Metal Resources Research Articles

Simulation optimization and experimental research on heat-treatment process for ring remanufacturing of TBM disc cutters

In the context of the double carbon target, this study aims to reduce the metal resource consumption caused by the replacement of the failed disc cutter rings of tunnel boring machine (hereafter referred to as cutter rings). For this purpose, for the first time, a cutter-ring remanufacturing method is introduced considering key heat-treatment processes of preheating and post-weld tempering through metal active gas arc welding. First, a finite element model was developed to simulate this remanufacturing process route, establishing the optimal parameter ranges for the preheating and tempering temperatures. Subsequently, a self-developed integrated experimental platform was designed combining heat treatment and surfacing remanufacturing. A three-factor and three-level orthogonal experiment was conducted within the optimized parameter ranges. Further, a weighted comparative and range analysis method is proposed, and the impacts of the critical heat-treatment processes on the remanufacturing performance of the cutter rings exhibiting a uniform wear are investigated, resulting in the identification of the optimal heat-treatment combination. Results revealed that these pivotal heat treatments are instrumental in curbing defects (e.g., cracks) and substantially decreasing the residual stress in remanufactured cutter rings. Furthermore, the post-weld tempering temperature is the primary factor influencing the comprehensive performance and an array of physical and mechanical properties, including indent depth, hardness, shear strength, and impact toughness. The comprehensive performance of the best-produced sample impressively surged by 10.5 % compared to a standard engineering cutter ring.

Investigating the impact of inoculation on bioleaching of copper flotation concentrate using a continuous reactor at pilot scale - study case: Tizert deposit

The world is witnessing a major challenge of energy transition which involves the decline of fossil fuels specifically, but which increasingly calls on metallic resources, base metals, mainly copper. The main methods of processing copper minerals are pyrometallurgical and hydrometallurgical processes. Biohydrometallurgy appeared as a very interesting and promising alternative way. In this context, the bioleaching process was studied for the treatment and upgrading of the Tizert concentrate from the Tizert deposit, located 160 km southeast of Agadir, Morocco. Chemical, mineralogical and metagenomic characterizations were carried out on samples from the Tizert deposit. Metagenomic analysis of deposit samples revealed the abundance of genera Paenibacillus (11.38 %), followed by Phynylobacterium (7.54 %) when DSM 670 medium was used while Acidithiobacillus (41.48 %) and Pseudomonas (35.01 %) were abundant when DSM 71 medium was used, indicating the need to use selected consortium species for copper bioleaching experiments. Inoculation with the three species Acidithiobacillus ferrooxidans DSM 583, Leptospirillum ferriphilum DSM 14647 and Acidithiobacillus thiooxidans DSM 14887 was carried out. Laboratory scale leaching experiments with and without inoculation with the bacterial consortium were carried out on the copper concentrate obtained by flotation pretreatment, to compare the copper leaching behavior and yield. Inoculation with exogenous bioleaching bacteria improved the copper yield to 91 % compared to the leaching process without inoculation. These results were confirmed by a pilot-scale study with a copper yield of 95 %.

A revised Proterozoic tectono-stratigraphy of the South Nicholson region, Northern Territory, Australia—insights from SHRIMP U–Pb detrital zircon geochronology

New SHRIMP U–Pb detrital zircon geochronology on Mesoproterozoic and Paleoproterozoic siliciclastic rocks from the South Nicholson region, in concert with recently acquired complementary regional geophysical datasets, have enabled comprehensive revision of the regional Proterozoic tectono-stratigraphy. The identification of analogous detrital zircon spectra of units deposited in half-graben hanging walls of major east-northeast-trending extensional faults, offers compelling evidence for regional tectono-stratigraphic correlation. This study sampled units from the hanging walls of the Benmara, Bauhinia, and Maloney-Mitchiebo (east-northeast-trending) faults, which identified immature proximal lithofacies hosting a small yet persistent population of ca 1660–1640 Ma aged zircon and lack Mesoproterozoic detritus. The timing of this event is consistent with deposition coincident with crustal extension during the extensional River Event at ca 1640 Ma, an event previously identified from the Lawn Hill Platform in western Queensland. This finding suggests the hanging wall sequences are chrono-stratigraphically equivalent to the highly prospective sedimentary rocks of the Isa Superbasin, host to world-class sediment-hosted base metals deposits across western Queensland and northeastern Northern Territory. Subsequent inversion of the extensional faults resulted in development of south-verging thrusts, and exhumation of late Paleoproterozoic hanging wall siliciclastic rocks through overlying Mesoproterozoic South Nicholson Group rocks as fault propagated roll-over anticlines. These geochronology data and interpretations necessitate revision of the existing stratigraphy and the renaming of a number of stratigraphic units in the South Nicholson region. Accordingly, the distribution of the highly prospective late Paleoproterozoic units of the McArthur Basin, Lawn Hill Platform and Mount Isa Province is greatly expanded across the South Nicholson region. These findings imply that the underexplored South Nicholson region is a highly prospective greenfield area for energy and mineral resources. KEY POINTS SHRIMP U–Pb detrital zircon geochronology provides a basis for revision of the Proterozoic stratigraphy in the South Nicholson region. Correlation of sedimentary units across the region is based on closely matching zircon age spectra, lithofacies and tectono-sedimentary setting. Revision of the Proterozoic stratigraphy increases the prospectivity for sediment-hosted base metal resources across the South Nicholson region.

Glass phase extraction for one-step separation and recovery of strategic metals from spent hydrofining catalysts

Spent hydrofining/selective catalytic reduction catalysts generated during the production of ultra-low-sulfur/nitrogen fuel are considered to be hazardous wastes. Furthermore, the sustainable supply of critical metal resources such as molybdenum (Mo), tungsten (W), nickel (Ni) and vanadium (V), which are present in high concentrations in spent catalysts, is challenged by the climate emergency, ore depletion and inefficient technologies for separating metals. Here, glass phase extraction is proposed as a novel approach for simultaneously separating metals and obtaining recovered products from spent hydrofining catalysts in one step. By constructing a glass network structure that satisfied a stable coordination environment for the target metal ions, 99.82 % of the Mo6+ was “melt-melt” separated with the glass phase as Na2MoO4, while the extraction efficiencies of Ni2+ and Al3+ were >99.16 %. The separation factors βMo/Ni and βMo/Al were as high as 65812.95 and 71944.85, respectively. The obtained results verify this method as a valuable synthetic route for refractory metal salts and transition metal ion-doped glass–ceramic materials, enhancing the prospect of achieving full-component resource recovery from hazardous wastes.

One-step selective separation and efficient recovery of valuable metals from spent lithium batteries by phosphoric acid-based deep eutectic solvent

With more and more lithium-ion batteries (LIBs) being put into production and application, precious metals such as lithium and cobalt are scarce, so it is imminent to recover various strategic metal resources from spent LIBs. Meanwhile, the complex and difficult problem of separating and recovering metals from leaching solutions has been an urgent question that needs to be resolved. In this work, a phosphoric acid-based deep eutectic solvent (DES) was developed for extracting metals from spent LIBs and one-step selectively separating and efficiently recovering transition metal. The prepared DES shows excellent extraction performance for Li (100%) and Co (92.8%) at 100 °C. In addition, the extraction system can effectively separate and precipitate Co through its own components, avoiding the introduction of new precipitants and the destruction of the original composition structure of DES. This also contributes to the good cycle stability of the extraction system with excellent extraction performance for Li (94.3%) and Co (80.8%) after 5 cycles. This work proposes a green method for one-step selectively separating and recovering valuable metals from spent LIBs.

Selective separation of aluminum, silicon, and titanium from red mud using oxalic acid leaching, iron precipitation and pH adjustments with calcium carbonate

Red mud discharged from alumina production is a valuable metal resource of great importance in the context of the requirement to reduce the impact of mining on the environment and resource consumption. The efficient dissolution of iron from red mud by oxalic acid has been reported. Although the concentrations of aluminum, silicon, and titanium were also high in the red mud-oxalic acid leachate after iron precipitation, they have received little attention. The present study aims to recover aluminum, silicon, and titanium from red mud-oxalic acid leachate after the precipitation of iron. The leaching efficiencies of aluminum, silicon, and titanium in 1.0 mol/L oxalic acid at 80 °C, reached 63–75% after 2 h. Sodium hydroxide, calcium oxide, and calcium carbonate were chosen to adjust the pH of the oxalic acid leachate, and the effective separation of silicon and titanium from the oxalic acid leachate could be achieved at pH 4.0 by stepwise separation using calcium carbonate. A silicon dioxide primary product with a purity of 70.8% was obtained in addition to the aluminum hydroxide primary product. The stepwise selective separation of aluminum, silicon, and titanium from red mud-oxalic acid leachate could assist the values recovery and simultaneously minimize environmental hazards of the acidic leachate.

Prediction of Au-Polymetallic Deposits Based on Spatial Multi-Layer Information Fusion by Random Forest Model in the Central Kunlun Area of Xinjiang, China

In recent years, there has been a growing emphasis on combining intelligent prospecting algorithms, such as random forest, with extensive geological and mineral data for the purpose of quantitatively predicting exploration geochemistry. This approach holds significant importance for enhancing the accuracy of target delineation. The central Kunlun area in Xinjiang possesses highly favorable ore-forming geological conditions, offering excellent prospects for mineral exploration. However, the depletion of shallow deposits coupled with a decade-long gap in geological exploration have presented increasing challenges in the quest to discover substantial metal resources. Consequently, there is now a severe shortage of reserve assets in the region, prompting an urgent need for the implementation of new theories, methods, and technologies in mineral resource investigation and evaluation efforts. The researchers used geological and regional geochemical data to construct a random forest metallogenic discriminant model for predicting the mineralization of gold polymetallic minerals in the central Kunlun area of Xinjiang and delineating the metallogenic target area. Two different sampling methods were compared to quantitatively predict gold polymetallic mineral resources. The results indicate that the selected training samples offer higher prediction accuracy and reliability by fully capturing the complex information of the original data. The random forest model using select training samples has valuable applications in metallogenic prospect prediction and potential division due to its ability to consider the actual exploration cost and identify small areas with high potential and a high proportion of ore. This study significantly improves prediction accuracy, reduces exploration risk, and expands the use of machine learning algorithms in mathematical geology in the central Kunlun area of Xinjiang.

Econometric modeling for the influence of economic variables on secondary copper production in India

The stocks and flows of primary metal resources, and the estimates of so generated secondary scrap metal flows are tracked and analysed utilizing the traditional analytical method of ‘material flow analysis’. However, the scrap availability and hence the secondary metal production is also influenced by fluctuating economic conditions. Here we utilize the autoregressive distributed lag approach to model the influence of selected economic variables on secondary metal production and hence the scrap availability in the country. We find electricity index, mining index, and electric power generation and distribution correlate with secondary copper production in long-run; and electricity index correlate with secondary copper production in short-run. A 1% increase in electricity index initially leads to 1.76% drop in secondary copper production in short-run, and 3.69% increase in secondary copper production in long-run. A 1% increase in both mining index, and electric power generation and distribution leads to 4.57% and 5.18% decrease in secondary copper production in long-run respectively. The CUSUM and CUSUMSQ charts show the developed ARDL model to be stable over time. Based on the model dependence, we suggest that the policy makers shall devise policies towards reducing copper mining activities thereby encouraging stakeholders to focus on effective collection and efficient recycling of copper towards conservation of natural metal resources.

Bioleaching Extraction of Valuable Metal From E-Wastes: A Mini Review

Abstract: Electrical waste (E-waste) is a significant global issue, with an annual generation of over 50 million tons, causing detrimental effects on both the environment and human health. However, E-waste is also known as a secondary valuable metal resource. Although hydrometallurgy and pyrometallurgy are still the preferred methods for metal recovery from E-wastes, bioleaching has gained significant attention as a promising alternative for metal recovery from E-wastes due to its sustainability, environmental friendliness, and cost efficiency. In this review, different chemical principles of bioleaching were first discussed. Major bacterial groups that can be applied in bioleaching were then introduced. The bioleaching procedures and applications have been summarized and analyzed. Finally, a few perspectives were made on potential future research on bioleaching.

About micro- and nanoscale gold in the veil of gold-bearing territories (on the example of a mineralization site in the basin of the river Adamikha, Amur region)

The article identifies the problem of the need to take into account micro- (1 mm to 0.12 microns) and nanoscale (<0.12 microns) gold in placers and weathering crusts in order to increase the objectivity of their and eroded ore objects potential assesment. The results of technological studies of gold-bearing deluvial deposits in the valley of the Adamikha river basin (Amur region) are presented. A quantitative assessment of the content of micro- and nanogold by fractions of loose material was made. It was found that in the studied sample of such material (weighing 50 kg), the major part (78%) refers to native gold with a dimension of <0.12 microns. Including 0.1% is in concentrator minerals, and 3.5% of the fraction (<3 microns), probably colloidal, is in technical solutions of wet sieve. Moreover, 3/4 of the total amount (18% visible and 57% invisible) of gold is concentrated in the fraction (1–0.5 mm). It is established that, taking into account the free invisible gold, the resources of the precious metal of the object under study increase by 3.4 times. The possibility of a more objective quantitative assessment of the Au potential of promising areas, taking into account the content of fine gold, is shown. Possible ways of solving the problem of a more reliable assessment of geological reserves and estimation of forecast gold resources, taking into account the knowledge of the quantities of micro- and nanoscale fractions, are proposed. The authors believe that studies of the forms of allocation and distribution, including invisible (<0.12 microns) gold in placers and weathering crusts will contribute to a more correct assessment of the studied gold-bearing objects and territories with the possibility of increasing the real resource potential of the precious metal in the region.

A Novel Process of Tungsten Flotation for Sustainable Exploitation of Tungsten Resources

Tungsten as key metal in various fields is indispensable metal resource for global economy. Sustainable exploitation of tungsten resources is still challenging. This work makes attempt to solve the difficulty in flotation separation of tungsten minerals from Yaogangxian tungsten ore. Systematical analysis of mineralogical properties of tungsten ore was performed. A process for tungsten flotation from tungsten ore was developed for exploitation of tungsten resources. The major valuable element in the ore is tungsten, and the grade of tungsten is 0.22%. The distribution of scheelite is nonuniform, and it is majorly distributed in 0.02~0.32 mm. The intergrowth and inclusion of scheelite occur with other minerals such as calcite, diopside, grossularite, and fluorite. The liberation of scheelite reaches 92.40% for -0.074 mm accounting for 75.48%. Process factors including Na2CO3, flotation collector, modified sodium silicate solution, and lead nitrate are studied, and the optimized conditions are Na2CO3 1600 g/t, GY-107 (640 g/t for roughing and 240 g/t for scavenging), modified sodium silicate solution 4200 g/t, and lead nitrate 400 g/t. The open-circuit and closed-circuit flotation processes for tungsten separation are designed, and it is verified for effective separation of tungsten minerals. For the closed-circuit flotation, the grade of tungsten concentrate is 7.30%, while the recovery reaches 85.89%. This work provides technical insights into tungsten separation from tungsten ore.

Recycling Cu(II) from complexing copper wastewater using ferrous sulfide stabilized by carboxymethyl cellulose: efficiency and mechanism insights

Investigating the Cu(II) recovery rate in complexing copper wastewater holds significant importance in achieving resource recycling and enhancing the sustainability of industrial processes. In this study, the ferrous sulfide stabilized by carboxymethyl cellulose (CMC-FeS) was synthesized as a promising strategy to treat complexing copper wastewater, which addressed issues of the stability of FeS nanoparticles and recycling Cu(II) from complexing copper wastewater. Experimentally, the Cu(II) recovery rate was found to be 99.8 % from cupric tartrate (Cu-TA) solutions (Cu(II) = 640 mg/L), as well as the Cu(II) recovery rate reached up to 99.9 % from micro-etching copper-containing wastewater (Cu(II) = 6276.65 mg/L), when treated by CMC-FeS with the molar ratio of [FeS]/[Cu] = 1.25. The underlying mechanism has been systematically elucidated through chemical equilibriums, FTIR/Raman spectral analysis, SEM-EDS analysis, and XPS analysis, providing a solid foundation for further development and application. CMC-FeS can effectively compete with Cu(II) ligands to recover Cu(II) from copper complex wastewater, which is an efficient countermeasure for the treatment of copper complex wastewater. This process involves a variety of mechanisms, such as sulfide precipitation, replacement or ion exchange, complex adsorption, and flocculating sedimentation, finally produces insoluble precipitates with CuS as the main component. This study provides a valuable reference for the treatment of heavy metal complex wastewater, especially the recycling and utilizing metal resources.

Evaluation of the central and local power batteries recycling policies in China: A PMC-Index model approach

The efficient and effective new energy vehicles (NEVs) power batteries recycling (PBR) plays a critical role in reusing scared metal resources, decarbonizing the transport sector and climate warming mitigation. The policy consistency from up to down in a big country lays a solid foundation for sustainable recycling. However, quantitative comparison or evaluation of power batteries recycling policies (PBRPs) from various levels of government is insufficient in the existing literature. In this paper, text mining technology and the Policy Modelling Consistency Index (PMC-Index) model are used to evaluate the longitudinal and horizontal consistency level of China's 13 central PBRPs as well as 25 local PBRPs from 2016 to 2022. The findings demonstrated that: (1) Longitudinally, the local governments present a high consistency level with the central government in the objective and content of PBRPs via comparison analysis of high-frequency words, which embodies the local governments firmly advocating the national strategy for retired battery recycling. (2) Horizontally, the number of central PBRPs with excellent and good consistency is five and seven, respectively, while the number of local PBRPs with excellent and good consistency is six and seven, respectively. One central and twelve local PBRPs are of acceptable consistency, indicating significant disparity in local governments' policymaking ability. (3)The drawbacks of those acceptable policies attribute to the policy tendency of traceability management, policy timeliness, policy content in terms of incentives and business recycling model. Finally, management implications were summarized to optimize China's PBRPs system and PBR performance based on the empirical result, an overview of PBRPs and recycling practices in developed countries.

Impact of the Mining Process on the Near-Seabed Environment of a Polymetallic Nodule Area: A Field Simulation Experiment in a Western Pacific Area.

With the consumption of terrestrial metal resources, deep-sea polymetallic nodule minerals have been widely exploited around the world. Therefore, the environmental impact of deep-sea polymetallic nodule mining cannot be ignored. In this study, for the first time, a field disturbance and observation device, integrated with multiple sensors, is used to simulate the disturbance process of mining on seabed sediments in the polymetallic nodule area of the western Pacific Ocean at a depth of 5700 m. The impact of the process of stroking and lifting on the bottom sediment in the polymetallic nodule area is 30 times higher than that caused by the waves or the current. The time for turbidity to return to normal after the increase is about 30 min, and the influence distance of a disturbance to the bottom bed on turbidity is about 126 m. The time it takes for density to return to normal is about four hours, and the influence is about 1000 m. At the same time, the resuspension of the bottom sediment leads to an increase in density anomaly and salinity. Moreover, suspended sediments rich in metal ions may react with dissolved oxygen in water, resulting in a decrease in the dissolved oxygen content and an increase in ORP. During the observation period, the phenomenon of a deep-sea reciprocating current is found, which may cause the suspended sediment generated by the continuous operation of the mining vehicle to produce suspended sediment clouds in the water near the bottom of the mining area. This could lead to the continuous increase in nutrients in the water near the bottom of the mining area and the continuous reduction in dissolved oxygen, which will have a significant impact on the local ecological environment. Therefore, the way mining vehicles dig and wash in water bodies could have a marked impact on the marine environment. We suggest adopting the technology of suction and ore separation on mining ships, as well as bringing the separated sediment back to the land for comprehensive utilization.

Study on the extraction and separation of precious metals from wastewater using a hydrophobic deep eutectic solvent

Efficient and sustainable recovery of precious metals from the acidic leaching solution of solid waste is considered to be the main solution to the scarcity of precious metal resources. In this study, a hydrophobic deep eutectic solvent (HDES) was synthesized using trioctylmethylammonium chloride (N263) and oleic acid (OA). HDES was then used for the efficient recovery of Ir, Pt, Ru, and Rh from leaching solution containing precious metals. The effects of different molar ratios between N263 and OA, the initial pH of the aqueous phase, the oscillation time, and the phase ratio O/A of the extraction process were investigated. The organic phases were characterized analytically using ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and electrospray ionization–mass spectrometry to further investigate the reaction mechanisms of the extraction process. The single-stage extraction percentages of Ir(IV), Ru(III), Pt(IV), and Rh(III) ions were 97.57%, 94.26%, 99.55%, and 15.1%, respectively. The high saturation extraction capacity of HDES enabled a high precious metal load, reaching 18.44 g L−1. Hydrogen bonds were formed between Cl-, which was bound by electrostatic force in the N263 structure, and H in the -COOH group in the OA molecule. During the extraction process, metal chloride complex ions replaced Cl- and entered the organic phase as 2[C17H33-COOH···N263+]IrCl62-, 3[C17H33-COOH···N263+]RuCl63-, 2[C17H33-COOH···N263+]PtCl62-, and 3[C17H33-COOH···N263+]RhCl63-. After scrubbing for effective removal of Cu and Fe in the loaded organic phase, different systems were used for stripping. The stripping percentage of precious metal ions reached more than 96.3%, providing efficient separation of the four precious metals from wastewater.

A Bioleaching Process for Sustainable Recycling of Complex Structures with Multi-Metal Layers

Industrial waste is accumulating, while primary metal resources are depleting. Bioleaching has been shown to be a cost-effective and environmentally friendly approach to metal recovery from waste, but improved designs are needed for large-scale recycling. Metal components that are manufactured by electrodeposition over a mandrel can be difficult to recycle using conventional techniques due to their complex geometry and inner Ag coating. A sustainable biotechnology for separating Cu and Ag from waste electrodeposited components is presented. Two-step bioleaching experiments were performed, during which Cu was solubilized by Fe3+ regenerated by Acidithiobacillus (At.) ferrooxidans CF3 and a consortium of ten acidophilic Fe2+-oxidizers. High Cu recovery rates were achieved in agitated flasks (22 °C, pH 1.9), with At. ferrooxidans solubilizing 94.7% Cu in 78 days and the consortium 99.2% Cu in 59 days. Copper bio-solubilization was significantly accelerated in a laboratory-scale bioreactor (32 °C, 1 L air min−1) using the bacterial consortium adapted to elevated Cu concentrations, reaching >99.6% Cu extraction in only 12 days. The bioreactor was dominated by Leptospirillum and Acidithiobacillus, with their proportions changing (from 83.2 to 59% of total reads and from 3.6 to 29.4%, respectively) during the leaching process. Dissolved Cu was recovered from the bioleachates (containing 14 to 22 g Cu L−1) using electrowinning; >99% of the Cu was deposited (with Cu purity of 98.5 to 99.9%) in 3.33 h (at current efficiency between 80 and 92%). The findings emphasize the importance of a bioleaching system design to achieve economical separation of base and precious metals from industrial wastes. The presented technology minimizes waste generation and energy consumption. On a larger scale, it has the potential to contribute to the development of industrial recycling processes that will protect natural resources and contribute to the Net Zero target.

Comparative study of electroplating sludge reutilization in China: environmental and economic performances.

Harmless disposal and reutilization of electroplating sludge (ES) attract growing interests due to the high content of heavy metals, which requires economical-affordable and environmentally friendly processing technologies. Main reutilization alternatives in China, i.e., acid leaching, bioleaching, smelting, ironmaking blast furnace co-processing (IBFC), and cement kiln co-processing (CKC), were evaluated and compared via life cycle assessment (LCA) and life cycle costing (LCC) methods. In addition, the heavy metal recovery potential of these scenarios was also evaluated to focus on the sustainable use of metal resources. LCA results show that acid leaching outperforms other scenarios due to the environmental benefits originating from recovering heavy metals, while smelting exhibits the worst due to high energy consumption. The environmental contribution analysis reveals that the product nickel sulfate has a significant positive impact on acid leaching and bioleaching scenarios, and energy consumption is the key factor for smelting, IBFC, and CKC. LCC results show that bioleaching outperforms others, while CKC performs the worst because only inorganic materials are utilized. Bioleaching has the lowest externality cost while CKC has the highest. The heavy metal recovery assessment indicates that bioleaching exhibits the greatest potential with recovery rates of 99%, 99%, 93%, 96%, and 95% for Cu, Cr, Ni, Zn, and Fe, respectively. In contrast, the target heavy metal recovery rate for both acid leaching and smelting is 93%. Acid leaching and bioleaching scenarios are more advantageous from a comprehensive comparison.

Application of the FUZZY TOPSIS method for selecting an underground mining method

Selecting the underground mining method is one of the most difficult decisions any mining engineer makes when designing a new mine or opening new parts in an existing mine. The underground mining method selection depends on many mining-geological, technical and economic factors. The process of selecting a mine excavation method is a multi-criteria decision-making process since many factors are considered when selecting a mining method. The selection of the most suitable mining method is of great importance for each mine, and this is especially evident in the phase of preparation and excavation of the ore deposit and optimization of the total cost of excavation. This paper uses the Fuzzy TOPSIS method to select the underground mining method for metallic mineral resources as one of the most important multi-criteria decision-making methods. The methodology presented will enable the application of other fuzzy methods to solve problems related to the mining method selection.

Simultaneous recovery of arsenic and copper from copper smelting slag by flotation: Redistribution behavior and toxicity investigation

Recovering arsenic from copper smelting slag (CS) into concentrate by flotation, along with copper, can effectively manage arsenic contamination and recover substantial metal resources. The present work selected a combined collector for the simultaneous recovery of arsenic and copper based on the mineral morphology of the critical elements in CS. The redistribution behavior of arsenic and copper during flotation and the toxicity characteristics of CS and its flotation products were investigated using multidisciplinary characterization techniques. The results show that the collection of loellingite and copper matte from CS is crucial for the recovery of arsenic and copper. First-principles calculations indicate that O-isopropyl ethylthiocarbamate possesses a strong capacity to collect loellingite, and flotation experiments confirm that mixing O-isopropyl ethylthiocarbamate with sodium butyl xanthate maximizes the recovery of arsenic and copper. Unrecoverable arsenic and copper exist either encapsulated within the gangue as fine micron-sized mineral particles or dissolved into glassy silicates. Environmental hazard and economic assessments reveal that the simultaneous recovery of arsenic and copper by flotation not only reduces the leaching toxicity of the tailings, but also brings substantial economic benefits. Overall, this study provides a novel perspective on the reclamation of CS and the mitigation of contamination risks associated with CS flotation tailings, contributing to the sustainability of the copper industry.

Organic carbon cycling and black shale deposition: an Earth System Science perspective.

Earth has a prolonged history characterized by substantial cycling of matter and energy between multiple spheres. The production of organic carbon can be traced back to as early as ∼4.0 Ga, but the frequency and scale of organic-rich shales have varied markedly over geological time. In this paper, we discuss the organic carbon cycle and the development of black shale from the perspective of Earth System Science. We propose that black shale depositions are the results of interactions among lithospheric evolution, orbital forcing, weathering, photosynthesis and degradation. Black shales can record Earth's oxygenation process, provide petroleum and metallic mineral resources and reveal information about the driver, direction and magnitude of climate change. Future research on black shales should be expanded to encompass a more extensive and more multidimensional perspective.