Process For Recovery Of Metals Research Articles

Catalytic recovery of metals from end-of-life polycrystalline silicon photovoltaic cells: Experimental insights into silver recovery

A steady increase in end-of-life (EoL) polycrystalline silicon photovoltaic (c-Si PV) panels is necessitating the development of recycling technologies to guarantee sustainable environmental management and a circular economy. Herein, we propose a comprehensive EoL c-Si PV recycling strategy with an emphasis on selective silver (Ag) recovery. Primarily, a combination of physical and thermal treatment led to the isolation of PV cell fraction from the EoL PV module. Thereafter, a less-toxic, sulphuric acid-hydrogen peroxide (1 M H2SO4- H2O2 1% (v/v %)) lixiviant was used for Ag leaching at 70 °C. A novel catalytic process using platinum-embedded activated carbon (Pt/AC) was used with only hydrogen gas and air to recover selectively and concentrate the Ag+ from the synthetic PV cells leachate. Finally, pure metallic silver (Ag > 99.0 %) was obtained by the conventional electrowinning process. This study also proposes an explicit recovery process for Al, Cu, and Si. In addition, the Pt/AC catalytic process could efficiently recover Cu from the PV cells, similar to Ag. Following the complete recovery of Ag and Cu through Pt/AC, there is sufficient scope to isolate other metals like Al and Pb leaving behind crude Si wafers. Hence, the as-proposed recycling and metal recovery process is a newer approach benefiting industrial implementation.

A multi-stage volatilization and condensation process for green and efficient recovery of valuable metals from High-Sb crude Sn

Circulation of Sb in an Sn refining system strongly affects the production process. In this study, an innovative multi-stage vacuum separation process was developed and successfully applied on an industrial scale. Our results indicate that Sn–Sb alloys can be completely separated by vacuum evaporation. In this study, we used single-factor experiments to investigate the effects of distillation temperature and time on several factors, such as the Sn content in the residue, Sb content in the volatile matter, separation rate, and direct recovery rate of Sb from high-Sb crude Sn. The purity of the obtained Sn and Sb products was above 99%, and the recovery rate of the metal was above 99% under the optimal distillation conditions of 1673 K and 150 min. In addition, we suggest that Sn volatilization occurs due to the presence of SbSn intermetallic compounds. A two-stage vacuum-separation process for high-Sb crude Sn was developed for industrial production. Continuous production data showed that the direct yields of Sn and Sb were 72.99% and 71.15%, respectively. The total power consumption of this process was as low as 1086 kWh/t, which is better than the corresponding parameters of other treatment processes.

Proteomic characterization of metal recovery process realized by marine bacteria bacillus subtilis Hyhel1expossed to bioleaching liquor

Proteomic characterization of metal recovery process realized by marine bacteria bacillus subtilis Hyhel1expossed to bioleaching liquor

A sustainable process for selective recovery of metals from gallium-bearing waste generated from LED industry

With the rapid development of the LED industry, gallium (Ga)-bearing waste generated is regarded as one of the most hazardous as it typically contains heavy metals and combustible organics. Traditional technologies are characterized by long processing routes, complex metal separation processes and significant secondary pollution emission. In this study, we proposed an innovative and green strategy to selectively recovery Ga from Ga-bearing waste by using a quantitative phase-controlling transition process. In the phase-controlling transition process, the gallium nitride (GaN) and indium (In) are converted to alkali-soluble gallium (III) oxide (Ga2O3) and alkali-insoluble indium oxides (In2O3) by oxidation calcination, while nitrogen is converted into diatomic nitrogen gas instead of ammonia/ammonium (NH3/NH4+). By selective leaching with NaOH solution, nearly 92.65% of Ga can be recycled with a leaching selectivity of 99.3%, while little emissions of NH3/NH4+. Ga2O3 with a purity of 99.97% was obtained from the leachate which is also economy promising by economic assessment. Therefore, the proposed methodology compared to the conventional acid and alkali leaching methods is potentially greener and more efficient process for extracting valuable metals from nitrogen-bearing solid waste.

Acid-free extraction of valuable metal elements from spent lithium-ion batteries using waste copperas

A large amount of hazardous spent lithium-ion batteries (LIBs) is produced every year. Recovery of valuable metals from spent LIBs is significant to achieve environmental protection and alleviate resource shortages. In this study, a green and facile process for recovery of valuable metals from spent LIBs by waste copperas was proposed. The effects of heat treatment parameters on recovery efficiency of valuable metals and the redox mechanism were studied systematically through phase transformation behavior and valence transition. At low temperature (≤460 °C), copperas reacted with lithium on the outer layer of LIBs preferentially, but the reduction of transition metals was limited. As the temperature rose to 460–700 °C, the extraction efficiency of valuable metals was greatly enhanced due to the generation of SO2, and the gas–solid reaction proceeded much fast than the solid–solid reaction. In the final stage (≥700 °C), the main reactions were the thermal decomposition of soluble sulfates and the combination of decomposed oxides with Fe2O3 to form insoluble spinel. Under the optimum roasting conditions, i.e., at a copperas/LIBs mass ratio of 4.5, and a roasting temperature of 650 °C and roasting time of 120 min, the leaching efficiencies of Li, Ni, Co and Mn were 99.94%, 99.2%, 99.5% and 99.65%, respectively. The results showed that valuable metals can be selectively and efficiently extracted from the complex cathode materials by water leaching. This study used waste copperas as an aid to recover metals and provided an alternative technical route for green recycling of spent LIBs.

Life Cycle Environmental Analysis of Valuable Metal (Ag) Recovery Process in Plating Waste Water

In 2018, the demand for silver (referred to as Ag) in the electrical and electronics sector was 249 million tons. The demand stood at 81 million tons in the solar module production sector. Currently, due to the rapid increase in solar module installation, the demand for silver is increasing drastically in Korea. However, Korea’s natural metal resources and reserves are insufficient in comparison to their consumption, and the domestic silver ore self-sufficiency rate was as low as 2.2% as of 2021. This implies that a recycling technology is necessary to recover valuable metal resources contained in the waste plating solution generated in the metal industry. Therefore, this study compared and analyzed, the results of the impact evaluation through life cycle assessment according to an improvement in the process of recovery of valuable metals in the waste plating solution. The process improvement resulted in reducing GWP (Global Warming Potential) and ADP(Abiotic Depletion Potential) by 50% and 67%, respectively. The GWP of electricity and industrial water was reduced by 98% and 93%, respectively, which significantly contributed to the minimization of energy and water consumption. Thus, the improvement in recycling technology has a high potential to reduce chemical and energy use and improve resource productivity in the urban mining industry.

Processing of automotive shredder residues: Economic evaluation of a process for energy and high-value metals recovery

Challenges in recycling heterogeneous waste remain untapped. Automotive shredder residue is one such heterogenous waste generated after processing End-of-Life Vehicles, making it difficult to process. There are two impediments to the recycling of ASR. One is the heterogeneity of the ASR (as received), and the other is not knowing what constituents to be extracted from the ASR. The ability of the thermochemical process to transform waste into beneficial products is well known. The objective of this work is based on a techno-economic evaluation of the recovery of energy and high-value metals from Automotive Shredder Residue. The equipment sizing and fabrication cost of each piece used in this process are calculated based on laboratory experiments. An integrated techno-economic study for processing heterogeneous waste ASR has not been studied in the literature previously. The economic evaluation was carried out assuming a plant life of 25 years. In addition, the plant's revenue was generated by the obtained products, and the payback period for energy and metal recovery was found to be 3 years respectively. The capital cost and operating cost for the ASR recycling plant with a combined approach of recovering energy and metals have been estimated from grass root stage. The outcome of this study confirms that ASR recycling has potential value for secondary resources and the process is economically viable. The resource recovery from ASR is an environmentally friendly technology where the maximum utilization rate is raised, along with energy saving and environmental protection by reduction of ASR waste in landfill.

Brassica juncea as a Feasible Hyperaccumulator of Chosen Potentially Toxic Metals Under Extreme Environmental Conditions

Nowadays, many sites are considered waste, due to high potentially toxic metal (PTM) concentration. Recycling of globally critical metals requires development of environmentally friendly processes for metal recovery. To study plants response to elevated Zn and Cu concentration in soil, a greenhouse experiment was designed using hyperaccumulator Brassica juncea. Plants were irrigated daily with PTM solutions, with final mass of both Zn and Cu added to the soil reaching 104.5, 209, 313.5, and 330 mg. After 8 weeks, samples were harvested, dried, weighed, and elemental analysis was conducted using atomic emission spectrometry (Agilent Technologies 4210 MP-AES). Phytotoxicity was determined based on visual observation, biomass, and chlorophyll measurements. The highest accumulation of Zn and Cu was found in the stem and leaf material, with observed concentrations of Zn in the leaf being 16.750 mg kg−1 and 7.170 mg kg−1 of Cu in the stem. The highest allocated in the biomass mass of Zn and Cu was in T4 treatment reaching 25.8 mg and 9.5 mg, respectively. Treatment with 330 mg Zn and Cu application displayed a 62.3% decrease in stem mass, a 25% decrease in average root mass (LD30 reached), and a 59% decrease in leaf mass when compared with the control. With increasing PTM concentration, root, biomass (from about 0.4 to 0.1 g; from about 3.8 to 2.0 g, respectively) and chlorophyll “a” (from about 24 to 19 μg/cm2) decline was observed, which correlates with observed chlorosis. This study reaffirmed the capabilities of B. juncea to bioaccumulate Zn and Cu from an enriched soil and provided further understanding as to how Zn and Cu translocate within plant tissues.

Urban mining of municipal solid waste incineration (MSWI) residues with emphasis on bioleaching technologies: a critical review.

Metals are essential in our daily lives and have a finite supply, being simultaneously contaminants of concern. The current carbon emissions and environmental impact of mining are untenable. We need to reclaim metals sustainably from secondary resources, like waste. Biotechnology can be applied in metal recovery from waste streams like fly ashes and bottom ashes of municipal solid waste incineration (MSWI). They represent substantial substance flows, with roughly 46 million tons of MSWI ashes produced annually globally, equivalent in elemental richness to low-grade ores for metal recovery. Next-generation methods for resource recovery, as in particular bioleaching, give the opportunity to recover critical materials and metals, appropriately purified for noble applications, in waste treatment chains inspired by circular economy thinking. In this critical review, we can identify three main lines of discussion: (1) MSWI material characterization and related environmental issues; (2) currently available processes for recycling and metal recovery; and (3) microbially assisted processes for potential recycling and metal recovery. Research trends are chiefly oriented to the potential exploitation of bioprocesses in the industry. Biotechnology for resource recovery shows increasing effectiveness especially downstream the production chains, i.e., in the waste management sector. Therefore, this critical discussion will help assessing the industrial potential of biotechnology for urban mining of municipal, post-combustion waste.

Automotive Paint Sludge: A Review of Pretreatments and Recovery Options

Automotive paint sludge (PS) is the waste product generated in the painting process of vehicle bodies. Although automotive spray painting is an automated operation, its efficiency is still quite low, since approximately 40–50% of the employed paint does not reach the target and, after being mixed with the collecting water, becomes PS. PS is a very complex material that contains several organic and inorganic components, in addition to 90% water immediately after production. Italian automotive factories produce from 2.5 to 5.0 kg of PS per painted car. If that figure is related to the number of vehicles produced worldwide every year, in the order of 100 million, it determines an annual PS amount in the order of 200,000–500,000 t. Consequently, a proper final destination for PS must be found. The waste management hierarchy and the principles of the circular economy require that we privilege solutions that foresee the recovery of valuable products or energy. This paper first reviews the processes and the machines that have been recently developed to obtain an enhanced mechanical dewatering of PS. The pretreatment of PS dewatering is often crucial in order to obtain high efficiency in the subsequent recovery process. Afterwards, the paper presents and discusses the recovery options that have been proposed and tested, at different scales, by several authors in the last thirty years. The processes for PS management can be grouped as follows: (i) direct employment of physically/chemically treated PS in the production of primers and sealants; (ii) utilization of PS for the production of building materials, as supplementary components of cement concrete, mortar, or bituminous mixtures; (iii) extraction of valuable organic and inorganic products by using thermal processes (pyrolysis, gasification); (iv) biological processes for PS detoxification, metal recovery, and stabilization before landfilling.

Investigating the leaching performance of ferric chloride solution for metallic alloys resulting from reduction smelting of spent lithium-ion batteries

Smelting reduction of spent lithium-ion batteries (LIBs) produces metallic alloys containing Co, Ni, Cu, Mn, and Fe. Finding suitable reagents in terms of efficiency, economics, and friendly environment for the dissolution of these metals from the alloys is very important for the recovery process of the metals. In this work, the employment of ferric chloride solution for the dissolution of the metals from the alloys was studied. The effect of parameters like FeCl3 concentration, temperature, time, and pulp density on the leaching efficiency of metals was investigated. Our results indicate that ferric ions in the leaching solutions act as oxidizing agents for the dissolution of the metals, while chloride anions as ligands for the formation of the complexes of the dissolved metal ions. The best conditions for the dissolution of full metals were 0.7 mol/L FeCl3, 12.5 g/L pulp density, 22oC, and 30 min. In comparison with HCl or H2SO4 leaching agents, ferric chloride shows some advantages like a decrease in the dosage of acids and oxidizing agents, fast reaction kinetics, and low energy consumption. With its advantages, ferric chloride solution is considered a potential leaching agent in the recovery process of valuable metals from spent LIBs.

Flotation Sludges from Precious Metal Recovery Processes: From Waste to Secondary Raw Material in Ceramics

In this study, we investigated flotation muds (FM) deriving from the recovery processes of precious metals contained in e-waste (wastes from electronics) and exhausted catalysts. FM consist of an amorphous phase, corresponding to a Ca- and Al-rich silicatic glass, potentially usable as a secondary raw material (SRM) to obtain a final ceramic product (CFM). A high FM amount was used in our ceramic tests, and suitably mixed with variable percentages of other phases. Chemical analysis, phase composition, microstructure, pore pattern and technological properties of the new ceramic products were determined using different analytical techniques, including bulk XRF, XRD, SEM-EDS and µCT. The CFM product predominantly consists of nepheline, pyroxene and wollastonite as the main crystalline phases, with a minor amorphous phase occurring as a compact interstitial matrix. The ceramic product has a porous interconnected microstructure. Nevertheless, this microstructure does not negatively affect the mechanical properties of the ceramic product, as testified by the geo-mechanical tests, revealing good properties in terms of bending and uniaxial strength. These preliminary results point out that FM recycling is feasible, at least at the laboratory scale.

Global Research Progress and Trends on Critical Metals: A Bibliometric Analysis

In the perspective of observing the latest worldwide and European strategies toward green transition and delivering a secured access to local resources, the objective of this study was to analyze the research progress on critical materials and, more specific, critical metals and review the future research hot-topics for critical metals. Consequently, a bibliometric analysis for the assessment of the current state of the art research, future trends as well as evolution through time of the critical metals research was performed in the present work. The study included four phases of work: (i) search string selection, (ii) data collection, (iii) data processing, and (iv) data interpretation. A total of 433 publications on critical metals were collected from Scopus database between 1977 and 2023, with an increasing yearly trend and a burst in 2013. The data retrieved showed a significant increase in publications related to the topic in the last 10 years. The results show that research interest is concentrated around six critical areas: (i) bioleaching as an important process of critical metal recovery, (ii) circular economy concepts and recovery of critical metals by urban mining from e-waste, (iii) resource recovery from waste landfills as urban mines, (iv) targeted studies on various critical elements (copper, zinc, gallium, silver, lithium), (v) rare elements as industry vitamins and, (vi) coal deposits and coal ashes as an alternative source of critical metals. This analysis could provide important guidance for further directions on the development of research for recovery of critical metals.

Investigations into the closed-loop hydrometallurgical process for heavy metals removal and recovery from biosolids via mild acid pre-treatment

Biosolids contain heavy metals (HMs), restricting their beneficial reuse in agricultural land. However, these metals can be a valuable resource in many applications if recovered efficiently. Therefore, the removal and recovery of HMs and other limiting contaminants in biosolids without degrading the organic nutrients of the resulting treated biosolids demands holistic investigations. A closed-loop hydrometallurgical treatment process for metal removal and recovery from biosolids was developed in this study. Firstly, mild acid treatment using 3% v/v H2SO4 at 25 °C, 600 rpm for 30 min was performed in a 1 L continuous stirred tank reactor to extract common HMs (such as As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) from biosolids into the aqueous phase. The effects of solids concentration and acid types on the HMs extraction efficiency were studied. Then, the primary acid leachate stream was continuously recycled for metal extraction from biosolids until the dissolved metals in the solution reached saturation concentration. After that, the dissolved metals were recovered in staged NaOH precipitation and adsorption. Low solids contents (<5% w/v) using mineral acids having pH <2 and oxidation-reduction potential (ORP) ∼500 mV (versus SHE) favoured HMs solubilisation from biosolids with an average extraction efficiency of 70%. The dissolution of ferric iron (Fe3+) by H2SO4 and subsequent in-situ formation of ferric sulfate enhanced the metal extraction strength of the spent leachate stream during recycling. However, the solids loading in each leaching process must be kept low to prevent ferric concentration build-up and precipitation as the leachate pH steadily increases above 2 during recycling. Amongst the metal recovery methods investigated, H2O2 oxidation prior to 2-stage NaOH precipitation had the highest efficiency with 75–95% HMs recovery. The clarified stream was used to neutralise the acidic treated biosolids to close the process loop. The complete process flowsheet was developed with mass balances, and the fate of nutrients (mainly C, N, and P) and major per- and polyfluoro alkyl substances (PFAS) were overviewed.

Removal of impurity Metals as Phosphates from Lithium-ion Battery leachates

Recovery of critical materials from end-of life (EOL) lithium-ion batteries (LIB) is gaining interest as demands for materials grows. Hydrometallurgical processes start with an intermediate product known as black mass which contains critical materials of interest (Co, Ni, Li, and graphite) as well as impurities such as Cu, Al, and Fe. These impurities are deleterious to downstream separation processes, as well as impact functionality of the final products. These impurities effectively compete with most solvent extraction (SX) and metal recovery processes to diminish the overall yields of the desired materials. In this work, a process flowsheet is presented where a previously reported electrochemical leaching (ECL) process is followed by selective precipitation using diammonium hydrogen phosphate (DAP) to remove Cu, Al, and Fe from LIB leachate solutions. The electrochemical leach process removes Cu and produces a pH-adjusted leachate, ca. pH 2, without requiring an extra Cu extraction step. The addition of the precipitant DAP to leachate by slightly adjusting the pH to 3–4 at 45 °C, precipitates 95–99% of Al and Fe as their phosphates and the leachate retains >95% of Co, Ni and Li. After the filtration of phosphate impurities, the solution is ready for further processing, such as SX. As an unexpected result from the leachate processing, 20–30% of the Ni and Co co-crystalize as the double salt after cooling to room temperature, which could provide a shorter route to their recovery.

Accelerated CO2 mineralization and utilization for selective battery metals recovery from olivine and laterites

The reduction of CO2 emissions through both carbon capture utilization and storage and clean energy transition is accelerating all over the world. However, the global supply of required battery metals for clean energy transition is in deficit and the effective CO2 mineralization for permanent CO2 storage is still in challenge. It has been found in this study that CO2 mineralization can be significantly accelerated by complexation reaction and can be utilized simultaneously to recover critical battery metals. An integrated process of CO2 mineralization and synergistic battery metal recovery has been developed and is robust for various feed materials including nickel-barren olivine and all-types of nickel-rich laterites. In this novel approach, CO2 is a reagent used to convert basic silicate minerals to stable mineral carbonates and in return critical battery metals can be selectively recovered. Each tonne CO2 sequestered can be used to recover 98.7 kg nickel and 2.7 kg cobalt with over 90% nickel and cobalt recovery and around 60% CO2 mineralization efficiency. The process utilizes the strong competition between carbonate precipitation and complexation formation during the simultaneous metal extraction and enhanced CO2 mineralization. This work can make significant contributions to the clean energy transition with enhanced supply of critical battery metals and to CO2 emission reduction with enhanced CO2 storage and utilization.

Research on recycling and disassembly of waste crystalline silicon solar cells

Past two decades have witnessed a rapid increase in the application of photovoltaics which is being vastly produced considering the fact that they are the crucial elements that contribute to the transition from conventional finite fossil energy to new-generation renewable energy. In order to offset the undesirable environmental impact attached to the mass production of Photovoltaics and also recover valuable metals, a comprehensive and environmentally friendly strategy of solar cells disposal and recycling handling are indispensable. Systematical analysis of different contemporary distinctive methods involved in end-of-life solar cell handling is needed for gaining a deep insight into the recycling process. This article mainly focuses on summarizing and comparing three highly effective methods for solar cells recycling and disassembly: physical treatment, chemical treatment, thermal treatment. Our results show that the physical method is mostly seen as a preliminary process that is indispensable before chemical or thermal treatment and that despite chemical treatments using solvents are crucial for the elimination and recovery process of valuable metals, there are several drawbacks, like harmful waste and damage to recovered silicon bulk, all of which are not contained by thermal treatment.

Physical, Static, and Kinetic Analysis of the Electrochemical Deposition Process for the Recovery of Heavy Metal from Industrial Wastewater.

Through the electrodeposition technique, toxic metals in wastewater can be removed and deposited on a chosen substrate with excellent selectivity. In this work, we use this technique to extract lead cations from simulated wastewater by using fluorine-doped tin oxide (FTO) substrate at various temperatures. In situ tracking of lead nucleation at advanced stages has been achieved by chronoamperometry. According to the experimental results, the theoretical models developed to study the kinetic growth of lead deposits in 2D and 3D are in good agreement. Nucleation rate and growth rate constants, for example, were found to be strongly influenced by temperature. Cottrell's equation is used to calculate the diffusion coefficient. X-ray diffraction, scanning electron microscopy, and energy-dispersiveX-ray techniques were used to investigate and characterize the lead deposits. The reported results could provide insight into the optimization of electrodeposition processes for heavy metal recovery from wastewater and electronic wastes.

A Sustainable Process for Selective Recovery of Metals from Gallium-Bearing Waste Generated from Led Industry

A Sustainable Process for Selective Recovery of Metals from Gallium-Bearing Waste Generated from Led Industry

Recent advances and prospects in electrochemical coupling technologies for metal recovery from water.

With the development of our society, the desire to recover valuable metal resources from metal-containing wastewaters or natural water bodies is becoming increasingly stronger nowadays. To overcome the limitations of single techniques, coupling technologies with synergistic effects are attracting increasing attention regarding metal resource recovery from water with particular interest in electrochemical coupling technologies in view of the advantages of electrochemical methods. This state-of-the-art review comprehensively presented the mechanisms and performance of electrochemical coupling systems for metal recovery from water. To give a clear overview of current research trends, technologies coupled with electrochemical processes can be categorized into six main types: electrochemical techniques, membrane modules, adsorption/extraction techniques, sonication technologies, energy supply techniques and others. The electrochemical coupling system has shown synergistic advantages (e.g., improving metal recovery efficiency, reducing energy consumption) over single technologies. We then discuss the remaining challenges, present corresponding solutions, and put forward future directions for current electrochemical coupled systems towards metal recovery. This review is conducive to broadening the potential applications of electrochemical coupling processes for metal recovery and sustainable water treatment.