Sergio Gómez-Salazar

Ciprofloxacin (CIP) is a persistent fluoroquinolone antibiotic frequently detected in water bodies, and its efficient mineralization remains a challenge in wastewater treatment. In this work, iron oxide–chitosan macroporous nanocomposite hydrogels were developed as heterogeneous catalysts for the electro-Fenton degradation of CIP. The materials were synthesized via Pickering high internal phase emulsion templating, yielding monoliths with a three-dimensional interconnected porous structure, an average pore size of 18.9 ± 0.7 µm, a window size of 8.1 ± 0.7 µm, an openness degree of 39.6%, a specific surface area of 1.77 m² g⁻¹, an iron content of 64.2 mg g⁻¹, and a crosslinking degree of 92.1%. The monoliths exhibited controlled swelling in aqueous medium at pH 3, with a gravimetric water uptake of 142.1 ± 2.3% and a volumetric swelling of 39.3 ± 1.2% at equilibrium. Iron oxide particles remained exposed on the porous surface, providing accessible catalytic sites, while the interconnected porosity favored reactant diffusion. Compared with direct anodic oxidation, which achieved 32% total organic carbon removal after 20 min, the heterogeneous electro-Fenton process using the synthesized monoliths as catalysts showed superior performance, reaching nearly 95% removal within 2 min and complete mineralization within 15 min. This enhanced performance was associated with higher hydroxyl radical generation (~3.5 µM) than that observed for anodic oxidation alone (~1.5 µM). These findings highlight the potential of biodegradable iron oxide–chitosan macroporous hydrogels as sustainable catalysts for antibiotic removal from water.

Research on using biochar as an adsorbent of contaminants in aqueous matrices has gained significant relevance in recent years due to the surface chemistry and porous structure of biochar, which facilitate the retention of a wide range of pollutants. This study explores the adsorption performance of a novel biochar produced from agave bagasse—a readily available agro-industrial waste in Mexico—through low-temperature pyrolysis. The biochar was evaluated for its capacity to remove conventional water quality parameters (chemical oxygen demand (COD), nitrates (NO₃⁻), total nitrogen (TN), total phosphorus (TP), ammonium (NH₄⁺), turbidity, apparent color, and true color) from water samples collected from the polluted Bustillos Lagoon in Chihuahua, Mexico. Additionally, the removal of emerging pharmaceutical contaminants, specifically acetaminophen (Act) and diclofenac (Dfc), was assessed in synthetic aqueous solutions. Potentiometric titration analyses revealed a significant contribution of surface acidity in the adsorption of pharmaceutical derivatives, highlighting the relevance of functional groups retained during low-temperature pyrolysis. The biochar derived from agave bagasse (BBAF1) was tested in a fixed-bed column system and compared with two commercial activated carbons (CACCF2 and CVCF3). The BBAF1 biochar achieved average removal efficiencies ranging from 50% to 90% for all conventional parameters. In contrast, those of ACT and DFC were between 0.43 and 0.67 mg g⁻¹ (59–85%) and 0.34 and 0.62 mg g⁻¹ (37–79%), respectively, demonstrating their potential as an adsorbent material for improving water quality. This work supports the development of circular economic strategies by valorizing agricultural residues while offering an effective solution to environmental pollution challenges.