Di-cationic epoxy resin one-step crosslinked chitosan/cellulose hydrogel for efficient dye and oily wastewater remediation

Introducing functional groups plays a critical role in improving the adsorption capacity of bio-polymer hydrogel absorbents. In this work, a novel di-cationic epoxy resin (N,N'-diglycidyl-N,N,N',N'-tetramethyl-1,3-propane diammonium dichloride, DCER) cross-linker is successfully synthesized. Chitosan/cellulose (CH/CU) hydrogels are obtained by simply one-step crosslinking by DCER. FT-IR and XPS spectra reveal that a large number of quaternary ammonium groups are introduced into CH/CU hydrogel. SEM image shows that the freeze-dried CH/ CU hydrogel has interconnected microporous structure. The ECER crosslinked hydrogel shows extremely high adsorption efficiency for Congo red (CR) and the saturated adsorption capacity is 1404.5 mg/g, which is higher than most bio-polymer hydrogels. Isotherm and kinetic studies indicate that the adsorption of CR on DCER CH/ CU hydrogel fits Langmuir isotherm and pseudo-second-order kinetic better. Unlike most reported biopolymer hydrogel adsorbents only exhibit good adsorption performance under a certain pH, DCER CH/CU hydrogel has high adsorption capacity in a wide pH range of 3-11. In addition, DCER CH/CU hydrogel can be used as a gel coating for superhydrophilic modification of polyester textile. The hydrogel coated fabric shows good oil resistance and can separate different types of oil/water mixtures with high efficiency and good durability. Hence, this multifunctional DCER CH/CU hydrogel has great potential for water remediation.

Automated summary

In this study, a novel di-cationic epoxy resin cross-linker was successfully synthesized to obtain chitosan/cellulose hydrogels. The hydrogels exhibited a microporous structure with a large number of quaternary ammonium groups, and showed high adsorption efficiency for Congo red in a wide pH range. Additionally, the hydrogel-coated fabric demonstrated good oil resistance and efficient separation of oil/water mixtures.