Photothermal Coupled Catalytic Water Decontamination and Solar Ammonia Recovery

Selective resource recovery from waste streams is essential for sustainable nitrogen management. However, conventional ammonia recovery from ammonium (NH4+)-and volatile organic compound (VOC)-containing wastewater is highly energy-intensive, and VOC-NH3 coevaporation further undermines product purity. Here we report an advanced oxidation processes-interfacial solar steam generation (AOPs-ISSG) platform based on a cobalt oxide-loaded nitrogen-doped carbon catalyst (Co-NC) that integrates photothermal conversion and catalytic oxidation. By exploiting the differing adsorption, electron-transfer, and reactive oxygen species (ROS) reactivity of VOCs and NH3, the system achieves selective VOC oxidation while preserving ammonia. Combined with alkaline solar interfacial evaporation, this selectivity supports concurrent VOC removal and efficient NH3 recovery. Under simulated wastewater conditions (pH = 9), the Co-NC/AOPs-ISSG system achieves 90.1% NH3 recovery and 95.3% VOC removal. It also demonstrates broad operational resilience across pH 7–10 and solar intensities up to 1.4 kW m–2, consistently yielding high-purity ammonia suitable for direct reuse, as validated by plant experiments in which recovered-ammonia irrigation promoted ∼40% greater pea seedling growth compared with untreated wastewater. Solar utilization and process integration reduce operating cost and carbon emissions by 23.2% and 27.7% compared with conventional NH3 recovery. These results highlight a low-carbon, economically viable pathway for selective ammonia recovery and sustainable nitrogen management.