Strong Tribocatalytic Degradation of Organic Pollutants by Natural Shell Particles

This study presents a waste-valorization strategy by developing calcined natural shell particles (CNSP) derived from waste oyster shells as an efficient tribocatalyst for degrading high-concentration organic pollutants, a challenge for which conventional photocatalytic approaches are hindered by light shielding. The CNSP catalyst, confirmed as calcite CaCO₃ with low surface area and stable crystalline structure, demonstrated exceptional efficacy in degrading Rhodamine B (RhB) solutions across a wide concentration range (50–300 mg/L) under mechanical friction, achieving 99% removal of 50 mg/L RhB in 1 h and 300 mg/L RhB in 18 h with a 0.5 g catalyst. This catalyst maintained a degradation efficiency of over 95% in a continuous six-cycle process. Mechanistic studies revealed that the tribocatalytic process generates reactive oxygen species (ROS), primarily hydroxyl (•OH) and superoxide (•O₂⁻) radicals, which drive the decomposition of dye molecules. Electron paramagnetic resonance (EPR) spectroscopy directly confirmed the generation of these radicals. These findings establish CNSP as a promising, low-cost, and environmentally benign catalyst for wastewater treatment. This work not only provides a novel strategy for high-concentration dye removal but also reduces the environmental burden of aquaculture shell disposal. Further work is needed to evaluate its performance in real industrial effluents and with mixed pollutants.