Growth of BiOBrxI1-x solid-solutions with tunable band-gaps on carbon fiber cloth as flexible membrane-shaped photocatalyst for purifying antibiotic wastewater

Abstract

Integrated membranes with filtration and photocatalytic functions have been considered as an effective strategy for purifying flowing wastewater, but the design and preparation of high-efficiency and low-cost membranes is still of great urgency. Herein, we report efficient recyclable BiOBrxI1-x fibrous filter membranous photocatalyst prepared through the in-situ growth of BiOBrxI1-x solid-solutions with tunable band-gaps on carbon fiber cloth (CFC). The fabrication was performed via a facile dipping-solvothermal synthesis of BiOBrxI1-x solid-solutions nanoplates on CFC with different I/Br ratios in the precursor solution. With the increase of I/Br ratio from 0 to 4, CFC/BiOBrxI1-x solid-solutions exhibit a re-shifted in the photoabsorption edge from 420 to 620 nm, leading to the tuning of the band-gap from 2.49 to 1.81 eV. Under visible light illumination for 120 min, CFC/BiOBrxI1-x solid-solutions have the tuned photocatalytic activity, where CFC/BiOBr0.8I0.2 shows the highest degradation efficiency toward various antibiotics (such as levofloxacin (LVFX, 94.1%), ciprofloxacin (CIP, 94.5%), and tetracycline (TC, 98.9%)) as well as dyes (such as acid orange 7 (AO7, 91.4%). Especially, when CFC/BiOBr0.8I0.2 is used as a flexible membrane to a construct multi-grade unit for treating the flowing sewage, the degradation efficiency of LVFX goes up from 3.9% in the first grade to 96.2% in the tenth grade. Therefore, the present CFC/BiOBr0.8I0.2 not only possesses great potential as a flexible membrane-shaped photocatalyst for purifying the flowing sewage efficiently but also provides some insights for developing new types of purifying membranes and devices.