Carbon quantum dots decorated heteroatom co-doped core-shell Fe0@POCN for degradation of tetracycline via multiply synergistic mechanisms

In this study, novel core-shell catalyst with a new ternary heterostructure was synthesized (Fe-0@POCN/CQDs) for the degradation of tetracycline (TC). The TEM results showed that the Fe-0 particles were wrapped in POCN material and many nano CQDs were uniformly dispersed in the material. The new ternary nanocomposite exhibits excellent photocatalytic activity for the removal of TC, which was approximately 4.76 times higher than that of GCN. The enhancement of photocatalytic activity was attributed to the effective heterojunction as well as the multiply synergistic effects of POCN combined with Fe-0 and CQDs, which was beneficial for retardation of recombination rate of photogenerated electron-hole pairs and generation of more free radicals for the oxidation of TC. Besides, the reactive oxygen species (ROS) of h(+), center dot O-2(-) and center dot OH played pivotal roles in the degradation of TC by Fe-0@POCN/CQDs during the photocatalytic reaction. At the same times, sulfate radical (SOT) and hydroxyl radical (center dot OH) highlighted the dominant role in the degradation process compared with other free radicals under persulfate hybrid mixture system (PS system), which was further confirmed by radical scavenger experiments and electron spin resonance (ESR) analysis. The response surface methodology (RSM) study indicated that the optimal removal parameters of tetracycline could reach 97.57% within 30 min under PS system. In addition, the possible degradation pathway intermediates of TC were studied by HPLC-MS and the reaction catalytic activity mechanism of Fe-0@POCN/CQDs/persulfate system was discussed. (C) 2020 Published by Elsevier Ltd.

Automated summary

The novel ternary Fe-0@POCN/CQDs catalyst showed excellent photocatalytic activity for the degradation of tetracycline, with the enhancement attributed to effective heterojunction and synergistic effects of POCN, Fe-0, and CQDs. The degradation process involved key reactive oxygen species and was optimized using response surface methodology, achieving a 97.57% removal of tetracycline within 30 minutes under persulfate system.