An Al/Cu²⁺ self-filtering galvanic cell for energy-neutral copper separation from acidic wastewater and in situ catalyst upcycling

Copper-bearing acidic wastewater from printed circuit board (PCB) manufacturing, electroplating, and hydrometallurgical operations typically contains 20–10,000 mg L⁻¹ Cu²⁺ at intrinsic pH 0–3, posing a persistent separation challenge and representing a significant loss of a strategic metal. Conventional recovery methods, including chemical precipitation, ion exchange, membrane separation, and electrowinning, either generate large volumes of secondary sludge or consume 3000–3500 kWh per ton of Cu, limiting their deployment at scale. Here, we develop a cable-shaped self-filtering Al/Cu²⁺ galvanic cell that integrates pump-free wastewater transport, spontaneous Cu²⁺ separation, and in situ electrocatalyst synthesis into a single energy-neutral operation. Hydrophilic hollow cotton ropes function simultaneously as a capillary-driven flow distributor and an ionic separator between a sacrificial aluminium anode and a Graphite@Ti cathode, eliminating external power and mechanical pumping. Under conditions representative of acidic Cu-bearing effluents (pH 1, 30 mM Cu²⁺), the device delivers a peak power density of 5.1 mW cm⁻² and > 85% Cu²⁺ removal, while producing a compact crystalline Cu⁰ coating on the Graphite@Ti cathode with >85% Faradaic efficiency at Cu²⁺ concentrations ≤3 mM. COMSOL multiphysics simulations coupling capillary flow, Darcy transport, and adsorption retardation resolve the separation dynamics inside the porous rope and identify uncontrolled bulk‑copper deposition as the mass-transport failure mode beyond 30 mM. The in situ generated Cu@Graphite@Ti electrodes are directly employed as electrocatalysts for nitrate-to-ammonia conversion, yielding 97.6% nitrate conversion, 98.7% NH₃ selectivity, and 89.3% Faradaic efficiency at −0.33 V vs. RHE. A screening-level techno-economic analysis with Monte-Carlo sensitivity shows a baseline total cost of approximately 354 USD kg⁻¹ Cu and a benefit-to-cost ratio (BCR) of 1.02 under the assumed module-value-retention scenario, with P(BCR > 1) = 86.9% across the sampled uncertainty space. This work establishes a pump-free, integrated separation and valorization platform for circular copper-resource management from acidic industrial effluents.