An Eco‐Friendly Polyvinyl Alcohol/Graphene Oxide‐Based Hydrogel as a Methylene Blue Adsorbent

Abstract Recently, hydrogels have been introduced for wastewater treatments as eco‐friendly and efficient adsorbents. Polyvinyl alcohol (PVA)‐based hydrogel reinforced with graphene oxide (GO) can be used for methylene blue (MB) removal from water. PVA/GO hydrogels (5 wt. % PVA and 0.5–2 wt. % GO) were prepared via the freeze‐thaw method, and the effect of GO weight percentage, freezing time, and cycle numbers were investigated. Regarding the results, the composite containing 1 wt. % GO, prepared by six‐hour freezing, and five cycles of freeze‐thawing, had the highest compressive strength (1.6±0.1 MPa) among the studied samples. Furthermore, by adding aloe vera to the PVA/GO composite containing 2 wt. % GO, the removal efficiency of MB was increased from 96 % to 99 % after 72 h, although the surface area was decreased from 31.6 m 2 g −1 to 3.9 m 2 g −1 . Adsorption investigations were also highlighted PVA/GO and PVA/GO/aloe vera hydrogel composites follow the pseudo‐second‐order kinetics and Langmuir isotherm models.