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

Abstract

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, Cu-Fe@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.

Keywords: Adsorbed copper ions; Exhausted magnetic biochar; Low cost; Low metal leaching; Peroxymonosulfate activation.