Sustainable design of photo-Fenton-like oxidation process in actual livestock wastewater through the highly dispersed FeCl anchoring on a g-CN substrate.

Photocatalytic technology emerges as a promising solution for the sustainable treatment of contaminated wastewater. However, the practical implementation of designed photocatalysts often faces challenges due to the intricate 'high carbon footprint' process and limited outdoor laboratory investigations. Herein, a simple yet versatile impregnation approach is proposed to anchor highly dispersed FeCl on a g-CN substrate (Fe-CN) with minimal energy consumption and post-processing. Fe-CN enhances photocatalytic reactivity for antibiotic degradation via a synergistic photo-Fenton-like oxidation technique, efficiently removing antibiotic pollutants from actual livestock wastewater. The Fe-CN catalyst exhibited consistent degradation performance over five cycles in laboratory conditions, maintaining a degradation efficiency exceeding 90 % for tetracycline hydrochloride (TCHCl). Furthermore, we engineered a straightforward Fe-CNNaSiO reactor for treating livestock wastewater, achieving an 81.8 % removal of TCHCl in outdoor field tests conducted in the winter and summer in China. The Fe-CN catalyst demonstrated high feasibility in treating antibiotic-contaminated livestock wastewater under year-round climatic conditions, leveraging synergistic effects. The stabilization of Fe-CN for the degradation of antibiotic-containing wastewater under sunlight represents a significant advancement in the practical application of photocatalysts, marking a crucial milestone from experimental conception to implementation. Acute toxicity estimation suggested that intermediates/products generated exhibited lower toxicity compared to TCHCl, indicating their practical applicability. Density functional theory (DFT) analysis successfully predicted significant electron transfer between Fe-CN and TCHCl, indicating efficient interfacial interactions on the TCHCl surface. To ensure the environmental sustainability of Fe-CN, a life cycle assessment (LCA) was conducted to compared this photocatalyst with other commonly used emerging photocatalysts. The results demonstrated that Fe-CN exhibits a two orders of magnitude lower CO equivalent emission compared to the ZnO photocatalyst, indicating a cost-effective and efficient synergistic photo-Fenton-like catalytic approach. This low-cost photocatalyst, moving from the laboratory to real-world wastewater applications, provides a powerful and more sustainable solution for the efficient treatment of wastewater containing antibiotics from livestock farming.