Efficient toxicity elimination of aqueous Cr(VI) by positively-charged BiOClxI1-x, BiOBrxI1-x and BiOClxBr1-x solid solution with internal hole-scavenging capacity via the synergy of adsorption and photocatalytic reduction

The ecological toxicity of photocatalysts and toxicity reduction of Cr(VI) have attracted much attention. The development of environmentally-friendly photocatalysts with adsorption and internal hole-scavenging capacity for toxicity reduction of aqueous Cr(VI) via facile preparation method is desirable. In this study, visible-light-active BiOClxBr1-x, BiOClxI1-x and BiOBrxI1-x solid solutions were prepared by simple solvothermal strategy. The BiOCl0.3Br0.7, BiOCl0.7I0.3 and BiOBr0.7I0.3 solid solutions exhibited excellent adsorption capacity and photoreduction ability. The removal efficiency of Cr(VI) by BiOCl0.3Br0.7 was 97.7% within 60 min. BiOCl0.7I0.3 and BiOBr0.7I0.3 can remove Cr(VI) almost completely within less than 30 min, which were much higher than those by BiOCl (81.6%) and BiOBr (67.4%) due to joint effect of adsorption and photoreduction. More importantly, the toxicity evaluation confirmed nontoxicity of BiOClxBr1-x, BiOClxI1-x and BiOBrxI1-x, and rapid toxicity elimination process of Cr(VI).