Preparation of Co-CNK-OH and Its Performance in Fenton-like Photocatalytic Degradation of Tetracycline

In this study, Co-modified alkalinized g-C3N4 (named Co-CNK-OH) was prepared for the Fenton-like photocatalytic degradation of tetracycline (TC) via a simple yet effective calcination–impregnation method. In all samples of CNK-OH with different Co2+ loadings, Co-CNK-OH catalyst with the optimal content (9%) exhibited the highest catalytic activity, with 87.1% tetracycline removal and 50% removal efficiency of the total organic carbon (TOC). Mechanism studies revealed that the 9%Co-CNK-OH catalyst had the lower electrical resistance after alkalization treatment and Co2+ modification, leading to a significantly accelerated interfacial charge transfer to the electron acceptor as well as effectively separating electrons and holes. The intermediates generated during the TC degradation in the photo-Fenton process were detected by HPLC-MS, which proved that the holes, superoxide radicals, and singlet oxygen are the key reactive species in the Fenton-like photocatalysis. This study provides a new option for the treatment of TC in wastewater.