Supported carbon dots decorated with metallothionein for selective cadmium adsorption and removal

Carbon dots are prepared and immobilized onto spherical SiO₂ through a one-step thermal oxidation and then decorated with metallothionein (MT), a protein with high affinity towards thiophilic metals. The MT-carbon dots composites are characterized by means of FT-IR, SEM and TGA, giving rise to a MT loading amount of 823 μg g^-1. The adsorption of cadmium by the composites is a fast process and follows Langmuir model. In comparison with native SiO₂, a 2- and 2.4-folds improvement on the static and dynamic adsorption capacity of the composites for cadmium are obtained, respectively. Moreover, the adsorption efficiency is not affected by the presence of other metals. Finally, the composites are successfully applied for the removal of cadmium in a series of environmental water samples.