One step hydrothermal synthesis of green Iron-Modified Catalyst by food waste biogas residue for Ozonation of Ciprofloxacin: Characterization, Degradation Mechanism, DFT study and Reactive Oxygen Species role

Recently, Biogas has been a well-known energy source due to global energy crises and huge urban leftover food waste by hospitality or food delivery. Still, it produces untreated biogas residue (BR), which causes heavy metals, and hazardous compounds leaching. Additionally, the proliferation of antibiotics such as ciprofloxacin (CIP) in the dairy and veterinary industry results in continuous release into water, posing a serious threats to ecological health. Herein, this study presents the hydrothermal synthesis of a series of Iron (Fe)-modified catalysts derived from eco-friendly ball milling boosted biogas residual biochar (BRB) to remove CIP via catalytic ozonation degradation. Fe-modified biochar with 2.5 wt. % iron loading and synthesized at 240 ℃ (2.5Fe-FBRB-240 ℃) exhibited the highest removal efficiency of 98.61% and stability for ten cycles of 20 min each. An optimal catalyst has demonstrated potential for CIP degradation in river and tap water, and ICP-MS has shown safer Fe-leaching. Toxicity assessment, mechanism, and degradation pathways were also proposed. Electrochemical studies, density functional theory (DFT) calculations, and Electron paramagnetic resonance (EPR) analysis confirmed the involvement of electron transfer and reactive oxygen species, like hydroxyl radicals (•OH), sulfate radicals (SO4•−), and singlet oxygen (1O2) in CIP degradation. This study provides a novel perspective for eliminating organic contaminants using biogas residue biochar-based catalysts.

近年来，受全球能源危机与餐饮、外卖行业产生的大量城市餐厨剩余垃圾影响，沼气（biogas）已成为广受关注的能源来源。然而其会产生未经处理的沼渣（biogas residue, BR），该类副产物会引发重金属与有害化合物溶出的问题。此外，环丙沙星（ciprofloxacin, CIP）等抗生素在乳业与兽药行业的大量使用，导致其持续释放至水体中，对生态健康构成严重威胁。
本研究以环保球磨工艺强化的沼渣生物炭（biogas residual biochar, BRB）为原料，通过水热合成法制备了一系列铁（Iron, Fe）改性催化剂，用于催化臭氧氧化降解环丙沙星。其中，铁负载量为2.5 wt.%、合成温度为240℃的铁改性生物炭（2.5Fe-FBRB-240℃）展现出最高的去除效率（98.61%），且在每次20分钟、共计10次的循环实验中保持良好稳定性。该最优催化剂在河水与自来水中均表现出优异的环丙沙星降解潜力，电感耦合等离子体质谱（inductively coupled plasma mass spectrometry, ICP-MS）分析结果证实其铁溶出量处于安全水平。
本研究还开展了毒性评估、反应机制及降解路径的相关研究。电化学测试、密度泛函理论（density functional theory, DFT）计算与电子顺磁共振（electron paramagnetic resonance, EPR）分析证实，电子转移过程与羟基自由基（•OH, hydroxyl radicals）、硫酸根自由基（SO4•−, sulfate radicals）、单线态氧（1O2, singlet oxygen）等活性氧物种共同参与了环丙沙星的降解反应。
本研究为利用沼渣生物炭基催化剂去除有机污染物提供了全新的研究视角。