Tandem 1O2 oxidation and anodic mineralization over electro-assisted lignin biochar activating peroxydisulfate for imidacloprid removal

The recalcitrance of pesticides imidacloprid (IMI), alongside the susceptibility of conventional persulfate (PS) activation to complex water matrices, presents significant challenges for pollutants remediation. Although biochar and electrochemical activation have proven effective for PS activation, they are hindered by electron transfer kinetics and energy consumption, respectively. In this study, an electro-coupled lignin-derived biochar system (E/L-BC/PDS) was designed to provide synergistic effects between a low-current electric field and L-BC. Comparative experiments revealed that the standalone E/PDS system achieved less than 50% total organic carbon (TOC) removal, whereas the L-BC/PDS system resulted in less than 15% TOC removal. In contrast, the integrated system accomplished complete degradation of IMI (100%) within 120 min and an exceptional 95% TOC removal under optimized conditions (15 mg L −1 L-BC, 58 mg L −1 PDS, pH 3). Mechanistic insights indicated a cascade synergy: the electric field accelerated electron transfer from surface carbonyl (C=O) groups and graphitic nitrogen on L-BC, promoting PDS activation to generate singlet oxygen ( 1 O 2 ) as the primary reactive species for the selective degradation of IMI, while concurrent anodic oxidation provided the thermodynamic driving force for the deep mineralization of intermediates. Consequently, the system exhibited stable IMI removal (72%) and TOC removal (48%) in a simulated wastewater containing Cl − , HCO 3 − , and humic acid. Toxicity assessments confirmed the formation of environmentally benign intermediates, with over a 90% reduction in bioconcentration potential. This study presents a strategy for valorizing agricultural lignin waste into high-performance electrocatalysts, offering insights into the design of robust and matrix-tolerant advanced oxidation processes.