Cationic poly(diallyldimethylammonium chloride) based hydrogel for effective anionic dyes adsorption from aqueous solution

Treatment of wastewater which containing organic dyes has attracted great attention in the last decades since organic dyes were produced in an increasing quantity. Hydrogel adsorbent, as a promising candidate for organic dye removal from aqueous solution, has been studied by many researchers in recent years. However, it's still a challenge to create hydrogel adsorbent with high adsorption capacity and short contact time concurrently. Herein, we present a polyelectrolyte hydrogel adsorbent for anionic dyes removal which constructed by cationic monomer diallyldimethylammonium chloride (DADMAC) and acrylamide (AAm). Using calcium hydroxide nano-spherulites (CNS) as crosslinker, this physical hydrogel adsorbent showed a loosely crosslinked network structure. In optimal condition, the obtained P(AAm-DADMAC)/CNS hydrogel adsorbent showed a maximum adsorption capacity of 409 mg/g for methyl orange with a short contact time of 135 min. In addition, the adsorption process of this hydrogel adsorbent was well described by pseudo-first-order kinetic model and Langmuir adsorption isotherm model. Moreover, our P(AAm-DADMAC)/CNS hydrogel adsorbent also exhibited high adsorption capacities for other anionic dye, including Congo red (862 mg/g), Eriochrome black T (1139 mg/g) and methyl blue (722 mg/g). These results indicated that the P(AAm-DADMAC)/CNS hydrogel was a promising adsorbent material in wastewater treatment application.