Ring-like structured chitosan-metal hydrogel: Mass production, formation mechanism and applications.

To improve the solid/liquid separation of chitosan adsorbents as well as the adsorption ability, chitosan was molded in several shapes. However, the ring-like structures of chitosan which have relatively larger surface area and higher chemical accessibility, but low-pressure drops than their plate-like counterparts has not been reported. In this study, we put forward a novel concept to fabricate a kind of highly efficient ring-like structured chitosan hydrogel through a sulfate ionic crosslinking method, its mass production and formation mechanism has been fully proposed. The ring-like chitosan-Fe(III) hydrogel exhibits the outstanding performance with AR73 removal rate of 98.53% and Cr(VI) removal rate of 90.53%, respectively. The adsorption of AR73 is well described by the pseudo-second-order model and Langmuir isotherm model, which indicates chitosan-Fe(III) hydrogel ring possesses a considerable adsorption capacity of 205.2mg/g. In addition, chitosan-Fe(III) hydrogel ring could efficiently adsorb both AR73 and Cr(VI) simultaneously (96.9% and 85.9%, respectively). Overall, this work provides a facile method to prepare ring-like structured chitosan-metal hydrogel, which can be mass-produced as multifunctional materials for practical application.