BiOBr nanoparticle-modified Ti₃C₂T_<i>x</i> MXenes for photocatalytic degradation of organic arsenic in wastewater

Arsenic (As) contamination in water remains a serious concern due to its high toxicity and harmful effects on human health and the environment. Herein, we successfully synthesized a novel photocatalyst (BiOBr/Ti₃C₂) by <i>in situ</i> inserting BiOBr nanoparticles into Ti₃C₂T _<i>x</i> MXenes for the photocatalytic degradation of organic arsenic roxarsone (3-nitro-4-hydroxyphenylarsonic acid) in wastewater. BiOBr/Ti₃C₂ exhibited a unique morphology characterized by uniform BiOBr nanoparticles within more dispersed Ti₃C₂T _<i>x</i> layers. Heterojunctions were formed between Ti₃C₂T _<i>x</i> and BiOBr, which were conducive to photogenerated charge separation and electron transfer in Ti₃C₂T _<i>x</i> layers. An optimal BiOBr/Ti₃C₂ photocatalyst achieved a removal efficiency of 1.27 mg g_cat. ^-1 h^-1 for 2 mg L^-1 of roxarsone wastewater within 0.5 h and a higher removal rate (about 1.5 times at 3 h) than pure Ti₃C₂T _<i>x</i> . In addition, BiOBr/Ti₃C₂ exhibited an apparent quantum yield (AQY) of 29.5% and good reusability for 4 cycles. The enhanced photocatalytic performance was mainly attributed to the intercalation of BiOBr nanoparticles within Ti₃C₂T _<i>x</i> layers, which increased reaction space and improved the separation and transport of photocarriers. Holes (h⁺) and ˙OH in the valence band (VB) of BiOBr/Ti₃C₂ were involved in the main route of roxarsone oxidative mineralization. The present BiOBr/Ti₃C₂ system provides fundamentals for the sustainable photocatalytic treatment of wastewater containing organic arsenic.