Synthesis of hydrogels for adsorption of anionic and cationic dyes in water: ionic liquid as a crosslinking agent

Abstract In this work, we synthesized an ionic liquid (IL)—(Dimethylamino)ethyl Methacrylate maleate ([DMAEMA]MA) as the crosslinker, through one-pot to synthesized hydrogels with high adsorption capacity for dye in water. Both anionic dyes (methylene blue, rhodamine B) and cationic dyes (congo red, eosin B) could be adsorbed by this type of hydrogel with different adsorption mechanism, and its adsorption capacity for methylene blue (MB), rhodamine B (RHB), congo red (CR), eosin B (EB) were 489.1, 463.2, 465.5 and 462 mg/g (amount of dye adsorbed per gram of hydrogel), respectively. The surface structure of the hydrogel before and after adsorption was observed and compared by scanning electron microscope (SEM). After studying the adsorption isotherms of the hydrogel adsorbent, it was found that the hydrogel adsorbent had two adsorption mechanisms. This was not found in reported literatures previously.