First insight on the effective removal of pentoxifylline drug under visible-light-driven irradiation with ZnO catalyst obtained via precipitation.

This work demonstrates for the first time that a ZnO catalyst, prepared by precipitation and calcined at 450 °C (ZnO_450), can effectively degrade the drug pentoxifylline (PTX) under visible-light irradiation. Under all evaluated conditions, the kinetics of photocatalytic degradation followed a pseudo-first-order model. The catalyst performance was found to be optimal at a dosage of 0.8 g/L, a drug concentration of 1 mg/L, and under alkaline conditions (pH 11), achieving a pollutant elimination efficiency of 94 % after 150 min of reaction time. The key reactive species involved in PTX degradation were identified as HO·, [Formula: see text] and e-, as confirmed by scavenger tests using isopropyl alcohol, benzoquinone, potassium persulfate and ammonium oxalate. It was observed that the pollutant photodegradation remained efficient in the presence of inorganic ions (chloride, nitrate, and bicarbonate), in real water samples, and that the catalyst maintained its stability across five consecutive catalytic cycles, confirming its chemical stability and photocatalytic reliability. Density functional theory calculations were further used to understand the initial steps in the degradation process of PTX concerning its ability to be adsorbed on electron-rich (conduction band) and hole sites (valence band). Finally, phytotoxicity tests confirmed a consistent decrease in toxicity in photocatalytically treated solutions, highlighting that the ZnO_450/vis setup is a promising option for the removal of emerging water contaminants.