Enhanced tetracycline degradation through nonradical processes by modulating the exposure of active sites on the iron nanoconfined catalysts

Abstract

There is an urgent need to develop effective and sustainable methods for reducing water pollution. Non-homogeneous Fenton catalysts are commonly used to eliminate pollutants from water. However, the effectiveness of these catalysts is limited by the restricted availability and accessibility of the active site (AS). In this work, we presented a strategy for modulating the exposure of active nanometallic particles to fully expose the AS at the nanoscale. We also confined the AS in carbon frameworks with micropores and mesopores to enhance the effectiveness of AS utilization in Fenton-like reactions. The experimental results indicate that the Fe-out@N-C/PMS system achieved complete degradation of tetracycline within 10 min and maintained an efficient degradation rate of over 91% after five consecutive cycles. The degradation of contaminants was due to an effective non-radical mechanism, as shown by free radical quenching experiments, EPR reactive species capture tests, in situ Raman, and PMSO probe experiments. Furthermore, density-functional theory (DFT) calculations revealed that iron nanoparticles supported on nitrogen-doped carbon acted as active sites, enhancing electron transfer capacity (N-C (0.24 e) vs. Fe-out@N-C (0.69 e)). Finally, the intermediates have a limited environmental impact because of their extremely low concentrations, despite having a high relative toxicity. The exposed metal nanoparticle catalysts provide a new approach for effectively activating PMS to efficiently degrade organic contaminants with a high mineralization rate via the non-radical pathway.