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With the development of nuclear energy, large amounts of radionuclides are inevitably released into the natural environment. It is necessary to eliminate radionuclides from wastewater for the protection of environment. Nanomaterials have been considered as the potential candidates for the effective and selective removal of radionuclides from aqueous solutions under complicated conditions because of their high specific surface area, large amounts of binding sites, abundant functional groups, pore-size controllable and easily surface modification. This review mainly summarized the recent studies for the synthesis, fabrication and surface modification of novel nanomaterials and their applications in the efficient elimination and solidification of radionuclides, and discussed the interaction mechanisms from batch experiments, spectroscopy analysis and theoretical calculations. The sorption capacities with other materials, advantages and disadvantages of different nanomaterials are compared, and at last the perspective of the novel nanomaterials is summarized. [ABSTRACT FROM AUTHOR]

To design new and efficient supramolecular recognition material, a macroporous organic-inorganic bis( n-amyloxy)calix[4]arene-crown-6 (BnACalix[4]C6) material for separation of cesium from acidic solution was developed. The results of SEM, TG-DSC, FT-IR, Si NMR, and XRD characterizations indicated that BnACalix[4]C6 molecules were successfully impregnated into the pores of SiO-P support. Cs(I) was shown to be both strongly and selectively adsorbed by this material at 3.0 M HNO. The total organic carbon values showed that the leakage of BnACalix[4]C6 from BnACalix[4]C6/SiO-P was below 0.1 %. Thus, BnACalix[4]C6/SiO-P is a promising candidate for separation of Cs(I) from acidic HAW in SPEC process. [ABSTRACT FROM AUTHOR]

To design novel phenanthroline-derived soft ligands for selectively separating minor actinides from lanthanides, four tetradentate phenanthroline-derived heterocyclic ligands (BTPhen, BPyPhen, BPzPhen, and BBizPhen) were constructed and their complexation behaviors with Am(III) and Eu(III) were systematically investigated by density functional theory (DFT) coupled with relativistic small-core pseudopotential. In all the 1:1-type species, the metal ion is in the center of the cavity and coordinates with two nitrogen atoms (N1 and N1′) of the phenanthroline skeleton and the other two nitrogen atoms (N2 and N2′) of the auxiliary groups. The bond lengths of Am-N are comparable to or even shorter than those of Eu-N bonds because the ionic radii of Am(III) are larger than those of Eu(III). Additionally, the negative ΔΔ G value for the reaction of [M(HO)(NO)] + L → ML(NO) + 4HO indicates that the complexation reaction of Am(III) is more energetically favorable than that of Eu(III); this can be considered as an important design criterion to screen phenanthroline-derived ligands for MA(III) extraction. According to this criterion, the selectivity of tetradentate phenanthroline-derived ligands for separating Am(III) over Eu(III) follows the order of BTPhen > BBizPhen > BPyPhen > BPzPhen. [ABSTRACT FROM AUTHOR]

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis( iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO-P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO-P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO-P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO-P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO-P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO-P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated. [ABSTRACT FROM AUTHOR]

Hydrotalcite (HTC), a typical layered compound, is a promising adsorbent for removal of organic pollutants. To partition azo dye from aqueous solution, Mg-Al HTCs intercalated with dodecanoic acid (DA) modifier, DAHTCs, were prepared by ion exchange and calcination-rehydration methods. The structures of HTCs and DAHTCs were characterized by powder XRD and FT-IR techniques. The introduction of DA broadened the spacing of interlayers and provided more space for ion exchange. The effects of pH value, contact time, adsorbent amount, temperature and different intercalated modifiers on the adsorption of azo dye onto HTCs and DAHTCs were determined. The optimum pH of uptake was around 3.0 and all the lower or higher pH values proved to decrease the adsorption properties. The pseudo-second-order model was found to best describe the adsorption dynamics of all adsorbents. Meanwhile, the size and polarity of intercalated modifiers might be crucial for adsorption of azo dye. [ABSTRACT FROM AUTHOR]

To develop a separation process of Sr(II), a macroporous silica-based 4,4′,(5′)-di( tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) polymeric material, (DtBuCH18C6+Oct)/SiO-P, was synthesized by impregnating and immobilizing DtBuCH18C6 and 1-octanol into the pores of the macroporous SiO-P particles support. DtBuCH18C6 was modified with 1-octanol through hydrogen bonding. The adsorption of simulant elements of some typical fission products Ru(III), Pd(II), Ba(II), Mo(VI), La(III), Y(III), Sr(II), Cs(I) and those of non-fission products Na(I) and K(I) onto (DtBuCH18C6+Oct)/SiO-P were studied at 298 K. The effects of the HNO concentration in a range of 0.1-5.0 M and contact time on the adsorption were investigated. (DtBuCH18C6+Oct)/SiO-P showed excellent adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). Partitioning of Sr(II) from a 2.0 M HNO solution containing ~5.0 × 10 M of the tested metals was conducted utilizing (DtBuCH18C6+Oct)/SiO-P packed column. Pd(II), Mo(VI), Y(III), La(III), Ru(III), K(I), Cs(I), and Na(I) showed no adsorption and flowed into effluent along with 2.0 M HNO. Sr(II) was retained on (DtBuCH18C6+Oct)/SiO-P and was eluted effectively by HO, while Ba(II) showed similar elution behavior. The bleeding of total organic carbon leaked from (DtBuCH18C6+Oct)/SiO-P was evaluated. It was demonstrated that the macroporous silica-based (DtBuCH18C6+Oct)/SiO-P materials are promising in separation of Sr(II) from high level radioactive waste. [ABSTRACT FROM AUTHOR]

To separate Sr(II), one of the heat emitting nuclides, from high level liquid waste (HLLW), a macroporous silica-based DtBuCH18C6 polymeric composite, DtOct/SiO2-P, was synthesized by means of molecular modification of 4,4′,(5′)-di( tert-butylcyclohexano)-18-crown-6 (DtBuC H18C6) with a long-chain 1-octanol. It was performed by impregnating and immobilizing DtBuCH18C6 and 1-octanol molecules into the pores of the SiO2-P particles, the macroporous silica-based support. The adsorption of Sr(II) and some co-existent typical elements Na(I), K(I), Cs(I), Ru(III), Mo(VI), Pd(II), Ba(II), La(III), and Y(III) contained in highly active liquid waste (HLW) towards DtOct/SiO2-P was investigated at 323 K. The effects of contact time and the concentration of HNO3 in a range of 0.1–5.0M on the adsorption of the tested metals were examined. The macroporous silica-based DtOct/SiO2-P polymeric composite showed strong adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). The optimum acidity of Sr(II) adsorption onto DtOct/SiO2-P was determined to be 2.0M HNO3. The bleeding behavior of DtOct/SiO2-P in aqueous phase was evaluated using total organic carbon (TOC) analysis. The content of TOC increased with increasing the HNO3 concentration and contact time. It resulted from the decrease in the stability of the associated species, C8H17-OH• DtBuCH18C6 formed through hydrogen binding, because of high temperature. [ABSTRACT FROM AUTHOR]

Removal of 99TcO4− from legacy defense nuclear tank waste at Savannah River Site is highly desirable for the purpose of nuclear safety and environmental protection, but currently not achievable given the extreme conditions including high alkalinity, high ionic strength, and strong radiation field. Herein, we present a potential solution to this long-term issue by developing a two-dimensional cationic metal organic framework SCU-103, showing ultrahigh stability in alkaline aqueous media and great resistance to both β and γ radiation. More importantly, it is very effective for 99TcO4− separation from aqueous media as demonstrated by fast exchange kinetics, high sorption capacity, and superior selectivity, leading to the successful removal of 99TcO4− from actual Savannah River Site high level tank waste for the first time, to the best of our knowledge. In addition, the uptake mechanism is comprehensively elucidated by molecular dynamics simulation and density functional theory calculation, showing a unique chemical recognition of anions with low charge density. Separation of 99TcO4− from nuclear waste at the Savannah River Site is hampered by the extreme conditions. Here, the authors propose a solution by developing an alkaline-resistant metal organic framework material featuring unique recognition sites for selective incorporation of 99TcO4− anions. [ABSTRACT FROM AUTHOR]

Direct removal of 99TcO4− from the highly acidic solution of used nuclear fuel is highly beneficial for the recovery of uranium and plutonium and more importantly aids in the elimination of 99Tc discharge into the environment. However, this task represents a huge challenge given the combined extreme conditions of super acidity, high ionic strength, and strong radiation field. Here we overcome this challenge using a cationic polymeric network with significant TcO4− uptake capabilities in four aspects: the fastest sorption kinetics, the highest sorption capacity, the most promising uptake performance from highly acidic solutions, and excellent radiation-resistance and hydrolytic stability among all anion sorbent materials reported. In addition, this material is fully recyclable for multiple sorption/desorption trials, making it extremely attractive for waste partitioning and emergency remediation. The excellent TcO4− uptake capability is elucidated by X-ray absorption spectroscopy, solid-state NMR measurement, and density functional theory analysis on anion coordination and bonding. [ABSTRACT FROM AUTHOR]

Lanthanides possess similar chemical properties rendering their separation from one another a challenge of fundamental chemical and global importance given their incorporation into many advanced technologies. New separation strategies combining green chemistry with low cost and high efficiency remain highly desirable. We demonstrate that the subtle bonding differences among trivalent lanthanides can be amplified during the crystallization of borates, providing chemical recognition of specific lanthanides that originates from Ln3+ coordination alterations, borate polymerization diversity and soft ligand coordination selectivity. Six distinct phases are obtained under identical reaction conditions across lanthanide series, further leading to an efficient and cost-effective separation strategy via selective crystallization. As proof of concept, Nd/Sm and Nd/Dy are used as binary models to demonstrate solid/aqueous and solid/solid separation processes. Controlling the reaction kinetics gives rise to enhanced separation efficiency of Nd/Sm system and a one-step quantitative separation of Nd/Dy with the aid of selective density-based flotation. [ABSTRACT FROM AUTHOR]