Photocatalytic degradation of bisphenol A over a ZnFe2O4/TiO2 nanocomposite under visible light.

Abstract A ZnFe 2 O 4 -TiO 2 nanocomposite combining p-type ZnFe 2 O 4 and n-type TiO 2 was successfully fabricated. The ZnFe 2 O 4 -TiO 2 nanocomposite greatly enhanced the bisphenol A (BPA) photodegradation under visible light irradiation at 465 ± 40 nm. Loading TiO 2 with 1 wt% of ZnFe 2 O 4 produced high photocurrent and low charge transfer resistance. The photodegradation rate of BPA by ZnFe 2 O 4 -TiO 2 , which was highly dependent on the water chemistry including pH, anions, and humic acid, was 20.8–21.4 times higher than that of commercial TiO 2 photocatalysts. Chloride and sulfate ions enhanced BPA photodegradation mostly due to the production of more radical species; whereas nitrate, dihydrogen phosphate, and bicarbonate ions decreased the photodegradation rate of BPA due to the scavenge of hydroxyl radicals. The photoactivity and recyclability of ZnFe 2 O 4 -TiO 2 in lake water was also assessed. A near complete BPA removal from lake water was observed under visible light irradiation. Furthermore, >90% of photocatalytic activity toward BPA degradation was achieved in 5 cycles of continuous addition of BPA to the lake water. The BPA degradation intermediates were identified by HPLC/MS/MS and possible reaction pathways were proposed. Results clearly demonstrate the excellent visible-light-sensitive photocatalytic degradation of BPA over ZnFe 2 O 4 -TiO 2 composite which has a great application potential for the decomposition of emerging contaminants in impaired waters. Graphical abstract Unlabelled Image Highlights • TiO 2 doped with 1.0-wt% ZnFe 2 O 4 exhibited the highest visible-light BPA photodegradation. • The k obs of BPA photodegradation followed the order: pH 9.0 > pH 7.0 > pH 5.0 > pH 3.0 > pH 11.0. • Cl− and SO 4 2− enhance and humic acid inhibits BPA degradation over ZnFe 2 O 4 -TiO 2. • Near complete BPA removal (>90%) in lake water was observed under visible light irradiation • BPA degradation over ZnFe 2 O 4 -TiO 2 in lake water was high for at least five continuous cycles. [ABSTRACT FROM AUTHOR]