A novel synthesis of porous TiO2 nanotubes and sequential application to dye contaminant removal and Cr(VI) visible light catalytic reduction

[Display omitted] •A novel synthesis route to porous TiO2 nanotubes (PTNTs) was developed.•The PTNTs exhibited excellent adsorption to Congo Red (CR, model dye).•The CR-PTNTs can be reutilized for visible light-induced reduction of Cr(VI).•This strategy is applicable to other non-coexisting scenarios of organics/Cr(VI). Porous TiO2 nanotubes (PTNTs) were successfully prepared by a versatile sepiolite-sacrificed template method. The PTNTs possess a unique porous structure and a high specific surface area (120 m2 g−1). It exhibits significantly enhanced adsorption performance for azo dye Congo Red (CR, model dye pollutant) with maximum adsorption capacity of 540 mg g−1, which is much better than common TiO2-based materials, as well as some other semiconductor adsorbents. The dye-impregnated PTNTs (CR-PTNTs) were re-utilized as a photocatalyst for the visible light-induced reduction of Cr(VI). The results show that the CR-PTNTs exhibit significantly superior photocatalytic reduction ability to Cr(VI), and such performance can be attributed to the huge adsorption of CR molecules on the PTNTs and the unique porous structure of PTNTs. Current work not only reports an effective adsorbent for dye CR removal, but also put forward a reutilization strategy of the spent adsorbent for efficient visible-light photocatalytic reduction of Cr(VI), applicable to the other non-coexisting dyes and Cr(VI) pollutant scenarios.