Pharmaceutical compounds, especially antibiotics, represent an emerging class of water pollutants with significant environmental and public health impacts due to their persistence and contribution to antimicrobial resistance. This study presents a novel approach by utilizing apple waste biomass to prepare cost-effective, sustainable biochar-based adsorbents and further functionalizing them with metal oxides (Fe₃O₄ and NiO), which, to our knowledge, has not been extensively explored for multi-antibiotic removal. In this study, cost-effective biochar-based adsorbents were prepared from apple waste biomass, activated and further functionalized with metal oxides (Fe₃O₄ and NiO), and evaluated for antibiotic removal from water. The materials were characterized by transmission/scanning electron microscopy, energy dispersive spectroscopy, Brunauer-Emmett-Teller analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, and Raman analysis, revealing significant structural and chemical differences induced by activation and metal oxide incorporation. The systematic comparison between activated biochar and biochar functionalized with Fe₃O₄ or NiO provides new insights into the relationship between textural properties and adsorption performance. Activation of the biochar led to a highly developed porous structure, resulting in a specific surface area of 1208 m²/g for the activated sample (A-ac), while Fe₃O₄ functionalization obtained a large surface area of 1065 m²/g. Quantitative comparison showed that unmodified biochar (A) exhibited low adsorption efficiencies, removing only 88.18% of trimethoprim, 2.94% of ciprofloxacin, and 14.06% of tetracycline. Activation (A-ac) enhanced performance, achieving 99.51% removal of ciprofloxacin, 100% for trimethoprim, and 49.31% for tetracycline. Fe₃O₄-functionalization (A-ac-Fe₃O₄) further improved tetracycline removal to 60.42%, while NiO-containing materials performed poorly due to pore blockage and low surface area, demonstrating the clear quantitative advantage of activation and selective metal oxide functionalization. These results not only quantify the adsorption efficiency of novel biochar-based materials but also establish clear correlations between surface area, porosity, and antibiotic removal, contributing new knowledge to the design of sustainable adsorbents for water remediation. The experiments were conducted under preliminary batch conditions using synthetic water. The performance of the prepared biochar-based adsorbents in real wastewater, which may contain complex matrices and competing contaminants, was not evaluated in this study. Future work will focus on investigating the adsorption mechanisms and the reusability of the most effective materials identified here (A-ac and A-ac-Fe₃O₄), to further validate their potential for practical water remediation applications.
Stegarescu et al. (Wed,) studied this question.