A novel, efficient and sustainable magnetic sludge biochar modified by graphene oxide for environmental concentration...

Environmental concentration imidacloprid (IMI) has become a potential risk to ecological safety and human health, therefore an efficient, sustainable and environment friendly approach was urgently needed for its removal. In this study, a novel graphene oxide supported magnetic sludge biochar composite (GO/CoFe₂O₄-SBC) was first time synthesized and assessed for IMI removal at environmental concentration level. The maximum adsorption capacity of GO/CoFe₂O₄-SBC for IMI was 8.64 × 10³ μg g^-1. Physicochemical characteristics, kinetics (pseudo-second-order), isotherms (Freundlich and Temkin), thermodynamics and environmental factors analysis suggested that its outstanding adsorption performance was mainly attributed to pore filling, π-π conjugation and functional groups interaction. The mechanisms analysis indicated that intraparticle diffusion was the main rate-limiting step and its adsorption was a spontaneous, endothermic and randomness increased process. The magnetic sensitivity enabled it to be easily separated from water. The sustainable adsorption capacity (>90% of the initial adsorption capacity) of GO/CoFe₂O₄-SBC was well maintained by ethanol extraction even after five reuse cycles. GO/CoFe₂O₄-SBC also exhibited environmental security with its leaching concentrations of Fe and Co were below 0.5 mg L^-1 in a wide pH range. The performance of GO/CoFe₂O₄-SBC suggested that it could be served as a promising adsorbent for environmental concentration IMI removal.