Photon Flux and Water Matrix Effects in Sn-Doped Ti-Zr Oxide Photocatalysts: Transformation Products and Phytotoxicity

Abstract

The photocatalytic degradation of erythromycin (ERY) was investigated using a Sn-doped Ti-Zr oxide photocatalyst in two water matrices: reverse osmosis (RO) water and real underground (UG) water. Two photon fluxes emitted by 9 W (low) and 18 W (high) UV-A lamps were evaluated to determine how the complexity of the water matrix affects photocatalytic performance. Although ERY removal was accelerated by a high photon flux, similar degradation was achieved using low photon flux with significantly lower energy consumption. Light penetration was reduced, and energy demands were increased by dissolved organic matter and inorganic compounds in UG water. Substantially more energy was required for ERY mineralization than for its degradation. In RO water, phenolic compounds and cyclic alcohol were produced during ERY degradation, whereas in UG water, aromatic compounds—likely reflecting aquifer contamination—were generated. Toxicity to A. cepa and L. sativa was observed in some treated samples, possibly due to the formation of harmful byproducts and the presence of fluorine ions. This work underscores the critical need to consider the impact of real-world water matrices on photocatalytic processes and highlights the importanceof comprehensive risk assessments for effective water treatment.