Recovery Of Valuable Elements Research Articles

Assessment of the Risk of the Loss of Supply, the Recycling Rate and the Degree of Substitutability of Elements in the NdFeB Magnets of a Small Wind Farm Generator

Existing shortages on the market of critical and strategic raw materials and problems with the supply chain of selected raw materials, mainly those from China, indicate the need to develop recycling technologies for devices containing the above-mentioned materials. The aim of this work should be to ensure a sustainable supply of raw materials for industry in the EU. One potential source of raw materials may be small-power wind turbine generators equipped with permanent magnets (NdFeB). This research allowed for the development of a methodology for disassembling a generator containing NdFeB magnets in order to determine the shares of individual elements. Due to the significant shares of critical and strategic elements in permanent magnets, a detailed economic analysis was carried out. Based on the research results, economic benefits resulting from the recovery of valuable elements were indicated. The significant market value of critical and strategic raw materials contained in neodymium magnets was demonstrated. The risk of the loss of supplies, the recycling rate and the possibility of replacing the elements in permanent magnets were assessed.

Research progress of leachate treatment in waste transfer station

The garbage leachate generated by the waste transfer station has the characteristics of scattered water sources, relatively small water quantity, large fluctuations in water quality and quantity, and high concentrations of organic matter, ammonia nitrogen, suspended solids, and other pollutants. These characteristics make it prone to environmental hazards. This paper analyzes the characteristics and hazards of leachate from waste transfer stations and introduces the current research status of physico-chemical, biological, and combined treatment of leachate from waste transfer stations. Meanwhile, this paper introduces engineering practices for leachate treatment in waste transfer stations, offering a valuable reference for research and engineering practices in this field. Finally, this review discusses pretreatment, economic, low-carbon, and high-efficiency treatment methods and facilities, the recovery of valuable elements, energy recycling technologies, and the demand outlook for high-standard deep treatment processes.

Acid Leaching of CIGS Solar Cells: A Focus on Silver and Indium

Solar electricity from photovoltaics (PV) contributed to about 4.5 % of the global electricity production in 2022 and is expected to continue increasing by 2050 [1]. Therefore, both manufacturing waste and end of life waste are expected to reach a considerable volume in the upcoming decade. However, recycling methods for this type of waste are still at a very early stage of development. The thin film CIGS PV technology achieves high energy conversion efficiencies [2] and it is also used in promising newer technologies, namely multijunction solar cells. However critical elements like indium (In) and gallium (Ga), and often valuable silver (Ag) as conductive grid, are essential for the achievement of such efficiencies. Therefore, environmental, economic and resource depletion reasons demand the recovery of these elements.In industrial scale, there is currently no established recycling activity on CIGS containing materials. In lab scale, research mainly focuses on recycling of pure CIGS material production waste, which are free of any other element except for their 4 constituent elements in contrast to the real solar cells or PV. However, monitoring and controlling the impurity levels in the recycling of complex waste is of outmost importance, since the higher the purity of the recovered materials, the more economically viable their recycling business becomes. At the same time, the existing literature on the recycling of pure CIGS waste suggests the use of strong mineral acid solutions and high temperatures for the recovery of their elements. The case is similar for Ag, with some studies on its recovery only from another PV technology, namely silicon PV, being available and describing similarly harsh recovery conditions. Although such conditions can be efficient in many cases, they are not environmentally friendly and can be costly for the industry as well. To the best of our knowledge, the only available research work on the recovery of valuable elements from CIGS solar cells (Ag, In and others) using more benign recovery conditions compared to the ones that have been investigated so far (i.e. lower acid concentrations and room temperature), is our recent research work on leaching with nitric acid (HNO3) [3].In our current work we investigated the leaching of flexible CIGS solar cells with a stainless steel substrate production waste at room temperature and acid concentrations no higher than 2 M. The leaching efficiency of Ag and In was studied under different leaching times, acid leaching agents and concentrations, as well as geometrical surface area to liquid ratios (A:L). The elemental composition of all the elements that were likely to be present in the solar cell was measured in all the leachates with ICP-OES. The solid materials left on the cell’s surface after the treatment were characterized in terms of morphology and elemental composition with SEM-EDS, when necessary.The results proved that the choice of the leaching agent plays an important role in the recovery of the different elements present in the cell. It was also confirmed that higher acid concentrations achieve higher leaching recoveries for the same leaching conditions, as expected. As far as the A:L ratio is concerned, in many cases, higher A:L ratios achieved higher efficiencies, probably due to better oxygenation of the solutions.An example of the efficiency of the method is presented in Fig. 1, in which the Ag grid line of the untreated sample (Figure 1a, b) looks white under SEM due to the presence of Ag particles. After the acid treatment of the cell with 2 M HNO3 for 24h, the Ag particles of the Ag grid lines have disappeared, making the line look black (Figure 1c).In total, two important conclusions were drawn: a) selective leaching of various elements for achievement of higher purity products is possible by adjusting the leaching parameters and b) a complete recovery of Ag is possible within one day with more environmentally friendly conditions than the ones suggested so far.

Separation and recovery of valuable elements from acid leachate of spent carbon cathode by fractional precipitation method

Spent carbon cathode (SCC), a hazardous waste from aluminum electrolysis industry, has been confirmed that it can be direct treated and purified by hydrothermal acid leaching in the previous study. This work focuses on a hydrometallurgical process to separate and recover the valuable elements from the acid leachate of SCC by fractional precipitation method. Thermodynamic calculation, single factor experiment and characterization of the products are utilized to obtain the ion-transformation mechanism, optimize the conditions of process and confirm the physicochemical properties of the products. The results indicate that 92.6 % Si, 93.07 % Al and more than 99 % Fe, Ca are recovered from the acid leachate in the form of Na2SiF6, Na3AlF6, Fe(OH)3 and CaF2 respectively and concentration of F- in acid leachate decrease from 3115 mg/L to 6.6 mg/L when the conditions attach the optimal. Finally, Na and Cl in acid leachate is recovered in the form of NaCl via evaporation crystallization. The whole process completes the separation and recovery of all elements in acid leachate of SCC, which has no wastewater discharge and is a closed-cycle route.

Preparation of vanadium electrolyte from vanadium shale leaching solution with high concentration chloride using D2EHPA

A process for preparing vanadium electrolyte accompanied by the recovery of valuable elements from vanadium shale was proposed. The results showed that under the optimal extraction conditions of the feed solution at a pH of 2.6, D2EHPA concentration of 20%, phase ratio (O/A) of 1:1, extraction time of 8 min, H2SO4 concentration of 4 mol/L, and stripping time of 30 min, the vanadium extraction rate was 99.3% and the vanadium stripping rate was 99.8%. The composition and electrochemical performance of the electrolyte were studied in detail. The solution chemical and FTIR analysis showed that chloride ions in the leaching solution formed complexes with vanadium ions, promoting vanadium extraction. The proposed method in this study realized the comprehensive utilization of vanadium shale and prevented toxic environmental pollution in the preparation process of vanadium electrolyte.

Waste Treatment and Resource Utilization: Removal and recovery of soluble impurities from nitric acid leaching residue of phosphate rock by electrokinetic

Electrodynamic cleaning techniques for removing and recycling soluble impurities (phosphorus, fluorine, Sr, Pb, Cr, Cu, and Mn) in nitric acid leaching residues of phosphate rock (NG) were investigated. The PO43− concentration of the anode chamber was increased to 207.94 mg/L, while the F− concentration of the cathode chamber rose to 28.33 mg/L. Besides, the soluble phosphorus levels in the cathode regions (R1 and R2) were decreased by 98.02% and 90.16%, respectively. Moreover, the dissolved heavy metals, namely Mn, Cr, Cu and Pb in NG were enriched in the anode chamber, and Sr was enriched in the cathode chamber. The synergistic effects of electrocoagulation and electrodeposition lowered the levels of phosphate, fluoride, and heavy metals in the cathode, thus reducing the decreasing electrical conductivity. The migration and accumulation behaviors of soluble impurities in an electric field were regulated by electromigration, electro-osmotic flow, and electrolysis reaction. Considering that, this paper provides support for the harmless treatment of NG and the recovery of valuable elements, which is conducive to developing the wet-process phosphoric acid process and reducing the large-scale storage of phosphogypsum.

Mechanical Activation-Assisted Recovery of Valuable Metals from Black Mass in the Form of Fe/Cu Alloys

Pyrometallurgy is a popular industrial method that is employed in the recovery of valuable elements from black mass (BM), which is produced by pretreatment of Li-ion batteries. This method struggles with some downsides, such as the incineration of graphite and high energy consumption. In this study, the goal is to utilize graphite in the BM to produce a master alloy in an attempt to decrease the energy input requirement. To achieve this, metal oxides (Fe2O3 and CuO) are added to the BM to produce an Fe/Cu-based alloy containing Co/Ni as alloying elements. Mechanical activation is also employed to decrease the energy requirement and to increase the amount of metal oxide that can be reduced by the graphite in the BM. The results revealed that it is possible to produce the aforementioned alloys, the efficiency of which can be improved by applying mechanical activation. After 1 h of milling, the required heat flow for producing Fe- and Cu-based alloys is lowered for ~10 and ~25 kWh, respectively. Plus, the direct CO2 emission decreases for 13–17% in the iron system and 43–46% in the copper system.Graphical

Eco-design for perovskite solar cells to address future waste challenges and recover valuable materials

Photovoltaic development should be steered by the circular economy. However, it is not. In case of perovskite photovoltaics even current environmental directives divert from profitably recycling. Here, we study the profitability of noble metals recovery from wasted perovskite solar cells depending on recycling routes. Our results show that substrates play a major role in the recovery of precious metals and in contrast to previous research even recycling carbon-based devices could reach profitability. Going beyond the recovery of valuable elements, our findings show that revival of the perovskite solar cells is strongly dependent on the device architecture, so far viable for mesoscopic structures with carbon back contacts. Perovskite solar cells are still at the development stage, but the window of opportunity to ensure eco-design will close with market entry, and device complexity might compromise profitability recycling and even result in failure of recovery critical materials. Therefore, its eco-design should be prioritized by materials researchers to develop devices, where valuable components can be separated and liberated with safe and low energy processes.

Experimental study on the preparation of ferrophosphorus alloy using dephosphorization furnace slag by carbothermic reduction

Abstract With the development of the duplex converter process, the amount of dephosphorization furnace slag is increasing, and it has relatively low basicity. It has been indicated that the recovery of valuable elements from dephosphorization slag by carbothermic reduction has great environmental and economic benefits due to its high content of P, Fe, and Mn. In this work, the experimental slag was reduced by carbon powder in a resistance furnace at 1,550°C. The results show that 76.82% of P, 99.60% of Fe, and 11.82% of Mn in the slag are recycled at basicity 1.0, and the recovery ratios of P, Fe, and Mn are 34.58, 78.89, and 13.85% at basicity 2.0, respectively. The ferrophosphorus obtained from the reduction of the dephosphorization furnace slag can be used as a raw material for steel-making alloy, and the residual steel slag can be used as cement and other building materials. This work provides a reference for recycling and resource utilization of dephosphorization furnace slag.

Oxidized pellets production from stainless steel solid wastes: induration characteristics and harmful elements migration behavior

Stainless steel solid wastes (SSSW) treatment and recycling has attracted wide attention in recent years because of more stringent environment laws and regulations. Recycling of SSSW through carbothermal reduction of chromite (SRC)-electric furnace (EF) process is favorable to the effective treatment of SSSW and recovery of valuable elements. In this paper, SSSW are used to manufacture sufficiently strong oxidized pellets with the coexistence of chromite concentrates for ferrochrome production based on the SRC-EF process. The induration characteristics and harmful element migration behavior during oxidation of pellets are investigated and revealed. It is found that the oxidized pellets made from 100% SSSW possess low mechanical strength. Increasing the ratio of chromite concentrate from 0% to 80% can significantly improve the pellet strength from 460 N/pellet to 1868 N/pellet when preheating at 1000 °C for 12min and roasting at 1275 °C for 15min. Oxidized pellets made from SSSW and chromite are mainly dominated by the solid-phase consolidation due to the recrystallization of iron-rich spinel phases and sesquioxide derived from oxidation of ferrous oxides. In addition, slag bonding of CaO–CaF2–SiO2–FeO system also plays an important role in the consolidation of oxidized pellets. As for pellets made from 32% SSSW and 68% chromite concentrate, 39.96% F, 91.06% S, 66.73% Cl can be removed from the pellets when preheating at 1000 °C for 12 min and roasting at 1275 °C for 15 min.

Facile preparation of a remarkable MOF adsorbent for Au(III) selective separation from wastewater: Adsorption, regeneration and mechanism

The recovery of valuable elements from wastewater could reduce pollution and increase resource utilization. A novel Zr-based MOF (DONA-MOF) was synthesized using an organic linker and several chelates as adsorbent. The successful preparation of DONA-MOF was confirmed by SEM, EDS, FTIR and XRD. The adsorption performance of DONA-MOF is systematically evaluated through a series of adsorption experiments. DONA-MOF has an excellent removal effect on Au(III) in pH 2–9. The adsorption reaches equilibrium in 120 min at 100 mg·L-1. 637.5 mg·g−1 is the maximum adsorption capacity of DONA-MOF at 303 K. The kinetics and isotherm models show that the adsorption behavior of Au(III) on DONA-MOF is monolayer chemisorption. In addition, thermodynamic study indicates a spontaneous and endothermic adsorption behavior. Wastewater experiments show that DONA-MOF can preferentially adsorb Au(III). The adsorption-desorption experiments show that DONA-MOF still has an excellent removal effect after five cycles. The R2 of Xm2r linear fitting is 0.99005, which indicates that the chelation interaction is involved in the adsorption process. The results of zeta potential and XPS show that electrostatic attraction, chelation and reduction are the main adsorption mechanism. Since DONA-MOF has significant adsorption capacity and excellent selectivity to Au(III), it is expected to be applied in practice.

The potential of Pseudomonas for bioremediation of oxyanions.

Non-metal, metal and metalloid oxyanions occur naturally in minerals and rocks of the Earth's crust and are mostly found in low concentrations or confined in specific regions of the planet. However, anthropogenic activities including urban development, mining, agriculture, industrial activities and new technologies have increased the release of oxyanions to the environment, which threatens the sustainability of natural ecosystems, in turn affecting human development. For these reasons, the implementation of new methods that could allow not only the remediation of oxyanion contaminants but also the recovery of valuable elements from oxyanions of the environment is imperative. From this perspective, the use of microorganisms emerges as a strategy complementary to physical, mechanical and chemical methods. In this review, we discuss the opportunities that the Pseudomonas genus offers for the bioremediation of oxyanions, which is derived from its specialized central metabolism and the high number of oxidoreductases present in the genomes of these bacteria. Finally, we review the current knowledge on the transport and metabolism of specific oxyanions in Pseudomonas species. We consider that the Pseudomonas genus is an excellent starting point for the development of biotechnological approaches for the upcycling of oxyanions into added-value metal and metalloid byproducts.

Cobalt Electrochemical Recovery from Lithium Cobalt Oxides in Deep Eutectic Choline Chloride+Urea Solvents.

Electrochemical recovery of the cobalt in deep eutectic solvent shows its promise in recycling and recovery of valuable elements from the spent lithium-ion battery due to its high selectivity and minimal environmental impacts. This work unveiled the roles of the substrates, applied potentials, and operating temperatures on the performance of cobalt electrochemical recovery in a deep eutectic choline chloride+urea solvent. The solvent contains cobalt and lithium ions extracted from lithium cobalt oxides - 3an essential lithium-ion battery cathode material. Our results highlight that the substrate predetermines the cobalt recovery modes via substrate-cobalt interactions, which could be predicted by the cobalt surface segregation energies and crystallographic misfits. We also show that a moderate cathode potential under -1.0 V vs. silver quasi-reference electrode at 94-104 °C is essential to ensure a selective cobalt recovery at an optimal rate. We also found that the stainless-steel mesh is an optimal substrate for cobalt recovery due to its relatively high selectivity, fast recovery rate, and easy cobalt collection. Our work provides new insights on metal recovery in deep eutectic solvents and offers a new avenue to control the metal electrodeposition modes via modulation of substrate compositions and crystal structures.

Kinetics on Chromium-Bearing Vanadia-Titania Magnetite Smelting with High-Basicity Pellet

The effects of high-basicity pellet on smelting chromium-bearing vanadia-titania magnetite are investigated via thermodynamic smelting and non-isothermal kinetics experiments. The thermodynamic results indicated that the high-basicity pellet significantly affects and ameliorates the softening-melting-dripping behaviors during the smelting process. As the high-basicity pellet ratio increased from 0 wt.% to 52 wt.%, the range of softening temperature [T40–T4] decreased from 121 °C to 84 °C and the melting-dripping temperature [Td–Ts] decreased from 224 °C to 169 °C. Moreover, the apparent activation energy of non-isothermal kinetics also decreased from 99.91 kJ·mol−1 to 66.74 kJ·mol−1. Additionally, the reaction mechanism of high-basicity pellet on smelting chromium-bearing vanadia-titania magnetite was investigated via thermodynamic calculations of Gibbs free energy and characterizations of the titanium slag. Therefore, combined with the lowest permeability index, the fastest non-isothermal reduction rate, the highest recovery of valuable elements and the minimum content of titanium carbonitride, the preferable high-basicity pellet ratio was considered to be 11~23 wt.%.

Dependence on the distribution of valuable elements and chemical characterizations based on different particle sizes of high alumina fly ash

Understanding the influence of the particle size on the distribution of various elements of high alumina coal fly ash (HAFA) is of significance to the utilization of valuable elements in fly ash. The distribution of valuable elements and the chemical characterizations of various particle sizes of HAFA were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis etc. in this work. It indicated that the contents of most of the metal oxides, including Al2O3, Fe2O3, CaO, Ga2O3, TiO2, and Li2O, decreased as the particle sizes of HAFA increasing. The contents of the nonmetal oxides, including SiO2 and organics, however, increased with the sizes increasing. For the phases distribution, the spherical mullite crystalline phase and the corundum phase were more abundant in the smaller particle sizes, while the amorphous glass phase and quartz were more abundant in the larger particle sizes. In addition, the desilication efficiency increased from 38.08% to 39.30% though mechanical pretreatment method. Interestingly, it was observed that the glass phase Al2O3 reacted with the sodium silicate solution to form zeolites, which accounted for a 22.85% of the mass after desilication. Classification may be an important pretreatment step in the recovery of valuable elements from HAFA due to the differences between the different granularities.

Multianalysis Characterization of Mineralogical Properties of Copper-Lead-Zinc Mixed Ores and Implications for Comprehensive Recovery

Copper-lead-zinc mixed ore in Tibet, China, is a complex and refractory polymetallic ore resource; thus, ascertaining its mineralogical properties is very important for comprehensive recovery of valuable elements. In this work, the mineralogical properties of this copper-lead-zinc mixed ore have been characterized in detail following a multidisciplinary approach, including chemical, phase, x-ray diffraction (XRD), electron microprobe, and mineral liberation analyses. The results show that the raw ore contained 0.53% Cu, 1.29% Pb, and 0.54% Zn; the oxidation rates of copper, lead, and zinc were 40.21%, 79.31%, and 84.83%, respectively. The Au and Ag contents in the raw ore were 0.28 g/t and 23.6 g/t, which can be comprehensively utilized along with the recovery of copper, lead, and zinc. The gangue mainly contained SiO2, CaO, and Al2O3. Copper in the raw ore mainly existed in bornite, duftite, chalcopyrite, and chrysocolla; lead mainly existed in cerussite, duftite, and galena; zinc mainly existed in willemite, hemimorphite, and sphalerite. The complexity in the embedding and wrapping relationships, fine-grained dissemination, high oxidation, and considerable differences in the floatability of various minerals result in difficulties in recovering the target minerals using a single method. Based on the systematic mineralogical properties obtained, an integrated technology of “bulk flotation-oxidation roasting-hydrometallurgy” has been proposed to enrich and separate copper, lead, and zinc in the ore, providing new ideas for the comprehensive and efficient utilization of polymetallic mineral resources in Tibet.

Characterization of Two Sludges from a Pyrometallurgical Copper Smelting Complex for Designing a Se and Pb Recovery Proposal

Gas scrubbing sludge (SS) and fine dust of converters (SC) are wastes generated in the off-gas cleaning system of smelting and converting processes. Both wastes are considered hazardous materials due to their high metal contents and leaching characteristics. The main purpose of this study was to gain essential knowledge on the recovery of valuable elements contained in these wastes. Thus, an exhaustive characterization was carried out to determine the composition, mineral phases, particle size, and leachability of both wastes (SS and SC) as a preliminary step to select the most appropriate applications and treatment for them. These wastes are composed of fine particles (~ 95% 20%) as anglesite (PbSO4), while SS presents a high concentration of Se (34%), which is mainly identified as metallic selenium. Therefore, these residues could be used as secondary sources of Pb and Se. The recovery of Se by roasting process and Pb recovery by hydrometallurgical route seem to be the best options for the management of these wastes.

Kırmızı Çamurdan Değerli Elementlerin Geri Kazanımına Yönelik Yapılan Araştırmaların Derlenmesi

An alternative application is the recovery of valuable elements from red mud. Red mud contains appreciable amounts of industrial metals such as Fe, Al and Ti and rare earth elements like Sc, Ce and La. Extensive researches have been carried out into the topic worldwide. Parallel with the other countries worldwide, researches have also been carried out in Turkey on the utilization of Seydisehir red mud. Application of red mud in construction materials, ceramic and glass industry, water purification and as coloring or catalytic agent has been proposed in the literature. However, these applications are not noticed by the companies and investors because the relatively low economic value of the products or because of their limited market which cannot respond to the huge amounts of red mud disposal. Red mud is a waste material of the Bayer process for alumina production from bauxite ore. Red mud is generally pumped to disposal in an artificial pond. In addition to the vast area of the land occupied, red mud pollutes water resources and leads to environmental issues because of its high alkalinity. This paper reviews and classifies the researches into the extraction of valuable elements from the red mud carried out in Turkey and worldwide.

Separation and Recovery of Valuable Elements from Spent CIGS Materials

A separation–recovery method was proposed in this study to recover valuable elements from spent copper–indium–gallium–selenium (CIGS) materials based on the different physical and chemical properties of their components. Spent CIGS materials were first roasted at 1000 °C to achieve phase transformation. During the transformation, 99.9% selenium was volatilized and recovered via oxidation into selenium dioxide. Meanwhile, other metals were converted from selenides to oxides. Subsequently, the indium and gallium in the roasting product were separated from copper via sulfuric acid leaching and precipitation. After the precipitation product was roasted, mixed oxides that contained 90.59% indium oxide and gallium oxide were obtained. The recovery rates of indium and gallium were 97.74% and 97.41%, respectively. Lastly, 99.83% of the copper in the filtrate was recovered via solvent extraction. The selective separation and recovery of valuable metals can be achieved through the rational utilization of the physic...

Desulfurization of aged gold-bearing mine tailings

Desulfurization is a novel approach for the reclamation of abandoned mine sites that can have environmental and economic benefits, particularly when combined with the recovery of valuable elements. Desulfurization by flotation produces sulfide-lean tailings, which can be used as cover materials, and sulfide-rich concentrates, which may contain valuable sulfide-associated metals such as gold. Because unreclaimed, aged tailings are often at advanced stages of the weathering process the surfaces of sulfide minerals are usually encapsulated by oxidation products. This surface oxidation reduces sulfide hydrophobicity and, thus, flotation efficiency. Therefore, the main goal of this study was to evaluate how effectively various mechanical pretreatment processes enhance the flotation process for aged tailings. After initial characterization of an aged tailings sample, various parameters were adjusted to optimize the desulfurization process. Subsequently, several mechanical pretreatments (i.e., agitation, attrition, regrinding) were tested. Results show the possibility to produce a concentrate rich in sulfides and gold.