Synthesis, characterization, and performance evaluation of ion-imprinted crosslinked chitosan (with sodium tripolyphosphate) for cadmium biosorption

This study examined the removal of cadmium from aqueous solution using novel Cd(II)-imprinted chitosan hydrogel beads crosslinked by sodium tripolyphosphate. The synthesis of ion-imprinted and non-imprinted crosslinked chitosan beads was confirmed using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis (TGA). Brunauer-Emmett-Teller (BET) analysis showed an increase in surface area after the ion imprinting process. Batch adsorption tests were performed to determine the adsorption process parameters such as initial pH (7.0), adsorbent dosage (0.65 g/L), and contact time (48 h). Isotherm investigation showed that the Langmuir model could well describe Cd(II) adsorption, and the maximum adsorption capacity of the ion-imprinted chitosan was 21 +/- 5% higher than that of the nonimprinted one. The computed thermodynamic parameters at three different temperatures (25, 40, 55 degrees C) showed the spontaneity and endothermic nature of Cd(II) adsorption on the synthesized bio-sorbents. The kinetics data were best fitted by the pseudo-second-order equation with a coefficient of determination of 0.99. Additionally, desorption tests employing a solution of NaCl and H2SO4 were undertaken, yielding acceptable results.