Treatment of Aqueous Amoxicillin Solutions with Sunlight Using a Pelletized Macrocomposite Photocatalyst

We report on the preparation and characterization of a cost-effective, durable, and reusable macrocomposite, prepared in the form of pellets and designed for the photodegradation of water pollutants, using amoxicillin (AMX) as a model compound. Using the wet impregnation method, kaolin clay and TiO₂-P25 composites were doped with copper (Cu²⁺) and cobalt (Co²⁺). The produced materials were characterized by SEM-EDS, XRD, XRF, textural property analysis, and their potential lixiviation of components by ICP-MS. The photodegradation efficiency under solar irradiation was evaluated by varying the acidity of the medium, the concentration of AMX, and the amount of catalyst. The performance of the recycled photocatalysts was also studied. The photodegradation of AMX was monitored by UV-Vis and UV-Vis/HPLC spectrophotometry. The optimal formulations, Cu (0.1%)/TiO₂ and Co (0.1%)/TiO₂, achieved up to 95% degradation of 5 mg·L^-1 AMX in 3 h at pH 5.9, with a catalyst loading of 1 g·L^-1. The Cu-doped material showed a slightly faster reaction rate and higher total-organic-carbon removal (80.4%) compared to the Co-doped material (59%) under identical conditions. The same photodegradation intermediates were identified by LC-MS/MS for both doped macrocomposites, and a reaction mechanism is proposed. These macrocomposites showed efficient and consistent recyclability over more than five reuse cycles, showing their potential to be used for antibiotic pollution abatement in water-treatment facilities.