pH-Sensitive Nanocomposite Hydrogels Based on Poly(Vinyl Alcohol) Macromonomer and Graphene Oxide for Removal of Cationic Dyes from Aqueous Solutions

In this study, a pH-sensitive nanocomposite hydrogel based on poly(vinyl alcohol) (PVA)/graphene oxide (GO) was prepared and used as a potential adsorbent for the removal of crystal violet (CV) and methylene blue (MB) from aqueous solutions. The prepared nanocomposite hydrogels were fully characterized and their swelling capacity and gel content were investigated by changing the GO and acrylic acid (AA) content. Adsorption experiments were carried out as a function of contact time, concentration, temperature, pH and dosage. The adsorption process was favored at higher pHs, followed pseudo second-order kinetics while the adsorption equilibrium data well fitted to the Langmuir isotherm model with the maximum capacity of 173.2 and 169.6 mg g −1 for MB and CV, respectively. A thermodynamic study showed the spontaneity nature of the adsorption process for MB and CV. The removal percentage of MB dye increased with increase of temperature from 25 to 55 °C while the adsorption of CV dye showed the opposite trend. This different trend can be attributed to the differences in the pattern of adsorption. Graphic Abstract