Martínez Boubeta, CarlosBalcells, LuisBeltrán Fínez, Juan IgnacioMartínez Peña, G. I.Virgiliou, C.Kalaitzidou, K.Vourlias, G.Teran, F. J.Salutari, F.Spadaro, M. ChiaraArbiol, J.Simeonidis, K.2025-11-252025-11-252025-08-20C. Martinez-Boubeta, Ll. Balcells, J.I.B. Finez, G.I. Martinez-Peña, C. Virgiliou, K. Kalaitzidou, G. Vourlias, F.J. Teran, F. Salutari, M.C. Spadaro, J. Arbiol, K. Simeonidis, Real-time Cr(VI) monitoring and remediation using Fe3O4 nanoparticles: Insights into Fe-Cr Spinels, Journal of Water Process Engineering 77 (2025) 108496. https://doi.org/10.1016/j.jwpe.2025.108496.2214-714410.1016/j.jwpe.2025.108496https://hdl.handle.net/20.500.14352/126510© 2025 The Authors. PTQ2021-012178An analytical approach for the rapid and remote determination of Cr(VI) in water samples is demonstrated using Fe3O4 nanoparticles and a cost-effective portable AC magnetometer. Cr(VI) reduction by surface Fe²⁺ leads to Fe/Cr precipitate formation, which alters the nanoparticles’ magnetic properties. Validation in natural water spiked with Cr(VI) showed a linear correlation between magnetic remanence and Cr(VI) concentrations from 0 to 10 mg/L, with a R2 value of 0.99. Limitations of the method emerged at loadings above 10 mg/g, where extensive chromite (CrxFe3-xO4) coverage reduced the magnetic hysteresis area. Advanced characterization and DFT calculations revealed changes in spin-dependent properties, including magnetization reversal, electrical conductivity and magnetoresistance. This robust correlation between collective magnetic properties and Cr(VI) exposure enables, for the first time, milligram-per-liter detection via ultra-fast AC magnetometry, paving the way for real-time insight into redox processes in liquid environments and novel strategies for environmental remediation.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/journal articlehttp://doi.org/10.1016/j.jwpe.2025.108496https://www.sciencedirect.com/science/article/pii/S2214714425015697?via%3Dihubopen access538.9544Drinking water monitoringPollutant sensorsHexavalent chromiumMagnetite nanoparticlesMagnetic anisotropyAC magnetometryDFT calculationsXPS analysisFísica de materialesAguaFísica (Química)2210 Química Física