Adsorption Properties of Sepiolite in Relation to Uranium and Lanthanide Ions

Abstract

The batch technique was used to study the adsorption of La(III), Eu(III), Lu(III), and U(VI) ions on sepiolite and ODTMA–sepiolite under ambient conditions. The effects of pH, time, and initial concentration were investigated. The highest U(VI) adsorption was found on ODTMA-sepiolite in the pH range of 6–8, while in the case of lanthanide ions, adsorption on sepiolite was 80% in the pH range of 4–8 and 98% for pH values above 8. The adsorption capacity of ODTMAsepiolite was found to be 285.6 mg/g for uranium, and raw sepiolite: 142.8 mg/g for U(VI), 91.6 mg/g for La(III), 91.4 mg/g for Eu (III), and 104.9 mol/g for Lu(III). ODTMA–sepiolite turned out to be a weak sorbent for lanthanide ions. Two short- and long-lived fluorescence species were observed in the TRLFS spectra of U(VI) adsorbed on sepiolite at pH 6.5. The average lifetimes of short- (τ1) and long-lived (τ2) fluorescence are τ1 = 2420 ± 430 ns and τ2 = 37950 ± 5710 ns for U-sepiolite; τ1 = 3523 ± 160 ns and τ2 = 45400 ± 1830 ns for U-ODTMA–sepiolite.

Optimal Synthesis of Novel Phosphonic Acid Modified Diatomite Adsorbents for Effective Removal of Uranium(VI) Ions from Aqueous Solutions

“…The chemical characterization of the surface of the diatomite-based samples with the phosphonic groups and the determination of the structure of the functional layer was performed by solid state 29 Si and 31 P MAS NMR spectroscopy (Figures 3 and 4). The magnitude of the chemical shift and the width of the 31 P MAS NMR signal is an important tool for explaining the interactions of phosphonic acids with the matrix based on the oxide materials [27,46]. The 31 P CP/MAS NMR spectra of the DIT-Vin sample with contact times of 0.5, 2.0, 5.0, and 10.0 ms are shown in Figure 4.…”

“…Carbon was the main element of the algae plant. The C-H peak was instead related to the organo-modified materials rather than to the other natural silica-based minerals [27]. The band at 3750 cm −1 corresponded to the single silanol groups (SiO-H), and the broad band at 3425 cm −1 represented the H-bonding vibration of the OH-groups from the Al-OH, Mg-OH, and Si-OH fragments.…”

“…A variety of adsorbents with different ligands have been designed for the exaction of radionuclides, such as graphene oxide, layered double hydroxide(LDH) [9,10], nanoscale zero-valent iron and direct-reduced iron (sponge iron) [11], magnetite [8,[12][13][14], resin [15], goethite [16,17], europium hydroxide [18], self-assembled monolayers on nanocomposites [19][20][21], silica [22] and polymeric derivatives [23][24][25], carbon nanotubes, modified biowaste [26], natural minerals [27], and nano-sized filtration membranes [28]. The surface of these materials can be modified with functional groups or molecules, such as natural polymer (chitin or chitosane) [21], aminoacids [18], acidic [29] and chelating [10] groups, amidoxime-functionalized macroporous fibrous polymeric [23], poly(acrylic acid) [24], and activated cellulose and silica grafted cellulose [30].…”

“…The 29 Si MAS NMR spectrum of the natural diatomite, besides the major signals at −92.7 ppm (Q 3 = HO−Si(OSi) 3, MgO−Si(OSi) 3 , or AlO−Si(OSi) 3 sites) and −107.6 ppm (Q 4 = [Si−(OSi) 4 ] sites of quartz), showed that the peaks for DIT-Vin, DIT-Vin-PA in , and DIT-Vin-PA cov samples could be assigned to different Q species, i.e., geminal silanols (Q 2 , δ = −99.1 ppm), single silanols (Q 3 , δ = −102.9 ppm), and siloxane groups (Q 4 ; δ = −110.2 ppm), and contained different T n species (1 < n ≤ 3), where n is related to the number of siloxane bonds formed between the surface and the functional center at −60.9 and −65.1 ppm that can be assigned to T 3 [R−Si−(OSi) 3 ] and T 2 [R 2 −Si−(OSi) 2 ] groups, respectively. The effect of the silanization corresponding to the covalent Si-C bond on the surface of adsorbents indicated the presence of the polycondensed layer of organo-silane on the diatomite surface.The magnitude of the chemical shift and the width of the 31 P MAS NMR signal is an important tool for explaining the interactions of phosphonic acids with the matrix based on the oxide materials[27,46]. The 31 P CP/MAS NMR spectra of the DIT-Vin sample with contact times of 0.5, 2.0, 5.0, and 10.0 ms are shown in Figure4.…”

Structural properties and adsorption of uranyl ions on the nanocomposite hydroxyapatite/white clay

“…As the pH increases, the adsorption of metal ions increases as the number of hydronium ions decreases and it is the highest in the range of approximately pH = 4. This is due to the fact that the sorbent surface becomes negatively charged as a result of the deprotonation reaction [Thakur et al 2005, Gładysz-Płaska 2019. Accordingly, the repulsive force that exists between the metal ions in the solution and the active groups of sorbents is reduced, thereby increasing the removal of metal ions from the solution.…”