Dendritic Chelating Agents. 2. U(VI) Binding to Poly(amidoamine) and Poly(propyleneimine) Dendrimers in Aqueous Solutions

Abstract

Chelating agents are widely employed in many separation processes used to recover uranyl [U(VI)] from contaminated aqueous solutions. This article describes an experimental investigation of the binding of U(VI) to poly(amidoamine) [PAMAM] and poly(propyleneimine) [PPI] dendrimers in aqueous solutions. We combine fluorescence spectroscopy with bench scale ultrafiltration experiments to measure the extent of binding and fractional binding of U(VI) in aqueous solutions of these dendrimers as a function of (i) metal-ion dendrimer loading, (ii) dendrimer generation, (iii) dendrimer core and terminal group chemistry, and (iv) solution pH and competing ligands (NO 3 -, PO 4 3-, CO 3 2-, and Cl -). The overall results of this study suggest that uranyl binding to PAMAM and PPI dendrimers in aqueous solutions involves the coordination of the UO 2 2+ ions with the dendrimer amine, amide, and carboxylic groups. We find significant binding of U(VI) to PAMAM dendrimers in (i) acidic solutions containing up to 1.0 M HNO 3 and H 3 PO 4 and (ii) in basic solutions containing up to 0.5 M Na 2 CO 3 . However, no binding of U(VI) by PAMAM dendrimers is observed in aqueous solutions containing 1.0 M NaCl at pH 3.0. These results strongly suggest that PAMAM and PPI dendrimers can serve as high capacity and selective chelating ligands for U(VI) in aqueous solutions.

Multiscale Modeling for Host-Guest Chemistry of Dendrimers in Solution

“…Dendrimers have received increasing attention over the past several decades as attractive candidate materials for a variety of applications such as therapeutic delivery systems [1][2][3][4][5], imaging agents [4,6,7], templates for catalytic metal nanoparticles [8][9][10], and extraction agents for the removal of organic pollutants and toxic metals from water and soil [11][12][13][14]. The breadth across applications is attributed to dendrimers being well-defined, monodisperse nanostructures with tunable critical nanoscale design parameters [15,16], such as size, shape, rigidity, surface functionality, and solvent affinity.…”

“…The breadth across applications is attributed to dendrimers being well-defined, monodisperse nanostructures with tunable critical nanoscale design parameters [15,16], such as size, shape, rigidity, surface functionality, and solvent affinity. For this reason, dendrimers have been studied as hosts for a number of guest species: drugs [1][2][3][4], gene [17][18][19], contrast agents [7,20,21], metal ions [9][10][11][12][13][14], polymers [22], and organic pollutants [23,24]. Astruc and coworkers have written an exceptionally comprehensive review on dendrimers functioning as hosts [25].…”

Dense-shell glycodendrimers: UV/Vis and electron paramagnetic resonance study of metal ion complexation

“…In other words, 2 is suited to complex different heavy and noble metal ions, as well as the lanthanide Eu(III) and the actinide UO 2 (VI) by the dendritic scaffold in the aqueous phase. In this context, the terms 'to complex' and 'complex' will be used generally to mean, for example, that metal ions can form strong complexes with the dendritic tertiary amino scaffold (Zhao & Crooks 1999;Diallo et al 2008) or that physical encapsulation has occurred (Diallo et al 2004).…”

Characterization of an engineered cellulose based membrane by thiol dendrimer for heavy metals removal

“…A commercial poly(amidoamine) dendrimer (PAMAM) has been used in separation systems for recovery heavy metals from aqueous solution by means of chelating agents in pollution remediation processes. Particularly, aqueous heavy metal solutions treated with PAMAM previous to pass them through a membrane (ultrafiltration technique) has been proposed for water and soil remediation [23][24][25][26][27]. Other researchers have obtained functionalized membranes with PAMAM, hydroxyl PAMAM and carboxyl PAMAM for CO 2 /N 2 separation and as models for adsorption of dye molecules [28][29][30][31].…”