Adsorption behaviors and mechanisms of polyvinyl alcohol/xanthan gum/graphene oxide porous hydrogel for methylene blue and congo red

In response to significant water pollution stemming from dyes, it is crucial to develop affordable adsorbents capable of effectively removing leftover contaminants from wastewater. A novel hydrogel, made from polyvinyl alcohol (PVA) and xanthan gum (XG), exhibiting notable swelling characteristics and adsorption abilities toward methylene blue (MB) and congo red (CR), was produced using freeze-thaw cycling and freeze-drying techniques. The stability against turbulence of the porous composite hydrogel improved from 65.73 % to 84.8 % with the incorporation of graphene oxide (GO) into the PVA/XG-based framework. We discussed and analyzed the impact of the adsorbent dosage, initial dye concentration, aqueous solution temperature, pH value, and contact time on the adsorption capacity of the prepared hydrogel. The maximum adsorption capabilities, derived from the Langmuir isotherm, were measured as 289.31 mg/g for MB and 255.06 mg/g for CR. The thermodynamic analysis indicated the spontaneous nature of the dye adsorption process conducted in this study. In conclusion, the results indicated that the synthesized hydrogel may act as a potent adsorbent for the removal of dyes from water-based solutions.