Reducing nitrate into ammonium by Fe0-phenolic network with spatiotemporal proton delivery for food sustainability

The excessive discharge of nitrate (NO₃⁻) from agricultural and industrial activities disrupts global nitrogen cycles and threatens environmental security, yet conventional remediation methods often fail to reconcile efficient NO₃⁻ removal with sustainable resource recovery. Herein, we design a Fe⁰-phenolic network anchored on wood fibers (GaFe⁰-WF) to convert NO₃⁻ into agriculturally valuable ammonium (NH₄⁺) in fixed-bed column. For the GaFe⁰-WF, the natural polyphenol is introduced to stabilize zero-valent iron (Fe⁰) nanoparticles on the surface of residual wood fibers, and spatiotemporally control H⁺ ions release for driving 8-electron reduction of NO₃⁻ into NH₄⁺. Meanwhile, the hierarchical architecture of wood fiber ensures efficient mass transfer. Thus, the GaFe⁰-WF achieves complete NO₃⁻-N removal (concentration ≤10 mg L^–1) with high NH₄⁺-N selectivity (>70 %), outperforming traditional nanoscale Fe⁰ by suppressing intermediates formation. The removal performance for real-world water samples from the Yangtze River, Jialing River, Minjiang River, and Jinsha River confirms its potential in large scale processing systems. Moreover, barley irrigated with NH₄⁺-containing water reduced by GaFe⁰-WF exhibits enhanced growth. This work advances sustainable development by synergizing wastewater transformation with fertilizer production, offering a critical closed-loop nutrient management for sustainable agroecosystems.