Synergistic effect of iron and nitrogen on porous carbon to improve electron transfer efficiency resulting in the enhancement of tetracycline hydrochloride removal

Developing transition metal/nitrogen carbon catalysts for efficient pollutant removal presented an attractive option for water environment remediation. In this work, the iron (Fe), nitrogen (N) co-doped porous carbon nanoparticles (FeN/C) were prepared for heterogeneous activation of peroxymonosulfate and efficient oxidation of tetracycline hydrochloride (TC). Fe nanoparticles were encapsulated in the carbon to reduce the loss of Fe during the catalysis processes. As a catalyst, the sample of 20FeN/C exhibited an excellent catalytic activity of tetracycline hydrochloride with a removal rate of 91.2 % and a rate constant of 0.6653 min−1 in peroxymonosulfate (PMS) system. And the prepared catalysts presented the strong adaptability, which was worked efficient in a wide range pH and some anions solution. The high efficiency could attribute to the interaction of Fe and N, which effectively improved the electron transfer efficiency in this 20FeN/C activated PMS system. Combining with the results of electron paramagnetic resonance (EPR), in-situ Raman spectra, and X-ray photoelectron spectroscopy (XPS), electrons transfer was confirmed as a dominating non-radical process of TC degradation. It was confirmed that the doping of iron and nitrogen could collectively promote the electron transfer between material and PMS, and the activated PMS* reacted with TC via electron-rich nitrogen active sites of the material surface, then the TC degradation was enhanced. The received finding is of great significance to supplement the mechanism of electron transfer and provides a new idea on the synthesis of iron/nitrogen co-doped carbon catalysts to achieve high efficiency of TC removal.