Interlayer-expanded LDH@biochar nanoreactors via sodium citrate mediation: Unlocking hidden active sites for persulfate-driven imidacloprid removal

The widespread usage of imidacloprid (IMI) has led to its frequent detection in aquatic environments, posing significant risks to ecosystems and human health. To address this issue, we developed a sodium citrate modified layered metal hydroxide (LDH) and biochar (BC)-based catalyst, SC-FCL@BC-2, for the activation of peroxymonosulfate (PMS) to efficiently remove IMI. Our findings demonstrate that within 15 min, the degradation rate of IMI (5 mg L −1 ) reached 95.6 % using 0.3 g L −1 SC-FCL@BC-2 catalyst and 2 mM PMS, surpassing both the FCL@BC/PMS system (70.4 %) and the FeCo-LDH/PMS system (61.5 %). The incorporation of sodium citrate as an interlayer anion enhanced IMI adsorption onto SC-FCL@BC-2, facilitated Fe 2+ /Fe 3+ and Co 2+ /Co 3+ cycling, and provided abundant active sites. Additionally, SC-FCL@BC-2 exhibited excellent stability across a wide pH range of 4.0 to 10.0, maintaining a degradation efficiency of 86.0 % after four cycles. The catalyst demonstrated broad applicability by effectively degrading more than 82.3 % of five neonicotinoid insecticides (NNIs) and maintaining over 73.7 % efficiency across various water matrices. Quenching experiments, electron paramagnetic resonance analysis, and electrochemical experiments confirmed that ·OH, ·SO 4 − , 1 O 2 , and electron transfer collectively promoted IMI degradation. By elucidating the efficacy and mechanistic basis of SC-FCL@BC-2, this study not only provides valuable insights into enhancing LDH@biochar-based Fenton-like catalysts but also advances their practical application in water treatment. • We designed dual active SC-FCL@BC with multistage pores via sodium citrate modification. • SC-FCL@BC-2/PMS system can achieve 95.6 % removal rate of IMI within 15 min. • Sodium citrate modification adjusts LDH interlayer spacing and optimizes electronic structure. • ·SO 4 − , ·OH, 1 O 2 , and electron transfer pathways combine to promote imidacloprid degradation.