Preparação e caracterização de biocarvões ativados magnéticos derivados de biomassa de oliva para a remoção do antibiótico ciprofloxacino de soluções aquosas

Abstract

The search for sustainable solutions in wastewater treatment requires exploring innovative precursors for the production of activated biochars. This study synthesized magnetic activated biochars (BOMs) with specific surface areas of 743.6 and 595.2 m² g⁻¹ and coercivities ranging from 22.6 to 24.2 Oe, using a rapid one-step method combining chemical activation with microwave-assisted pyrolysis. Olive biomass (OB) was used as the carbon source, while ZnCl₂ and NiCl₂ (in proportions of 1:1:1 for BOM-1 and 1:1:1.5 for BOM-1.5) were used as the activating and magnetic agents. The resulting magnetic biochars (BOMs) were characterized using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N₂ adsorption/desorption analysis, vibrating sample magnetometry (VSM), pH at the point of zero charge (pHPZC), and isoelectric point (IP) measurements. These analyses revealed distinct structural and textural properties influenced by the proportions of magnetic agents. Furthermore, the interactions between the BOMs and the antibiotic ciprofloxacin (CP) were evaluated through batch adsorption experiments. The kinetic experimental data were best fitted to the nonlinear Avrami fractional-order model. The MOBs exhibited rapid adsorption kinetics, with t₀.₉₅ = 44.31 min for BOM-1 when the initial concentration (C₀) was 80 mg L⁻¹. The equivalent value for BOM-1.5 (t₀.₉₅) was 82.11 min when C₀ = 80 mg L⁻¹. The nonlinear Liu isotherm model indicated slightly higher maximum adsorption capacities for BOM-1 (218.44 mg g⁻¹) compared to BOM-1.5 (216.76 mg g⁻¹). Spectroscopic, adsorption, and thermodynamic studies confirmed an endothermic and spontaneous adsorption process governed by physisorption, including hydrogen bonding and π-π interactions. This work paves the way for a greener future in wastewater treatment by demonstrating the potential of olive biomass as a raw material for producing magnetic activated biochar, which can be easily removed from the solution using an external magnetic field. Finally, it is worth highlighting that this study aligns with the United Nations Sustainable Development Goals (SDGs), specifically SDG 6, "Clean Water and Sanitation," which aims to improve global water quality; SDG 14, "Life Below Water"; and SDG 15, "Life on Land," by addressing the harmful impacts of contaminants on aquatic and terrestrial ecosystems, promoting biodiversity preservation, and encouraging the sustainable use of natural resources.