Impact of reaction parameters for photodegradation pharmaceuticals in wastewater over gold/titania photocatalyst synthesized by pyrolysis of NH2-MIL-125(Ti)

The efficient remediation of pharmaceuticals, including wastewater, remains a remarkably challenging issue for water regeneration. Herein, porous Au/TiO2 synthesized by pyrolysis of NH2-MIL-125(Ti) was utilized to be an efficient photocatalyst for mineralization of trimethoprim (TMP) and Metronidazole (MNZ) as the parent compound. The effects of different factors, including TMP and MNZ concentrations, light intensity, H2O2 concentration, Au/TiO2 dosage, and pH value of reaction solution on the degradation and mineralization performances during UV and visible light (VIS), were addressed. The porous Au/TiO2 photocatalyst exhibited superior photocatalytic degradation of TMP and MNZ under UV and VIS illumination. The optimum pH values were 4; the optimum dosage of Au/TiO2 was 1.5 g/L, H2O2 concentration was 9.8 mM, TMP and MNZ concentrations was 10 ppm, and their photodegradation efficiency was 100% after 30 min illumination time and mineralization efficiency 98.2% after 3 h illumination for TMP and MNZ, respectively under UV illumination, however, the photodegradation efficiency was 100% after 50 min illumination and mineralization efficiency 96.3% after 4.5 h illumination time for TMP and MNZ, respectively under VIS illumination. The real wastewater matrix with 10 mg/L of TMP and MNZ were subjected to 60 min of illumination under similar optimum conditions of synthetic solution. The results indicated that photodegradation efficiency was determined to be 100% after 70 min illumination time for removal of both TMP (k = 3.4 × 10-2 min-1) and MNZ (k = 2.87 × 10-2 min-1). This is ascribed to the incorporation of Au NPs onto TiO2, reducing the photoinduced electron-hole recombination, thus promoting the photocatalytic performance. The possible mechanism for photodegradation of antibiotics was also discussed. The demonstration of photocatalysis mechanism over Au/TiO2 photocatalyst can provide some directing in the enhancement of novel photocatalysts based on MOFs doped by noble metal.