Contribution of boron-specific resins containing N-methylglucamine groups to immobilization of borate/boric acid in a permeable reactive barrier comprising agglomerated MgO

Nanoscale Surface Compositions and Structures Influence Boron Adsorption Properties of Anion Exchange Resins

“…In particular, for the borate anions adsorbed on the NMDG-functionalized resin, the relatively narrow 11 B signal intensities (full-width-at-half-maximum of 200 Hz) and displacements of 11 B signals to lower frequencies (0–20 ppm) suggest the presence of tetrahedrally coordinated borate anions in chelate complexes . Based on the 11 B signal assignments of tetrahedrally coordinated borate anions in chelate complexes in the literature, ,, the 11 B intensities at 8.2 and 13.1 ppm in Figure a are assigned to borate anions in mono- and bischelate complexes, respectively.…”

“…The molecular-level origins that account for selective boron adsorption as bischelate complexes have been challenging to establish. It has been hypothesized that the borate anions electrostatically interact with the residual metal cations present on the NMDG-functionalized resin surface . For the NMDG-functionalized PSDVB-resin, ICP atomic emission spectroscopy analyses showed that trace amounts of metal cations were present, although their absolute and relative quantities were small (Supporting Information, Table S1).…”

“…In particular, many commercial boron-adsorption ion-exchange resins are based on polymers grafted with NMDG functional groups. ,,, For such materials, the hydroxyl groups of the NMDG moieties exhibit high binding affinity toward borate anions. , This imparts the NMDG-functionalized polymers with high boron adsorption capacities and correspondingly favorable separation efficacies, compared to other approaches such as reverse osmosis, , electrodialysis, polymer-enhanced ultrafiltration, and sorption, , which tend to rely on weak noncovalent interactions. The reversible interactions of borate anions with hydroxyl groups have been exploited in the development of boron sorbents based on nitrogen-doped graphene oxide surface-grafted with hydroxyl groups, diol-functionalized silica particles, and Nylon-6 fibrils grafted with NMDG moieties .…”

“…This has been due, in part to (i) poor solubility of the resins in aqueous or organic solvents, which makes solution-state characterization methods impractical, and (ii) the heterogeneity of resin surfaces, which limits the utility of X-ray scattering, electron microscopy, and standard surface characterization methods. Nevertheless, boron-adsorbing resins have been characterized by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), mass spectrometry (MS), and NMR spectroscopy . Such methods provide structural information on complementary length and time scales, though until now they have provided limited insights on site-specific molecular-level interactions and adsorption behaviors of borate anions adsorbed on the heterogeneous resin surfaces.…”

“…In particular, many commercial boron-adsorption ionexchange resins are based on polymers grafted with NMDG functional groups. 12,13,24,25 For such materials, the hydroxyl groups of the NMDG moieties exhibit high binding affinity toward borate anions. 20,26 This imparts the NMDG-functionalized polymers with high boron adsorption capacities and correspondingly favorable separation efficacies, compared to other approaches such as reverse osmosis, 27,28 electrodialysis, 29 polymer-enhanced ultrafiltration, 30 and sorption, 31,32 tend to rely on weak noncovalent interactions.…”