A magnetically recyclable polyampholyte hydrogel adsorbent functionalized with β-cyclodextrin and graphene oxide for cationic/anionic dyes and heavy metal ion wastewater remediation

Abstract

• A novel dual-purpose polyampholyte hydrogel adsorbent was synthesized. • Hydrogel showed good stability, mechanical, and magnetically recyclable property. • The q m for MB, MG, CR, and Cu 2+ were respectively 3185, 3315, 1058 and 140 mg/g. • Hydrogel column could efficient removal of contaminants from model wastewater. Manufacturing multifunctional, stable, and recyclable adsorbents for treating contaminants with charge diversity from wastewater remains challenging. Herein, a β-cyclodextrin/magnetic graphene oxide/triethylenetetramine functionalized magnetically polyampholyte hydrogel adsorbent P(AA-MMA)/MGO/CA-CD/NH 2 with high-density carboxyl and amino groups was prepared via simple one-pot polymerization and ammonolysis. The morphology structure, physicochemical, mechanical, and magnetic characteristics of as-resulting hydrogel adsorbent have been comprehensively investigated through various characterization methods. Its adsorption behaviors towards cationic/anionic dyes (Methylene blue (MB), Malachite green (MG)/Congo red (CR)) and heavy metal ion (Cu 2+ ) were further systematically investigated through batch adsorption and column filtration experiments. The pseudo-second-order kinetic and Langmuir isotherm models were revealed to well describe the adsorption behaviors of hydrogel for dyes and heavy metal ion. Besides, by altering the solution pH could be endowing hydrogel with selective and simultaneous adsorption properties towards cationic and anionic dyes. Meanwhile, as-designed adsorbent has synergistic adsorption performance towards anionic dye and cationic heavy metal ion. The adsorption mechanism of hydrogel towards contaminants was studied by FTIR, Raman, and XPS analyses. Additionally, the as-prepared adsorbent displayed no significant adsorption capacity loss even after eight adsorption–desorption cycles, manifesting that it is of superb recyclability and stability. Finally, it was demonstrated that the adsorption column packed with hydrogel could quickly purify contaminants in the model textile wastewater through filtration.