Solar‐Powered Electrokinetic Filtration using Hierarchical Porous Membranes for the Off‐Grid Removal of Ultrafine Contaminants

The removal of ultrafine suspended solids from water remains a critical challenge due to the tradeoffs among permeability, energy consumption, and fouling resistance. Electrokinetic techniques offer a membrane-free alternative; however, they are limited by low throughput, heavy reliance on auxiliary equipment, and technically demanding operations. Herein, a scalable, solar-powered nanoelectrokinetic filtration platform is proposed, which enables the efficient removal of nanoparticles (NPs), organic dyes, and Escherichia coli (E. coli) using micrometer-scale porous membranes. The core component is a hierarchically structured membrane, consisting of a biodegradable cellulose-cotton scaffold coated with ion-exchange resin and Nafion, forming confined microchannels and ion-selective nanochannels that generate stable electrokinetic repulsion under an applied electric field. Powered by a photovoltaic module and operated under gravity-driven flow (<1 kPa), the system achieves >99.9% removal of sub-50-nm particles, including species <10 nm, at high fluxes (>400 L m^-2 h^-1), and efficiently rejects gold NPs, dyes, and E. coli, with stable voltage and energy consumption (≈10 Wh L^-1) under tap water conditions. Moreover, the antifouling washable membrane retains its performance over 20 reuse cycles and supports linear scalability. Overall, the present study establishes a new class of electrokinetic-assisted filtration systems with high potential for off-grid water purification in resource-limited environments.