Olive biomass-derived magnetic activated biochar for ciprofloxacin removal: Integrated kinetic, isotherm, thermodynamic, and spectroscopic analysis

Olive biomass waste was converted into novel magnetic-activated biochars (MOBs) using a simple single-step chemical activation process combined with microwave-assisted pyrolysis. Biomass served as the carbon source, while ZnCl2 and NiCl2 were used as activating and magnetic agents (with ratios of 1:1:1 for MOB-1 and 1:1:1.5 for MOB-1.5). The synthesized MOBs were characterized using SEM-EDS, FTIR, XRD, N2 adsorption/ desorption, VSM, pHPZC, and IP techniques, revealing distinct structural and textural properties influenced by the magnetic agent ratios. MOB-1 and MOB-1.5 exhibited specific surface areas of 743.6 and 595.2 m2 g- 1, respectively, with coercivities ranging from 22.6 to 24.2 Oe. The interactions between MOBs and ciprofloxacin (CP) antibiotic were systematically investigated. Adsorption studies showed rapid CP uptake, best described by the nonlinear Avrami fractional model, with maximum adsorption capacities of 218.4 mg g- 1 for MOB-1 and 216.8 mg g- 1 for MOB-1.5, according to the Liu isotherm. Spectroscopic and thermodynamic analyses confirmed an endothermic, spontaneous adsorption process. Additionally, physisorption governs the process, driven by hydrogen bonding and it-it interactions. This work demonstrates the potential of olive biomass as a sustainable feedstock for magnetic biochar production, enhancing wastewater treatment efficiency and promoting the circular economy.