Facile synthesis of aluminum oxyhydroxide-PVA films and its adsorptive evaluation for the removal of methylene blue dye from water: kinetics, optimization studies and mechanism

Aluminum oxyhydroxide-polyvinyl alcohol films were synthesized by the sol–gel method with varying metal-polymer ratios. The results of the characterization confirmed the formation of aluminum oxyhydroxide and the incorporation of metal into the polymer. The adsorption isotherms of the film exhibited type IV isotherms indicating the mesoporous nature with a non-uniform pore size distribution. The optical profilometric studies confirmed the surface roughness of the film. The adsorptive nature of the film was tested for the removal of methylene blue dye from the aqueous solution. Optimization studies were conducted to investigate the effect of various parameters on the adsorption process. The adsorption isotherms of methylene blue fit with the Langmuir isotherm model and follow a pseudo-second-order equation. A suitable reaction mechanism was proposed, which confirms the adsorptive nature of the film is due to the electrostatic attraction. The synergetic effect of the metal-polymer blend, surface roughness and pore size of the film, which ranges from 0.01 to 0.025 nm, enhances the adsorption of methylene blue. The comparison of results obtained in the current study with earlier reports confirms that the aluminum oxyhydroxide-polyvinyl alcohol films can be considered an eco-friendly, cost-effective adsorbent for removing methylene blue.