Jianxun Song

Arsenic is used in compound semiconductors, optoelectronic materials, specialty alloys, and fine chemicals owing to its distinctive chemical and electronic properties. However, arsenic is generated as an associated element in nonferrous-metallurgical and resource-recycling processes, including flue dusts, slags, and aqueous wastes, where its toxicity needs to be properly and safely controlled. This review examines arsenic separation from arsenic-bearing materials and arsenic-product preparation, with emphasis on reaction principles, requirements of raw materials, and the typical processing and preparation techniques. Pyrometallurgical approaches include roasting, vacuum roasting/distillation, reduction smelting, and bath smelting; hydrometallurgical approaches include acidic and alkaline leaching, precipitation-based immobilization, ion exchange, adsorption, and solvent extraction. For complex arsenic-bearing materials, multiple metallurgical methods need to be used for processing. Product-preparation methods are summarized for crude and refined As₂O₃, metallic arsenic, high-purity arsenic, AsH₃, GaAs, InAs, and Zn₃As₂. Further work is needed to improve separation selectivity, verify the long-term stability of immobilized arsenic, and refine processes for high-purity arsenic production. Recovery should be limited to applications with defined product specifications and justified demand, rather than expanded into low-value uses.

Indium zinc oxide (IZO, typical mass ratio of indium oxide to zinc oxide is 9:1) is widely employed in advanced electronic devices. During the preparation and application of IZO, a large amount of spent IZO is generated. However, the recycling of spent IZO commonly confronts significant challenges, including high energy consumption, severe environmental pollution, and complex pretreatment requirements, which impede the sustainable utilization of strategic metal resources. To address these issues, this study proposes a green electrochemical method for recycling In and Zn from spent IZO at room temperature. Operating in an environmentally benign sodium salt aqueous electrolyte, this process achieves efficient and continuous electro-deoxidation of IZO. It demonstrated that the method enables highly efficient recovery of metallic indium and zinc, achieving a recovery rate of 98.4%, while effectively removing impurities including Al, Si, and Fe. The entire process is characterized by low carbon emissions, absence of toxic reagents, and a less environmental burden.

Spent indium tin oxide (s-ITO, the mass ratio of In ₂ O ₃ to SnO ₂ is approximately 9:1) represents the main secondary resource for the rare metal indium, possessing exceptionally potential for reutilization. However, traditional hydrometallurgical or pyrometallurgical recycling methods grapple with substantial challenges, including low product purity, lengthy processes, and environmental pollution. This paper presents an electrochemical upcycling strategy for spent ITO based on charge-induced deconstruction, effectively addressing the aforementioned issues. In this approach, spent ITO serves as the anode in an aqueous electrolysis system. The number of oxygen vacancies on the ITO surface increases drastically under charge excitation, leading to weakened metal-oxygen bonds and the subsequent release of indium and tin ions into the electrolyte. These ions then migrate to the cathode, where high-purity indium tin alloy is obtained by leveraging the differences in electrochemical properties between impurity ions and the target metal ions. Notably, the electrolyte employed in this process can be reused, which significantly reduces wastewater generation. Through systematic optimization of electrolysis parameters, a cathode current efficiency of 71.12% and an energy consumption of 4.87 kWh kg ⁻¹ are achieved in a hundred-ampere scale trial, fully demonstrating the industrial applicability of this method.

The production and disposal of indium tin oxide (ITO) targets are rapidly increasing with the expansion of cutting‐edge optoelectronic and display technologies. To reduce reliance on indium (In) resources, there is an urgent need to develop efficient recycling strategies for spent ITO (s‐ITO). Here, we propose a facile electrochemical recovery approach in which s‐ITO serves as both the anode and cathode in Na ₂ SO ₄ solution. This dual‐function system enables selective anode conversion of s‐ITO into nanoscale Sn‐doped In ₂ O ₃ particles and cathode electro‐deoxidation into an In–Sn alloy, delivering an overall current‐utilization efficiency exceeding “120%.” Combined experiments and density functional theory (DFT) reveal fundamentally differentiated electrode pathways: anodic conversion proceeds through lattice oxygen mechanism (LOM) deconstruction with oxygen‐vacancy formation and structural destabilization, whereas cathodic recovery is governed by oxygen removal and in situ alloying. The process remains stable under 150 A scale‐up electrolysis over eight cycles, with the anode enabling parallel recovery and the cathode enabling recovery toward the In–Sn alloy. These findings establish a mechanism‐informed, acid‐free, and dual‐functional route for the closed‐loop upcycling of s‐ITO.

The production and disposal of indium tin oxide (ITO) targets are rapidly increasing with the expansion of cutting‐edge optoelectronic and display technologies. To reduce reliance on indium (In) resources, there is an urgent need to develop efficient recycling strategies for spent ITO (s‐ITO). Here, we propose a facile electrochemical recovery approach in which s‐ITO serves as both the anode and cathode in Na ₂ SO ₄ solution. This dual‐function system enables selective anode conversion of s‐ITO into nanoscale Sn‐doped In ₂ O ₃ particles and cathode electro‐deoxidation into an In–Sn alloy, delivering an overall current‐utilization efficiency exceeding “120%.” Combined experiments and density functional theory (DFT) reveal fundamentally differentiated electrode pathways: anodic conversion proceeds through lattice oxygen mechanism (LOM) deconstruction with oxygen‐vacancy formation and structural destabilization, whereas cathodic recovery is governed by oxygen removal and in situ alloying. The process remains stable under 150 A scale‐up electrolysis over eight cycles, with the anode enabling parallel recovery and the cathode enabling recovery toward the In–Sn alloy. These findings establish a mechanism‐informed, acid‐free, and dual‐functional route for the closed‐loop upcycling of s‐ITO.

High-purity nickel is critical in the electronics and semiconductor industries due to its excellent conductivity and ferromagnetism. Aqueous soluble-anode electrolytic refining has become the predominant technology due to its operational simplicity and high direct recovery rate. Nevertheless, achieving deep removal of impurities such as Fe, Cu, and Zn, while suppressing hydrogen evolution, remains essential for enhancing product purity and current efficiency. This study investigates the electrochemical behavior of Ni-based multi-metal systems and optimizes electrolyte composition. Thermodynamic calculations and electrochemical measurements were employed to elucidate the oxidation-reduction sequences and synergistic/competitive co-deposition mechanisms of Ni, Fe, Cu, and Zn. The influences of Ni ²⁺ concentration, initial pH, and additive selection on cathodic deposit morphology and purity were systematically examined. Under optimized conditions, current efficiency exceeds 99%, with impurity removal rates reaching up to 72.9% for Cu, 68.3% for Fe, and 89.5% for Zn (maximum values achieved under specific parameter combinations). These findings provide rigorous theoretical guidance and process optimization strategies for high-purity nickel electrolytic refining, offering substantial potential for industrial implementation.

Vanadium is a strategically significant metal, indispensable to modern industries due to its unique physical and chemical properties. In this study, three dynamic optimisation challenges are addressed: controlling ionic valence states, regulating irregular product morphologies, and reducing carbon dioxide (CO ₂ ) emissions. A simple and innovative method for producing metallic vanadium via electrolysis of a nitrogen‐doped vanadium consumable anode (VC _x N _y O _z ) is proposed and validated. The research compares the polarisation behaviour and reduction mechanisms of vanadium ions to metallic vanadium using two types of consumable anodes (VC _x N _y O _z and VC _x O _y ). Nitrogen doping stabilises the V ²⁺ ion through sp ² ‐hybridised C–N coordination, promoting the formation of a stable [VN ₆ ] ^3– octahedral complex via V–N bond interactions. The study demonstrates that the VC _x N _y O _z anode effectively regulates the valence state of vanadium ions in molten salt systems, enabling a uniform dendritic morphology and achieving a 30% reduction in CO emissions compared to the VC _x O _y anode.

Electrochemistry is versatile, less subject to external influences, and has great potential for the exploration of the unpredictable space environment. This work analyzes the available resources in space and discusses the application scenarios and challenges of electrochemical methods in four areas: metallurgical processing of mineral resources, water resources utilization, the carbon cycle in daily extraterrestrial life, and electrical energy storage. By examining these pivotal areas, this work elucidates the unique advantages and limitations of electrochemical technologies in space exploration. Furthermore, the paper explores the innovative application scenarios of electrochemistry in space, presenting fresh insights into how these technologies can be adapted and optimized for extraterrestrial environments. This comprehensive analysis not only provides a strategic direction for the breakthrough and advancement of electrochemical applications in space but also serves as an invaluable reference for the development of human extraterrestrial exploration and resource harvesting programs, guiding future research endeavors and technological innovations in this fascinating frontier.