A review on spent Mn-containing Li-ion batteries: Recovery technologies, challenges, and future perspectives.

Mn-containing Li-ion batteries have become primary power sources for electronic devices and electric vehicles because of their high-energy density, extended cycle life, low cost, and heightened safety. In recent years, Li-ion batteries (LIBs) have undergone rapid updates, paralleling the swift advancement of the lithium battery industry, resulting in a growing accumulation of LIB scraps annually, necessitating comprehensive recovery strategies. This article reviews the recent progress in recovering spent Mn-containing LIBs (SM-LIBs), specifically focusing on LiMn2O4 and ternary LiCoxMnyNizO2 (NCM). Initially, the study analyzes the current resource profile of SM-LIBs and elucidates their service mechanisms. Subsequently, the study explores the recovery of SM-LIBs, discussing various methods such as the hydrometallurgical approach, combined pyrolytic treatment-wet leaching process, bioleaching pathway, and electrochemical extraction. These discussions include recovery processes, reaction principles, and technological features. In addition, this study evaluates the potential applications of these recovery technologies, considering aspects such as complexity, economic viability, energy consumption, environmental sustainability, and scalability. Finally, it summarizes the challenges associated with the comprehensive recovery and resource utilization of SM-LIBs and offers insights into future directions.

Copper recovery from printed circuit boards leaching solution with bioelectricity generation using microbial fuel cell.

Recovery of valuable metals via leaching printed circuit boards (PCBs) has gained moment recently. This work studied the Microbial fuel cell (MFC) performances for recovery of Cu from a Cu2+ solution by examining key operating parameters. A dual-chamber MFC with 6 cm × 6 cm × 7 cm dimensions was constructed. Both anode and cathode electrodes were made of a carbon cloth sheet. The anodic and cathodic chambers were separated by a Nafion membrane. The highest Cu recovery efficiency was 99.7% after 240 h batch mode operation, yielding 102 mW/m2 MFC power density output using 1 g/L Cu2+ solution as the catholyte (initial pH 3) and an anolyte containing 1 g/L sodium acetate inoculated with a sludge from a wastewater treatment plant's anaerobic pond, with 2 cm distance between the electrodes made of polyacrylonitrile polymer. The highest open circuit voltage, current density (based on cross-section cathode area) and power density with an external load of 1 kΩ was 555 mV, 347 mA/m2 and 193 mW/m2, respectively. Additionally, recovery of Cu in the leachate of PCBs using sulfuric acid leaching after 48 h was performed and the highest Cu recovery was 50% in 48 h.

Recycling and reutilization of smelting dust as a secondary resource: A review.

Smelting dust is a toxic waste produced in metal-mineral pyrometallurgical processes. To eliminate or reduce the adverse environmental impacts of smelting dust, valuable components need to be selectively separated from the toxic components present in the waste. This paper reviews the chemical composition, phase composition and particle size distribution characteristics of smelting dust, and the results show that smelting dust has excellent physicochemical characteristics for recovering valuable metals. The process flow, critical factors, development status, advantages and disadvantages of traditional technologies such as pyrometallurgy, hydrometallurgy and biometallurgy were discussed in depth. Conventional treatment methods typically prioritize separating and reclaiming specific elements with high concentrations. However, these methods face challenges such as excessive chemical usage and limited selectivity, which can hinder the sustainable utilization of smelting dust. With the increasing scarcity of resources and strict environmental requirements, a single treatment process can hardly fulfil the demand, and a physical field-enhanced technology for releasing and separating valuable metals is proposed. Through analysing the effect of electric field, microwave and ultrasound on recovering valuable metals from smelting dust, the enhancement mechanism of physical field on the extraction process was clarified. This paper aimed to provide reference for the resource utilization of smelting dust.

Adsorption of valuable metals from leachates of mobile phone wastes using biopolymers and activated carbon.

In this work, chitin (CTN), chitosan (CTS) and activated carbon (AC) were used as adsorbents to recover valuable metals from leachates of mobile phone wastes. The mobile phone wastes (contactors) were collected and characterized. The valuable metals were extracted by thiourea leaching. The adsorption of valuable metals from leachates was studied according to the kinetic and equilibrium viewpoints. It was found that the contactors were composed by Au, Ni, Cu and Sn. The thiourea leaching provided extraction percentages of 68.6% for Au, 22.1% for Ni and 2.8% for Cu. Sn was not extracted. The leachate presented 17.5 mg L-1 of Au, 324.9 mg L-1 of Ni and 573.1 mg L-1 of Cu. The adsorption was fast, being the equilibrium attained within 120 min. The adsorption of Au, Ni and Cu onto CTN and AC followed the Langmuir model, while, the adsorption of these metals onto CTS, followed the Freundlich model. Removal percentages higher than 95% were obtained for all metals, depending of the type and amount of adsorbent. It was demonstrated that the adsorption onto chitin, chitosan and activated carbon can be an alternative to recover valuable metals from leachates of mobile phone wastes.

Valuable Metals-Recovery Processes, Current Trends, and Recycling Strategies.

This Review provides an overview of valuable metals, the supply of which has been classified as critical for Europe. Starting with a description of the current state of the art, novel approaches for their recovery from primary resources are presented as well as recycling processes. The focus lies on developments since 2005. Chemistry strategies which are used in metal recovery are summarized on the basis of the individual types of deposit and mineral. In addition, the economic importance as well as utilization of the metals is outlined.

Bioleaching mechanism of Zn, Pb, In, Ag, Cd and As from Pb/Zn smelting slag by autotrophic bacteria.

A few studies have focused on release of valuable/toxic metals from Pb/Zn smelting slag by heterotrophic bioleaching using expensive yeast extract as an energy source. The high leaching cost greatly limits the practical potential of the method. In this work, autotrophic bioleaching using cheap sulfur or/and pyrite as energy matter was firstly applied to tackle the smelting slag and the bioleaching mechanisms were explained. The results indicated autotrophic bioleaching can solubilize valuable/toxic metals from slag, yielding maximum extraction efficiencies of 90% for Zn, 86% for Cd and 71% for In, although the extraction efficiencies of Pb, As and Ag were poor. The bioleaching performance of Zn, Cd and Pb was independent of leaching system, and leaching mechanism was acid dissolution. A maximum efficiency of 25% for As was achieved by acid dissolution in sulfursulfur oxidizing bacteria (S-SOB), but the formation of FeAsO4 reduced extraction efficiency in mixed energy source - mixed culture (MS-MC). Combined works of acid dissolution and Fe(3+) oxidation in MS-MC was responsible for the highest extraction efficiency of 71% for In. Ag was present in the slag as refractory AgPb4(AsO4)3 and AgFe2S3, so extraction did not occur.

Recovery technology of spent hydrogenation catalysts -A review.

Spent hydrogenation catalysts (HDCs) contain many Mo, V, Co, Ni, and Al2O3 carriers, which are valuable secondary resources. However, improper disposal can also lead to environmental pollution risks. In the past decade, research reviews on the recovery of valuable metals from spent HDCs have been somewhat reported, mainly summarizing basic technical processes. Based on previous work, this article reviews the emerging recycling technologies of spent HDCs in recent years. The research trend of furnace optimization in the pyrometallurgical process was innovatively proposed, and the importance of developing new mild leaching agents for the high-quality recycling of Al2O3 carriers in the hydrometallurgical process was clarified.

Enhanced reducing capacity of citric acid for lithium-ion battery recycling under microwave-assisted leaching.

The management and sustainable recycling of spent lithium-ion batteries (LIBs) holds critical importance from both economic and environmental standpoints. H2O2 and ascorbic acid are widely used inorganic and organic reductants in the hydrometallurgical process for battery recycling. In this study, citric acid, as a reductant, was found to have superior metal leaching efficiencies under microwave-assisted leaching than H2O2 and ascorbic acid. The enhanced performance was attributed not only to the inherent reducing property of citric acid but also to the chelation of citric acid with Cu and Fe, resulting in the formation of reductive radicals under microwave. The effect of acid type, H2SO4 concentration, citric acid concentration, solid-liquid (S/L) ratio, reaction time, and temperature were investigated. 99.5 % of Li, 99.7 % of Mn, 99.5 % of Co, and 99.3 % of Ni were leached from spent lithium nickel manganese cobalt oxides (NCM) battery black mass using 0.2 mol/L H2SO4 and 0.05 mol/L citric acid at 120 °C for 20 min with a fixed S/L ratio of 10 g/L in the microwave-assisted leaching process. Leaching kinetic results were best fitted with the Avrami model, suggesting that the microwave-assisted leaching process was controlled by diffusion. The leaching activation energies of Li, Mn, Co, and Ni were 30.11 kJ/mol, 27.48 kJ/mol, 21.32 kJ/mol, and 33.29 kJ/mol, respectively, providing additional evidence that supports the proposed diffusion-controlled microwave-assisted leaching mechanism. This method provided a green and efficient solution for spent LIBs recycling.

Synergistic utilization of industrial solid wastes: Extraction of valuable metals from tungsten leaching residue by photovoltaic sawing waste.

Solid waste challenges in both the tungsten and photovoltaic industries present significant barriers to achieving carbon neutrality. This study introduces an innovative strategy for the efficient extraction of valuable metals from hazardous tungsten leaching residue (W-residue) by leveraging photovoltaic silicon kerf waste (SKW) as a silicothermic reducing agent. W-residue contains 26.2% valuable metal oxides (WO3, CoO, Nb2O5, and Ta2O5) and other refractory oxides (SiO2, TiO2, etc.), while micron-sized SKW contains 91.9% Si with a surface oxide layer. The impact of SKW addition on the silicothermic reduction process for valuable metal oxides in W-residue was investigated. Incorporating SKW and Na2CO3 flux enables valuable metal oxides from W-residue to be effectively reduced and enriched as a valuable alloy phase, with unreduced refractory oxides forming a harmless slag phase during the Na2O-SiO2-TiO2 slag refining process. This process achieved an overall recovery yield of valuable metals of 91.7%, with individual recovery yields of W, Co, and Nb exceeding 90% with the addition of 8 wt.% SKW. This innovative approach not only achieves high-value recovery from W-residue and utilization of SKW but also minimizes environmental impact through an efficient and eco-friendly recycling pathway. The strategy contributes significantly to the establishment of a resource-efficient circular economy, wherein the recovered high-value alloy phase return to the tungsten supply chain, and the harmless slag phase become raw materials for microcrystalline glass production.

Improving acid mine drainage treatment by combining treatment technologies: A review.

The mining and processing of some minerals and coal result in the production of acid mine drainage (AMD) which contains elevated levels of sulfate and metals, which tend to pose serious environmental issues. There are different technologies that have been developed for the treatment of wastewater or AMD. However, there is no "one-size-fits-all" solution, hence a combination of available technologies should be considered to achieve effective treatment. In this review, AMD treatment technologies and the possible alignment in tandem of the different treatment technologies were discussed. The alignment was based on the target species of each technology and AMD composition. The choice of the technologies to combine depends on the quality of AMD and the desired quality of effluent depending on end use (e.g., drinking, industrial, irrigation or release into the environment). AMD treatment technologies targeting metals can be combined with membrane and/or ettringite precipitation technologies that focus on the removal of sulfates. Other technologies can be added to deal with the secondary waste products (e.g., sludge and brines) from the treatment processes. Moreover, some technologies such as ion exchange and adsorption can be added to target specific valuable elements in AMD. Such combinations have the potential to result in effective AMD treatment and minimum waste production, which are not easily achievable with the individual technologies. Overall, this review presents combinations of AMD treatment technologies which can work best together to produce optimal water quality and valuable products in a cost-effective manner.

Application and development of foam extraction technology in wastewater treatment: A review.

With the advancement of technology, wastewater treatment has become a significant challenge limiting the clean and sustainable development of chemical and metallurgical industries. Foam extraction, based on interfacial separation and mineral flotation, has garnered considerable attention as a wastewater treatment technology due to its unique physicochemical properties. Although considerable excellent accomplishments were reported, there still lacks a comprehensive summary of process features and contaminant removal mechanisms via foam extraction. According to the latest research progresses, the principles and characteristics of foam extraction technology, the classification and application of flotation reagents are systematically summarized in this work. Then comprehensively commented on the application fields and prospects of iterative flotation technology such as ion flotation, adsorption flotation and floating-extraction. The shortcomings and limitations of the current foam extraction technologies were discussed, and the feasible process intensification techniques were highlighted. This review aims to enchance the understanding of the foam extraction mechanism, and provides guidance for the selection appropriate reagents and foam extraction technologies in wastewater treatment.

Crystal phase and nanoscale size regulation utilizing the in-situ catalytic pyrolysis of bamboo sawdust in the recycling of spent lithium batteries.

Current Li-ion battery (LIB) recycling methods exhibit the disadvantages of low metal recovery efficiencies and high levels of pollution and energy consumption. Here, products generated via the in-situ catalytic pyrolysis of bamboo sawdust (BS) were utilized to regulate the crystal phase and nanoscale size of the NCM cathode to enhance the selective Li extraction and leaching efficiencies of other valuable metals from spent LIBs. The catalytic effect of the NCM cathode significantly promoted the release of gases from BS pyrolysis. These gases (H2, CO, and CH4) finally transformed the crystal phase of the NCM cathode from LiNixCoyMnzO2 into (Ni-Co/MnO/Li2CO3)/C. The size of the spent NCM cathode material was reduced approximately 31.7-fold (from 4.1 µm to 129.2 nm) after roasting. This could be ascribed to the in-situ catalytic decomposition of aromatic compounds generated via the primary pyrolysis of BS into C and H2 on the surface of the cathode material, resulting in the formation of the nanoscale composite (Ni-Co/MnO/Li2CO3)/C. This process enabled the targeted control of the crystal phase and nanoscale size of the material. Water leaching studies revealed a remarkable selective Li extraction efficiency of 99.27 %, and sulfuric acid leaching experiments with a concentration of 2 M revealed high extraction efficiencies of 99.15 % (Ni), 93.87 % (Co), and 99.46 % (Mn). Finally, a novel mechanism involving synergistic thermo-reduction and carbon modification for crystal phase regulation and nanoscale control was proposed. This study provides a novel concept for use in enhancing the recycling of valuable metals from spent LIBs utilizing biomass waste and practices the concept of "treating waste with waste".

Novel electrochemical process for recycling of valuable metals from spent lithium-ion batteries.

Effective recovery of Li, Co, Ni and Mn from cathode materials of spent lithium-ion batteries (LIBs) has become a global concern. In this study, electrolysis of copper sulfate to produce sulfuric acid and electrons were utilized to recover Li, Co, Ni and Mn from spent LIBs. The obtained results showed that 93 % of Ni, 91 % of Co, 89 % of Mn and 94 % of Li were leached and 99 % of Cu was deposited during leaching process by adopting the 0.225 mol/L of copper sulfate with a solid/liquid ratio of 15 g/L at a current density of 50 mA/m2 and 80 °C for 4.5 h. Then, a current efficiency of 72 % for the cathode and 30 % for the anode was achieved at a current density of 40 mA/m2, 70 °C and pH 2.5 during electrodeposition process. The Ni-Co deposition followed the principle of anomalous codeposition and the complete deposition time of Co, Ni and Mn were 3 h, 9 h and 10 h, respectively. Eventually, the Ni, Co, Mn, Li and Cu can be recovered as Ni-Co alloy, MnO2 and Li2CO3 and Cu metals with the corresponding recovery rates of 99.40 %, 91.00 %, 90.68 %, 85.59 % and 89.55 %, respectively. This study proposes a promising strategy for recycling cathode materials from spent LIBs without addition of chemical reductants and acids.

The recovery of strontium ions from seawater reverse osmosis brine using novel composite materials of ferrocyanides modified roasted date pits.

In this study, three types of adsorbents were used to remove and recover strontium ions (Sr2+) from aqueous and brine solution of seawater reverse osmosis (SWRO), namely roasted date pits (RDP) and RDP modified using copper and nickel salts of potassium hexacyanoferrates to obtain RDP-FC-Cu, and RDP-FC-Ni, respectively. Additionally, the influence of various parameters, including pH, temperature, initial concentration, and co-existing ions was also evaluated. The results revealed that pH 10 was the optimum pH in which the maximum Sr2+ ions were adsorbed. Additionally, all adsorbents had a high adsorption capacity (99.9 mg/g) for removing Sr2+ ions at the highest concentration (100 mg/L) and a temperature of 45 °C was found to be the optimum temperature. A scanning electron microscopy for the adsorbents before and after the adsorption of strontium showed the remarkable pore filling onto the active sites of all adsorbents. The thermodynamics parameter demonstrated that the adsorption occurred in an endothermic environment, and that, the reaction was spontaneous, and favorable at all the temperatures investigated. According to isotherm studies, the Langmuir model was the best-fit isotherm model; indicating that strontium adsorption involved the formation of monolayers and multilayers at higher temperatures (45 °C). Furthermore, high desorption percentages (above 90%) were achieved for all the adsorbents when an HCl concentration of 0.5 M was used. This showed the high reusability of the adsorbents. Lastly, the adsorption of strontium from the SWRO brine containing a number of metal ions was extremely sufficient as all the adsorbents were efficient to adsorb a high amount of Sr2+ despite the presence of other competing ions.

Recovery of valuable metals from red mud: A comprehensive review.

As a bulk solid waste with high alkalinity, red mud (RM) not only occupies a large amount of land and requires high maintenance costs, but also unavoidably generates serious hazards to the surrounding ecological environment. The comprehensive treatment of RM has become an enormous challenge for the green, low-carbon and high-quality development of the global alumina industry. To minimize the RM destruction to the ecology and the waste of secondary resources, the sustainable utilization of RM was widely investigated in the past decades, especially for the recovery of valuable metals. This paper systematically summarized the research status of recycling valuable metals (Al, Fe, Na, Ti, Sc, Ga, V and RE) from RM in recent years. The recycling technology mainly includes physical beneficiation, hydrometallurgy, pyrometallurgy and electrodialysis. The technical principles and characteristics as well as the current problems of various recovery processes from RM were comprehensively introduced, and the future development directions of sustainable utilization were also prospected. The advantages and disadvantages based on the different aspects of recovery efficiency, energy consumption and environmental impact were also discussed. The proposal of new technologies for the harmless, high-value and full utilization of RM is beneficial to the future research on the comprehensive utilization of bulk industrial solid wastes.

Coupling the recovery of spent lithium-ion batteries and the treatment of phenol wastewater: A "treating waste with waste" strategy.

The recovery of spent lithium-ion batteries and the treatment of phenol wastewater are both environmental and social issues. In this study, the enhanced recovery of spent lithium-ion batteries and the efficient treatment of phenol wastewater are smartly coupled via a "treating waste with waste" strategy. Under optimal conditions, the leaching process involving phenol achieves 98% and 96% efficiency for Co and Li, respectively. After precipitation, Co and Li could be recovered as Co(OH)2 and Li2CO3, and the precipitated Co(OH)2 was further calcined to generate Co3O4. Furthermore, the organic contaminants that remained in the waste-leaching solution could be removed by a spent graphite-activating peroxymonosulfate (PMS) process. It is noteworthy that the total organic carbon (TOC) in the waste-leaching solution could be removed using fewer PMS compared with the original phenol wastewater owing to the pre-oxidation of phenol during the leaching process, further confirming the advantage of this "treating waste with waste" strategy.

Red mud recycling by Fe and Al recovery through the hydrometallurgy method: a collaborative strategy for aluminum and iron industry.

In this work, a collaborative strategy for the aluminum and iron industry based on red mud recycling through the hydrometallurgy method was proposed. In this method, Fe3+ and Al3+ were firstly separated from the red mud by using H2SO4 as a leaching agent, which was by-produced from the sintering process of an iron and steel industry. Multiple influence factors on the leaching process were investigated, with the H2SO4 addition amount showing the strongest influence on the leaching rates of Al and Fe. The main components of the filter residue were CaSO4, TiO2, and SiO2, which could be reused as additives in the building materials. Subsequently, the final Fe recovery product was obtained through the co-precipitation, Fe/Al separation, and Fe(OH)3 calcination. In the final product, the content of Fe2O3 reached 82.87%, and the iron grade was 58.01%, meeting the requirement being raw materials for sinter production.

Leaching of valuable metals from cathode active materials in spent lithium-ion batteries by levulinic acid and biological approaches.

Recycling of valuable metals from spent lithium-ion batteries (LIBs) is of paramount importance for the sustainable development of consumer electronics and electric vehicles. This study comparatively investigated two eco-friendly leaching methods for recovering Li, Ni, Co, and Mn from waste NCM523 (LiNi0.5Co0.2Mn0.3O2) cathode materials in spent LIBs, i.e., chemical leaching by a green organic solvent, levulinic acid (LA) and bioleaching by an enriched microbial consortium. In chemical leaching, mathematical models predicting leaching efficiency from liquid-to-solid ratio (L/S; L/kg), temperature (°C), and duration (h) were established and validated. Results revealed that LA of 6.86 M was able to achieve complete leaching of all target metals in the absence of reductants at the optimal conditions (10 L/kg, 90 °C, and 48 h) identified by the models. The evaluation of direct one- and two-step and indirect bioleaching indicated that the latter was more feasible for metal extraction from waste NCM523. L/S was found to impact the indirect bioleaching most significantly among the three operating variables. Pretreatment of waste NCM523 by washing with 1 vol% methanesulfonic acid significantly improved indirect bioleaching. The side-by-side comparison of these two leaching approaches on the same cathode active material (CAM) thus provided the technical details for further comparison with respect to cost and environmental impact.

Novel strategy towards in-situ recycling of valuable metals from spent lithium-ion batteries through endogenous advanced oxidation process.

Efficient and sustainable recycling of metal resources from spent lithium-ion batteries (LIBs) is critical for the metal resources security and environment protection. However, the intact exfoliation of cathode materials (CMs) from current collectors (Al foils) and selective extraction of Li towards the in-situ and sustainable recycling of cathodes from spent LIBs are still pending issues. A self-activated and ultrasonic-induced endogenous advanced oxidation process (EAOP) was proposed in this study for selective removal of PVDF and in-situ extraction of Li from CMs of waste LiFePO4 (LFP) to address the above issues. Over 99 wt% CMs can be detached from Al foils after EAOP treatment under the optimized operation conditions. High purity of Al foil can be directly recycled as metallic forms and nearly 100 % of Li can be in-situ extracted from the detached CMs and then recovered as Li2CO3 (>99.9 % in purity). With induction and reinforcement of ultrasonic, S2O82- was self-activated by LFP to generate an increased amount of SO4•- radicals that will attack the PVDF binders to ensure their degradation. The degradation pathway of PVDF and density functional theory (DFT) calculation can also support the analytical and experimental results. Then, the complete and in-situ ionization of Li can be achieved by the further oxidization of SO4•- radicals from LFP powders. This work provides a novel strategy towards efficient and in-situ recycling of valuable metals from spent LIBs with minimized environmental footprint.

Status of research on the resource utilization of stainless steel pickling sludge in China: a review.

The pickling sludge produced in the stainless steel pickling process is a hazardous waste and disposal in landfill poses a potential environmental risk. Stainless steel pickling sludge contains metal elements such as Fe, Cr, and Ni and substances such as SiO2 and CaO, which have good value for resource recycling. This paper briefly introduces the generation, nature, and hazards of stainless steel pickling sludge; and clustering analysis of relevant literature keywords in recent years; and detailed analysis and comparison of sludge obtained from different steel mills and resource utilization process. The current situation of pickling sludge resource utilization and the development of relevant policies in China in recent years are summarized, and new thoughts on the direction of its resource utilization are put forward.