Adsorption investigation of a composite of metal-organic framework and polyethylene oxide hydrogel

Abstract

Though adsorption techniques are eco-environmentally friendly, most lack the effectiveness of complete contaminant elimination leading to increasing concerns about the presence of aqueous contaminants on humans. Thus, synergistic combination of low adsorption capacity adsorbents may be an effective method to enhance their aqueous contaminant uptake. Sol-gel synthesized lanthanum-1,4-benzene dicarboxylate metal organic framework (LaBDC MOF) and polyethylene oxide (PEO) hydrogel were combined to prepare a synergistic composite adsorbent (PEO-LaBDC) for aqueous methylene blue (MB) adsorption. Major properties of the pristine LaBDC MOF and PEO hydrogel were expressed in the characterized composite indicating successful preparation. PEO-LaBDC composite MB removal rate of MB was at least twice as fast (60 min) to those of the pristine LaBDC MOF (120 min) and PEO hydrogel (125 min). The fitting of kinetics model was fractal in nature, and optimum adsorption was on the alkaline end of the pH spectrum for all adsorbents (pH = 12, 10, and 10, respectively). Comparatively, the composite exhibited a better adsorption performance of ≈177% higher than the pristine LaBDC MOF; buttressing the idea that synergistic combination of adsorbents in composites could enhance adsorption processes. Therefore, the PEO-LaBDC composite is a promising adsorbent for the remediation of aqueous MB.