Recycling exhausted magnetic biochar with adsorbed Cu2+as a cost-effective permonosulfate activator for norfloxacin degradation: Cu contribution and mechanism

Herein, we attempted to apply an exhausted magnetic biochar with adsorbed Cu2+ (Cu-Fe@BRC) directly as a PMS activator and explored the feasibility of this attempt. Density functional theory (DFT) and electrochemical analysis illuminated the adsorbed Cu2+ in Cu-Fe@BRC improved PMS activation and NOR degradation efficiency by elevating the adsorption capacity of PMS and performance of electron transfer. About 91.47% of norfloxacin (NOR) was rapidly degraded in Cu-Fe@BRC/PMS system with low Fe and Cu leaching. An in-depth mechanistic study was conducted with radical scavenging, radical capturing and solvent exchange, which demonstrated that the adsorbed Cu2+ could facilitate the formation of both different radicals and non-radical. Importantly, CuFe@BRC can maintain a long-term stable operation and excellent catalytic performance in surface water treatment. The potential toxicity of by-product generated in the NOR degradation process was also predicated, and results suggested that most identified by-products were less toxic than NOR itself. Notably, the preparation cost of exhausted adsorbent-based catalysts could be negligible, so the expenditure of the corresponding oxidation process is reduced accordingly. Based on above, this work provides not only a low-cost exhausted biochar-based catalyst for water purification but also the insight into the PMS activation by adsorbed transition metal ions.

Automated summary

This study investigated the application of exhausted magnetic biochar with adsorbed Cu2+ as a PMS activator, showing that the adsorbed Cu2+ improved PMS activation and NOR degradation efficiency. Furthermore, the method demonstrated long-term stable operation in surface water treatment.