Irma Robles

This study investigated the sorption of three widely detected non-steroidal anti-inflammatory drugs, naproxen, diclofenac, and ibuprofen, onto biochars and activated carbons derived from coconut shell and orange peel. Activated carbons were prepared under chemical activation with ZnCl₂ and H₃PO₄. The sorbent materials were characterized in terms of surface functional groups, acid–base properties, and pzc, while the pH was monitored along the sorption experiments. Results suggest that the activating agent played an important role in controlling surface chemistry and acid–base properties; ZnCl₂-activated carbons exhibited near-neutral pzc values and a balanced distribution of functional groups, while H₃PO₄-activated materials showed highly acidic surfaces with lower pzc. The solution pH evolved during sorption instead of remaining at its initial value. The sorption performance showed a clear dependance on surface chemistry, ZnCl₂-activated carbons exhibited a superior sorption capacity as well as faster kinetics under neutral conditions, this behavior may be associated to reduced electrostatic repulsion toward anionic model molecules. Under acidic conditions, some H₃PO₄-activated materials showed comparatively favorable sorption behavior, consistent with possible contribution from hydrogen bonding and hydrophobic interactions. Kinetic analysis showed time-dependent uptake profiles consistent with more than one mass-transfer contribution; however, no single rate-controlling mechanism could be established from the available data. The results indicate that NSAID sorption under the investigated conditions was associated with the surface acid–base properties of the carbon materials, the initial-to-final pH shifts, and the pH-dependent speciation of the pharmaceuticals. These findings provide an empirical basis for evaluating the performance of agroindustrial waste-derived carbon materials toward ionizable pharmaceuticals and highlight the importance of considering both surface chemistry and the measured solution pH when interpreting sorption behavior.

The Electro-Fenton (EF) process is a promising technology for the sustainable remediation of organic contaminants in complex wastewater. In this study, a weak magnetic field (~150 G) was applied to enhance the performance of an EF system using magnetite (Fe₃O₄) synthesized by a controlled co-precipitation route as a recyclable solid iron source. The magnetite was characterized by FTIR, SEM/EDS, and XPS, confirming the coexistence of Fe²⁺/Fe³⁺ species essential for in situ Fenton-like reactions. Under the selected operating conditions (90 min reaction time), magnetic-field assistance improved methylene blue decolorization from 14.2% to 46.0% at pH 3. FeSO₄ was used only as a homogeneous benchmark, whereas the magnetite-based system operated without soluble iron addition, minimizing sludge formation and secondary contamination. These results demonstrate the potential of magnetite-assisted and magnetically enhanced EF systems as a low-cost, sustainable alternative for the treatment of dye-containing industrial wastewater and other complex effluents.