High-Strength Chitin Based Hydrogels Reinforced by Tannic Acid Functionalized Graphene for Congo Red Adsorption

Abstract

In this study, a novel chitin based composite hydrogel reinforced by tannic acid modified reduced graphene oxide (TRGO) was prepared via a facile freezing–thawing approach. Epichlorohydrin (ECH) and TRGO sheets were employed as efficient crosslinkers to fabricate dually crosslinked TRGO/chitin composite hydrogels with advanced mechanical and adsorption properties. Results indicated that the TRGO reinforced chitin composites increased the mechanical property remarkably with exhibiting compression strength from 22.7 kPa for neat chitin hydrogel to 72.3 kPa for the hydrogel with loading of 7% TRGO. Multiple interactions such as hydrogen bonding between TRGO and chitin as well as the dually covalent crosslinking bonds were responsible for the extensive improvement in compression strength. Furthermore, the TRGO reinforced hydrogels exhibited an excellent adsorption capacity towards Congo red (CR). The maximum adsorption capacity of CR was 230.5 mg g−1 for chitin hydrogel with loading of 7% TRGO. The adsorption of CR was found following the Langmuir isotherm and pseudo-second-order models. Hence, the prepared TRGO/chitin hydrogels provide an easy and efficient way for the removal of CR dye from wastewater.