A screen of some native Australian flora and exotic agricultural species for their potential application in cyanide-induced phytoextraction of gold

The phytoextraction of gold is an exciting new area of research involving the use of plants to extract gold from a low grade ore and waste products. The aim of this study was to screen some Australian native plant species and exotic agricultural species for their potential use in cyanide-induced phytoextraction of gold from a crushed ore body. Plants were grown in an ore body with a gold grade of 1.75 g/ton gold and treated with 0.1 g/kg and 1 g/kg cyanide as aqueous NaCN. The above-ground biomass was harvested one week after treatment and the gold concentration determined. Mean gold concentrations of up to 27 g/ton (d.w.) were found in the plant tissue of Trifolium repens cv. Prestige. Higher gold concentrations were generally found in the stems and older leaves with the lowest gold concentrations in the young leaves. Plants grown in the 1 g/kg cyanide treatment generally had higher concentrations of gold in the plant tissue than plants grown in the 0.1 g/kg cyanide treatment. This study demonstrates the potential use of plants to extract and concentrate gold from a low grade ore and waste products.     

Antimony Mobilization through Two Contrasting Gold Ore Processing Systems,New Zealand

Antimony, a toxic metalloid similar to arsenic, is present at variable levels in most gold-bearing rocks. Antimony is soluble in the surface environment, so antimony (Sb) mobilization in mine waters is an environmental issue around gold mines. The Reefton gold mine was originally developed in gold-bearing quartz veins; Sb concentrations were low (<100 mg/kg) compared to arsenic (As) concentrations (>1,000 mg/kg), and the mine waters had low dissolved Sb (<0.1 mg/L). A second stage of gold mineralization at Reefton involved brecciation and cataclasis of quartz veins and wall rocks, with addition of stibnite (Sb₂S₃). Processing of this ore has resulted in higher dissolved Sb in mine waters (0.1–1 mg/L), even after water treatment that removes most dissolved As (to 0.01 mg/L) by adsorption to suspended iron oxyhydroxide. Competition between As and Sb for adsorption sites on iron oxyhydroxide particles may have resulted in partial exclusion of the more weakly adsorbed Sb. The high rainfall (2,000 mm/year) at Reefton ensures adequate dilution of mine waters after discharge. The Macraes gold mine has no stibnite, and most Sb is in solid solution in the abundant arsenopyrite (Sb up to 2,000 mg/kg). Pit waters have both Sb and As dissolved up to 0.1 mg/L, partly because of evaporative concentration in a low-rainfall environment. Macraes tailings waters have high As (up to 3 mg/L) but negligible Sb (<0.001 mg/L). Reefton mine gold-bearing concentrate, containing stibnite, is transported 700 km to be processed by autoclave oxidation and cyanidation at the Macraes mine. This introduction of additional Sb to the Macraes site substantially increases the Sb content of the process stream periodically. Tailings from this process have up to 3 wt% Sb, dispersed through As-rich iron oxyhydroxides that are formed in the autoclave. The Sb-rich tailings are strongly diluted (approximately 100:1) by the Macraes tailings, and adsorption of Sb to iron oxyhydroxides in the tailings piles ensures that there has been no increase in the Sb content of the tailings water since the Reefton concentrate has been added at Macraes.     

Ferrates performance in thiocyanates and ammonia degradation in gold mine effluents

Available technologies for cyanides (CN⁻) treatment in gold mine effluents marginally degrade the thiocyanates (SCN⁻). Commonly, they convert the CN⁻ into a less toxic compound, such as cyanates (OCN⁻), which afterwards are oxidized and generate ammonia nitrogen (NH₃-N). Thus, the pretreated effluents require additional steps for complete degradation of SCN⁻ and NH₃-N. Recent research shows that ferrates [Fe(VI)] might represent a sustainable option for the efficient treatment of gold mine effluents. In this context, the objective of the present study was to assess the performance of Fe(VI) in SCN⁻ and/or NH₃-N treatment, as well as in their by-products degradation. The performance of Fe(VI) was evaluated using three different synthetic effluents (solutions) and two gold mine effluents contaminated by SCN⁻ and/or NH₃-N. Results indicated that more than 97% of SCN⁻ were degraded with Fe(VI), while the NH₃-N increased up to 50%, after SCN⁻ oxidation of the presence of NH₃-N, within one hour of reaction time. Consequently, for effluents that contain SCN⁻ and NH₃-N, longer reaction time is required or complementary treatment technologies, such as nitrification – denitrification, should be evaluated for complete degradation of N-compounds.     

含砷金矿蜈蚣草除砷应用前景探讨

含砷金矿通常为难浸提金矿,因而选用经济、环保、有效的除砷预处理方法成为提高金回收提取效率的关键。综述了目前砷金矿预处理方法的优缺点和植物提取及砷转化的研究现状,结合超积累植物蜈蚣草在土壤砷污染植物修复方面的应用,提出了在砷金矿区种植砷超积累植物蜈蚣草来提取去除砷的设想,分析表明,植物预处理方法对于含砷较高的原矿、精矿,以及品位较低的含砷尾矿中的金回收具有广阔的应用前景。     

黑曲霉发酵液和过氧化钙协同强化黑麦草提取土壤中铀

以黑麦草为供试植物,通过温室大棚试验,开展铀表土植物提铀研究。研究CaO₂、黑曲霉发酵液及两者协同施用对黑麦草部分生理特性及其强化提铀能力的影响。结果表明,单独施加高剂量黑曲霉发酵液可促进黑麦草生长,但单独施加高剂量CaO₂及协同施用高剂量CaO₂+发酵液均对黑麦草生长有抑制。所有处理组都对黑麦草叶片可溶性蛋白积累有促进作用,其中单独施加40 mL/kg发酵液时,可溶性蛋白含量最高,比对照组相增加了511.11 %。单独施加黑曲霉发酵液使黑麦草叶片SOD活性和MDA含量降低,而单独施加高剂量CaO₂和协同施加高剂量CaO₂+发酵液可使SOD活性和MDA含量增加。所有处理组均提高了土壤溶液铀浓度和黑麦草富铀能力,其中1 g/kg CaO₂+20 mL/kg发酵液协同施用时效果最佳,黑麦草地上部分灰分中铀品位增加了622.80 %,对铀的富集量提高了483.65 %。     

Acid Mine Drainage at the Abandoned Kettara Mine (Morocco): 2. Mine Waste Geochemical Behavior

Weathering and humidity cell tests were used to predict the potential for acid mine drainage (AMD) and to estimate the mineral reaction rates and depletion of fine and coarse tailings from the abandoned Kettara mine, Morocco. The geochemistry of the fine and coarse mine wastes was similar and, as expected by static tests, the wastes produced significant amounts of AMD. The sulfate production rate of both fine and coarse tailings was very high (2,000–8,000 and 2,400–560 mg SO₄/kg/week, respectively) during the first weeks of kinetics tests. After 9 weeks, sulfate release became low, ranging between 600 and 78 mg SO₄/kg/week for fine tailings and 500–120 mg SO₄/kg/week for coarse tailings. Effluent water samples had low pH (2.9–4.2) and elevated concentrations of acidity, sulfate, iron, copper, and zinc. Most or all of the dissolved K, Na, Al, Mg, and Si in the AMD result from the acidic dissolution of silicates (chlorite, talc, muscovite, and albite). Fine tailings produce much higher concentrations of acidity and sulfate than coarse tailings. However, due to greater transport of oxygen and water within the coarse waste, coarse tailings could be of greater environmental significance than fine tailings. The coarse waste continued to release acid after 378 days of leaching, whereas the fine tailings naturally passivates. These laboratory results agree with field observations; the upper profile of the coarse waste rock dam is highly oxidized (75 cm) whereas oxidation in the fine tailings does not extend more than 5–15 cm beneath the surface. A comparison between weathering and humidity cell tests indicated that the general trend of dissolution of metals was essentially similar for both methods. However, sulfate depletion rates were higher for the weathering cell tests. These tests indicate that the Kettara tailings piles and dam will continue to release acid for a long time unless remedial action is taken.     

Impact of organic amendments on aerial biomass production,and phytoavailability and fractionation of copper in a slightly alkaline copper mine tailing

In the process of phytoremediation of mine tailing land, the bioavailability of heavy metals is an important factor. Greenhouse experiment was conducted to assess the availability and uptake of copper (Cu) by maize (Zea mays L.) grown on a slightly alkaline Cu-mine tailing amended with commercial compost and chelators. A second objective was to evaluate the distribution of Cu in cultivated Cu-mine tailings. The experimental design consisted of 12 treatments resulting from the combination of four rates (0, 5, 10 and 20%, by humid weight) of peat moss-shrimp wastes compost and three rates (0, 1.2 and 2.4 dm³) of organic complexing agents applied as a 0.0025 M EDTA + 0.001 M citric acid solution before plant harvest. The results showed that compost and chelators had a positive effect on top biomass production of maize. Compared with the control, the application of compost decreased Cu_CAR and increased Cu_ORG whereas the addition of chelating solution increased Cu_SOL and Cu_EXC and decreased Cu_CAR and Cu_ORG. The Cu lability in cultivated tailing and its availability to the maize plant are highly dependent on the metal speciation in tailing. In another series of experiments, sorption of Cu by cultivated mine tailings were examined. The amounts of Cu sorbed and K _d values were highest in tailing amended with highest compost rate, and were positively correlated with tailing organic matter (OM) content and Cu bound to Cu_ORG. The results indicate that peat moss and shrimp waste containing compost could be used as a phytostabilizer by supplying OM and nutrients and as a sorbent by mitigating Cu uptake by maize. This compost is able to improve the phytoremediation of Cu-mine tailings.     

Removal of Sulphate, Metals, and Acidity from a Nickel and Copper Mine Effluent in a Laboratory Scale Bioreactor

Abstract  Mine effluents should be treated so that they can either be re-used (e. g. for mining activities or irrigation purposes) or discharged into a river system. The results of this study showed that applying laboratory scale biological sulphate removal technology to a nickel/copper mine effluent (BCL mine, Botswana) consistently lowered sulphate concentrations from an average of 2000 to 450 mg/L, and increased the pH from 5.8 to 6.5. During this period, the hydraulic retention time varied from 24 to 12 h. The Ni and Zn concentrations were reduced from a maximum of 5.86 to 0.15 mg/L and from a maximum of 38 mg/L to 0.03 mg/L, respectively, presumably precipitated as metal sulphides.     

The influence of pH value and adding pulverized fuel ash on the SBR treatment system

According to a great deal of experimental findings and theoretical analysis, when the COD of inlet is 1 000∼1 200 mg/L, NH₃-N is 200∼250 mg/L, the periodic time of operation is 24 h, the aeration time is 16 h and the sludge density is 5 000∼7 000 mg/L, COD of outlet is 150∼200 mg/L, NH₃-N is less than 25 mg/L, the volume load of COD and NH₃-N remove 0.50 and 0.12 kg/(m³·d) respectively. Meanwhile, studied the influence of various crafts parameter change on the treating effect and absorbing the yielding water of the SBR reactor with pulverized coal ash for improving the removing effect of COD and chromaticity further.     

某铜矿尾矿氨浸影响因素试验研究

以某铜矿尾矿为研究对象,采用活化剂强化氨浸的一般碱法浸出技术来确定尾矿浸出影响因素及其影响水平。试验结果表明,铜浸出率与氨浓度、浸出周期、温度、液固比、活化剂等因素有关。本次试验所得最佳浸出条件：氨浓度在100 g/L左右,温度40 ℃,活化剂用量35 g/L,浸出周期1.5 h,液固比为3∶1。浸出率最高为29.80%,活化剂NH₃-NH₄HF₂体系的应用使得铜浸出率提高2%左右。     

Water Management Aspects of the Britannia Mine Remediation Project,British Columbia,Canada

Abstract.  The Province of British Columbia, Canada, is undertaking environmental remediation at Britannia Mine, located approximately 45 km north of Vancouver. Britannia Mine operated for 70 years and produced mainly copper and zinc concentrates. During its operating life, and since its closure in 1974, the mine has discharged large volumes of acidic water with elevated concentrations of potentially toxic metals, including copper, zinc, and cadmium. Prior to the recent remedial efforts, metal loadings to Howe Sound averaged 300 kg/day each of copper and zinc. In addition to the acid rock drainage, mine infrastructure and mineral processing activities provide secondary sources of metal contamination of soils, sediments, ground water, and surface water. Effective water management is key to the remedial plan for the mine: ground water and surface water are the primary transport pathways for the metal contamination reaching the local receptors of Britannia and Furry creeks, and Howe Sound. The remedial concept includes diversion of clean water from entering the mine, use of the mine workings as a storage reservoir to balance seasonal flows to a water treatment plant, prior to discharging to Howe Sound via a deep outfall, and the interception of a metal-contaminated ground water plume.     

Modelling copper adsorption on olivine process dust using a simple linear multivariable regression model

This paper investigates the adsorption of copper on process dust from the production of olivine aggregates as a function of pH and the concentration of copper in solution. The olivine process dust, containing more than 90% forsterite, was retrieved from the dust removal system at A/S Olivin’s processing plant at Åheim in western Norway. Following characterisation of the material, batch adsorption experiments were conducted at 25 °C at an ionic strength of 0.05 M using a fixed adsorbent dose of 10 g/l and initial copper concentrations ([Cu]_i) ranging from 20 to 600 μM (i.e. 1.27–38.1 mg/l). The final pH in solution (pH_f) was varied from approximately 4 to 6. The obtained results show that the olivine process dust is capable of greatly reducing the concentration of copper in solution, even when exposed to relatively high initial copper concentrations. A linear multivariable regression model (LMVR model) was fitted to the logarithmically transformed experimental data. The good fit of the LMVR makes it possible to estimate retention as a function of pH_f and the final copper concentration ([Cu]_f), or, alternatively, [Cu]_f as a function of pH_f and [Cu]_i. From an environmental engineering point of view, the latter would often be of greater interest since the success criteria usually are related to the resulting concentrations in solution.     

Survivorship and growth of Typha latifolia L. across a NaCl gradient: a greenhouse study

Oil sands surface mining operations in northeastern Alberta have created a substantial area of land needing to be reclaimed. Historically, these lands were a mosaic of uplands and boreal wetlands, particularly peatlands. While protocols for upland reclamation are well-defined, protocols for peatland reclamation are still in development. Two major concerns for peatland reclamations are (1) the ability of wetland plants to tolerate the increased sodicity present after surface mining and (2) the potential for the invasion of aggressive wetland plants, such as Typha latifolia, that could crowd out peatland plants and hinder the development of a peat layer. This study addresses these concerns by quantifying the response of T. latifolia seedlings to a sodium gradient. In the lowest two concentrations (0 and 300 mg L^?1), there was about 100% survival rate as compared to about 56% at sodium concentration of 2400 mg L^?1. At 300 mg L^?1, T. latifolia leaf health began to decrease, and at 600 mg L^?1, the health, plant height and the biomass aboveground decreased substantially. Our findings suggest that T. latifolia populations might be kept in check by keeping sodium concentrations within a range between 300 and 600 mg L^?1.     

Contents of Al,Cu, Fe,and Mo in Phalaris aquatica and Trifolium subterraneum grown on an unamended and amended gold-mine tailings-storage facility in central-western New South Wales,Australia

Phalaris aquatica and Trifolium subterraneum grown on a tailings-storage facility (control) and tailings-storage treated with either topsoil or biosolids in a gold–copper mine were analysed for Al, Cu, Fe, and Mo contents. Soil samples from the treatments were also tested for these metals and soil properties. Results indicated that higher levels of metals occurred in T. subterraneum than in P. aquatica; metal contents in both taxa were significantly greater in the control, and higher metal contents occurred in plants tested in May 2008 (autumn) compared with October 2008 (spring). A strong relationship existed between Cu, Fe, and Mo contents in T. subterraneum and Al content in the tested soils. A significant relationship was also observed between Al content in T. subterraneum and K, Na, and SO₄ levels in the soils. We recommend that tailings soil be amended with either topsoil or biosolids before grazing livestock to reduce the risk of either mineral deficiencies or toxicities.     

澳大利亚奥林匹克坝铜-铀矿山

摘要:澳大利亚奥林匹克坝铜-铀矿是世界上现有最大的铀矿床、第四大金矿床和第五大铜矿床。截至2011年6月,证实和控制储量为5.53亿t,含铜1.84%、U3O8 0.57kg/t、金0.69g/t和银3.41g/t。;测定和指示的矿石资源量为59.79亿t,含铜0.93%、U3O8 0.29kg/t、金0.34g/t和银1.68g/t。矿山采用胶结充填深孔分段空场采矿法开采矿石。选矿厂采用常规的磨矿-优先浮选硫化铜精矿的流程,得到含铀、金和银的铜精矿。浮选获得的铜精矿经酸浸/铜萃取/电积法获得阴极铜,硫酸浸出/萃取/沉淀/煅烧法获得氧化铀。2007年必和必拓公司提出矿山扩建计划,增补的环境影响评估报告（SEIS）已于2011年月10月得到政府批准。扩建工程分五个阶段进行。扩建完成后该矿山将成为世界上最大的铜矿山。矿山矿产品最终年产量达到:75万t/a矿产铜,1.9万t/a氧化铀、80万盎司金/a和290万盎司/a银。      

Metal Removal Potential by Three Aquatic Plants in an Acid Mine Drainage Wetland

This study was conducted to gauge the metal bioaccumulation potential of hydrophytic vegetation in a wetland constructed in McCreary County, Kentucky, USA, to treat a cole mine effluent averaging 787 mg/L Fe, 12.6 mg/L Al, 10.9 mg/L Mn, and 2,244 mg/L acidity. Three dominant plant species, cattail (Typha latifolia), bulrush (Scirpus validus), and tickseed sunflower (Bidens aristosa), were sampled and analyzed for Al, Fe, and Mn, so that relationships could be drawn about their capability to bioaccumulate metals from the wastewater. Results showed that Al and Fe were retained-mainly in the roots of the plants, while Mn was more mobile throughout the plant. Iron bioaccumulation was similar for all three plant species at high metal concentration gradients, but somewhat reduced in T. latifolia at low concentration gradients. Scirpus validus appeared to be the most Al-tolerant species, considering its greater Al bioaccumulation potential at high metal concentration gradients. In spite of the high metal load and acidity of the water, there were no visible toxicity effects, but B. aristosa and to a lesser extent S. validus seemed to prefer low-mental concentration environments. All plants bioaccumulated some Al, Fe, and Mn, but their concentrations were fairly miniscule compared to overall metal retention by the wetland substrate. This suggests that the main plant contribution is through substrate stabilization, microbial attachment, and rhizosphere oxidation rather than phytoremediation. Therefore, plant selection criteria for high metal load wetlands should mainly be based on metal tolerance and rhizosphere surface area rather than metal bioaccumulation potential.     

Geochemical Behavior of Mine Tailings and Waste Rock at the Abandoned Cu–Mo–W Azegour Mine (Occidental High Atlas, Morocco)

The abandoned Azegour mine is located in the High Atlas Mountains of Marrakesh (Morocco), and was mined for Cu, Mo, and W. About 850,000 t of waste rocks and tailings were deposited on the surface and have been exposed to weathering for 40 years. The remaining acid-producing potential (AP), acid-neutralizing potential, and geochemical behavior of the Azegour Cu-and Mo-rich tailings were investigated. The tailings were found to contain 9.6–19 wt% sulfur, mostly as sulfate (gypsum, anhydrite, and jarosite) while the waste rocks contain less (1.25–6.58 wt%) sulfur. The waste rocks and tailings contain 0.21–9.24 wt% Mo and 0.003–2.78 wt% Cu. The gangue is mostly composed of quartz, talc, chlorite, pyrophyllite, actonolite, clinoptilolite, and alusite. Lead, zinc, cobalt, arsenic, titanium, and nickel are also present. The calcium, which is mainly expressed as calcite, gypsum, scheelite, and powellite, is present at higher concentrations in the waste rocks (18–22 wt% Ca) than in the tailings (4.7–8.6 wt% Ca). Static ABA determinations showed that the Azegour mine wastes still have high AP, 38–205 kg CaCO₃/t in the waste rocks and 46–387.7 kg CaCO₃/t in the tailings. This was confirmed in weathering cell tests, where the Azegour tailings leachate had a pH range of 1.98–3.19 and high concentrations of SO₄ (468–45,400 mg/L), Ca (230–675 mg/L), Fe (3–55,900 mg/L), Mn (0.1–1,430 mg/L), and Cu (2.3–9,000 mg/L). The Mo concentrations were high (35 mg/L) during the two first weeks of kinetics tests; W concentrations were below the 0.005 mg/L detection limit.     

Antimony Mobilisation and Attenuation During Ore Processing at Orogenic Gold Mines,Southern New Zealand

Mine waters at the Reefton orogenic gold mine (active from 2007 to 2016) in southern New Zealand contained dissolved arsenic (As) and antimony (Sb) up to 5 mg/L during production of a sulfide concentrate that included arsenopyrite (FeAsS) and stibnite (Sb₂S₃). Ferric oxyhydroxide adsorption extracted As down to?<?0.1 mg/L but dissolved Sb remained elevated due to adsorption competition with As. The Reefton sulfide concentrate was transported 700 km to the Macraes orogenic gold mine (active from 1990) for processing through a pressure oxidation autoclave at 225 °C. The Macraes ore has low Sb contents, so the temporary introduction of a Sb-rich component produced a short-term Sb signal in the autoclave system and tailings waters. Oxidation of stibnite occurred rapidly in the autoclave, in parallel with the As in the arsenopyrite, producing ferric antimonate (tentatively identified as As-bearing tripuhyite) and ferric arsenate (FeAsO₄). Dissolved Sb in the Macraes tailings waters remained?<?0.1 mg/L throughout the period of Reefton concentrate addition. The formation of tripuhyite in the high-temperature autoclave stabilised Sb in the Macraes tailings, so that dissolved Sb?<?As, in contrast to the low-temperature processes at Reefton where dissolved Sb?>?As.

     

Is Treatment of Mine Dewatering Water Necessary Prior to Rapid Infiltration Basin Recharge? A Case Study

In Nevada, USA, the return of mine dewatering water (MDW) to the subsurface through rapid infiltration basins (RIBs) requires treatment if the quality exceeds the state’s Division of Environmental Protection (NDEP) Profile I reference values. However, a 2019 change to the Nevada Administrative Code allows discharge without treatment if the natural background groundwater solute concentrations are not exceeded. We developed a novel approach to demonstrate that groundwater will not be adversely affected by the untreated discharge of MDW. At the Cortez Gold Mine, dewatering will discharge water to the Grass Valley RIBs with 0.045 mg/L of As, exceeding the NV Profile I reference value (0.010 mg/L) and natural background (0.015 mg/L). A MODFLOW-SURFACT groundwater model incorporated empirical hydraulic conductivities to evaluate the extent to which changes in mound water depth and quality would occur. Modeling inputs were determined using column tests to assess SO₄ leaching from the alluvium and batch tests to quantify As partition coefficients (Kd_As?=?8.9 L/kg) to the alluvium. The results indicated that Profile I will be met at all compliance wells due to dispersion and attenuation. The Kd_As was also used to calculate the attenuation capacity of the alluvial mound water by adsorption (100-years), well beyond the 13-year operational span of the RIBs. Based on this analysis, and in conjunction with a similar analysis in the adjacent Crescent Valley, where 25 years infiltration of 0.045 mg/L As had not affected groundwater quality, the NDEP concurred that a dewatering water treatment plant was unnecessary. Overall, our analysis obviated construction of four treatment plants in the area and permitted direct discharge of mine dewatering water to the subsurface.

     

A novel low pH sulfidogenic bioreactor using activated sludge as carbon source to treat acid mine drainage (AMD) and recovery metal sulfides: Pilot scale study

In this work a pilot scale sulfidogenic bioreactor was used to treat acid mine drainage (AMD) from Zijinshang copper mine. In this process, S²⁻ produced in the Up-flow Anaerobic Sludge Bed (UASB) reactor were recycled in the two precipitation tanks for copper and iron precipitation, activated sludge from local waste water treatment plant was used as the carbon source. The reactor were steady operated in acid condition (with no pH control) for 4 month, AMD with a copper concentration of 100–120 mg/L, iron concentration of 170–200 mg/L, sulfate concentration of 2000–2500 mg/L and pH of 2.34–2.56, were feeding into the reactor under a feed rate of 1 m³/days and HRT of 3 days, copper and iron removal were 60.95%, 97.83% respectively. The precipitant in the precipitation tank containing 15.7% Cu and 22.66% Fe, thus indicating a recovery possibility of copper by pyrometallurgy process. From these results we can conclude that an SRB process would be a viable method of treating Zijinshan AMD.