Visible-light photocatalytic degradation of Mordant Blue 9 by single-phase BiFeO3 nanoparticles

[Display omitted] •BiFeO3 powder was obtained by ultrasound assisted sol-gel route at low temperature.•BiFeO3 nanoparticles exhibited the highest photocatalytic activity in basic medium.•Mechanism of photocatalytic degradation of Mordant Blue 9 dye was proposed.•Photodegradation products were identified. This paper presents a systematic study on the photocatalytic activity of single-phase BiFeO3 (BFO) nanopowder, under the simulated solar irradiation in the presence of highly polluting textile dye (Mordant Blue 9). BFO nanopowder was synthesized by the means of the ultrasound-assisted sol-gel route. The structural and morphology analyses confirmed phase-pure crystalline BFO nanopowder with particle size of 70 nm. UV–vis spectroscopy measurements have revealed favorably high absorbance of the visible light with the calculated band-gap value of 2.21 eV. Photodegradation process as a function of different pH values of dye aqueous solution (pH = 1, 6.7 and 12) and irradiation time was investigated and the complete degradation mechanism was revealed. Related photodegradation products were detected by high-performance liquid chromatography equipped with mass spectrometer (HPLC/MS-MS). BFO nanoparticles exhibited higher photocatalytic activity in the basic medium than in neutral and acidic medium. HPLC/MS-MS analysis of the solutions at pH = 1 and pH = 6.7 showed only decolorization process, with no detectable degradation products, while at pH = 12 three different degradation products were observed, and their concentration slightly decreased with time. Reusability test showed that BFO nanoparticles can be used in four successive photodegradation cycles, with no significant activity losses.