessary prior to discharge, in order to minimize potential health and environmental risks, resulting from the presence of toxic elements.In the present paper, all processes associated with the function of an organic cover are described and discussed, including potential health and environmental risks resulting from land application of municipal sewage sludge. In addition, preliminary laboratory data, derived from the application of organic covers over reactive sulphidic concentrates are presented and discussed, in order to evaluate the performance of the covers and to determine the critical factors affecting their performance. The final aim of this research work is the development of an experimental model, that predicts the performance of an organic cover, by taking into account critical parameters such as annual rainfall rate, organic material height, initial moisture and moisture under saturation conditions.     

Phosphate coating on pyrite to prevent acid mine drainage

Abstract

Acid mine drainage (AMD) is a serious environmental problem that preoccupies the Canadian Mineral Industry. Considerable amounts of money are spent every year in an effort to prevent or reduce the acid mine drainage phenomenon. AMD occurs when sulfide minerals (ex. pyrite) contained in rock are exposed to air and water and subsequently oxidize to produce low pH water. This acid effluent has the potential to mobilize any heavy metals contained in the rock. Coating the sulfide minerals with iron phosphate is a new promising technology to reduce AMD.Pyrite is treated with a solution containing H₂O₂, KH₂PO₄ and sodium acetate (NaAc). H₂O₂ oxidizes a small part of pyrite producing ferric iron (Fe³⁺) anions. These cations subsequently react with the PO₄ ^3? anions to produce FePO₄ that precipitates on the pyrite surface producing a passive coating. This iron phosphate coating can protect the grains of pyrite from oxidation. This paper presents a series of experiments that confirm that iron phosphate coating can considerably reduce AMD.     

Mine water quality deterioration due to acid mine drainage

Water quality deterioration due to acid mine drainage is of concern in the northeastern coalfield of India as the water in this area is severely polluted. The mine drainage water emanating from various collieries are highly acidic in character and contain high hardness, sulphate, total dissolved solids and iron coupled with low pH values—which further results in contamination of trace (heavy) metals at significant levels. Trace metals are highly toxic and undesirable and are injurious to human health. These acidic waters are also typically hard in character because of iron sulphate content rather than common Ca?Mg bicarbonate type hardness.     

煤矿酸性矿井水中有害元素的迁移特性

利用电感耦合等离子质谱（ICP-MS）、离子色谱（IC）和X射线衍射（XRD）等方法研究了马兰煤矿酸性矿井水及其沉淀物的化学成分和物相组成,并通过吸附解吸实验和PHREEQC水化学模拟计算研究了典型酸性矿井水样品中Pb,Th,U,Be,Zn,Ni,Co,Cd,Cu,As,Cr,V,Ba等有害元素的迁移特性.研究表明：① 煤矿酸性矿井水中SO^2-₄,Fe,Mn,Al,Pb,Th,U,Be,Zn,Ni,Co,Cu等离子含量较高,对环境存在潜在危害;② 酸性矿井水中有害元素的迁移主要受pH,Fe-Al-Mn含量和水体颗粒物矿物组成的控制;③ Fe,Al和Mn的含量随pH上升而迅速下降,并控制着Pb,Th,U,Be,Zn,Ni,Co,Cu等潜在有害微量离子的迁移行为; ④ 各离子随pH上升被去除的先后顺序为: Th>Fe>Pb >Cr>Al>Cu>Be>U>Zn>As>Cd>Mn>Co>Ni>Ba;⑤ 酸性矿井水中V不能够随pH的升高而去除,反而会有更多的V溶解在水中.