Hydrometallurgical Operations Research Articles

Recovery of Lesser-Known Strategic Metals: The Gallium and Germanium Cases

Being not as popular as other elements, such as cobalt, lithium, and rare earth elements, both gallium and germanium have wide use in target developments/industries, thus making them valuable and strategically critical metals. The principal sources for the recovery of both metals are secondary wastes of the bauxite (gallium) or zinc (germanium) industries; also, their recycling from waste materials is necessary. The characteristics of these materials make hydrometallurgical operations widely useful in recovering both gallium and germanium from the various sources containing them. The present work reviews the most recent applications (in 2024) of the various operations applied to the recovery of gallium or germanium from various resources.

Carbon Dioxide as a Sustainable Reagent in Circular Hydrometallurgy.

This review highlights the use of CO2 as a reagent in hydrometallurgy, with emphasis on the new concept of circular hydrometallurgy. It is shown how waste CO2 can be utilised in hydrometallurgical operations for pH control or regeneration of acids for leaching. Metal-rich raffinate solutions generated after removal of the valuable metals can serve as feedstocks for mineral carbonation, providing alternative avenues for CO2 sequestration. Furthermore, CO2 can also be used as a renewable feedstock for the production of chemical reagents that can find applications in hydrometallurgy as lixiviant, as precipitation reagent or for pH control. Mineral carbonation can be combined with chemical reactions involving metal complexation reagents, as well as with solvent extraction processes for the concurrent precipitation of metal carbonates and acid regeneration. An outlook for future research in the area is also presented.

Some Recent Advances in Germanium Recovery from Various Resources

Though nowadays germanium does not reach the range of popularity of other metals, i.e., rare earth elements, its utility in target industries makes it a strategic metal. Though germanium can be found in a series of raw materials, the principal source for its recovery is from secondary wastes of the zinc industry; also, the recyclability of germanium-bearing waste materials is becoming of interest. In this recovery and due to the size of the target materials, because the diffusion and reaction are to be considered, hydrometallurgy performs a key role in achieving this goal. The present work reviews the most recent applications (2023 and 2024 years) of hydrometallurgical operations on the recovery of germanium from different solid and liquid sources.

Emergence of Bio-hydrometallurgy to Achieve Sustainable Process Development Goals in Extractive Metallurgy

The stringent environmental regulations and growing awareness of the low-carbon economy are presenting immense challenges to metallurgical operations, one of the major sectors with high emissions. Hydrometallurgy has been identified as a lower-emission technology in comparison to the high-temperature smelting and melt-refining processes. The close monitoring of traditional hydrometallurgical operations, however, does not fulfil the criteria for a sustainable, low-emission process. Recently, biotechnology has emerged as a green alternative within the hydrometallurgical domain, albeit significantly different from the basics involved in the process. Although the application of microbial activity has been successfully established in chalcopyrite leaching and bio-oxidation of gold-bearing minerals, the acceptability of bio-hydrometallurgy for other minerals and materials is still limited due to a wide research gap to connect solution chemistry, microbial activity, and extractive metallurgy. In general, a large portion of the total chemical consumption occurs in pre-treatment and/or leaching operations; hence, the primary application of microorganisms at the forefront can significantly minimize the overall consumption. Demonstrated applications in waste printed circuit boards and spent automobile catalysts have curtailed excessive acid usage, while the energy-intensive baking/roasting of monazite is successfully altered by microbial processing. Furthermore, the remarkable reduction in carbon footprints by the green biotechnology application in hydrometallurgy has been evaluated, which indicates sustainability in process metallurgy.

Advances in the Removal of Cr(III) from Spent Industrial Effluents—A Review

The review presents advances in the removal of Cr(III) from the industrial effluents published in the last ten years. Although Cr(III) has low solubility and is less dangerous for the aquatic environment than Cr(VI), it cannot be released into the aquatic environment without limitations and its content in water should be restricted. The development of efficient techniques for the removal of Cr(III) is also a response to the problem of chromium wastewater containing Cr(VI) ions. Very often the first step in dealing with such wastewater is the reduction in chromium content. In some cases, removal of Cr(III) from wastewaters is an important step for pretreatment of solutions to prepare them for subsequent recovery of other metals. In the review, hydrometallurgical operations for Cr(III) removal are presented, including examples of Cr(III) recovery from real industrial effluents with precipitation, adsorption, ion exchange, extraction, membrane techniques, microbial-enhanced techniques, electrochemical methods. The advantages and disadvantages of the operations mentioned are also presented. Finally, perspectives for the future in line with circular economy and low-environmental impact are briefly discussed.

Heap leach pad mapping with drone-based hyperspectral remote sensing at the Safford Copper Mine, Arizona

Mapping the distribution of minerals, pipes, ponded lixiviant, and other surficial features on heap leach pads is a continuing challenge for hydrometallurgy operations, maintenance, and design. Recently, commercial drone technology has enabled remote sensing techniques to be deployed for some leach pad mapping and surveying applications, but applications to hydrometallurgical operations are still emerging. This project tested one potential mapping technology, drone-based hyperspectral remote sensing, for mapping leach pads, using the Safford mine as a test site.The results show that hyperspectral remote sensing can acquire information about mineral distribution, piping system, and lixiviant ponding. The main minerals detected on the leach pads are kaolinite, muscovite, and gypsum, although the detection of gypsum is probably due to the widespread sulfate precipitating from agglomerating acid and lixiviant. The path of the stacker loading rocks, lixiviant ponding, and drip lines can also be seen in the spectral images. Chlorite and biotite, long-term acid consumers, were not detected in the results, but are on the leach pads. Best practices for hyperspectral remote sensing in mapping leach pads include: building a reference library from ground-truth samples, using high spatial resolution for mapping piping systems and low spatial resolution for mapping minerals, scanning leach pads in sunshine, and scanning before leaching starts.

Переработка висмутистых окислов

Introduction. The paper is devoted to the creation of an environmentally safe, technologically efficient and cost-effective high-performance integrated scheme for the recycling of lead-containing industrial products and waste, in particular, bismuth oxides and drosses formed during the melting of copper-electrolyte sludge, with the production of commodity monoelement products. To solve the problem, a combined technology is used, which is based on hydrometallurgical operations that allow separating chemical elements with similar properties with high extraction into finished products. The aim of the work is to study and develop fundamental approaches and rational integrated technologies for recycling bismuth drosses and oxides-industrial products of refining rough lead, using reducing melts of raw materials and bismuth-enriched sludge, electrolysis of bismuth lead to obtain rough bismuth containing ≥ 90 % Bi with its direct extraction of ≥ 70 %. Methods and approaches: melting at a temperature of 1,100…1,150 oC a charge of optimal composition containing bismuth oxides, sodium carbonate, silicon dioxide and carbon. Novelty: a decrease in the content of noble metals and accompanying chalcogenes in secondary copper-containing raw materials with an increase in the amount of impurity elements. Results and discussion: joint melting (1,100…1,150 °C) of bismuth oxides, sodium carbonate, silicon dioxide and carbon, taken in the mass ratio 100 : (15‒66) : (11‒25) : (5‒7), allows to transfer 89.0 – 93.6 % of bismuth and 99.5 ‒ 99.7 % of lead from the initial oxides to bismuth lead containing ~7 % Bi and ~80 % Pb. The main phase of the Pb-Bi alloy is elemental lead. The increased flux consumption leads to an increase in the amount of recycled silicate slags that are poor in target metals, into which it passes,%: 1.4 Bi; 2 Pb; 47 Zn; 23 Sb; 33 Sn. Main slag phases are following: Na2CaSiO4, Na4Mg2Si3O10, MgO, Pb, ZnS, PbS. The practical relevance is determined by the optimal mode of reducing melting of bismuth oxides (100 %) to obtain lead bismuth, %: 66 Na2CO3, 25 SiO2, 5 C; the process temperature is 1,150 ° C. The presence of impurities makes it necessary to introduce reagent treatment of lead bismuth into the technological scheme for recycling bismuth oxides. Decontamination and alkaline softening will make it possible to obtain a Pb-Bi alloy suitable for pyroelectrometallurgical recycling.

Removal of chloride ions from a copper leaching solution, using electrodialysis, to improve the uranium extraction through ion-exchange

This study shows the technical feasibility to recover uranium from copper Pregnant Leaching Solutions (PLS) using ion-exchange, after a removal of chloride ions using the electrodialysis (ED) technique. The original copper PLS solutions came from the National Copper Corporation (CODELCO), from their hydrometallurgical operations, which contained high concentrations of chloride ions. These solutions contained average concentrations of 22 g/L chloride ions, pH 1.5 – 1.8 and 20 mg/L uranium. The high chloride contents made the uranium recovery technically unfeasible, because of the high volumes of chemical reagents needed to operate. To eliminate the chloride ions selectively, a modified electrodialysis (ED) process was developed. The ED process was made of a three–compartment cell. This system removed selectively the chloride ions, and replaced them with sulphuric ions, without modifying the composition of the copper PLS solution, to allow a continuous operation of the copper production plant. The ED process decreased the chloride content from 22 g/L to 6 g/L. Finally, static and dynamic load tests were performed for both the original PLS and the treated PLS, using 3 different anion-exchange resins: Dowex-1, Lewatit A365 and Lewatit MP62-WS. The loading capacity of the ion-exchange resins was increased 4 times approximately.

The adsorption of As(V) on poorly crystalline Fe oxyhydroxides, revisited: Effect of the reaction media and the drying treatment

Arsenic (As) adsorbed on Fe oxyhydroxides (adsorbent) is widely occurring in many environmental settings such as in acid mine drainage systems or in the hydrometallurgical operations to form Fe-As coprecipitates. However, the influence of the reaction media and the drying treatment on the microstructure of the directly formed adsorbents at various pHs was still not fully understood. In this work, As adsorption behaviors on various forms of Fe oxyhydroxides were systematically investigated by using XRD, FTIR, Raman, XANES, and HRTEM. The results revealed that at weak acidic pH, more As could adsorbed on the suspension adsorbent formed in sulfate and chloride media than that in nitrate media, possibly due to the microstructure alteration of the adsorbent in the presence of sulfate and chloride. Besides, the increasing crystallinity of the Fe oxyhydroxides and the aggregation effect after drying were the major reasons why less As could be hold by the dried adsorbents than that of the corresponding suspension adsorbents. These findings could shed more light on the nature of the Fe oxyhydroxides which may be helpful for more precisely predicting the fate of some toxic metal(loid)s in the environment.

Selective recovery of cobalt from mixed lithium ion battery wastes using deep eutectic solvent

• Exclusive extraction of copper was attained by leaching with DES at 90 °C. • An extraction yield of 90% for cobalt and only 10% for nickel was reached. • Role of DES degradation during leaching was investigated. • Recovered lithium cobalt oxide shows performance equal to commercial material. • DES solution was reused delivering fairly satisfactory leaching performances. Despite the efforts devoted to the development of new cathodic materials, cobalt-based lithium-ion batteries (LIBs) remain the first choice for many applications, turning cobalt into a critical raw material. Here, we report a method for the selective recovery of cobalt from mixed LIBs electrode materials. The method relies on the application of a green deep eutectic solvent (DES) and yields an extraction of 90% for cobalt and only 10% for nickel. A solvent extraction procedure was optimized to recover cobalt as cobalt oxalate, which was employed to produce lithium cobalt oxide cathode material. This produced cathode material delivered a discharge capacity of 150 mAh g −1 and a capacity retention between 10 and 100 galvanostatic cycles of 83%. Remarkably, the residual DES solution was reused delivering the same cobalt extraction attained using the fresh DES. Cobalt separation constitutes one of the major bottleneck during LIBs recycling, requiring costly and complex hydrometallurgical operations. The demonstrated selectivity of the implemented leaching method, along with the possibility to reuse the residual DES solution, paves the way to a green recycling alternative allowing for the reintroduction of strategic materials into the LIBs production chain.

Development of a 3D dual pore‒system leaching model: Application on metal extraction from oxide copper ore

Leaching from packed ore beds in hydrometallurgical operations involves various sub-processes, including flow of solution, transport of leaching agent and leached product, liquid-solid reactions at the mineral surface and transfer of reaction heat, in heterogeneous multi-scale porous media. A 3D dual pore‒system leaching model based on heterogeneous ore pack geometry reconstructed from X-ray computed tomography (CT) images was developed to account for the coupled flow–transport–reaction–heat transfer processes across the pore scales of inter-particle macro-pore and intra-particle micro-pore. The model was deployed to investigate the leaching kinetics of an oxide copper ore by sulphuric acid. Ultimately, the velocity field, mineral leaching rate, concentration of leached ions, concentration of leaching agent and temperature were solved numerically by finite element method. The influence of leaching agent concentration, irrigation rate and environment temperature on the competitive leaching of malachite and gangue minerals was revealed. The dual pore‒system model is able to provide insights into the heterogeneous leaching behaviours that otherwise cannot be revealed by models built on basis of uniform geometries.

Investigation of Alumina-Based Ceramic Production from Aluminum Black Dross

High-energy consumption in primary aluminum production (from bauxite ores) makes secondary aluminum production (from metallic raw materials such as scrap and dross) very critical. Aluminum dross, as a waste, arises in pyrometallurgical processes, and it is the mixture of metallic Al, Al2O3, other metal oxides, metal halides, and some other compounds like AlN. Aluminum dross has two subgroups (white and black) with respect to its metallic aluminum content. White dross is a secondary aluminum resource because of its high metallic aluminum content, whereas black dross, having low metallic aluminum content, is generally disposed in dumping areas. In the present study, it was aimed to develop a simple technique to valorize aluminum black dross in the form of alumina-based ceramic materials through pyrometallurgical (calcination) and hydrometallurgical (leaching) operations. Moreover, thermochemical simulations were conducted by using HSC Chemistry 6.12 software to simulate calcination conditions. After leaching experiments, an alumina-based ceramic containing approximately 36.8% Al2O3, 61.4% MgAl2O4 with 1.8% Na2FeO4, which might be available to use as a spinel refractory in steel smelting furnaces, was obtained in the experiment carried out in a solution containing 10 mL H2SO4 and 40 mL distilled water (3.5 M). Moreover, the sinterability of the alumina-based ceramic was investigated at the temperatures from 1350 to 1550 °C. In the sample which was sintered at 1550 °C, a density value of 3.15 g cm−3 and a hardness value of 69.58 HV were measured.

Hydrometallurgical operations in complex technology of limonite ores processing

Hydrometallurgical operations in complex technology of limonite ores processing

The effect of the chloride ion on chemical degradation of LIX 984N extractant

Water supply is becoming an increasingly important aspect of hydrometallurgical operations due to water deficiency. This problem may significantly lessen if the extraction processes can incorporate the usage of saltwater throughout the whole hydrometallurgical operation. In this research, the effect of chloride ion on the chemical degradation of LIX 984N was investigated. It was shown that chloride does not directly degrade LIX 984N. However, it has a catalytic effect on the hydrolysis and nitration of the extractant. The synergic effect of chloride on the extractant degradation through hydrolysis and nitration mechanism was assessed at different acidities and mixing times for up to three months. The presence of chloride ion accelerated the degradation of LIX 984N through both hydrolysis and nitration processes. Additionally, the impact of degradation processes on copper maximum loading, extractant viscosity, copper extraction, impurity entrainment, extraction selectivity, and copper stripping were assessed. The structure of the degraded extractant and its compositional changes was studied using Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC–MS) analysis. Degradation of the extractant resulted in a decrease in maximum copper loading, increasing entrainment of impurities, increasing extractant viscosity, lower copper extraction, and less efficient stripping of copper. Samples degraded in the presence of chloride functioned less efficiently in comparison to samples degraded in the absence of chloride. Moreover, structural changes were more noticeable in samples mixed with an aqueous solution containing chloride.

Izdvajanje kobalta iz primarnih i sekundarnih materijala - pregled

<b>Introduction/purpose:</b> Cobalt is a strategic metal for industrial application. Cobalt recovery from oxidic ores such as laterite and sulphidic ores, and from secondary materials during acidic treatment and precipitation is a highly used strategy ensuring different products such as cobalt hydroxide, cobalt oxide, and finally metallic cobalt. <b>Methods:</b> Familiarity with cobalt behavior in hydrometallurgical processes such as dissolution at atmospheric and high pressure, precipitation, neutralization, filtration and hydrogen reduction is most important for cobalt recovery from ores and secondary materials. Pyrometallurgical methods such as roasting and flash smelting are applied for the treatment of sulphidic ores combined with solvent extraction and electrolysis in order to obtain cathodic cobalt. <b>Results:</b> Powders of nickel-cobalt hydroxide were obtained from ores using sulphuric acid under high pressure in an autoclave and after precipitation with MgO. Solvent extraction was used to separate cobalt from nickel. The final step of cobalt recovery from a solution is using electrolysis. Cobalt and cobalt compounds such as cobalt carbonate and cobalt hydroxide can be obtained from secondary materials in hydrometallurgical operations. <b>Conclusion:</b> Hydrometallurgical and pyrometallurgical processes are mostly applied for cobalt recovery from primary ores (oxidic and sulphidic compounds) and from secondary materials (cemented tungsten carbide, polycrystalline diamond blanks, and waste cathodic materials from lithiumion batteries).

The importance of sample preparation in the hydrometallurgical processing of refractory gold concentrates

The article indicates the importance of thorough preparation of concentrate samples before hydrometallurgical operations; the experiments on studying of the factor of the size of the material are described. The comparative analysis of particle size after conventional and fine grinding is carried out. As obligatory stage of preparation of the crushed concentrate before autoclave leaching, the decarbonization process is studied. On the basis of the conducted experiments, the optimal regime of the autoclave leaching process is revealed, which provides the oxidation degree of sulfide sulfur of the order of 99%.

Uranium and molybdenum recovery from copper leaching solutions using ion exchange

This work shows the technical feasibility to recover uranium and molybdenum from industrial copper leaching solutions (PLS). Both were obtained as by-products from hydrometallurgical operations of the Chilean copper mining industry, using the ion exchange technique. This process recovered uranium and molybdenum, without disturbing or changing the normal operation of the overall copper production process. Uranium concentration was 17 mg/L, while molybdenum concentration was 50 mg/L. Four different anionic resins were tested, along with the influence of impurities over the breakthrough and saturation points achieved. In a first instance, two resins were chosen based on their Langmuir parameters, namely, maximum load capacity (Qmax) and separation factor (RL): L-MP62 and M43. The overall dynamic process consisted in a pre-conditioning step for the resin, using a weak hydrochloric acid solution. Next, the copper PLS solution feeds the fixed bed of the ion exchange column. Once the PLS solution saturates the anionic resin, a hydrochloric solution extracts uranium, and a sodium hydroxide solution extracts molybdenum. The final products were purified elution solutions with 500 mg/L uranium and 800 mg/L molybdenum, respectively.

A study of the metallic silver dissolution with the MEA-NH3-Cu system

Leaching of silver from minerals has been studied for decades. Recently, research has been focused on the substitution of cyanide (because of its high toxicity) from hydrometallurgical operations. In this sense, the development of alternative-green leaching solutions for the recovery of metallic silver from minerals and urban mines is necessary. In this research, a thermodynamic-kinetic study of the alternative system “monoethanolamine (MEA)-ammonium sulfate-cupric sulfate” was performed for the dissolution of metallic silver, varying the pH and the cupric ion concentration at room temperature. Furthermore, this research aims to evaluate the silver dissolution behavior at a pH lower than 10.2, elucidating the rate determining step of the silver dissolution process at these conditions of pH and cupric ion concentration. Thermodynamic results confirm that the MEA and NH3 can complex silver generating the species: Ag(MEA)2 +, AgMEA-, Ag(NH3)2 +, AgNH3 + respectively. It was evaluated the effect of varying the pH (8.8, 9.9 and 9) and the cupric sulfate concentration (0.1, 0.15 and, 0.2 M at pH 9) on the kinetics of silver dissolution. The results revealed, the possibility to leach a 39% of silver using a leaching solution containing: 0.15 M cupric sulfate, 0.05 M MEA and 0.4 M ammonium sulfate at pH 9. The kinetic analysis showed that the silver dissolution is controlled by the diffusion of fluid species through a porous layer composed of copper oxides, which was ratified by SEM and EDS analysis. Finally the present paper, open the possibility to optimize the molar ratio MEA:NH3 to maximize the silver dissolution kinetics. Keywords: Leaching, metallic silver, MEA, ammonium.

Leaching method selection for Caldag lateritic nickel ore by the analytic hierarchy process (AHP)

Leaching is an important process in hydrometallurgical operations. This process is used to extract metals from the ores by dissolving them in a lixiviant. It is desired that the leaching method is able to provide high extraction rate at minimal capital and operational costs. There are many parameters that can affect the leaching efficiency and thus, the process of selecting a leaching method is complex. In this study, the use of Analytic Hierarchy Process (AHP) method to select an appropriate leaching method for Caldag lateritic nickel ore has been performed. The application of AHP is assisted with the use of ExperChoice® 2000 Software. The results shown that heap leaching (HL) is the most attractive leaching method with a rating of 0.592, followed by atmospheric leaching (AL), and high pressure acid leaching (HPAL) with ratings of 0.293 and 0.115, respectively. In addition, sensitivity analyses have been applied to investigate the impact of the main criteria on the alternative leaching methods. It was found that HPAL can be selected when economical main criteria decreased from 76.1% to 16.3%.

Numerical simulations of liquid-liquid flow in a continuous gravity settler using OpenFOAM and experimental verification

In several applications involving solvent extraction, crude oil processing, hydrometallurgical operations; separation of liquid-liquid dispersions is a challenging task. In the present work, we report numerical simulations of liquid-liquid flow in a continuous gravity settler and their experimental validation. The twoPhaseEulerFoam module available in open source CFD code OpenFOAM was developed further to simulate three-phase flow of aqueous and organic phases in a continuous gravity settler with free gas region at top (freeboard region). The predicted dispersion band thickness and spatial variation of organic phase volume fraction were verified using the measurements performed in a laboratory-scale settler. While the measured and predicted dispersion band thickness agreed well, owing to the constant drop size considered in the present work, the predicted organic phase volume fraction was found to be lower than the measurements. The effects of liquid flow rate, drop diameter, inlet baffle position and organic phase density were investigated. With the increase in drop diameter, interestingly, it was found that the dispersion band thickness was reduced and significant fluctuations in the local organic phase volume fraction were observed. The fluctuations were found to decrease with increase in the total liquid flow rate. The experimentally validated computational model will be useful in designing large-scale continuous gravity settlers and optimize their separation performance.