Simultaneous detection and removal of cobalt ions from aqueous solution by modified chitosan beads

Abstract In this paper, we modified chitosan beads in order to simultaneously detect and adsorb Co 2+ from aqueous solution. Firstly, 4-(5-chloro-2-pyridylazo)-1,3-phenylenediamine (5-Cl-PADAB) was used as selective probe for Co 2+ with color changing from yellow to pink, and the UV–Vis spectra showed that the λ max changed from 439 to 504 nm. Then a novel biomaterial was synthesized with 5-Cl-PADAB (metal indicator), chitosan (biosorbent) and EDTA anhydride (cross-linker and chelating agent). The analysis of Fourier transform infrared and energy-dispersive X-ray spectra proved that 5-Cl-PADAB and EDTA were successfully connected to chitosan. The modified chitosan bead was selective probe for Co 2+ with a remarkable color change from white to pink, and the UV–Vis spectra showed that the λ max changed from 441 to 459 nm. The adsorption of cobalt ions onto the modified chitosan beads followed pseudo-second-order ( R 2  = 0.99) kinetics and the Langmuir isotherm model ( R 2  = 0.80). Comparing with chitosan beads, the q e of the modified one increased from 2.00 to 7.97 mg/g. The modified chitosan beads are promising biomaterial for simultaneous detection and removal of Co 2+ from aqueous solution. Graphical Abstract