Photocatalytic performance of buoyant TiO2-immobilized poly(ethylene terephthalate) beads for the removal of the anticonvulsant drug pregabalin from water and leachate

The application of TiO2 nanoparticles as photocatalyst for the removal of pharmaceutical compounds from water is extensively applied as an alternative to the conventional treatment processes. However, application of TiO2 as a powder requires energy costing separation stages to remove the catalyst at the end of the process. Thus, immobilization of the catalyst can be an attractive solution. Aiming to find a good support material for TiO2, in this study, the synthesis and characterization of three different PET/TiO2 photocatalytic beads are described along with their application in the photocatalytic degradation of the anticonvulsant drug pregabalin (PGB). The PET/TiO2 beads with different contents of TiO2 filler (10 wt%, 20 wt% and 30 wt%) were synthesized by using an anti-solvent precipitation method and were characterized by different techniques, such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Among the different composites, PET/TiO2 30 wt% beads proved to be the most efficient, achieving almost complete degradation of PGB within 6 h of treatment. The stability and reuse of the synthesized catalysts were also evaluated. Furthermore, the effect of matrix was examined, revealing slower kinetics in high loaded matrices like a leachate. Identification of the arising transformation products (TPs) was conducted using LC-HRMS analysis. Twenty-two TPs were identified, out of which fifteen were detected for the first time herein, stemming from hydroxylation, amidation, oxidation and oxidative deamination of PGB. Finally, the in silico prediction of their toxicity was conducted based on ECOSAR software revealing mainly the formation of non-toxic compounds. However, amidation can cause the formation of toxic/harmful by-products but they are susceptible to photocatalysis thus being eliminated until the end of treatment.