Hydrogeochemical Characteristics of Groundwater at the Xikuangshan Antimony Mine in South China

The hydrogeochemical influence of the Xikuangshan antimony mine on groundwater quality was investigated by analyzing groundwater from 24 springs in the area for major and trace elements. The samples had a pH of 7.6–8.5; total dissolved solids ranged from 125 to 607 mg/L. The groundwater was dominated by alkaline earths (Ca²⁺ + Mg²⁺) over the alkalies (Na⁺ + K⁺), and weak acids \(\left( {{\text{HCO}}_{ 3}^{ - } } \right)\) over strong acids \(\left( {{\text{SO}}_{4}^{2 - } + {\text{Cl}}^{ - } } \right)\). Calcite was generally supersaturated and gypsum was always undersaturated, while dolomite was undersaturated in 34 % of the samples. Iron was negatively correlated with Ca²⁺, Mg²⁺, and \({\text{SO}}_{ 4}^{ 2- }\), which is consistent with Fe removal during acid buffering. Scatter diagrams and correlation coefficients between the major ions indicate dissolution of carbonates and gypsum as major processes, which could promote calcite precipitation.     

Influence of Drainage with High Levels of Water-Soluble Salts on the Environment in the Verhnekamskoe Potash Deposit,Russia

Saline drainage from slurry storage facilities can deteriorate the properties of clay barriers in the beds of embankment dams and slurry ponds and cause saline drainage to infiltrate into groundwater. The chemistry of slurry material, drainage, springs, surface water, and soils was studied near the slurry storage facility of the Verhnekamskoe potash mine (Russia). Our study showed that the Na–Cl type mine drainage water, with high amounts of nitrogen compounds, increased the salinity of the groundwater and surface water, and the river valley ecosystems. As a result of ion exchange and leaching, the soil, groundwater, and surface water have elevated levels of \({\text{C}}{{\text{a}}^{2+}}\), \({\text{M}}{{\text{g}}^{2+}}\), \({\text{SO}}_{4}^{{2 - }},\) and \({\text{F}}{{\text{e}}_{{\text{total}}}}\), and extremely high \({\text{~N}}{{\text{a}}^+}\) and \({\text{C}}{{\text{l}}^ - }{\text{~}}\) values. Iron-rich precipitates and hydrogen sulfide tend to form down-gradient in the saline, water-logged seepage areas.     

Biotic and Abiotic Sequestration of Selenium in Anoxic Coal Waste Rock

Mobile selenium oxyanions (\({\text{S}}{{\text{e}}^{{\text{VI}}}}{\text{O}}_{4}^{{2 - }}\) and \({\text{S}}{{\text{e}}^{{\text{IV}}}}{\text{O}}_{3}^{{2 - }}\)) can be sequestered by biotic or abiotic reduction to non-mobile species or by adsorption to mineral surfaces. Microbial analyses and geochemical batch testing with samples collected from a coal waste rock dump in the Elk Valley, British Columbia, Canada were conducted to assess whether Se can be sequestered in anoxic, waste rock by these mechanisms. Bacteria that reduce Se(IV) and Se(VI) to Se(0) were isolated from the waste rock. Isolates that reduce Se(IV) to Se(0) were present in a water sample collected from an underlying rock drain. Three isolates were affiliated with Pseudomonas and Arthrobacter. One isolate was a putatively novel species. The production of Se(0) was confirmed by X-ray absorption near edge spectroscopy of a red precipitate isolated from a broth media containing rock-drain water. No adsorption or reduction of Se(VI) was observed in anoxic, abiotic (sterile) batch tests conducted with waste rock and a 1.0 mg/L Se(VI) solution, whereas Se(IV) was adsorbed by the waste rock and subsequently reduced to Se(0) in abiotic batch tests with a 0.7 mg/L Se(IV) solution. In non-sterile batch tests using waste rock and rock-drain water (0.39 mg/L Se(VI)), Se(VI) was biologically reduced to Se(IV), which was subsequently removed from solution by a combination of bioreduction, adsorption, and possibly abiotic reduction. This study suggests that, under anoxic conditions, Se sequestration in waste rock may occur via biotic reduction of Se(VI) to Se(IV) followed by adsorption of Se(IV) and abiotic and biotic reduction of Se(IV) to Se(0).     

Assessment of Soil and Water Contamination at the Tab-Simco Coal Mine: A Case Study

In 1996, the Tab-Simco site, an abandoned coal mine 10 km southeast of Carbondale, Illinois, was listed as one of the most highly contaminated AMD sites in the mid-continent region. A suite of impacted soil and water samples were collected from various locations to characterize the current extent of AMD pollution, following standard U.S. EPA protocols. The mean pH of soil and water samples were found to be 2.69 and 2.07, respectively. The mean sulfur content of the soil samples was 0.5 %. The AMD-impacted soils contained high concentrations of Fe, Zn, Ni, Cr, Cu, Pb, and As. The AMD also contained high concentrations of Fe, As, Zn, Pb, Cr, Al, Cd, Cu, and Ni, as well as \({\text{SO}}_{4}^{2 - }\), all of which were significantly above their U.S. EPA permissible limits for surface water.     

Incorporation of arsenic during the formation of Mg-bearing minerals at alkaline condition

The release of toxic anions during the chemical weathering of alkaline wastes such as blast furnace slag and coal fly ash presents a serious problem to public health and the environment. This study investigated arsenate sorption behavior onto Mg-bearing minerals formed in the Mg–Si–Al system at alkaline pH conditions in order to understand the safe removal and encapsulation of arsenate by Mg-bearing minerals under such conditions.Sorption experiments were performed during and after mineral formation and leaching tests using phosphate bearing solution were conducted to understand arsenic association with the minerals. The results revealed that brucite (Mg(OH)₂), hydrotalcite (Mg₆Al₂(CO₃)(OH)₁₆·4(H₂O)) and serpentine (MgSi₂O₅(OH)₄) have high uptake capacity for arsenate. However, arsenic incorporation was only observed during the formation of high Al content hydrotalcite and serpentine minerals and was greatly enhanced at higher temperature. This implies that by controlling pore water chemistry of alkaline wastes with high reactivity, the irreversible fixation of arsenic by Mg-bearing minerals in alkaline conditions can be expected.     

Geochemistry and Isotopic Composition of H2S-rich Water in Flooded Underground Mine Workings,Butte, Montana,USA

Abstract.   Groundwater being pumped from the flooded West Camp mine workings of Butte, Montana, is elevated in hydrogen sulfide (H₂S), has a circum-neutral pH, and has high arsenic but otherwise low metal concentrations. The daily flux of H₂S and As pumped from the extraction well are each estimated at roughly 0.1 kg. Isotopic analysis of coexisting aqueous sulfide and sulfate confirms that the H₂S was produced by bacterial sulfate reduction. the mine waters are close to equilibrium saturation with amorphous FeS, amorphous ZnS, siderite, rhodochrosite, calcite, and goethite, but are undersaturated with orpiment (As₂S₃). The higher solubility of orpiment relative to other mental sulfides allows concentrations of dissolved arsenic (~ 100 g/L) that are well above human health standards. The West Camp waters differ markedly from the acidic and heavy metal-rich mine waters of the nearby Berkeley pit-lake. These differences are partly attributed to geology, and partly to mining history.     

Geomechanical conditions for quasi-resonances in geomaterials and block media

Conclusions  Based on voluminous information about relations between the dimensions of the central zones of crustal earthquakes and various energy classes of underground explosions, as well as mine shocks and man-induced tremors, therefore, the hypothesis that we had previously advanced relative to the quasi-resonant mechanism of their manifestation is confirmed. Here, the geomechanical conditions for the development of quasi-resonances associated with the inducement of pendulum waves are characterized by the dimensionless energy criterion k:

Treatment of Mine Water for Sulphate and Metal Removal Using Barium Sulphide

Abstract.   The integrated barium sulphide process consists of: preliminary treatment with lime, sulphate precipitation as barium sulphate, H₂S-stripping, crystallization of CaCO₃, and recovery of barium sulphide. Our tests showed that during lime pre-treatment, sulphate was lowered from 2 800 mg/L to 1 250 mg/L by gypsum crystallization; metals were precipitated as hydroxides. The BaS treatment then lowered sulphate to less than 200 mg/L. Sulphide was lowered from 333 to less than 10 mg/L (as S) in the stripping stage, using CO₂ gas for stripping. The stripped H₂S-gas was contacted with Fe (III)-solution and converted quantitatively to elemental sulphur. The alkalinity of the calcium bicarbonate-rich water was reduced from 1 000 to 110 mg/L (as CaCO₃) after CO₂-stripping with air due to CaCO₃ precipitation. Fe (II), after sulphur production, was re-oxidized to Fe (III) using an electrolytic step. The running cost of the BaS process is R2.12/m³ (US$1 = SAR6.5) for the removal of 2 g/L of sulphate.     

Geochemical Evolution of a Surface Mine Lake with Alkaline Ash Addition: Field Observations vs. Laboratory Predictions

Abstract.  In the Eastern Middle Anthracite field of Pennsylvania, a formerly acidic (pH = 3.6) surface mine lake (initially approximately 45,000m³ in volume) is being reclaimed using fluidized bed combustor (FBC) ash. The pH of the water in the pit dramatically increased when the alkaline ash was added. The pH of the water is now well buffered, and has not dropped below a value of 11.0 since March 2000. Analysis of data from samples collected over the past six years indicate that the lakes alkalinity is controlled by carbonate, silicate, and hydroxide reactions. The relative importance of these factors varies with ash input, and can be determined in a predictable fashion. Laboratory tests determined that the mass of CaO was more significant than the particle surface area on the pH of the solution. Using only alkaline material, the transition between caustic and carbonate alkalinity was apparent, though this did not account for interaction with silicate minerals, which should be considered when using alkaline ash for reclamation. Field data indicate that with time, the pH will again decrease but will be buffered by calcite present on both the upper walls of the mine pool and within pores of the FBC ash. Less than 1% of the ash is currently used to increase the pH and alkalinity, so a large reserve exists for long term buffering capacity.     

Treatment of Acid Leachate from Coal Discard using Calcium Carbonate and Biological Sulphate Removal

Abstract.   An integrated approach is proposed for treating acidic coal discard leachate, consisting of CaCO₃ handling and dosing, CaCO₃-neutralization, and biological sulphate removal. It was found that: powdered CaCO₃ can be slurried to a constant density and used to neutralize the acid water, remove Fe (II), Fe (III), and Al, and partially remove the sulphate (to saturation level); biological sulphate removal can be used to lower the sulphate to less than 200 mg/L using ethanol as the carbon and energy source; CO₂ produced during calcium carbonate treatment can be used for H₂S-stripping and; H₂S gas recovered in the sulphate removal stage can be used for iron removal.     

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.     

Anaerobic Bioremediation of Acid Mine Drainage using Emulsified Soybean Oil

Abstract  Batch incubation and flow-through column experiments were conducted to evaluate the use of emulsified soybean oil for in situ treatment of acid mine drainage. Addition of soybean oil, soluble substrates, and a microbial inoculum to the batch incubations resulted in complete depletion of SO₄, 50% reduction in Fe, and an increase in pH to >6. A one time injection of emulsified soybean oil, lactate, yeast extract, and a microbial inoculum stimulated SO₄ and metal ion reduction for ≈300 days in laboratory columns packed with mine tailings receiving influent solutions with a pH≈3 and≈5. In all emulsion treated columns, SO₄ and Fe were reduced, pH increased to >6, and Al, Cu and Zn removal efficiency was 99% or greater. Cu, Fe, Mn and Zn were removed as metal sulfides and/or carbonates with removal efficiency decreasing with increasing metal sulfide solubility. The low pH and high heavy metals concentrations did not significantly inhibit biological activity. However, SO₄ removal with associated precipitation of metal sulfides may have been limited by the short hydraulic retention time (6-7 days) of the columns. There was a significant hydraulic conductivity loss in one of the four treated columns, indicating that hydraulic conductivity loss may be an issue under certain conditions.     

Surface properties of enargite in MAA depressant solutions

Enargite (Cu₃AsS₄) is a common penalty mineral in the copper mining industry. Different treatment methods have been proposed to passivate the enargite surface for effective flotation of non-arsenic copper minerals, including pulp potential control, pre-oxidation and chemical depression. Magnesium ammonium mixture (MAA) has been previously tested, showing good selectivity for arsenic rejection. It was hypothesised that MAA would make the enargite surface hydrophilic by adsorption of magnesium ammonium arsenate hexahydrate (MgNH₄AsO₄·6H₂O). Here we show that MAA does not selectively adsorb onto the enargite surface as conjectured. X-ray photoelectron spectroscopy and cyclic voltammetry show that magnesium compounds do not precipitate onto the enargite surface at pH 10, whereas magnesium hydroxide on the enargite surface is formed at pH 12. MgNH₄AsO₄·6H₂O was not observed at either pH 10 or pH 12. The effect of pre-oxidation to promote dissolution of (AsO₄)³⁻ before conditioning with MAA, which could help catalyse the formation of MgNH₄AsO₄·6H₂O, was also tested. However, the results were the same as those without pre-oxidising the sample. Our investigation shows that under alkaline conditions it is not possible to passivate the enargite surface in MAA solutions for effective flotation of non-arsenic copper minerals.     

A Tragic Disaster Caused by the Failure of Tailings Dams Leads to the Formation of the Stava 1985 Foundation

Abstract.   This paper summarizes the dynamics and causes of the Stava disaster, and highlights some risky design procedures that led to the 19 July 1985 tailings dam failure. It then presents the Stava 1985 Foundation, which was formed to focus attention on such risks and to strengthen the culture of respect for human lives and safety.     

湖北枣阳细粒原生金红石矿浮选分离研究

湖北枣阳金红石矿含Ti O23.06%,主要有用矿物为金红石,脉石矿物为角闪石、钙铁榴石,矿石嵌布关系复杂,为细粒难选矿石。针对该难选矿石,进行了浮选试验研究,捕收剂采用C5⁹羟肟酸+苄基砷酸(BAA)组合用药,浮选闭路试验表明采用二者组合用药,可获得金红石粗精矿Ti O2品位43.30%、回收率67.98%,基本实现金红石的有效分离,试验指标良好。     

Buffering of Acidic Mine Lakes: The Relevance of Surface Exchange and Solid- Bound Sulphate

Abstract.  Buffering mechanisms in an acidic mine lake in Lusatia, Germany were investigated. The titration curve has four sections with different buffering mechanisms: (1) buffering by free hydrogen ions and hydrogen sulphate (pH = 2.55-2.9), (2) buffering by Fe with bound SO₄ (pH = 2.9-4.3), (3) buffering by Al with bound SO₄ (pH = 4.3-5.5), and (4) buffering by surface exchange of SO₄ and basic cations (pH > 5.5). Three different phase models were applied to simulate the titration curve: (1) an iron and aluminium hydroxide model; (2) an iron and aluminium hydroxysulphate model; and (3) an iron hydroxide model with surface exchange for SO₄, Ca, and Mg, coupled with an aluminium hydroxysulphate model. The uncertainty of model input parameters was accounted for in a sensitivity analysis. Only the third model, which considers surface exchange, was able to adequately reproduce the measured titration curve.     

Chemical and Biological Oxidation of Iron in Acid Mine Water

Abstract.   Prior to limestone neutralization of acid water, ferrous iron needs to be oxidized to prevent downstream oxidation and the formation of acid. This study assessed the effect of various parameters on the biological and chemical rate of iron oxidation, both chemically and biologically. In batch experiments, it was found that although the use of support media had no effect on the chemical iron oxidation rate, it was important when iron was oxidised biologically. Under continuous flow conditions, the highest oxidation rate occurred when the initial Fe (II) concentration was between 4.5 to 4.8 g/L, geotextile was used as the support medium, and when nutrients were added to the reactor. The optimal iron oxidation rate was achieved at a hydraulic retention time of 8 h. The chemical iron oxidation rate depends on the concentration of suspended Fe(OH)₃ and CaSO₄, which act as catalysts. The biological iron oxidation rate was dependent on the bacterial growth, which was influenced by several parameters (support media, nutrients, CO₂, and oxygen).     

A New Application of Solvent Extraction to Separate Copper from Extreme Acid Mine Drainage Producing Solutions for Electrochemical and Biological Recovery Processes

Over the last decade, AMD waters have gained more attention as a potential source of metals due to the emerging need to recover or recycle metals from secondary resources. Metals recovery supports sustainability and the development of a circular economy with benefits for resource conservation and the environment. In this study, five extractants (Acorga M5640, LIX 54, LIX 622, LIX 622 N, and LIX 864) diluted (15% (v/v)) in Shell GTL with 2.5% (v/v) octanol were compared and evaluated for Cu recovery from an extreme AMD sample (5.3?±?0.3 g/L Cu) collected at the inactive São Domingos Mine in the Iberian Pyrite Belt of Portugal. Of the five extractants, Acorga M5640 showed the best selective efficiency. Further tests showed that 30% (v/v) of this extractant was able to selectively extract ≈ 96.0% of the Cu from the AMD in one extraction step and all of the remaining Cu (to below detection) in three steps. Among the different stripping agents tested, 2 M sulfuric acid was the most efficient, with ≈ 99% of the Cu stripped, and the recyclability of the organic phase was confirmed in five successive cycles of extraction and stripping. Furthermore, contact time tests revealed that the extraction kinetics allows the transfer of ≈ 97% of the Cu in 15 min, and aqueous to organic phase ratios tests demonstrated a maximum loading capacity of ≈ 16 g/L Cu in the organic phase. Raising the concentration of Cu in the stripping solution (2 M sulfuric acid) to ≈ 46 g/L through successive striping steps showed the potential to recover elemental Cu using traditional electrowinning. Finally, a biological approach for Cu recovery from the stripping solution was evaluated by adding the supernatant of a sulfate-reducing bacteria culture to make different molar ratios of biogenic sulfide to copper; ratios over 1.75 resulted in precipitation of more than 95% of the Cu as covellite nanoparticles.

Graphical Abstract

     

Flotation separation of copper sulphides from arsenic minerals at Rosebery copper concentrator

The removal of arsenic bearing minerals from concentrates is becoming more important as environmental laws become ever stricter with regard to smelter emissions. The onus is shifting to concentrate producers to remove these minerals from their product, with penalties applying to materials containing greater than background amounts.The arsenic content of Rosebery copper flotation feed is mainly present as arsenopyrite (FeAsS), containing approximately 46.0% arsenic with the remainder of the arsenic in copper sulphosalts (tennantite (Cu₁₂As₄S₁₃)), in a solid solution series with tetrahedrite (Cu₁₂Sb₄S₁₃). Tennantite contains approximately 20.3% arsenic. Characterisation of the rougher and cleaner concentrates obtained during a plant survey showed that the arsenopyrite was appropriately rejected in the copper flotation circuit. However, tennantite showed similar flotation behaviour to the copper sulphide minerals so that the high arsenic content of the final copper concentrate was mainly in the copper sulphosalts. In this study, regrinding the copper rougher concentrate was investigated to reject tennantite in cleaner flotation. It was found that although finer grinding increased the mass fraction in the ultrafine fraction, the tennantite liberation only increased slightly. The copper selectivity against arsenic was improved significantly although the recovery of copper, silver and arsenic was lower. The difference in floatability of copper sulphide minerals and tennantite appears to increase at finer sizes. In this study, pH and Eh were also manipulated to further improve the selectivity of copper flotation against tennantite at fine particle sizes with some promise. In order to find an application in the Rosebery circuit, any changes must have a net economic benefit and the trade-offs and implications are discussed in this paper.     

钒铬溶液中杂质砷的去除工艺

以浓度为30%的H₂O₂作为氧化剂、Fe₂（SO₄）₃为除砷剂,采用砷酸铁沉淀法对钒铬溶液进行除砷条件试验。结果表明：在反应初始pH=3.0、n(Fe)/n(As)=5、反应温度为40 ℃、反应时间为2 h条件下,钒铬溶液除砷率可达92.07%,钒、铬损失率均在5%以下。最佳除砷条件下获得的钒铬溶液经浓硫酸水解,水解产物沉淀过滤后添加硫酸铵纯化,纯化物烘干后在温度为500 ℃的马弗炉中煅烧3 h,最后得到粉状V₂O₅,可以满足YB/T 5304-2011中牌号V₂O₅ 98质量要求。