Simultaneous Detection and Adsorptive Removal of Cr(VI) Ions by Fluorescent Sulfur Quantum Dots Embedded in Chitosan Hydrogels

Water pollution caused by hexavalent chromium [Cr(VI)] ions has attracted increasing attention because Cr(VI) ions are highly toxic and carcinogenic, which may cause serious harm to aquatic organisms and human health. More and more research has focused on the sensing or adsorption of Cr(VI) ions. However, so far, it is still a challenge to prepare advanced materials that can simultaneously detect and adsorb Cr(VI) ions. Herein, we present a facile and effective strategy to prepare a chitosan–sulfur quantum dots (CS-SQDs) composite hydrogel with both excellent sensing and uptake capability toward Cr(VI) ions. The CS-SQDs show excellent fluorescence stability against pH variation, high ionic strength, UV–light irradiation, and long-term storage. Moreover, the CS-SQDs exhibit sensitive and selective fluorescence responsiveness to Cr(VI) ions. The detection limit can reach 176.2 nM. Additionally, the CS-SQDs also show high uptake capability and favorable reusability for the adsorptive removal of Cr(VI) ions with a maximum adsorption capacity of 186.22 mg g–1. The adsorption behavior is spontaneous, and the adsorption process conforms to Langmuir isotherm and pseudo-second-order kinetic models. This work provides an effective strategy for the preparation of multifunctional hydrogels with the potential to simultaneously monitor and remove water contaminants.