Cyclodextrin functionalized 3D-graphene for the removal of Cr(VI) with the easy and rapid separation strategy.

As a useful heavy metal ion, chromium has seen its applications in various fields. While it is also a toxic contaminant in water and may cause serious threats to the environment and human health. To develop a novel material with good adsorption capacity and easy solid-liquid separation strategy was necessary and significant. In this paper, the β-cyclodextrin (β-CD) functionalized three-dimensional structured graphene foam (CDGF) was successfully synthesized with the facile and one-step hydrothermal method. The SEM, BET, XRD, FT-IR and XPS analysis were carried out and the results confirmed the successfully grafting of β-CD onto GF. The batch adsorption of Cr(VI) was also taken out and the CDGF possessed good selectivity compared with other metal ions at pH = 3. The adsorption capacity reduced gradually as the initial pH of the Cr(VI) solution grew higher, which was because the anionic species of Cr(VI) were partial to the positively charged surface of CDGF. The easy separation strategy of the CDGF was also demonstrated and the CDGF could be taken out easily with a tweezer after the adsorption of Cr(VI), which significantly simplified the separation procedure and reduced time. By comparing the FT-IR and XPD analysis results, the adsorption mechanism was explored and the hydroxyl groups on CDGF played the main role in the adsorption process. This work brings a novel material for the adsorption of Cr(VI) from water and provides an innovative direction for the easy and fast solid-liquid separation strategy in the adsorption and other application fields.