CaCO3-activited N-doped diatom biochar for the degradation of tetracycline

In this study, a N-doped diatom biochar (DBC) was prepared by one-step pyrolysis, where CaCO₃ formed by marine diatom-mediated calcification was employed as an activator. Due to the activation effect of CaCO₃, the specific surface area of the obtained DBC increased by more than 10 times, and the nitrogen presented as pyrrolic nitrogen (58.9%), pyridinic nitrogen (29.7%), and graphitic nitrogen (11.4%) in the DBC. In addition, the effects of important parameters and co-existing ions on the catalytic decomposition of tetracycline (TC) by DBC were investigated by using TC as a typical pollutant and PDS as an oxidant. The DBC/PDS system exhibited high activity over a broad pH range. Through radical scavenging experiments, electron spin resonance, and electrochemical results analysis, it was found that the degradation of TC in the system included both radical and nonradical pathways, and the most dominant reactive species was ¹O₂. Furthermore, the surficial reactive complexes formed by PDS on the catalysts also played an important role in attacking the adsorbed TC molecules. This study proposes an eco-friendly and economical technique to construct a clean advanced oxidation process capable of treating TC wastewater by utilizing the native biomass of diatom as a metal-free and efficient biochar catalyst while simultaneously reducing the use of chemical reagents.