Copper is everywhere in modern life, from power grids and electric vehicles to renewable-energy technologies, data centers and household electronics. But the metal’s growing importance comes with a costly environmental side effect: mining and processing copper generate large volumes of wastewater contaminated with dissolved copper ions. These streams can be toxic to aquatic ecosystems, while the copper they contain represents a valuable resource that is often difficult and expensive to recover. A new study published in Nature Sustainability reports an electrochemical system designed to address both problems at once. The approach removes copper from wastewater, converts it into high-value metallic copper and generates electricity during the process.
The technology is built around sulfur, which serves as a reversible chemical intermediary between dissolved copper and an electrochemical device. In the system, sulfur can undergo a conversion to copper sulfide, specifically Cu₂S, when it reacts with copper ions. This reversible sulfur-to-copper-sulfide transformation allows the sulfur electrode to repeatedly capture copper from contaminated water and later release it in a controlled electrochemical step. Rather than functioning simply as a passive electrode, sulfur acts as a redox mediator: a material that shuttles electrons and chemical species between different stages of the recovery process. This design is intended to overcome several weaknesses of conventional copper-removal technologies, including limited extraction efficiency, poor selectivity and the production of low-value copper compounds.
The central challenge in treating industrial wastewater is that copper rarely exists alone. Streams produced by mining, ore refining and metal processing can contain mixtures of metal ions, salts and other dissolved contaminants. A recovery system that removes copper indiscriminately may require additional purification, increasing both energy consumption and operating costs. According to the researchers, the sulfur-mediated electrode demonstrated a strong preference for Cu²⁺, the positively charged copper ion commonly found in acidic industrial wastewater. The selectivity arises from the chemical compatibility between sulfur and copper during the formation of Cu₂S, allowing copper to be concentrated even when other ions are present. Once captured, the copper-bearing sulfur electrode can be regenerated, supporting repeated use rather than creating a rapidly exhausted waste material.
To turn this chemistry into an electricity-producing treatment process, the researchers paired the sulfur electrode with a sacrificial iron electrode in a two-chamber electrochemical device. In an electrochemical cell, oxidation occurs at one electrode and reduction occurs at the other, with electrons moving through an external circuit. Here, iron supplies electrons as it is gradually consumed, while the sulfur-based electrode participates in the copper-capture reaction. The movement of electrons through the circuit produces an electrical current. This means the wastewater treatment process is not powered solely by an external energy source; under the reported configuration, chemical energy associated with the reactions can be harvested as electricity. The iron electrode is described as sacrificial because it is consumed during operation, a trade-off that must be considered in future designs and economic assessments.
The device separates the wastewater-side chemistry from the counter-reaction in two chambers, allowing the researchers to control the flow of ions and electrons more precisely. The sulfur electrode first captures copper from the wastewater through the formation of Cu₂S. The copper is then recovered in a separate deposition cell, where electrochemical conditions drive the reduction of Cu²⁺ to elemental copper. During this step, copper ions gain electrons and become solid metallic copper at a deposition electrode. This is a crucial distinction from treatment systems that merely precipitate copper as a sulfide or hydroxide sludge. Metallic copper is easier to handle, transport and potentially sell, and it preserves more of the metal’s economic value. The two-stage design therefore separates copper capture from copper purification and recovery.
The reported results suggest that the sulfur electrode combines high copper-loading capacity with robust reusability. In practical terms, a high extraction capacity means that a relatively small amount of electrode material can process a larger quantity of contaminated water before regeneration is required. Reusability is equally important because electrode replacement can quickly dominate the cost and environmental footprint of an industrial treatment system. The researchers’ strategy depends on sulfur cycling between chemical forms rather than being irreversibly consumed after a single treatment step. This reversible operation could reduce solid waste generation and make continuous processing more realistic. The system also showed strong Cu²⁺ selectivity, a property that may help simplify downstream processing when wastewater contains a complex mixture of dissolved metals.
The team tested a flow-type cell with real wastewater for approximately 250 hours, moving beyond short laboratory demonstrations in which synthetic solutions are treated for only a few cycles. Over that period, the system produced a cumulative electricity output of 1.00 kilowatt-hour per square meter and recovered 2.02 kilograms of copper per square meter. These area-based figures describe performance relative to the active electrode or cell area, making them useful for comparing device configurations and estimating the scale required for industrial operation. Stable behavior during extended flow operation is significant because real wastewater can fluctuate in composition, acidity and contaminant concentration. However, long-term deployment would still require testing under a wider range of industrial conditions, including variations in flow rate, suspended solids, competing ions and electrode fouling.
The prospect of producing electricity while recovering copper gives the technology a potentially powerful economic narrative. Wastewater treatment is often viewed as an energy-intensive obligation, particularly when pumps, chemical reagents, heating or high-voltage separation systems are required. A process that extracts a valuable metal while exporting electrical energy could reduce the net cost of treatment and offset part of the energy demand of related operations. The study’s life cycle assessment indicated favorable environmental performance, while its life cycle costing suggested economic advantages. Such analyses typically consider material inputs, energy use, emissions, equipment and operating costs across the system’s life. Their conclusions do not guarantee profitability at every site, but they indicate that the combined value of copper recovery and electricity generation may improve the case for scale-up.
The researchers envision the sulfur-mediated system as a platform for continuous resource recovery rather than a one-time cleanup method. Its most important test will be whether the chemistry remains selective and stable when integrated into larger flow systems with uneven wastewater composition and industrially relevant throughput. The supply, recovery and eventual replacement of iron, the durability of sulfur electrodes and the efficiency of metallic copper deposition will all influence its real-world footprint. The process may also need to connect with existing wastewater-treatment infrastructure, where solids separation, pH adjustment and final water polishing are already common. Even with those challenges, the reported combination of copper removal, selective recovery, electrode reusability and net electricity generation represents a notable shift in how contaminated water could be viewed: not only as a pollution problem, but also as a source of materials and energy. As demand for copper accelerates, technologies that recover the metal in usable form while reducing treatment burdens could become increasingly important to a more circular industrial economy.
Subject of Research: Sulfur-mediated electrochemical recovery of copper from wastewater with simultaneous electricity generation
Article Title: Sulfur-mediated electrochemical copper recovery from wastewater with net electricity generation
Article References: Bi, S., Demichelis, F., Xu, S. et al. Sulfur-mediated electrochemical copper recovery from wastewater with net electricity generation. Nat Sustain (2026). https://doi.org/10.1038/s41893-026-01912-w
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41893-026-01912-w
Keywords: copper recovery, wastewater treatment, sulfur electrode, Cu₂S, electrochemistry, electricity generation, metallic copper, resource recovery, sustainability, life cycle assessment
