Enhanced and Efficient Extraction of Uranyl Ions from Aqueous Waste Using Graphene/CNT-PAMAM Nanocomposites

The increasing threat of uranium contamination to the environment and human health due to its radiotoxicity demands the development of efficient adsorbents for remediation. In this study, we investigated the potential of poly(amidoamine) (PAMAM) dendrimers of generations 1-4 (G1-G4) functionalized with graphene and carbon nanotubes (CNTs) as adsorbents for uranyl ion removal from aqueous solutions. By combining atomistic molecular dynamics (MD) simulations with experimental validation, we examined the influence of pH, uranyl ion concentration, and dendrimer generation on the adsorption behavior. Our study revealed that uranyl ion adsorption was greater when PAMAM was grafted onto graphene/CNT than when PAMAM was grafted onto pristine PAMAM. However, PAMAM-grafted CNTs exhibited superior adsorption capacity at specific uranyl concentrations due to their curvature and abundant accessible binding sites. Higher-generation PAMAM dendrimers grafted onto graphene/CNTs exhibited a greater adsorption capacity due to the increased availability of binding sites, which is consistent with experimental observations. The adsorption capability for uranyl ions in all four generations of the PAMAM dendrimer increased as the concentration of uranyl ions increased. The adsorption capacity increased with increasing uranyl ion concentration, and adsorption occurred on both PAMAM and graphene/CNT surfaces, with saturation observed at higher concentrations. This study provided insights into the adsorption mechanisms and highlighted the potential of PAMAM-based nanocomposites for efficient uranyl ion extraction and environmental remediation.