Enhanced norfloxacin removal by eco-friendly MgFe2O4 modified sugarcane bagasse biochar: adsorption performances and mechanisms

Abstract

In this study, sugarcane bagasse biochar (SBBC) and its MgFe₂O₄ modified composites with different MgFe₂O₄/SBBC mass ratios were fabricated to remove norfloxacin (NOR) from aqueous solutions. The results showed that MgFe₂O₄@SBBC (1 : 2) prepared via impregnation coprecipitation exhibited excellent adsorption performance and environmental friendliness. The increased surface area, improved pore structure, abundant surface functional groups, and decreased pH_pzc endowed MgFe₂O₄@SBBC (1 : 2) with a higher adsorption efficiency (16.9 mg g⁻¹, 84.3%) than that of SBBC (9.76 mg g⁻¹, 48.8%). The pseudo-second-order model better described the kinetic process, indicating that chemisorption mainly occurred on both biochars. Isotherm fitting results indicated that NOR was adsorbed on SBBC primarily by multilayer adsorption, whereas monolayer adsorption was observed for MgFe₂O₄@SBBC (1 : 2). The adsorption of NOR onto both biochars was spontaneous, endothermic, and highly pH-dependent. Combined with BET, FTIR and XPS results, NOR adsorption by SBBC was controlled by pore filling, hydrogen bonds, and π–π electron donor acceptor interactions. In addition to these mechanisms, electrostatic attraction and surface complexation jointly strengthened the adsorption capacity of MgFe₂O₄@SBBC (1 : 2).