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γ-raysand pulse radiolysis of aqueous solutions of Ni2+ionsin the presence of polyacrylate (PA–) and 2-propanolleads to the formation of metastable species absorbingat 540 nm that are ascribed to “pink” oligomeric clustersof a few nickel atoms only. The molar absorption coefficient is evaluatedas ε540 nm= 3300 ± 300 L mol–1cm–1per Ni0atom. The successive stepsfrom the reduction of Ni2+into Ni+ions tothe formation of the pink clusters at 540 nm under conditions of complexationby PA–are investigated by pulse radiolysis. Theyield of the formation of pink clusters increases markedly with theirradiation dose rate, demonstrating the occurrence of the disproportionationof the [Ni+, PA–] complex after a singleelectron pulse. The reduction and nucleation mechanisms, includingrate constants, in competition with the back oxidation by protons,particularly at low dose rate, are discussed. [ABSTRACT FROM AUTHOR]

The absorption spectra of Br2•̵ and Br3̵ in aqueous solutions are investigated by pulse radiolysis techniques from room temperature to 380 and 350 °C, respectively. Br2•̵ can be observed even in supercritical conditions, showing that this species could be used as a probe in pulse radiolysis at high temperature and even under supercritical conditions. The weak temperature effect on the absorption spectra of Br2•̵ and Br3̵ is because, in these two systems, the transition occurs between two valence states; for example, for Br2̵ we have 2Σu→2Σg transition. These valence transitions involve no difiuse final state. However, the absorption band of Br̵ undergoes an important red shift to longer wavelengths. We performed classical dynamics of hydrated Br̵ system at 20 and 300 °C under pressure of 25 MPa. The radial distribution functions (rdfs) show that the strong temperature increase (from 20 to 300 °C) does not change the radius of the solvent first shell. On the other hand, it shifts dramatically (by 1 Å) the second maximum of the Br-- O rdf and introduces much disorder. This shows that the first water shell is strongly bound to the anion whatever the temperature. The first two water shells form a cavity of a roughly spherical shape around the anion. By TDDFT method, we calculated the absorption spectra of hydrated Br̵ at two temperatures and we compared the results with the experimental data. [ABSTRACT FROM AUTHOR]

Transient radicals (hydrated electron, (SCN)[sub 2][sup .-] and CO[sub 3][sup .-]) formed in supercritical water have been observed by the pulse radiolysis technique. The change of spectra of these radicals with temperature has been measured. It was found that the spectra and absorption coefficients of the radicals, e[sup -][sub aq] and (SCN)[sub 2][sup .-], are strongly dependent on the temperature of the water. Since it was found that the absorption spectrum and molar absorption coefficient of CO[sub 3][sup .-] radical seem to be almost independent of temperature, G-values of OH and e[sup -][sub aq] could be derived. Then, the absolute values of the absorption coefficients for the radicals could be calculated. The G-values of the radical products in water radiolysis tend to increase with increasing temperature up to 400°C. Based on the above observation, radiolysis of supercritical water is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Radiolysis mechanism and radiolytic pathways of DAPhen were investigated. • Radiolysis of DAPhen is mainly through the cleavage of amide bonds and N C bonds. • HNO 3 enhanced the extraction and An/Ln separation performance of DAPhen after irradiation. • Radiolytic products of DAPhen were verified by DFT calculations to have extraction ability for U. The stability of organic extractant molecules against radiolysis is critical in the field of actinides and lanthanides (An/Ln) separations. In order to evaluate the radiolytic effects on the extraction performance, the solutions of N,N '-diethyl- N,N '-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) in n -octanol were subjected to γ-irradiation in the presence and absence of 3 mol/L HNO 3 aqueous phase. Et-Tol-DAPhen diluted in n -octanol was almost completely decomposed after irradiation and exhibits decreased extraction ability at an absorbed dose of about 384 kGy, along with the appearance of various degradation products. Et-Tol-DAPhen, which was diluted in n -octanol, was completely decomposed upon irradiation in the presence of 3 mol/L HNO 3 aqueous phase. However, it exhibited higher D U and SF U/Eu values than before irradiation, as well as degradation products that were also generated. The structures of some isomers of radiolytic products were investigated by density functional theory (DFT) calculations, the radiolysis pathways and products of Et-Tol-DAPhen extractants were obtained, and the radiolysis pathways and products of Et-Tol-DAPhen extractants was proposed. The radiolytic products mainly originated from amide bond and N C bond cleavage of side group substituents, and some resulted from interaction with n -octanol radicals generated during radiolysis. The presence of HNO 3 can inhibit the radiolysis of Et-Tol-DAPhen to a certain extent and cause enhanced extraction ability. Moreover, the DFT calculations reveal that the radiolytic products produced in presence of 3 mol/L HNO 3 aqueous phase also have efficient extraction performance towards UO 2 2+. The understanding of the radiolysis pathways and products of extractants, based on radiation chemical effects is expected to be helpful for developing new strategies for extractants with long-term performance. [ABSTRACT FROM AUTHOR]

The separation and recovery of Li+ from high-ratio Mg/Li salt lake brines possess a big significance, especially the demand for Li+ has grown rapidly in recently years. The ionic liquid [C 2 mim][NTf 2 ] with tributyl phosphate (TBP) and sulfonated kerosene system was hired as an extractant to extract Li+ from salt lake brines with a high-ratio of Mg/Li experimentally by using a homemade membrane emulsification circulation (MEC) extractor. From the single-element extraction, the extraction efficiency of Li+ could be up to 96.0 % within 8 min. In view of the multi-element experiment, the MEC extractor manifested better extraction performance compared with oscillating and stirring extraction. The extraction ability of the extractant for Li+ could reach the ideal level without the addition of any co-extraction agents (Fe3+ and ClO 4 −). The new extraction system could have extensive applications since the extraction performance was insensitive to pH and temperature. The optimal extraction conditions for Li+ were V TBP : V [C 2 mim][NTf 2 ]: V kerosene = 8:1:1, R(O/A) = 1. In addition, the stripping efficiency of Li+ could be improved by increasing the A/O and stripping stage. When the stripping stage reached 3, 94.5 % of Li+ could be extracted successfully by using 2 mol/L HCl. The slope method and FT-IR analysis manifested that the TBP-[C 2 mim][NTf 2 ]-sulfonated kerosene system extracted Li+ by an anion coordination mechanism in the form of [Li·2TBP]+ org. The DFT calculations were used for revealing the reaction between Li+ and P = O. The results are expected to provide experimental data and a theoretical basis for practical application. Fast and high-efficiency separation for Li+/Mg2+ from salt lake brines by a homemade membrane emulsification circulation (MEC) extractor using the TBP-[C 2 mim][NTf 2 ]-sulfonated kerosene system as an extractant could be achieved with an extraction efficiency of 85.0 % for Li+ and only 2.0 % for Mg2+ within 6 min. [Display omitted] • The ionic liquid [C 2 mim][NTf 2 ] could effectively strengthen the extraction performance. • The proposed novel extraction system represented good selectivity for Li+/Mg2+. • DFT calculations and FT-IR analysis indicated that Li+ mainly combined with P = O in TBP. • Fast and efficient separation of Li+/Mg2+ could be achieved by the MEC extractor. • A process for extracting Li+ from salt lake brines was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchically porous boron nitride (HPBN) was modified with diamide pyridine (DAPy). • Assistance of radiation-induced hydroxylation was essential to modify inert HPBN. • Hierarchically porous structure endowed HPBN-DAPy ultrafast adsorption kinetics. • HPBN-DAPy selectively adsorbed U due to the strong affinity between uranyl and DAPy. • HPBN-DAPy retained 86% of the original adsorption amount after 5 cycles. Uranium (U) released by nuclear accident raises concerns about human health owing to its long half-life and toxicity. Diamide-pyridine-modified hierarchically porous boron nitride (HPBN-DAPy) was prepared for efficient removal of U. HPBN, which could hardly adsorb U, gained the ability to uptake U only after functionalization with diamide pyridine (DAPy) groups. The hierarchically mesoporous structure with bimodal mesopores around 20 and 3 nm endowed HPBN-DAPy with unique adsorption kinetic. Uranyl ions (UO 2 2+) easily approached the adsorption sites in those large mesopores and thus the adsorption rapidly reached temporary equilibrium within 0.5 min with a relatively high adsorption of amounts (q e) of 87.5 mg g−1 (adsorbent dosage = 0.4 g L−1, [U] 0 = 100 mg L−1, pH = 4.0 ± 0.1, T = 298 ± 1 K), which was beneficial for rapid decontamination. Small mesopores and the inner large mesopores, which were connected through small mesopores, provided extra adsorption sites, leading to a further increased q e of 115.7 mg g−1 after achieving final equilibrium. Investigation of adsorption mechanism showed that UO 2 2+ were chemically adsorbed in monolayer at a low initial concentration while they were physically adsorbed in the form of polynuclear complexes at a high initial concentration. Benefited from the strong affinity between UO 2 2+ and DAPy, HPBN-DAPy performed excellent selectivity for UO 2 2+ toward other most concerned radionuclide ions. Furthermore, HPBN-DAPy also exhibited adequate salt tolerance and outstanding reusability, which should be promising in removal of U from contaminated water. [ABSTRACT FROM AUTHOR]

[Display omitted] • BCN was functionalized by Phenanthroline diamide with high density. • Functionalized BCN exhibited ultrahigh adsorption capacity for U(VI). • Functionalized BCN showed excellent selectivity for U(VI) from lanthanides. • Adsorption mechanism was explored by combining two-site model and DFT calculations. Separating and recovering uranium (U(VI)) efficiently from lanthanides is crucial for mitigating the radioactive hazard generated by hydrometallurgical residual solutions of lanthanide minerals and ensuring the long-term sustainability of uranium resources. The present work exploited phenanthroline diamide functionalized porous carbon doped boron nitride (BCN-DAPhen) as an adsorbent, which displayed outstanding adsorption performance for the separation of U(VI) from lanthanides. The results of batch adsorption tests indicated that BCN-DAPhen exhibited rapid adsorption kinetics and the adsorption process achieved equilibrium within 10 min. BCN-DAPhen also performed ultra-high maximum adsorption capacity that was calculated to be 2050.8 mg g−1 by fitting with the two-site Langmuir model. Theoretical calculation and experimental results of adsorption were combined to illustrate the adsorption mechanism as well, the results showed that two structures of DAPhen groups on BCN performed discrepant adsorption properties for U(VI). BCN-DAPhen retained excellent adsorption ability owing to the strong affinity of DAPhen groups with U(VI) even in the solution with high concentration of salt and acid. The selectivity coefficients of U(VI) toward various lanthanides were beyond 192.5 at a high nitric acid concentration of 5 mol L−1. This study suggested a general technique for the functionalization of porous BCN, which is expected to be useful in the treatment of residual solution in lanthanides hydrometallurgy. [ABSTRACT FROM AUTHOR]

The optical absorption spectra of the hydrated electron (e(aq) (-)) in supercritical (heavy) water (SCW) are measured by electron pulse radiolysis techniques as a function of water density at three temperatures of 380, 390, and 400 degrees C, and over the density range of approximately 0.2-0.65 g/cm(3). In agreement with previous work, the position of the e(aq) (-) absorption maximum (E(A(max) )) is found to shift slightly to lower energies (spectral "redshift") with decreasing density. A comparison of the present E(A(max) )-density data with other measurements already reported in the literature in subcritical (350 degrees C) and supercritical (375 degrees C) water reveals that at a fixed pressure, E(A(max) ) decreases monotonically with increasing temperature in passing through the phase transition at t(c). By contrast, at constant density, E(A(max) ) exhibits a minimum as the water passes above the critical point into SCW. These behaviors are explained in terms of simple microscopic arguments based on the crucial role played by local density and configurational fluctuations (associated with criticality) in providing pre-existing polymeric clusters, which act as trapping sites for electrons.

The reactions of OH* or SO4*- radicals with carboxymethyl chitin (CM-chitin) and its deacetylated product, carboxymethyl chitosan (CM-chitosan), were investigated in aqueous solutions using a laser photolysis technique. The rate constants of the reactions of OH* and SO4*- radicals with CM-chitosan are always higher than those for CM-chitin, indicating that the amino-group could increase the reactivity of carboxymethylated chitin derivatives. The rate of the reactions of CM-chitin and CM-chitosan with OH* radical was found to decrease at lower pH when polymers chains tend to the coiled conformation. In comparison, the rate constant of the reaction of SO4*- radicals with CM-chitin or CM-chitosan decreased with pH, indicating that CM-chitin or CM-chitosan has a higher reactivity with the SO4*- radical at low pH due to the protonation of the amino group.