Anodic electrochemical regeneration of a graphene/titanium dioxide composite adsorbent loaded with an organic dye

A nanocomposite of graphene and titanium dioxide (G/TiO2) was prepared using the sol-gel method for use in an electrochemical adsorption/regeneration process. The effect of annealing temperature on electrochemical characteristics of the nanocomposites was investigated by cyclic voltammetry and constant current electrochemical regeneration, using methylene blue (MB) as the adsorbate. The G/TiO2 could be regenerated more rapidly and with less corrosion than the bare graphene. The G/TiO2 annealed at 400 degrees C had a higher proportion of anatase phase TiO2 (ca. 7% rutile TiO2) compared to that annealed at 500 degrees C (ca. 40% rutile TO2). Cyclic voltammetry indicated that the G/TiO2 annealed at 400 degrees C had a higher activity for MB oxidation than the nanocomposite annealed at 500 degrees C. Similarly, the regeneration of MB loaded G/TiO2 annealed at 400 degrees C was much faster than for the nanocomposite annealed at 500 degrees C. Complete regeneration of the G/TiO2 annealed at 400 degrees C was obtained after an electrochemical charge of 21 C per mg of adsorbate. The G/TiO2 annealed at 400 degrees C was regenerated in half the time required for the bare graphene. TEM studies showed that the bare graphene was rapidly corroded, while corrosion was not observed for the G/TiO2 nanocomposites. (C) 2019 Elsevier Ltd. All rights reserved.