Search Results (111)

Due to the increasing demand for lithium resources, the efficient exploitation and utilization of low-grade hard-rock deposits has become an inevitable trend. This study conducted comprehensive heavy liquid separation (HLS), numerical simulation, and dense medium separation (DMS) tests using a laboratory dense medium cyclone (DMC) on a low-grade spodumene ore to demonstrate the potential role of DMS technology in this task. HLS tests verified the feasibility of directly producing qualified concentrate and rejecting waste under different separation densities. A two-stage DMS circuit was then proposed, with the influence of key parameters investigated by numerical simulations using the two-fluid model and dispersed model. The optimized set of structural and operational parameters was finally identified by DMS tests. A continuously operated test conducted on −8 + 0.5 mm ore produced a spodumene concentrate grading 5.68% Li₂O with over 80% lithium recovery while rejecting 0.13% Li₂O waste to tailings with ~70% disposal rate but only 7.44% lithium losses. The middling with a yield of 12.66% can be further subjected to a traditional grinding-flotation process. The findings underscore the importance of parameter matching in the DMS and demonstrate the application potential of DMS in the development of low-grade spodumene from other hard-rock occurrences. Full article

In the face of the global depletion of natural resources and increasing demand for sustainable development, processing industrial waste, such as tailings from processing plants, is becoming essential. This study focuses on combined processing technologies, including flotation concentration and concentrate processing, allowing the efficient recovery of valuable components. This study aims to investigate the possibility of thermochemical enrichment and the opening of low-grade copper tailings of processing plants with the transfer of silicon and rhenium in the form of silicate-ions and perrhenate-ions into a solution with the output of a multifactor multiplicative model and obtaining tabular nomograms. Multifactor experiments on the thermochemical enrichment of rough copper concentrates made it possible to construct partial dependences of silicon and rhenium extraction into a solution and to obtain multiplicative Protodyakonov–Malyshev models of these processes and multifactor nomograms over a wide range of temperatures, durations, and alkali-to-concentrate ratios to determine the maximum recovery rates. The developed multifactor models made it possible to establish the optimal intervals of changes in the concentrate sintering parameters, providing high recovery rates (over 85% of silicon and 98% of rhenium) during subsequent water leaching. Optimal sintering conditions (temperature of 350 °C, the duration of 90 min, and the ratio of NaOH to concentrate = 1:2) ensured a recovery of up to 85% of silicon and 98% of rhenium from the concentrate into the solution. This recovery rate reduces the need for primary raw materials and positively affects the production’s environmental performance because it minimizes the amount of industrial waste disposal. Full article

The high consumption of coal in thermal power plants generates a significant amount of bottom ash, most of which is currently disposed of in landfills. However, the presence of unburned carbon in bottom ash limits its potential applications. To enable its use in construction materials, it is essential to reduce the unburned carbon content. Flotation is a promising technique for removing or recovering unburned carbon due to its high throughput and efficiency. This study aimed to optimize key parameters in the flotation process for recovering unburned carbon from bottom ash. The target was to achieve a tailing loss on ignition (LOI) of less than 6%, in accordance with ASTM C618 standards for concrete applications. The parameters evaluated in this study included the frother dosage, collector dosage, air flow rate, and pH. Optimization was conducted using the Taguchi method, which identified frother dosage as the most influential factor in flotation recovery, contributing 80.55%. Additionally, the air flow rate was found to have the greatest impact on combustible recovery (73.34%) and carbon content in the concentrate (41.05%). The optimized process resulted in a tailing LOI of 5.3%, meeting ASTM C618 requirements. These findings demonstrate the effectiveness of the Taguchi method in optimizing the flotation process for bottom ash treatment. Full article

Zinc processing tailings (ZPTs) of the Kharzet Youcef processing complex, Setif, Algeria, are mainly stockpiled in tailing dumps without use, occupying significant surfaces and negatively influencing the human environment and health. Incorporating ZPTs into building materials manufacturing is an effective solution to meet the dual objectives of environmental protection and economic development. This study investigates the influence of firing temperature and integrating ZPTs as a partial replacement for clay on the physic-mechanical properties of fired clay bricks (FCBs). Microstructural, chemical, and mineralogical analyses of ZPTs and clay were carried out by SEM-EDS, XRF, and XRD, respectively. Seven mixtures were produced with various percentages of ZPTs added to clay (0%, 5%, 10%, 15%, 20%, 25%, and 30%) and were fired at two different temperatures (900 and 1000 °C) at a ramp rate of 5 °C. Physic-mechanical tests were carried out on different brick specimens, and the results obtained showed that the FCBs incorporated with 10% of ZPTs produced the highest flexural strength of 6.24 MPa, compressive resistance of 29.78 MPa, bulk density of 1.37 g/cm³, and water absorption of 15.1% at 900 °C. Therefore, the recycling of ZPTs for FCBs manufacturing is feasible and an effective alternative waste disposal solution for sustainable development while reducing negative environmental impacts. Full article

This paper examines sustainable industrial practices in Serbia, particularly in the mining and energy sector, focusing on the potential of flotation tailings and fly ash, as materials with the largest share in disposed waste in Serbia in 2023 (95%). It highlights the environmental challenges of mining waste and explores innovative approaches to waste management within the circular economy framework. The study analyzes the current state of mining waste in Serbia, particularly in copper mining regions in the east of the country. It discusses the potential for metal recovery from waste and its reuse in various industries. The research also investigates the use of fly ash from thermal power plants as a valuable resource in the construction industry and other sectors. The paper reviews existing initiatives and legislation in Serbia in order to promote sustainable mining practices and waste utilization. By presenting case studies and potential applications, the study demonstrates how implementing circular economy principles in the mining sector can contribute to environmental protection, resource conservation, and economic growth in Serbia. The comprehensive overview of the current state in Serbia provides a solid foundation for establishing a higher degree of circularity in the mining and energy sectors. Full article

In modern nickel mineral processing operations, the aim is to separate pentlandite from gangue minerals. One of these gangue minerals, pyrrhotite, contains up to 1 wt% Ni but is disposed of as waste, i.e., as tailings. Declining sulfide ore grades and increasing nickel demand have led to renewed interest in extracting nickel from pyrrhotite tails. One proposed process is thermal concentration, which aims to recover the nickel as a ferronickel alloy via thermal treatment at temperatures greater than 900 °C. Achieving these temperatures requires substantial energy input as the reactions involved are highly endothermic. In the present research, microwave radiation was used to process a reaction mixture consisting of a concentrate of pyrrhotite tails, iron ore, and metallurgical coke. The fundamental property that determines the interaction of microwaves with a material is complex permittivity. It was found that the reaction mixture had very high real and imaginary permittivities, making it a good candidate for microwave treatment. An input power of 800 W of microwave radiation (2450 MHz) was then employed to heat various reaction mixtures for thermal treatment times of 120, 300, and 600 s. The ferroalloy grades (6–7.5 wt% Ni) were comparable to those produced by conventional heating and to those obtained by other authors using conventional heating techniques. The microwaved samples had increased metallization of nickel, which was attributed to increased melting due to the higher internal temperatures. Full article

There are still no appropriate technologies for the disposal of waste below 10 mm in order to prevent it from being deposited in a landfill, while it constitutes a significant mass stream, with little studied composition, often varying in quantity and seasonally. There is also a lack of concise and clear literature outlining the issues surrounding this waste. These are wastes of both municipal and industrial origin, from various sources and varying in composition. The aim of this paper is to present the results of a literature analysis of the quantity, composition, and sources of waste in the fraction below 10 mm, with a view to defining the possibilities of its recovery, recycling, and disposal. The sources of generation included municipal waste recovered at the screens of the sorting plant for mixed and sorted municipal waste, waste from the recovery and reclamation of raw fractions, and brownfield, tailings, and ash from coal combustion and construction. Defining the sources of their generation and determining their quality will allow the targeting and development of recovery and recycling methods for these wastes. An analysis of the literature has shown that the most valid option for dealing with waste below 10 mm is to incorporate it into new products, for example, building materials. Full article

The composition of oil sands tailings is a complex mixture of water, fine clay, sand, silt, and residual bitumen that remains after the extraction of bitumen. Effective tailings disposal management requires an understanding of the mechanisms controlling water movement, surface settlement rates and extents (hydraulic conductivity and compressibility), and strength variation with depth. This investigation examines the self-weight consolidation behavior of oil sands tailings, typically assessed by utilizing large strain consolidation (LSC) methods such as the multi-step large strain consolidation (MLSC) test and seepage-induced consolidation test (SICT). These methods, however, are time consuming and often take weeks or years to complete. As an alternative, centrifuge testing, including both geotechnical beam type and benchtop devices, was utilized to evaluate the consolidation behaviors of three untreated high water content oil sands tailing slurries: two high-plasticity fluid fine tailing (FFT) samples and one low plasticity FFT. The centrifuge-derived compressibility data closely matched the LSC testing compressibility data within the centrifuge stress range. However, the hydraulic conductivity obtained from centrifuge testing was up to an order of magnitude higher than the LSC test results. Comparing centrifuge and large strain modeling results indicates that centrifuge test data demonstrate average void ratios 10–33% lower than those predicted by simulations using LSC parameters, highlighting a notable deviation. To examine the scale effect on result accuracy, validation tests indicated that the benchtop centrifuge (BTC) yielded comparable results to the geotechnical beam centrifuge (GBC) for the same prototype, saving time, resources, and sample volumes in the assessment of tailings consolidation behavior. These tests concluded that the small radius of the benchtop centrifuge had a minimal impact on the results. Full article

Copper flotation tailings (FTs), resulting from the separation and beneficiation processes of ores, are a significant source of environmental pollution (acid mine drainage, toxic elements leaching, and dust generation). The most common disposal method for this industrial waste is dumping. However, due to their favorable physical and chemical properties—the high content of aluminosilicate minerals (60–90%)—flotation tailings can be effectively treated and reused through geopolymerization technology, thereby adding value to this waste. The objective of this study was to evaluate the potential of utilizing the geopolymerization of FTs to produce sustainable materials. Geopolymers based on natural zeolite (NZ), sodium-modified natural zeolite (NaZ), and fly ash (FA) were prepared using 20%, 35%, and 50% of FTs, activated with a 10 M NaOH solution. The study investigated the influence of Ca/Si, Si/Al, and Na/Al molar ratios on the structural, thermal, and mechanical properties (XRD, TG/DTG and unconfined compressive strength, UCS), and contaminant immobilization (TCLP method) of geopolymers. Geochemical modeling via the PHREEQC program was employed to interpret the results. The findings indicated that the UCS value decreased in zeolite-based geopolymers as the content of FT increased due to the inertness of the tailings and the low calcium content in the system (Ca/Si ≤ 0.3), in contrast to the FA-based geopolymer. The highest UCS of 44.3 MPa was recorded in an FA-based geopolymer containing 50% flotation tailings, with optimal molar ratios of 0.4 for Ca/Si, 3.0 for Si/Al, and 1.1 for Na/Al. In conclusion, the geopolymerization process has been determined to be a suitable technological approach for the sustainable treatment and reuse of FTs. Full article

Every year, large amounts of shrimp waste are disposed of in the environment, causing serious environmental problems. The prospect of recycling shrimp waste helps to reduce waste and protect the environment. In this study, three different shrimp species were used, including Pleoticus muellieri, Litopeneus vanamei, and Parapenaeus longirostris, separated into shells (PLMUS, LIVAS, PALOS) and tails (PLMUT, LIVAT, PALOT), and transformed into novel carbonaceous materials. Their adsorption properties were investigated using different chemical compounds (MB, MR, phenol, astaxanthin) in aqueous means. The materials were characterized through FTIR, BET, and SEM–EDS analyses. According to the results, the carbonaceous adsorbents presented high adsorption percentage of MB and astaxanthin (>90%), and low adsorption percentage of phenol and MR, owing to the different bonds that were formed between the functional groups of the organic substances and the corresponding groups on the surface of the materials. The results of the FTIR analysis show the presence of C=C groups from the aromatic rings of the adsorbed MB and MR at 1636 cm⁻¹, the presence of O-H functional groups from the adsorbed phenols at 3330 cm⁻¹, and the presence of C=C or C=O groups at 1730 cm⁻¹ after the adsorption of astaxanthin. According to the BET analysis, the increase in the specific surface area follows the order: LIVAS > PLMUS > PALOT > PALOS > PLMUT > LIVAT. SEM–EDS analysis presented compact structures with the main elements of C (37–56%), O (25–35%), and Ca (12–23%) for all materials. Kinetic analysis showed that the experimental adsorption data of all the organic substances can be best described by the pseudo-second order model, indicating that chemisorption is the prevailing mechanism. Consequently, such methods promote the sustainable management and zero-waste fish farming practices, fostering the production of high-added value materials not only for decontamination purposes but also for the isolation of bioactive substances. Full article

Anaerobic fermentation is a potentially cost-effective approach to disposing of metal-contaminated biowaste collected during phytoremediation. However, the compound heavy metals contained in the biowaste may limit the efficiency of anaerobic fermentation. In this study, anaerobic fermentation with alfalfa harvested from an iron tailing as the feedstock was set up and further enhanced by granular activated carbon (AC). The results showed that adding AC improved the cumulative biogas yields of alfalfa contaminated with metals (AM) by 2.26 times. At the biogas peak stage, plenty of microbes were observed on the surface of the AC, and the functional groups of AC contributed to better electron transfer, lower heavy metal toxicity and higher CH₄ contents. AC increased the richness and decreased the diversity of bacteria while reducing both the richness and diversity of archaea. The AC addition resulted in higher relative abundance of Prevotella_7, Bacteroides and Ruminiclostridium_1, which enhanced the hydrolysis of substrate and produced more precursors for methanogenesis. Meanwhile, the relative abundances of Methanosarcina and Methanobacterium were remarkably increased together with the metabolism of cofactors and vitamins, indicating the enhancement of both the acetoclastic and hydrotrophic methanogenesis. The present study provided new insights into the microbial responses of the anaerobic fermentation in heavy-metal-contaminated plants and proved the possibility of enhancing the biogas production by AC. Full article

The extraction of mining resources, as well as processing processes such as ore beneficiation and smelting, generate large amounts of tailings that are difficult to directly utilize. Meanwhile, substantial filling materials are required for the voids formed after mining operations, and the environmental issues and safety hazards brought on by massive solid waste disposal cannot be ignored. By utilizing solid waste with alkaline and pozzolanic activity as the binder component and gold tailings as filler aggregate to prepare filler material to fill up the void areas, the purpose of waste treatment can be achieved. In this study, salt sludge, steel slag, ground granulated blast furnace slag, and gold tailings were used to prepare all-solid waste fluidized filling material for filling mine void areas, which not only solves the engineering safety problem of easy collapse of the mine airspace in the mining process but also ensures a backfill effect with high strength, which continuously guarantees the uninterrupted progress of the mining project. At the same time, the preparation of fluidized materials can consume a large amount of tailings and other solid waste, solving the problem of their stockpiling. The components of the solid wastes used are all general industrial solid wastes, so the preparation of the fluidized materials will not have an impact on the surrounding environment. The effects of binder ratios on the workability of the filling materials were investigated by means of the slump and slump flow tests. Combined with the unconfined compressive strength test, the change in backfill material strength with curing age and the water–binder ratio was studied. The experimental results showed that the slump and slump flow value of the filling material were positively correlated with the water–binder ratio. The water–binder ratio range satisfying a slump value of 180~260 mm and a slump flow value not less than 400 mm was 0.95~1.106. However, the strength decreased with the increase in the water–binder ratio, conforming to a hyperbolic relationship. The all-solid waste fluidized filling material had strengths not less than 0.22, 1.09, and 1.95 MPa at 3, 7, and 28 d, respectively, meeting the workability requirements. Finally, a method for determining the optimal range of water–binder ratio considering both workability performance and strength is proposed based on the relationship between slump value, slump flow value, unconfined compressive strength, and the water–binder ratio. Full article

The mining and steelmaking industries, while vital for economic and social development, produce and dispose of waste that contributes to environmental instability and discomfort. In this context, this study aimed to develop novel polymer composites intended for Artificial Ornamental Stone (AOS) application by incorporating iron ore tailings (IOTs), quartzite waste (QTZ), and steel slag (SS) into an epoxy (EP) matrix. The chemical, mineralogical, physical, mechanical, morphological, and thermal properties of the materials were assessed. Three waste mixtures were proposed using the Modified Andreassen Curve method, each with 35, 45, and 55 v/v% of EP. The composite properties were evaluated, showing that the composite with QTZ, SS, and 55 v/v% EP exhibited the lowest porosity (0.3%), water absorption (0.1%), and highest flexural strength (41 MPa). The composite containing the three wastes with 55 v/v% EP presented 1.0% porosity, 0.4% water absorption, and 34 MPa flexural strength. Lastly, the composite with IOTs, QTZ, and 55 v/v% EP exhibited 1.1% apparent porosity, 0.5% water absorption, and 23 MPa flexural strength. Therefore, the polymer composites developed with IOTs, QTZ, SS, and EP demonstrated suitable properties for wall cladding and countertops, presenting a potentially sustainable alternative to reduce environmental impacts from the mining and steelmaking industries. Full article

Despite its vital importance to the contemporary economy, some drawbacks are mainly associated with waste derived from mining activity. This waste consists of tailings that are hydraulically disposed of in large impoundments, the tailings dams. As the dams are enlarged to accommodate higher amounts of materials, the stress states at which the deposited tailings are submitted change. This may be a concern for the stability of such structures once the geotechnical behavior of this material may be complex and challenging to predict, considering the existing approaches. Thus, the present study concerns the mechanical response of bauxite tailings under a wide span of stresses, ranging from 25 kPa to 4000 kPa. One-dimensional compression tests and isotropically drained and undrained triaxial tests were carried out on intact and remolded samples of the bauxite tailings. The after-shearing grain size distribution was characterized via sedimentation analysis. The results have shown a stress-dependency of the critical state friction angle for the intact material, which may be related to fabric alterations derived from structure deterioration and particle breakage. Overall, this research provides valuable insights into the response of structured and de-structured bauxite tailings, which are helpful for future constitutive modeling of such material. Full article

The disposal of tailings has always been a focal point in the mining industry. Semi-dry tailings stockpiling, specifically high-concentration tailings stockpiling, has emerged as a potential solution. To enhance the stability of tailings stockpiling and minimize its costs, the incorporation of a low-cost curing agent into high-concentration tailings is essential. Therefore, this study focuses on the development of a curing agent for high-concentration unclassified tailings stockpiling. The composition of a low-cost curing agent system is determined based on theoretical analysis, and the curing reaction mechanisms of each composition are researched. Subsequently, an orthogonal experiment is designed, and the strength of the modified unclassified tailings solidified samples at different curing ages is measured. Furthermore, the rheological properties of the modified unclassified tailings slurries are tested, and the feasibility of industrial transportation of the unclassified tailings slurries modified with the optimized curing agent is analyzed. Lastly, the microscopic morphologies of each material and the modified unclassified tailings solidified samples are characterized, their chemical compositions are tested, and the action mechanism of the curing agent in the curing system is further investigated. The results show that the optimal proportions of each material in the curing agent are as follows: slag, 58%; quicklime, 15%; cement, 8%; gypsum, 9%; and bentonite, 10%. The dominance of industrial waste slag exceeding 50% reflects the low-cost nature of the curing agent. Under this condition, the modified unclassified tailings slurry with a mass concentration of 75% exhibited a yield stress of 43.62 Pa and a viscosity coefficient of 0.67 Pa·s, which is suitable for pipeline transportation. These findings lay a foundation for subsequent decisions regarding stockpiling processes and equipment selection. Full article