Efficient removal of tetracycline by H2O2 activated with iron-doped biochar: Performance, mechanism, and degradation pathways

In this study, novel iron-doped biochar (Fe-BC) was produced using a simple method, and it was used as an H2O2 activator for tetracycline (TC) degradation. Generally, iron loading can improve the separation performance and reactivity of biochar (BC). In the Fe-BC/H2O2 system, 92% of the TC was removed within 30 min with the apparent rate constant (k(obs)) of 0.155 min(-1), which was 23.85 times that in the case of the BC/H2O2 system (0.0065 min(-1)). The effects of the H2O2 and Fe-BC dosage, initial pH, and TC concentration on the TC removal were investigated. The radical quenching and electron paramagnetic resonance (EPR) measurements demonstrated that the removal of TC using the Fe-BC/H2O2 process involved both radical ((OH)-O-center dot and O-2(-center dot)) and non-radical pathways (O-1(2) and electron transfer). In addition, the performance of the catalyst was also affected by the persistent free radicals (PFRs) and defective sites on the catalyst. Moreover, the degradation pathways of TC were proposed according to the intermediate products detected by LC-MS and the ecotoxicity of intermediates was evaluated. Finally, the Fe-BC/H2O2 showed high resistance to inorganic anions and natural organic matter in aquatic environments. Overall, Fe-BC is expected to be an economic and highly efficient heterogeneous Fenton catalyst for removing the organic contaminants in wastewater. (c) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

In this study, a novel iron-doped biochar (Fe-BC) was prepared and used as an activator for tetracycline (TC) degradation by H2O2. The Fe-BC/H2O2 system showed significantly enhanced TC removal compared to the BC/H2O2 system, indicating the improved separation performance and reactivity of Fe-BC. The removal process involved both radical and non-radical pathways, and the catalyst performance was influenced by persistent free radicals (PFRs) and defective sites.