B–Sn/TiO2 nanoparticles for photodegradation of metronidazole antibiotics under different lights

A novel B and Sn co-doped TiO2 (B–Sn/TiO2) nanoparticle photocatalyst with different compositions was synthesized using the sol-gel method. The weight ratios of B and Sn in TiO2 were 1:9, 6:6, and 2:3, respectively. The resultant nanoparticles have completed a detailed characterization examination using XRD, FTIR, FESEM-EDS, TEM, UV–vis DRS, PL, BET, Zeta potential, and XPS. The photocatalytic activity of B–Sn/TiO2 nanoparticles was investigated for the degradation of aqueous metronidazole (MNZ) solution with UV-C and natural sunlight irradiation. Among the different compositions of the nanoparticles, B–Sn/TiO2 (1:9) exhibited better photocatalytic activity because of its high charge separation ability, confirmed by significant PL quenching. Under ideal conditions (MNZ concentration of 10 mg/L, pH 9, catalyst dosage of 20 mg), a maximum MNZ removal efficiency of ∼96% was obtained in UV-C irradiation within 120 min. However, under the same experimental conditions in natural sunlight, the removal efficiency of MNZ was ∼94% in just 60 min. The mineralization of MNZ up to ∼53% in 3 h under sunlight was studied from the decrease in TOC values. The scavenger test was used to estimate a plausible photocatalytic degradation mechanism of MNZ, and it was observed that the •O2− radical was potentially active in the degradation of MNZ. Cyclic experiments showed that B–Sn/TiO2 (1:9) was reusable for up to four cycles, confirming that it can be used as a cost-effective and environmentally friendly photocatalyst.