Heterogeneous photocatalysis is a promising technique for removing pollutants from water. In this work, supercritical antisolvent (SAS)-micronized ZnO (ZnOSAS) is coupled with commercial anatase TiO2 (PC50) to study the photocatalytic degradation of ceftriaxone under UV and visible light. Diffuse ultraviolet-visible reflectance (UV-vis DRS) measurement revealed that the presence of ZnO leads to a slight absorption in the visible region. Wide-angle X-ray diffraction (WAXD) analysis showed the presence of both ZnO wurtzite and TiO2 anatase crystalline phases in the composite. Photocatalytic tests proved that the activity of the ZnOSAS/PC50 composite is higher than that of commercial ZnO, SAS-micronized ZnO, and PC50, allowing complete ceftriaxone degradation under UV light after only 2 min of irradiation time. In contrast, about 90% of ceftriaxone degradation is achieved after 180 min of visible-light irradiation. The photocatalytic results for an experiment carried out in the presence of probe scavenger molecules for reactive oxygen species show that hydroxyl radicals and positive holes are both reactive species involved in the ceftriaxone photocatalytic degradation mechanism. Finally, reuse cycles of the ZnOsas/PC50 composite are performed, demonstrating the stability and recyclability of the photocatalyst.
Keywords: ZnO/PC50; ceftriaxone; composite photocatalyst; degradation; photocatalysis; supercritical antisolvent.