Processing Of Low-grade Ores Research Articles

Biohydrometallurgy: Paving the Way for a Greener Future of Mineral Processing in Indonesia

Biohydrometallurgy has been around since the 1960s, and it uses microorganisms to facilitate the extraction of metals. As environmental rules get stricter and the quality and complexity of ore available for processing decrease, this technology presents an alternate option for mineral processing. Several countries, including South Africa, Russia, Chile, Australia, the United States, China, Burma, New Zealand, Peru, Uzbekistan, and Ghana, have used this method commercially in copper processing plants and gold and silver processing plants. In Indonesia, this approach has neither been developed nor implemented on an industrial basis. In Indonesia, biohydrometallurgical processing is worth proposing as a solution to future mineral processing issues, particularly the problem of limited capital and low-grade ore processing. Globally, a significant amount of focus is placed on the investigation of biohydrometallurgy. However, only the Bandung Institute of Technology (ITB) does biohydrometallurgy-related research in Indonesia. This investigation began in 2009 for the extraction of nickel from laterite ores. Additional research has also been conducted on the extraction of metals such as copper and gold. The research findings thus far have generated an intriguing and highly potential outlook that can be scaled up through a pilot plant and industrialized in Indonesia.

Eco-Friendly Recycling of Lithium Batteries for Extraction of High-Purity Metals.

The significant increase in lithium batteries consumption produces a significant quantity of discarded lithium-ion batteries (LIBs). On the one hand, the shortage of high-grade ores leads to the necessity of processing low-grade ores, which contain a low percentage of valuable metals in comparison to the discarded LIBs that contain a high percentage of these metals, which enhances the processing of the discarded LIBs. On the other hand, the processing of discarded LIBs reduces the negative environmental effects that result from their storage and the harmful elements contained in their composition. Hence, the current study aims at developing cost-effective and ecofriendly technology for cobalt and lithium metal ion recovery based on discarded LIBs. A novel synthesized solid-phase adsorbent (TZAB) was utilized for the selective removal of cobalt from synthetic solutions and spent LIBs. The synthesized TZAB adsorbent was characterized by using 13C-NMR, GC-MS, FT-IR, 1H-NMR, and TGA. The factors affecting the adsorption of cobalt and lithium ions from synthetic solutions and spent LIBs, including the sorbent dose, pH, contact time, temperature, and cobalt concentration were investigated. The conditions surrounding the recovery of cobalt and lithium from processing discarded LIBs, were investigated to optimize the maximum recovery. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models were used to study the kinetics of the adsorption process. The obtained results showed that high-purity CoC2O4 and Li3PO4 were obtained with a purity of 95% and 98.3% and a percent recovery of 93.48% and 95.76%, respectively. The maximum recovery of Co(II) from synthetic solutions was obtained at C0 = 500 mg·L-1, dose of 0.08 g, pH 7.5, T = 25 °C, and reaction time = 90 min. The collected data from Langmuir's isotherm and the adsorption processes of Co agree with the data predicted by the D-R isotherm models, which shows that the adsorption of Co(II) onto the TZAB seems to be chemisorption, and the results agree with the Langmuir and D-R isotherm models.

Eco-Friendly Collectors for Flotation of Fine Hematite and Malachite Particles

The separation of fine mineral particles, especially using environmentally friendly approaches, is one of the main problems in the processing of low-grade ores and the re-processing of mining tailings. This work assesses the potential of biosurfactants as collectors in the flotation of ultrafine (smaller than 20 μm) particles of hematite and malachite. As biosurfactants, we test acetylated acidic (ac-ASL) and lactonic sophorolipids (ac-LSL). In addition, n-dodecyl-β-D-maltoside (DDM) is used as a model non-ionic alkyl disaccharide surfactant, and sodium oleate (NaOl) is used as a reference. The biosurfactants are characterized using surface tension and foam analysis. The interaction of the minerals with the surfactants is characterized using zeta potential, solubility, and single-mineral flotation. The collecting properties of the surfactants are compared for the ultrafine (− 20 μm) and coarser (38–90 µm) particle size in the two-mineral flotation of hematite and malachite against quartz. The ultrafine particle size improves the grade in the oleate flotation of hematite, as well as the grades in the DDM flotation of hematite and malachite, which is explained by the weak interactions of the metal oxides with fatty acids and DDM. At the same time, the flotation with ac-LSL and ac-ASL is highly tolerant to the ultrafine particle size. These results indicate that biosurfactants are an interesting alternative to conventional petroleum-based surfactants in the flotation of Fe and Cu oxides. Moreover, a proper selection of surfactants can help combat the problem of fines.Graphical

Selective Comminution Applied to Mineral Processing of a Tantalum Ore: A Technical, Economic Analysis

There is an increasing demand to simulate and optimize the performance and profit of comminution circuits, especially in low-grade ore processing, as is the case with critical metals minerals. Recent research has shown that the optimization result is greatly influenced by quality aspects of the products, such as cost, profit, and capacity. This paper presents a novel approach to performing a multi-objective technical and economic analysis of tantalum ore processing to increase the production of critical metals minerals. The article starts with mineral composition analysis to highlight the potential of strategies for balancing the process layout for maximized production. The introduction of a combined technical and economic analysis presents the possibility of improving the profit by rearranging the mass flow given the rock’s mineral composition. Results show that selective comminution can improve process capacity by 23% and decrease production cost by 10% for the presented case.

Chalcocite (bio)hydrometallurgy—current state, mechanism, and future directions: A review

There has been a strong interest in technologies suited for mining and processing of low-grade ores because of the rapid depletion of mineral resources in the world. In most cases, the extraction of copper from such raw materials is achieved by applying the leaching procedures. However, its low extraction efficiency and the long extraction period limit its large-scale commercial applications in copper recovery, even though bioleaching has been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores. Overcoming the technical challenges requires a better understanding of leaching kinetics and on-site microbial activities. Herein, this paper reviews the current status of main commercial biomining operations around the world, identifies factors that affect chalcocite dissolution both in chemical leaching and bioleaching, summarizes the related kinetic research, and concludes with a discussion of two on-site chalcocite heap leaching practices. Further, the challenges and innovations for the future development of chalcocite hydrometallurgy are presented in the end.

Incorporation of Rheological Characterization in Grinding and Tailings Slurries to Optimize the CMP Magnetic Separation Plant

Compañía Minera del Pacífico (CMP) is the main iron producer on the Pacific coast of the American continent. The Cerro Negro Norte (CNN) operation of CMP is facing important challenges, such as the processing of low-grade ores containing complex gangue minerals which negatively affect the performance of the magnetic separation, grinding and solid–liquid separation stages. CMP is working on a program, aimed at optimizing the efficiency of the CNN plant, which considers a rheological characterization of the slurries produced by the different ores treated, information which will be useful to optimize the performance of the physical separation processes. The objective of this work was to characterize the slurries obtained from the secondary grinding and tailings thickener stages through rheological measurements. The rheological data were correlated with the physical, chemical and mineralogical characteristics of the different geological units (GU) tested. The results show that the rheological flow curves of the slurries taken from the secondary grinding product display a pseudoplastic behavior which follows a Casson model pattern. An exponential model was used to correlate the Casson yield stresses with the solids content of the slurries taken from the secondary grinding product. The results of this fitting process indicate that the yield stresses increase with the % −325# Tyler mesh and with the percentage of minerals with a tendency to generate fines (MTF = smectite + illite/mica + talc + chlorite + kaolinite), and in contrast the yield stresses decrease with the ore iron grade (Fe). For the tailings characterization, the results of settling rates and turbidity values of the supernatant obtained from tests with different GU samples show no significant differences. A linear regression model was used to correlate the results of yield stresses of compacted tailings with the chemical and mineralogical characteristics of the GU. The results of the fitting process indicate that the MTF content in the head ore samples influence the rheological properties of the tailings, which correlates with the behavior of the secondary grinding product. The increase in the GU iron grades also reduced the Casson yield stress. The experimental results were explained in terms of the microrheological effects and the physicochemical properties of the different types of phyllosilicates existing in the ore samples tested in this work.

Geoenvironmental Study of Gold Mining Tailings in a Circular Economy Context: Santa Barbara, Minas Gerais, Brazil

We characterized the tailings from the Santa Barbara tailings dam, which is located in Minas Gerais, southeastern Brazil, to: (i) identify its chemical, mineralogical, and metallurgical properties, and (ii) perform an environmental evaluation of the water at the surface of the tailings facility. The potential recovery of elements such as Sb, As, and Au was also considered for potential tailings reuse. The water was alkaline, with maximum pH values of ≈ 10, and contained potentially toxic elements, such as Sb (up to 0.500 mg/L), As (up to 0.080 mg/L), and Cu (up to 20 mg/L). Gold enrichment areas were found in the tailings dam, with concentrations up to 0.5 g/t. Alignment exists among tailings management, demand for critical raw materials, and increased interest in the processing of low-grade ores and mining waste, which is important in the context of the circular economy. They suggest that valorisation of tailings, although challenging, can be achieved by economic recovery of the more valuable metals.

Assessment of the Possibility of Hydrometallurgical Processing of Low-Grade Ores in the Oxidation Zone of the Malmyzh Cu-Au Porphyry Deposit

The geochemical features of the ores present in the oxidation zone of the gold-copper Malmyzh mineral deposit are characterized. This deposit is located in the the Nanaian region of the Khabarovsk Territory in the Russian Federation, and a technological assessment of ores present was carried out. The initial gold content in the oxidized ore is 0.1–1.2 ppm, and the leachability of gold from different size fractions by hot cyanide revealed the fact that the ore is not refractory and characterized by increased cyanide consumption. The results demonstrated a high gold content in fine size fractions. Different leaching reagents were applied for oxidized ore testing. These reagents were used both for oxidative pretreatment and leaching process. Activation of solutions was carried out by electrolysis and UV radiation. Different reagent combinations were tested in laboratory with the highest gold recovery (94%) provided by the chloride system with peroxide-sulfuric pretreatment of the oxidized ore. The same reagent combination resulted in 91–94% gold recovery during the column leaching of crushed (−10 mm) ore.

Pre-concentration at crushing sizes for low-grade ores processing – Ore macro texture characterization and liberation assessment

Mineral processing of low-grade ores requires high processing flow rates. Pre-concentration is a clever technological solution for this challenge because the rejection of barren rock, in the early stages of the processing flowsheet, leads to increasing the head grade of the concentration plant and reducing the corresponding input flow rate.As pre-concentration at crushing sizes depends on the ore texture and consequently, it relies on the achieved mineral liberation degree, a straightforward methodology to assess quantitative mineralogical data of the ore macro-texture, based on image analysis, was developed.For the purpose, photos of hand samples collected at the mine site were converted into a digital image representative of the ore macro-texture. Then, a random comminution algorithm simulating a coarse crushing stage, to generate particles in size range 19.3/6.7 mm was applied. The surface grade of each particle was calculated by pixel counting, allowing for the computation of the Grade Histograms (wt%) and then for the construction of ultimate upgrading descriptors, which has been proved to be a useful tool to assess pre-concentration feasibility and the separation efficiency.This methodology was applied to a Li-Mica lepidolite ore from Alvarrões deposit (Portugal) by simulating several separation scenarios. The separation efficiency of an optical sorting separation was also assessed using the proposed methodology. Furthermore, the influence of mineral liberation at different size ranges on the global separation efficiency was predicted.This paper intends to underline the importance of quantitative mineralogical data in the study of the pre-concentration process. Data acquisition must be improved, taking advantage of the more accurate and faster systems, such as the modern multispectral analytical devices and ore sorting technologies.

Investigation of liquid extraction and thermodynamic studies on uranium from sulfate solution by Alamine 336 as an extractant

This paper presents a comprehensive study of the liquid–liquid extraction of uranium from 0.2 M sulfuric acid solution by tertiary amine (Alamine 336) and kerosene as an extractant and a diluent, respectively. For this purpose, the effects of operating parameters on the uranium extraction efficiency such as Alamine 336 concentration, contact time, initial aqueous phase pH, sulfate ion concentration, temperature and stripping process by different agents are investigated. The Gibbs energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) have been determined as thermodynamic parameters to prove exothermic and spontaneous reaction. Also, equilibrium constants, reaction equation and stoichiometric coefficients for uranium extraction with Alamine 336 in sulfate medium are specified. The proposed procedure can be applied to the recovery of uranium from low-grade ore processing and from wastewater in the different stages of the nuclear fuel cycle.

Unravelling the Complexity of Heap Bioleaching

Heap and dump leaching of sulphide minerals have become well-established techniques for the processing of low grade ores, especially of copper, over the past 30 years. The oxidative dissolution of sulphides in heaps can be significantly enhanced by microbial colonies, but the complexities of the heap leach process overall often counteract the potential advantages, or prevent microbial colonisation and bioleaching in the first place. This overview discusses the multiple layers of complexities that govern percolation leaching processes, such as the interactions between mineral grains, particle pores and leach solution, microbial responses to solution chemistry typical of heaps, solution and solute transport in heterogeneous unsaturated ore beds, as well as heap aeration and microbial response to CO2 supply. It becomes clear that economically successful heap bioleaching hinges on careful engineering and operation of the heap process as a whole to create an environment in which microbial colonies can thrive and the value metal is released sufficiently rapidly into solution.

A geospatial approach to uncovering the hidden waste footprint of Lake Superior’s Mesabi Iron Range

For decades, the Lake Superior Iron District produced a significant majority of the world’s iron used in steel production. Chief among these was the Mesabi Range of northern Minnesota, a vast deposit of hematite and magnetic taconite ores stretching for over 100miles in length. Iron ore mining in the Mesabi Range involved three major phases: direct shipping ores (1847–1970s), washable ores (1907–1980s), and taconite (1947–current). Each phase of iron mining used different technologies to extract and process ore. Producing all of this iron yielded a vast landscape of mine waste. This paper uses a historical GIS to illuminate the spatial extent of mining across the Lake Superior Iron District, to locate where low-grade ore processing took place, and to identify how and where waste was produced. Our analysis shows that the technological shift to low-grade ore mining placed new demands on the environment, primarily around processing plants. Direct shipping ore mines produced less mine waste than low-grade ore mines, and this waste was confined to the immediate vicinity of mines themselves. Low-grade ore processing, in contrast, created more dispersed waste landscapes as tailings mobilized from the mines themselves into waterbodies and human communities.

Microbiological Advances in Biohydrometallurgy

The most exciting advances in biohydrometallurgy are occurring in the field of microbiology. The two main technologies employed in biohydrometallurgy, agitated tanks for the processing of refractory concentrates and heaps and dumps for the processing of low-grade ores, are technologically sound and widely practised at commercial scale, but their development began at a time when very little was known of the microorganisms that assisted metals extraction from sulfide ores. During and subsequent to those developments it has been shown that microbial communities in metals extraction are more diverse than originally thought, and extremely robust and adaptable to different and variable environments. Recent advances in genomics and proteomics, exploiting hugely increased computing power and speed, have made it possible to describe not only which microorganisms are present in bioleaching systems, but also what physiological functions are being exercised. The body of knowledge being acquired through the application of molecular biology methods will be used increasingly to monitor microbial behaviour, optimise conditions for more appropriate microbiological activity and/or infer the “microbiological health” of bioreactors (tanks and heaps).

A case in support of implementing innovative bio-processes in the metal mining industry.

The metal mining industry faces many large challenges in future years, among which is the increasing need to process low-grade ores as accessible higher grade ores become depleted. This is against a backdrop of increasing global demands for base and precious metals, and rare earth elements. Typically about 99% of solid material hauled to, and ground at, the land surface currently ends up as waste (rock dumps and mineral tailings). Exposure of these to air and water frequently leads to the formation of acidic, metal-contaminated run-off waters, referred to as acid mine drainage, which constitutes a severe threat to the environment. Formation of acid drainage is a natural phenomenon involving various species of lithotrophic (literally 'rock-eating') bacteria and archaea, which oxidize reduced forms of iron and/or sulfur. However, other microorganisms that reduce inorganic sulfur compounds can essentially reverse this process. These microorganisms can be applied on industrial scale to precipitate metals from industrial mineral leachates and acid mine drainage streams, resulting in a net improvement in metal recovery, while minimizing the amounts of leachable metals to the tailings storage dams. Here, we advocate that more extensive exploitation of microorganisms in metal mining operations could be an important way to green up the industry, reducing environmental risks and improving the efficiency and the economy of metal recovery.

Microbial Leaching of Copper from Tailings of Low Grade Sulphide Ores in Zambia

Demand for copper is growing in the world,which makes it increasingly necessary to process low-grade ores and tailings that used to be considered as wastes. The development and application of bioleaching by acidophilic chemolithotrophic microorganisms, which obtain energy from the oxidation of sulfide minerals and use carbon dioxide for constructive metabolism, has been a major approach for processing the low-grade copper ores. In this study, mixed culture consisted of six iron and sulfur oxidizing microorganisms were used in leaching of flotation and acid-leaching tailings obtained from Zambia sulfide ores. The result showed that 62.7% and 61.7% copper were dissolved by bioleaching, while 53.8% and 57.4% by acid leaching in flotation and acid leaching tailings, respectively. In addition, mineralogical forms of copper were quite noteworthy since copper sulfide mineral extraction was significantly improved in bioleaching. XRD analysis showed wollastonite and diopside in acid tailing were undetectable after 23 days while others were difficult to be dissolved. No jarosite or sulphur was detected by XRD in residues.

Sustainable Mining in Myanmar

Myanmar is endowed with abundant natural and mineral resources. However, environmentaldegradation and social impacts have increased in recent years due to foreign investment in the mining sector and the application of modern technology in mining and processing methods to increase productivity. The growing trend towards new mining methods, particularly the shift from underground to open-cut method to mine and process low-grade ores contribute to generation of large volumes of waste rock and tailings, presenting a major disposal challenge. Wastes containing sulfides will further degrade the environment. Absence of an efficient legal framework for Artisanal and Small Scale Mining (ASM) for gold and gemstones, and the application of mechanized mining both contribute to adverse environmental and social impacts of mining operations. Myanmar’s newly-promulgated environmental law (2012) provides no details about environmental and social impact assessment and participation of communities and their role in conservation of the environment. Efficient guidelines are needed and continuous monitoring and Life Cycle Assessment (LCA) are essential for the greening of Myanmar’s mining sector.

Selective flotation of fine-ingrained carbonate-fluorite ore in pulp of increased dispersion uniformity

The studies into the fine-ingrained high-carbonate fluorite ore concentration show that increasing of pulp dispersion uniformity results in higher selectivity of flotation. The researchers find out availability of quality fluorite concentrate in processing of low-grade ore with carbonate index less than 1 at CaF2 recovery up to 70%.

Bioleaching of Covellite from Low Grade Copper Sulphide Ore and Tails

The economic importance of copper production in Chile has prompted the study of new strategies for the optimal management of mineral resources, including processing of low grade ore and even processing tails (processed ore). Currently, heap bioleaching is the most convenient technology to treat low grade copper sulphide ores bearing chalcopyrite, chalcocite and covellite. Covellite is a secondary copper sulphide occurring in copper sulphide deposits and it is also formed by acidic dissolution of chalcocite. In leaching processes, the main factors influencing the dissolution of covellite are the electrochemical potential (Eh) and temperature.This work aimed at assessing the effect of different concentrations of total iron (3.0 and 6.0 g/L) and temperatures (30 and 50°C) in the bioleaching of covellite contained in a low grade copper ore and the same ore after a previous process of bioleaching at ambient temperature. Initial composition of low-grade ore was chalcocite (0.58%), chalcopyrite (0.56%), covellite (0.30%) and pyrite (2.73%), while the processed ore contained chalcopyrite (0.47%), covellite (0.28%), chalcocite (0.10%) and pyrite (3.32%). Covellite was mostly dissolved (>90%) in both unprocessed and processed ore, independently of the temperature and total iron concentrations. However a higher total copper recovery was achieved in tests performed at 50°C due to higher dissolution of primary ores, especially in unprocessed ore. The microbial activity was confirmed by Most Probable Number (MPN) analyses of iron and sulfur oxidizing microorganisms. The microbial population was dominated by Acidithiobacillus spp. in tests operated at 30°C, while in tests operated at 50° Sulfobacillus spp. were the most abundant organisms.

Recycling of copper tailings as an additive in cement mortars

Increasing demands for copper and copper allied products have made the processing of low grade ores with high volume waste output unavoidable. Presently, billions of tons of copper tailings can be found in major copper producing countries. The impact of copper tailings at 0%, 5% and 10% addition level by mass of cement on the fresh and hardened properties of mortars were determined. Results showed that dry copper tailings affect mixture consistency negatively. However, the use of pre-wetted tailings reduced this drawback. Copper tailings blended mortars showed higher strength and abrasion resistance. Similarly, rate of water absorption, acid and chloride resistance higher than those of the control mixture were observed. The use of pre-wetted tailings at 5% addition level seems to be the best reuse approach.

Electrokinetic cleaning of industrial residues

Processing of low grade ores for metal extraction leaves behind a huge mass of residue, which may be disposed by land filling. However, prior removal of toxic heavy metals is imperative to prevent ground water pollution. Electrokinetic remediation used for treating contaminated soils could be adapted for the removal of heavy metals from industrial residues. Preliminary electrokinetic cleaning experiments on dichromate residue showed the feasibility of removal of Cr(VI) from residue along with pH modification. From an initial concentration of 1758 mg kg−1, the concentration of Cr(VI) could be brought down to 615 mg kg−1, besides the drop in pH from 10·9 to 6·8 in 72 h. The residue thus can be a start-up material for other remediation processes such as phytoremediation.