Comparative study of TiO2 and graphene oxide enhancement of the removal of methylene blue dye using PVA/PEO hydrogels synthesized by gamma irradiation

Water pollution from industrial effluents, particularly textile dyes, represents a significant environmental challenge. In this study, polyvinyl alcohol (PVA)/polyethylene oxide (PEO)/poly(acrylic acid) (PAAc) hydrogels were synthesized via gamma irradiation (30 kGy) and modified with titanium dioxide (TiO₂) and graphene oxide (GO) nanoparticles to enhance methylene blue (MB) dye removal. Comprehensive characterization using FTIR, XRD, AFM, SEM, and TGA confirmed the successful incorporation of the nanofillers and their influence on the structural and physicochemical properties of the hydrogels. The addition of TiO₂ and GO significantly improved the gel fraction from 65% (neat hydrogel) to 99% and 98%, respectively. Swelling behavior showed a pH-dependent response, with maximum swelling observed at pH 10 after 24 h, following the order: PVA/PEO/PAAc < PVA/PEO/PAAc/TiO₂ < PVA/PEO/PAAc/GO. Batch adsorption experiments were conducted under controlled conditions (pH 10, adsorbent dosage 0.1 g, initial MB concentration 20 mg/L, and contact time 24 h). The removal efficiencies reached 64%, 98%, and ~ 100% for PVA/PEO/PAAc, PVA/PEO/PAAc/TiO₂, and PVA/PEO/PAAc/GO, respectively. Adsorption kinetics were better described by the pseudo-first-order model, indicating that physisorption plays a dominant role in the rate-controlling step. Isotherm analysis showed good agreement with the Langmuir model, suggesting predominantly monolayer adsorption on relatively homogeneous surfaces. Overall, both TiO₂- and GO-reinforced hydrogels exhibited enhanced adsorption performance compared to the neat hydrogel. The superior performance of GO-based hydrogels is attributed to their higher surface area and abundance of oxygen-containing functional groups, which facilitate dye–adsorbent interactions. These findings demonstrate the potential of radiation-synthesized nanocomposite hydrogels as efficient materials for dye removal, while further studies are required to evaluate their performance under realistic wastewater conditions.