A novel polydopamine-loaded copper sulfide (CuS@PDA) for activating H2O2 to eliminate tetracycline via 1O2 dominated oxidation pathway

Abstract

The frequently detected antibiotics in aquatic environments can induce antibiotic-resistance genes, thereby posing significant risks to both ecosystems and human health. Thus, it is imperative to remove antibiotics from water environments. We constructed a novel polydopamine-loaded copper sulfide (CuS@PDA) through a simple hydrothermal method to activate H₂O₂ to degrade tetracycline (TC). Compared to CuS/H₂O₂, the CuS@PDA/H₂O₂ system not only achieved efficient TC removal with kinetic rate constant of 0.20 min⁻¹, but also showed much lower Cu²⁺ ions leaching (3.81 mg/L from CuS vs. 0.21 mg/L from CuS@PDA). Besides, CuS@PDA exhibited remarkable recyclability with 93 % removal in the fifth consecutive cycle. Mechanisms analysis revealed that Cu and S contributed to the H₂O₂ activation and S promoted the conversion of Cu(II) to Cu(I), beneficial for the production of reactive oxygen species. ¹O₂ was found to play the dominant role in the degradation of TC on the basis of quenching tests and electron paramagnetic resonance (EPR) analysis. PDA in CuS@PDA composites facilitated easier complexation with H₂O₂ and conferred stronger oxidation capability. Lastly, the TC degradation pathway by CuS@PDA/H₂O₂ was proposed, and the ecotoxicity of its degradation intermediates was estimated. In conclusion, this work demonstrates that the use of PDA can not only improve the catalytic activity and recyclability of CuS towards H₂O₂ activation for organic pollutants degradation, but also greatly mitigate copper ions leaching.