Membrane technology emerges as a key route to recover critical metals from battery and mineral waste

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The transition toward zero-carbon energy systems has placed unprecedented pressure on the supply chains of several critical metals, and this pressure is unlikely to ease in the coming decades. Copper and nickel underpin electrical infrastructure and current collectors, cobalt and lithium define the performance and longevity of lithium-ion battery cathodes, and rare earth elements remain indispensable for the permanent magnets found in wind turbines and electric vehicle motors. Primary mining of these elements carries substantial environmental burdens, including habitat disruption, acid mine drainage, and energy-intensive beneficiation of ever-lower-grade deposits. As ore grades decline globally, the energy and reagent costs per kilogram of recovered metal rise, which strengthens the economic argument for treating industrial wastes, tailings, and spent devices as secondary ore bodies. In this framing, a heap of discarded battery packs or an abandoned tailings pond is not merely a liability to be contained but a reservoir of strategically important elements awaiting selective extraction.

Membrane-based separation processes occupy a distinctive position among the technologies available for this task. Unlike solvent extraction, which relies on bulk contact between aqueous and organic phases and often requires large inventories of volatile or toxic diluents, membrane processes achieve separation through selective transport across a thin barrier. Pressure-driven operations such as nanofiltration and reverse osmosis exploit differences in hydrated radius and charge to discriminate between ions, while concentration-driven processes such as dialysis rely on gradients alone, and electromembrane methods including electrodialysis and membrane electrolysis add an electrical driving force that can be tuned with considerable precision. This portfolio of driving forces means that membrane systems can be configured to match the chemistry of a particular leachate or brine, whether the target is lithium at millimolar concentrations in a geothermal fluid or nickel and cobalt at higher concentrations in a hydrometallurgical stream. The modularity of membrane units also allows capacity to be scaled incrementally, which is attractive for operations processing variable or seasonal feedstocks.

The contributions gathered in this Research Topic illustrate the breadth of current activity. The review by Matebese and colleagues provides a valuable service by framing membrane applications within a techno-economic analysis rather than presenting performance data in isolation. Long-term stability in aggressive solution chemistries, particularly those involving high acidity, complexing agents, or elevated salinity, remains one of the principal obstacles to industrial adoption, and the authors’ treatment of membrane failure modes gives readers a realistic picture of where the technology stands. Their identification of the operating regimes in which membranes outperform conventional solvent extraction offers a practical decision framework for process engineers weighing capital expenditure against reagent consumption and waste generation. Solvent extraction, after all, carries ongoing costs in organic losses, effluent treatment, and solvent regeneration, whereas a membrane that maintains its selectivity over an extended lifetime can amortize its initial cost across years of continuous operation.

The characterization-focused review by Kim and Hallinan addresses a class of materials whose importance is easy to underestimate. Charged polymer membranes, in which fixed ionic groups are covalently bound to the polymer matrix, transport counter-ions while rejecting co-ions, and this intrinsic charge selectivity can be exploited both for desalination and for the fractionation of multicomponent metal salt solutions. The authors’ attention to the relationship between manufacturing method and membrane structure is particularly relevant to waste valorization, because the morphology of the active layer, including its porosity, tortuosity, and degree of swelling, governs how quickly ions permeate and how selectively they are separated. Their conclusion that charged polymer membranes are a driving technology for commercial desalination suggests a maturity that can be transferred to resource recovery, since the same transport phenomena that separate sodium from chloride can, with appropriate membrane chemistry, discriminate between lithium, sodium, potassium, magnesium, and calcium.

Selectivity for lithium deserves special attention because of the element’s peculiar position in the critical minerals landscape. Lithium is chemically similar to sodium and potassium, sharing the monovalent charge state, yet its smaller ionic radius and stronger hydration shell create subtle differences in hydration energy and transport behavior that membrane designers can exploit. The mini-review by Troitskiy and colleagues surveys lithium-selective membranes and evaluates them using permeate flux and selective ion separation coefficients, two metrics that together capture the essential trade-off in membrane design: a membrane that is highly selective often sacrifices throughput, and one that delivers high flux may admit unwanted co-ions. Reporting both quantities in a standardized way, as the authors advocate, enables meaningful comparison across studies and accelerates the identification of materials that are genuinely ready for scale-up. The dual feedstocks of geothermal brines and spent lithium-ion battery eluates represent complementary supply routes, one drawing on naturally occurring subsurface resources and the other on anthropogenic stocks accumulated over the past two decades of consumer electronics and electric vehicle deployment.

The experimental study by Castro and colleagues on commercial perfluorosulfonic acid membranes, specifically Nafion 115 and Aquivion E98-09S, offers a sobering reminder that membrane pretreatment, so often assumed to be beneficial, can be counterproductive when selective ion transport is the objective. Their finding that membrane morphology is critical for separation underscores a broader principle in membrane science: the performance of a membrane is determined not only by its bulk chemistry but by the mesoscale arrangement of its hydrophilic and hydrophobic domains. Perfluorinated ionomers form well-defined ionic clusters whose size and connectivity depend on thermal and chemical history, and treatments intended to condition a membrane may reorganize these domains in ways that alter ion pathways unpredictably. For practitioners seeking to separate monovalent cations, whether in battery recycling or in the polishing steps of hydrometallurgical circuits, the lesson is that process design and membrane preparation must be co-optimized rather than treated as independent variables.

The hybrid adsorption-membrane filtration process described by Kabay and colleagues represents a different strategy for achieving selectivity, one that delegates the recognition function to a solid adsorbent rather than to the membrane itself. In the classical fixed-bed configuration, an adsorbent column is loaded with the target ion and then eluted, but the bed must be taken offline during regeneration, which reduces overall productivity and requires substantial bed volumes. By suspending the adsorbent as fine particles in a stirred vessel and continuously filtering the slurry through a membrane, the hybrid process decouples adsorption kinetics from hydraulic residence time and allows saturated adsorbent to be replaced while the system continues to operate. The authors’ demonstration that lithium recovery from geothermal water improves when permeate and feed flow rates are manipulated and when saturated adsorbent is exchanged for fresh material illustrates how process parameters, not only material properties, determine overall yield. This integration of two mature unit operations into a single intensified process is characteristic of the direction in which resource recovery is moving.

Several cross-cutting themes emerge when these contributions are considered together. First, the chemistry of the feed solution is decisive. Leachates from spent batteries contain mixtures of lithium, nickel, cobalt, manganese, and often residual electrolyte decomposition products, while geothermal brines carry high concentrations of sodium, potassium, magnesium, and calcium alongside the lithium of interest. A membrane that performs admirably in a synthetic single-salt solution may fail in a real stream because of fouling by suspended solids, scaling by sparingly soluble salts, or degradation by oxidants and complexants. Second, the economics of recovery depend strongly on concentration. Membrane processes are generally more competitive when the target element is present at moderate to high concentration, since the energy and membrane area required per kilogram of product scale unfavorably at extreme dilution. This favors pre-concentration steps, whether by adsorption, precipitation, or evaporation, ahead of the selective membrane stage. Third, the environmental footprint of the recovery process itself must be weighed against the benefits of secondary sourcing. A recovery route that consumes large quantities of acid, base, or organic solvent may erode the sustainability gains that motivate recycling in the first place, which is one reason the low reagent intensity of many membrane processes is so frequently emphasized.

The outlook for membrane-based resource recovery is encouraging but conditional. Continued progress will require advances on several fronts simultaneously: membrane materials with higher selectivity and greater chemical robustness, process configurations that manage fouling and scaling over multi-month campaigns, standardized performance metrics that allow honest comparison between laboratories, and techno-economic models that account for the full life cycle of the recovered material. The Research Topic assembled here contributes to each of these fronts, and the editors hope that the questions it raises, particularly around long-term membrane stability and the conditions under which membranes displace solvent extraction, will stimulate further work across the membrane science and hydrometallurgy communities. Closing the supply chains for copper, nickel, cobalt, lithium, and rare earth elements will demand exactly this kind of interdisciplinary effort, in which materials chemists, process engineers, and economists collaborate to convert wastes that were once liabilities into resources that support a decarbonized economy.

Subject of Research: Editorial: Membrane processes for extraction of valuable materials from battery and other mineral wastes

Article Title: Editorial: Membrane processes for extraction of valuable materials from battery and other mineral wastes

Article References: Tshentu, Z., Pawlowski, S., & Bryjak, M. (2026). Editorial: Membrane processes for extraction of valuable materials from battery and other mineral wastes. Frontiers in Membrane Science and Technology, 5, Article 1932154. https://doi.org/10.3389/frmst.2026.1932154

Image Credits: AI Generated

DOI: 10.3389/frmst.2026.1932154

Keywords: Editorial, Membrane, processes, extraction, valuable, materials, battery, other, mineral, wastes, scientific research