In-situ recycling of waste ozonation catalysts into N-doped graphitic carbon-alumina structures induces a non-radical pathway towards water purification

Abstract

With the widespread application of catalytic ozonation in the advanced treatment of industrial wastewater, the increasing of waste ozonation catalysts has posed substantial environmental and economic challenges. Although waste catalysts represent an attractive resource, environmentally friendly and efficient recycling strategies remain elusive due to their complex structures and compositions. Herein, we propose a one-step pyrolysis strategy to ingeniously recycle waste catalysts into composite catalysts (Cu-Mn/NGC-Al₂O₃) for industrial wastewater treatment. This procedure involves the in-situ graphitization of extracellular polymeric substances from the waste catalysts onto the pristine Al₂O₃ substrates, and trace amounts of copper and manganese undergo redox-reactive recycling to form nanoparticles. Waste catalyst-derived Cu-Mn/NGC-Al₂O₃ demonstrates recovery of 80.83% activity of the original fresh catalysts, along with excellent stability. Unlike the radical oxidation of fresh catalysts, we identify that Cu-Mn/NGC-Al₂O₃ configuration induces a non-radical pathway based on singlet oxygen with a contribution of 84.09%. Life cycle assessment and economic analysis indicate that recycling waste catalysts to Cu-Mn/NGC-Al₂O₃ achieves a 93.89% reduction in carbon emissions and saves approximately 58.58% in costs. This study promotes the recycling of waste catalysts and maximizes the utilization of resources from waste catalysts, achieving the goal of the low-carbon transition.