Rhodamine derivative functionalized chitosan as efficient sensor and adsorbent for mercury(II) detection and removal

In this paper, a novel fluorescent adsorbent (CS-RC) was developed for mercury(II) (Hg 2+ ) detection and removal by grafting a rhodamine derived probe onto the surface of chitosan. The UV–vis spectra and Fourier transform-infrared spectroscopy confirmed the successful loading of rhodamine derived probe. Compared with traditional chitosan adsorbents, this type of adsorbent not only showed extraordinary adsorption and removal ability for mercury ions, but served as an excellent colorimetric and fluorescence turn-on “naked-eye” sensor. The sensing performance suggested that the resulting adsorbent showed exclusively distinguish Hg 2+ from various metal ions and the linear response of fluorescence emission intensity to the concentration of Hg 2+ was obtained over a wide range of 0–6.0   μM with a detection limit of 3.42   ×   10 −6   M. The adsorption and removal performance were also investigated and proved to be superior to pure chitosan. More importantly, this adsorbent still exhibited excellent adsorption performance after several regeneration cycles.