Preparation and application of BiOBr-Bi2S3 heterojunctions for efficient photocatalytic removal of Cr(VI)

Highlights: • BiOBr-Bi₂S₃ heterojunctions were prepared using an ion-exchange method. • B-2 exhibited the best photoreduction performance for Cr (VI). • Fast charge separation enhances the heterojunction photocatalytic performance. • BiOBr-Bi₂S₃ heterojunctions can be used as novel photocatalytic adsorbents. • The photocatalytic mechanism of Cr (VI) removal by heterojunctions was elucidated. Recently, the photocatalytic reduction of Cr(VI) has been extensively studied. Herein, we successfully prepared the BiOBr-Bi₂S₃ heterojunctions with high photocatalytic Cr(VI) reduction performance using an ion exchange method. The optimal BiOBr-Bi₂S₃ heterojunction (prepared with BiOBr, pH of 6.0, 2 mmol Na₂S₂O₃·5H₂O,) achieved 100% removal of Cr(VI) within 12 min. The performance of photo-reduced Cr(VI) was about 28.9 and 184.6 times higher than that of pure Bi₂S₃ and BiOBr, respectively. Besides, BiOBr-Bi₂S₃ heterojunctions had a good adsorption efficiency for Cr(III), suggesting that they could be applied as bifunctional photocatalyst. The formation process and photoelectric properties of the BiOBr-Bi₂S₃ heterojunctions were revealed by a series of characterizations. In conclusion, this work reported the synergistic effect of adsorption and photocatalysis of the BiOBr-Bi₂S₃ heterojunctions for Cr removal for the first time, suggesting that the BiOBr-Bi₂S₃ heterojunctions could act as a novel photocatalytic adsorbent to treat the Cr(VI)-containing wastewater.