Nanocomposite hydrogel adsorbents for removal of methylene blue from aqueous solutions: Optimization using the Taguchi experimental design

In this study, nanocomposite hydrogel adsorbents were prepared on the basis of polyvinyl alcohol (PVA) containing 0, 4, 8 and 12 wt% (based on the dried mass) of montmorillentenano clay (MMT) using a cyclic freezing-thawing method for the removal of the methylene blue (MB) as an industrial dye from water and aqueous solutions. The adsorption process was optimized by investigating the effects of four main factors, including the process temperature and pH, MMT loading level in nanocomposite hydrogel adsorbents and the MB concentration in the solution using the Taguchi method and the Design Expert software. The results showed that the nanocomposite hydrogel adsorbent containing 12 wt% of MMT at the processing temperature of 50 °C, solution pH of 9, and the MB concentration of 5 mol/L had the best MB adsorption performance. The results indicated that the MB removal efficiency was increased by increasing the process temperature and the MMT loading level in nanocomposite hydrogel adsorbents and also by decreasing the MB concentration in solution. The results also showed that the pH has no significant effect on the dye removal process. It was finally concluded that the prepared nanocomposite hydrogel adsorbents could be recognized as excellent candidates to be used as effective adsorbents in practical applications for wastewater treatment.