Fluorescent chitosan-based hydrogel incorporating titanate and cellulose nanofibers modified with carbon dots for adsorption and detection of Cr(VI)

To deal with heavy metal pollution, a novel fluorescent chitosan-based hydrogel incorporating titanate and cellulose nanofibers modified with carbon dots was prepared to effectively detect and remove Cr(VI). The composition and structure of this chitosan-based hydrogel were analyzed. The performance of the fluorescent chitosan-based hydrogel in Cr(VI) adsorption was evaluated through a contrast experiment with the normal chitosan hydrogel without carbon dots. The results showed that the fluorescent chitosan-based hydrogel had a higher adsorption ability of Cr(VI) (maximum adsorption capacity, 228.2 mg g−1). The effect of the initial concentration of Cr(VI) and the contact time were also evaluated. The results confirmed that the adsorption isotherm was according to the Langmuir model, and the adsorption kinetics followed the pseudo-second-order model. Furthermore, as a fluorescent sensor for Cr(VI), the detection sensitivity and selectivity were examined. The quantitative detection of Cr(VI) was achieved in the linear range of 10–80 mg L−1. Furthermore, for this fluorescent chitosan-based hydrogel, the mechanism for highly efficient adsorption and detection of Cr(VI) was analyzed via FTIR and XPS. These results showed that the excellent sorption and sensing abilities of Cr(VI) may be mainly attributed to the porous structures and the additional titanate and cellulose nanofibers modified with carbon dots improving sorption ability of Cr(VI) and providing a rapid visual response to Cr(VI).