Efficiently ion-enhanced adsorption of anion dyes by acrolein crosslinked polyethylenimine/chitosan hydrogel with excellent recycling stability

A novel adsorbent acrolein crosslinked polyethylenimine/chitosan hydrogel (A-PEI/CS) was developed with excellent recycling stability and ion-enhanced effect on removing anionic dye (acid blue 93, AB93) from aquatic environment. For AB93, A-PEI/CS was such an adsorbent with the characteristics of high adsorption capacity up to 1212.4 mg/g and continuous recyle ability of more than 15 times. After 15 desorption-regeneration cycles, the removal rate of A-PEI/CS for AB93 could still be as high as 96 % with imperceptibly downward trend. In addition, the addition of salts (KCl, NaCl and CaCl₂) could promote the adsorption of A-PEI/CS, and the removal rate would be enhanced with increasing concentration of the salt. The effects of pH (2-7), contact time (30-600 min), temperature (30-50 °C) on the adsorption performance of A-PEI/CS were systematically examined. Furthermore, the physicochemical properties of the adsorbent were analyzed by FT-IR, XPS and zeta potential. The adsorption mechanism can be explained by electrostatic interaction, hydrogen bond interaction, chemical interaction. Intriguing to note that, the adsorption energy of adsorbents was investigated by molecular simulation, and the low pH and common salt environment can promote the adsorption effect, indicating that the prepared adsorbent has excellent application value in the treatment of practical high-salinity wastewater.