Egg White/Polyvinyl Alcohol/Clay Bionanocomposite Hydrogel Adsorbents for Dye Removal

Abstract

In the current study, bionanocomposite hydrogels based on egg white and polyvinyl alcohol loaded with 0, 4 and 8 wt% of montmorillonite clay were prepared and utilized as effective adsorbents for removing the methylene blue from aqueous solutions. The structural characteristics of the prepared adsorbents were studied and the gel content, the influence of the pH of the medium on swelling kinetics and the methylene blue diffusion coefficient in the adsorbents were investigated. It was found that the swelling ratio and diffusion coefficient of bionanocomposite hydrogel adsorbents increased either with increasing the pH of the medium or decreasing the loading level of montmorillonite and gel contact had a direct dependency on the montmorillonite content. Taguchi method was utilized to determine the effects of main factors on the batch adsorption process, including the montmorillonite loading level in adsorbent, pH of the solution and dye initial concentration in adsorption solution. The optimum adsorption conditions by the Taguchi method were determined as montmorillonite loading level of 8 wt%, pH of 9 and methylene blue initial concentration of 5 mg/L. The experimental adsorption results were fitted to the various isotherms and kinetic models. It was shown that intra-particle diffusion was the best model for elucidating adsorbents' behavior in methylene blue removal. It was finally deduced that the prepared bionanocomposite hydrogel adsorbents could be recognized as effective eco-friendly adsorbents for removing the cationic dyes from wastewaters.