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.