One-Step Synthesis of Cationic Hydrogel for Efficient Dye Adsorption and Its Second Use for Emulsified Oil Separation

The removal of toxic dyes and insoluble oil from wastewater is a hot topic in both academic and industrial fields. Herein, we report a cationic absorbent poly(epichlorohydrin)–ethylenediamine hydrogel (PEE-Gel) via a simple one-step copolymerization and it can be successfully used for the removal of toxic dyes and insoluble oil from wastewater. The adsorption toward anionic dyes shows high efficiency and high selectivity at a wide pH range (from 2 to 12). The adsorption capacity at low equilibrium concentration (10 mg L–1) is as high as 1411.4 mg g–1 which is very close to the maximum adsorption capacity (1540.19 mg g–1). The adsorption of dye molecules onto PEE-Gel is very steady and can be difficult to be regenerated. The PEE-Gel with full dye adsorption (PEE-Gel-Dye) shows superoleophobicity under water, and PEE-Gel-Dye can be reused to separate toluene-in-water emulsion with high efficiency and durability. These results suggest that PEE-Gel is a promising and competitive candidate for water purification.