Eco-friendly polyvinyl alcohol/carboxymethyl cellulose hydrogels reinforced with graphene oxide and bentonite for enhanced adsorption of methylene blue
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Abstract
Eco-friendly polyvinyl alcohol/carboxymethyl cellulose (isolated from pineapple peel)
hydrogels reinforced with graphene oxide and bentonite were prepared as efficient
adsorbents for methylene blue (MB). The structure and morphology of the prepared hydrogels
were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron
microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential
scanning calorimetry (DSC). Introducing graphene oxide and bentonite into the hydrogels
evidently enhanced the thermal stability, swelling ability and MB adsorption capacity.
The effects of initial concentration of MB, pH, contact time and temperature on MB
adsorption capacity of the prepared hydrogels were investigated. Adsorption kinetics
and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Langmuir
isotherm model well, respectively. After introducing graphene oxide and bentonite
into the hydrogels, the maximum adsorption capacity calculated from the Langmuir isotherm
model reached 172.14 mg/g at 30 °C, obviously higher than the hydrogels prepared without
these additions (83.33 mg/g). Furthermore, all the prepared hydrogels also displayed
good reusability for the efficient removal of MB. Consequently, the prepared hydrogels
could be served as eco-friendly, stable, efficient and reusable adsorbents for anionic
dyes in wastewater treatment.