Adsorptive removal of imidacloprid by potassium hydroxide activated magnetic sugarcane bagasse biochar: Adsorption efficiency, mechanism and regeneration

Abstract Extensive presence of imidacloprid (IMI) in the worldwide water which has caused the potential risk to human health. An efficient and novel adsorbent of potassium hydroxide (KOH) activated magnetic (iron/zinc, Fe/Zn) sugarcane bagasse biochar (KOH + Fe/Zn-BBC) was first time synthesized in this study to adsorptive removal of IMI from water. Its maximum adsorption capacity was 313 mg g−1 at 298 K. Characterization, kinetic, isotherm, thermodynamic and environmental factors analysis suggested that both chemisorption and physisorption were involved in IMI adsorption process, which was a spontaneous, endothermic and randomly increasing process. Particularly, pore filling, π-π conjugation and oxygen-containing functional groups complexation were the main mechanisms. Intraparticle diffusion was considered as the main rate-limiting step due to its dominant microporous structure. The magnetic sensitivity of KOH + Fe/Zn-BBC enabled it to be easily separated from the solution, which was also beneficial for its reuse. Ultrasound cavitation and ethanol extraction co-processing could effectively regenerate the used adsorbent and maintain its efficient adsorption capacity. Additionally, KOH + Fe/Zn-BBC exhibited a stable adsorption performance and great environmental safety in a wide pH range. Therefore, this study suggests that KOH + Fe/Zn-BBC is an efficient, green and sustainable adsorbent for neonicotinoids removal.