Photovoltaics driven, IoT-monitored UV-LED packed-bed photocatalytic reactor with an immobilized TiO2/GO sponge for pharmaceuticals (amoxicillin and metronidazole) degradation in real wastewater matrices

This study demonstrates the operation of an off-grid, integrated IoT-monitored UV-LED packed-bed photocatalytic reactor for the degradation of pharmaceuticals mixtures (amoxicillin (AMX) and metronidazole (MNZ)) in real wastewater matrices with real-time monitoring and control. The photovoltaics powered water treatment system combines an immobilized titanium dioxide-graphene oxide (TiO2/GO) sponge photocatalyst, spectrally matched UV-LED irradiation, hydrodynamic evaluation based on residence time distribution analysis, and real-time monitoring of key physicochemical parameters. The TiO2/GO photocatalyst, deposited on a three-dimensional glucomannan sponge via a microwave-assisted route, showed good structural, chemical, and optical stability after photocatalytic operation, as confirmed by XRD, XPS, FTIR, and diffuse reflectance analyses. Under optimized hydrodynamic conditions (25–100 mL min-1), the reactor exhibited plug-flow behavior with axial dispersion and pseudo-first-order kinetics while residence time distribution analysis revealed hydrodynamic limitations at higher flow rates. The reactor achieved the highest performance at 100 mL min-1, reaching approximately 70% removal of AMX and 60% removal of MNZ after 6 h recirculation. The integrated system was further evaluated in hospital, industrial pharmaceutical, and municipal wastewater matrices, revealing clear matrix-dependent performance, with the highest removals observed in hospital wastewater (ca. 45% for AMX and 19% for MNZ). ESI-MS analysis enabled the proposal of degradation pathways for both antibiotics, whereas ECOSAR calculations indicated reduced predicted acute aquatic toxicity of the identified transformation products. In parallel, multiple linear regression models based on in situ pH, ORP, EC, and TDS data showed that real-time sensor signals can serve as indirect matrix-specific indicators of photocatalytic performance. The study demonstrates the feasibility of integrating photocatalyst design, UV-LED reactor operation, hydrodynamic analysis, and IoT-based monitoring within a single platform for the treatment of complex wastewater matrices.