Organic layer formation and sorption of U(vi) on acetamide diethylphosphonate-functionalized mesoporous silica

Abstract

Acetamide diethylphosphonate (AcPhos)-functionalized silica has been shown to have a high affinity for U(vi) in pH 2-3 nitric acid. Previous work with AcPhos-functionalized silica has focused on actinide and lanthanide extraction under various conditions, but has shown poor reproducibility in the functionalization process. For this work, four AcPhos-functionalized SBA-15 materials were synthesized and evaluated based on their U(vi) sorption capacity and their stability in nitric acid. Materials synthesized using pyridine as a basic catalyst were shown to form a greater fraction of polymeric structures at the silica surface, which correlated with higher structural integrity upon contact with acidic solutions. Single-pulse P andH NMR spectra of these materials show evidence of phosphonic acid groups, as well as hydrogen-bonding interactions either between ligands or with the silica surface. Additionally, these materials were found to have significantly higher U(vi) sorption capacities and K values than the materials synthesized without pyridine, most likely due to the ion-exchange properties of the phosphonic acid groups. The P-P DQ-DRENAR NMR technique was used to compare the average strength of dipolar coupling interactions between phosphorus atoms for the four materials. Because the strength of dipolar coupling interactions depends on the number and proximity of neighboring spins, this technique provides information about the average density of ligands on the surface. The conventional functionalization procedure yielded materials with the lowest average surface ligand density, while those using extended reaction times and the pyridine base catalyst yielded materials with higher surface ligand densities.

Revisiting carboxylic group functionalization of silica sol–gel materials

“…On the other hand, phosphonate-functionalized silica surfaces are almost used exclusively for the adsorption and recovery of metal ions while anchored sulfonic acid groups have interesting applications as heterogeneous phase acid catalysts and electrostatic-based adsorbents. [12][13][14][15][16] In this context, the COOH groups have the advantage as a building block unit for further functionalization with biomolecules through stable amide or esters bonds. This adds to the aforementioned applications such as ion adsorption by complexation or as cation exchangers in the adsorption of contaminants.…”

Sorption properties of carbamoylmethylphosphonated-based polymer combining both sorption and thermosensitive properties: New valuable hydrosoluble materials for rare earth elements sorption

“…An alternative process consists in using extraction on solid phase, which doesn't need any organic solvent. Lanthanide/actinide sorbents could be organic (resins), [25]- [35] inorganic, [36], [37] or hybrid (organic/inorganic) [35], [38]- [40] materials. Organic or hybrid materials are generally functionalized with ion exchange or solvating sites with similar complexing motifs than those used in solvent extraction.…”

“…Organic or hybrid materials are generally functionalized with ion exchange or solvating sites with similar complexing motifs than those used in solvent extraction. [25], [27], [29], [33]- [35] However, these materials are generally designed in eluting column and thus they are difficult to industrialize in a continuous process, on the one hand and, energy consumer on the other hand. [38] New recovery processes are now emerging such as polymer enhanced ultrafiltration or polymer assisted ultrafiltration (PEUF/PAUF), which associates a functionalized polymer (soluble or insoluble) in order to complex metals with a membrane ultrafiltration step to recover the polymer after complexation.…”

The preparation of organophosphorus ligand-modified SBA-15 for effective adsorption of Congo red and Reactive red 2

“…[23][24][25][26][27][28][29][30][31][32][33][34][35] Phosphonic-based ligands form the most important ligand family, which have numerous interesting chemical structures such as phosphates, phosphonates or organophosphorus derivatives. [36][37][38] These ligands exhibit remarkable coordination abilities and high chemical resistance. 39 Therefore, phosphonic-based ligands are used for the surface modication of materials to enhance their adsorption capacity and adsorption efficiency, which are of great interest for adsorption-based applications.…”