Nanoclay sandwiched reduced graphene oxide filled macroporous polyacrylamide-agar hybrid hydrogel as an adsorbent for dye decontamination

Abstract

Herein, a simple three-step synthesis protocol was adopted to prepare reduced graphene oxide modified nanoclay decorating macroporous polyacrylamide-agar nanocomposite (PAAm-Agar/Clay@r-GO) hydrogel with an objective to treat wastewater. Double network structure of PAAm-Agar hybrid hydrogel was formulated through the in situ polymerization approach, followed by cooling at 4 °C, whereas; Clay/GO to Clay/r-GO transformation in hydrogel network was achieved via in situ reduction which also helps to promote macroporosity in hydrogel. As-synthesized Clay@GO and PAAm-Agar/Clay@r-GO hydrogel were characterized with XRD, FTIR, SEM, TEM and BET/mercury-porosimetry along with investigating swelling, rheological and thermal behaviors. Present study, demonstrated the high dye-adsorption capacity (qexp∼182 mg/g@MB, qexp∼179 mg/g@RhB and qexp∼110.3 mg/g@MO at pH∼7.0) of macroporous PAAm-Agar/Clay@r-GO nanocomposite hydrogel with a faster equilibrium time (∼5 h@MB/RhB and ∼12 h@MO). In basic environment (pH∼10), adsorption capacity is improved to ∼189 mg/g and ∼186.4 mg/g for MB and RhB, respectively. The adsorption behavior of PAAm-Agar/Clay@r-GO nanocomposite hydrogel followed the pseudo 2nd order kinetics along with the Langmuir adsorption pattern.