Glycerol-Modified Binary Layered Double Hydroxide Nanocomposites for Uranium Immobilization via Extended X-ray Absorption Fine Structure Technique and Density Functional Theory Calculation

Abstract

Novel, efficient, glycerol-modified nanoscale layered double hydroxides (rods Ca/Al LDH-Gl and flocculent Ni/Al LDH-Gl) were successfully synthesized by a simple one-step hydrothermal synthesis route and showed excellent adsorption capacities for U­(VI) from aqueous solutions under various environmental conditions. The advanced spectroscopy analysis confirmed the existence of abundant oxygen-containing functional groups (e.g., C–O, O–CO, and CO) on the surfaces of Ca/Al LDH-Gl and Ni/Al LDH-Gl, which could provide enough free active sites for the binding of U­(VI). The maximum adsorption capacities of U­(VI) calculated from the Sips model were 266.5 mg·g–1 for Ca/Al LDH-Gl and 142.3 mg·g–1 for Ni/Al LDH-Gl at 298.15 K, and the higher adsorption capacity of Ca/Al LDH-Gl might be due to more functional groups and abundant high-activity “Ca–O” groups. Macroscopic experiments proved that the interaction of U­(VI) on Ca/Al LDH-Gl and Ni/Al LDH-Gl was due to surface complexation and electrostatic interactions. The extended X-ray absorption fine structure analysis confirmed that U­(IV) did not transformation to U­(VI) on solid particles, and stable inner-sphere complexes were not formed by reduction interaction but by chemical adsorption. The density functional theory (DFT) calculations further evidenced that the higher adsorption energies (i.e., E ad = 4.00 eV for Ca/Al LDH-Gl-UO2 2+ and E ad = 2.43 eV for Ca/Al LDH-Gl-UO2CO3) were mainly attributed to stronger hydrogen bonds and electrostatic interactions. The superior immobilization performance of Ca/Al LDH-Gl supports a potential strategy for decontamination of UO2 2+ from wastewater, and it may provide new insights for the efficient removal of radionuclides in environmental pollution cleanup.

Novel synthesis of Ni/Fe layered double hydroxides using urea and glycerol and their enhanced adsorption behavior for Cr(VI) removal

“…As Shown in Fig. 2(c) it is interesting to note the presence of important bands of GL in the spectra of Ni/Fe LDH/GL Nano Composites indicated a successful loading of Gl in the Ni/Fe LDH host 55,56 . Besides Also, the intensity of some peak at 1357 cm −1 was decreased indicating the exchange of nitrate anions by the GL 56 .…”

Recent Advances in Composites of Graphene and Layered Double Hydroxides for Water Remediation: A Review

“…Hydrothermal treatment, also knowna st he "urea hydrolysis method", is af acile and environmentally friendly methodf or the synthesis of G@LDHcomposites. [35][36][37] Compounds with uniform morphology and excellent crystallinity can be obtained by using the hydrothermal method. [38][39][40] Typically,amixed solution is used that contains precursor salts (nitrates, chlorides, sulfates,o rh ydroxides), urea, and graphene.…”

Investigation of Adsorption Mechanism of Layered Double Hydroxides and Their Composites on Radioactive Uranium:A Review

“…图 5 (a) Ca-Al-LDH-Gl 和 Ni-Al-LDH-Gl 材料的 FTIR 光谱对比图 [68] ; (b) Ca-Mg-Al-LDH 和 Ca-Mg-Al-LDOx 的 XRD 光谱图 [58] ; Ca-Mg-Al-LDH 和 Ca-Mg-Al-LDOx 复合材料对 U(VI)的吸附动力学及相互作用机理 [58] Figure 5 (a) FT-IR spectra of as-prepared Ca-Al-LDH-Gl and Ni-Al-LDH-Gl samples [68] ; (b) XRD patterns of Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx samples [58] ; (c) Adsorption kinetics and interaction mechanism of U(VI) on Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx [58] 化 学 学 报 Figure 6 Deconvolution analysis of (a) C 1s, (c) N 1s, and (e) O 1s XPS spectra of Fe 3 O 4 -PDA-LDHs and (b) C 1s, (d) N 1s, and (f) O 1s XPS spectra of Fe 3 O 4 -PDA-LDHs＋U(VI) [66] 4.4 扩展 X 射线吸收精细结构谱 扩展 X 射线吸收精细结构谱(extended X-ray absorption fine structure, EXAFS)是 X 射线吸收限高能侧 30～1000 eV 范围内吸收系数随入射 X 光子能量增加而 起伏振荡的现象, 近年来它被广泛应用于测定多原子气 体和凝聚态物质吸收原子周围的局域结构, 成为结构分 析的一种新技术 [90] . 通过 EXAFS 分析技术可以研究指 定元素原子的近邻结构, 可测配位原子的种类、个数以 及原子间距等 [36,91] .…”

“…(3)浓度很低的样品, 百万分之几的 元素也能分析. 如图 7 所示, Zou 等 [68] [68] Figure 7 U L III -edge background subtracted, k 2 -weighted χ(k) data (a) and corresponding Fourier transformed EXAFS spectra (b) of standards (UO 2 2＋ or UO 2 ) and adsorption samples [68] 表 2 四种光谱分析技术的优缺点分析…”