Synergistic Radicaland Nonradical Dual Pathways EnableHigh-Efficiency Tetracycline Degradation over Hierarchical Nitrogen-DopedCarbon

Abstract

Although the advanced oxidation processes (AOP) based on the activation of persulfate over carbon materials to degrade organic pollutants has attracted enormous attention, the surface engineering of carbon catalysts is still desired to boost their performance. Meanwhile, the synthesis of the nitrogen (N)-doped carbon commonly relies on an excessive external N source, which not only causes the waste of raw materials but also makes it difficult to realize the good distribution of N dopants. Herein, N-doped porous graphene-like carbon was synthesized using a nucleobase as endogenous N precursors, during which zinc nitrate was adopted to modulate the surface structures and the chemical state of each element. The optimal sample NG-5 was highly adsorptive and effective for the activation of peroxydisulfates (PDS) to degrade tetracycline (TC), which could also work in a relatively wide pH range and demonstrated high stability. The porous structure and high surface area facilitated the catalyst to expose more active sites. In-depth studies suggested that the activation of PDS followed mixed routes, where both radical and nonradical paths made notable contributions. Superoxide radicals and singlet oxygen were mainly responsible for TC degradation, while the contribution of hydroxyl and sulfate radicals could be ignored.