Droplet-driven self-powered Pb^2 + extraction from industrial wastewater

Lead-containing wastewater poses serious environmental and health risks. Conventional Pb²⁺ removal methods often require external power, chemical reagents, or centralized treatment facilities. In this work, we develop a droplet-driven self-powered Pb²⁺ extraction unit (PUE) for in-situ lead removal. The PUE film adopts a three-layer Al-FEP-CF@ZIF-67@Cu@MXene-S structure. The Al electrode collects droplet-induced electrons, the superhydrophobic FEP layer promotes droplet rebound and interfacial charge separation, and the CF@ZIF-67@Cu@MXene-S layer provides Pb²⁺ adsorption sites, conductive pathways, and reduction interfaces. ZIF-67@Cu improves Pb²⁺ adsorption and reduction activity, MXene accelerates electron transport, and thiourea modification introduces sulfur-containing binding sites for selective Pb²⁺ capture. Under droplet impact, the device produces an open-circuit voltage of about 300 V and a short-circuit current up to 600 μA. The PUE system achieves a maximum Pb²⁺ extraction capacity of 242 mg/g, maintains high selectivity against competing ions, and operates effectively over pH 3-9. Product characterization confirms localized Pb deposition on the functional electrode, with crystalline PbO, Pb₃O₄, and PbO₂ formed after extraction. DFT calculations reveal that thiol groups selectively bind Pb²⁺ through Pb-S coordination, while Cu-assisted electronic regulation enhances interfacial charge transfer. This work provides a compact and self-powered strategy for decentralized lead-containing wastewater treatment.