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The efficient recovery of palladium from high level liquid waste (HLLW) is of growing importance for achieving sustainable development and resolving challenges in radioactive waste treatment. Nonetheless, the hunt for strong materials for the selective adsorption of palladium ion (Pd(ii)) at high acidity remains a formidable obstacle. In this work, hierarchically porous g-C3N4with high specific surface area was synthesized as a matrix of adsorbent that provides a rapid transport channel for Pd(ii). Subsequently, N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (DAPhen) was modified for integration into g-C3N4to create CN-DAPhen for obtaining an adsorbent with excellent selectivity and efficient adsorption for Pd(ii). The adsorption of Pd(ii) in HNO3medium was examined using batch experiments. CN-DAPhen displayed quick adsorption kinetics, and equilibrium was reached within 5 min. By fitting the data using the Langmuir model, the maximum adsorption capacity of CN-DAPhen was calculated to be 390.63 mg g−1. In practice, the functionalized nanomaterial was employed to recover Pd(ii) from simulated HLLW containing competing metal ions. The adsorption selectivity of CN-DAPhen for Pd and Ru was also explored by combining adsorption experiments and DFT calculation. On this basis, a continuous process was developed for separating Pd and Ru from HLLW. Furthermore, the excellent radiation resistance and reusability of CN-DAPhen endowed it with great practical potential for the treatment of HLLW. This study not only introduces a novel species with superior adsorbent capability in selectively recovering palladium but also reveals a potential strategy for the development of robust nanomaterials for nuclear waste cleanup.

Separation and recovery of U(VI) and Th(IV) from rare earth minerals is a very challenging work in rare earth industrial production. In the present study, a homemade membrane emulsification circulation (MEC) extractor was used to separate U(VI) and Th(IV) from rare earth elements by using Cyphos IL 104 as an extractant. Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104 could reach the extraction equilibrium within 30 min for all the three elements, i.e.,U(VI), Th(IV), and Eu(III). Besides, the MEC extractor possessed a strong phase separation ability. The extraction efficiencies of U(VI), Th(IV), La(III), Eu(III) and Yb (III) increased with the increase of pH. La(III), Eu(III) and Yb(III) were hardly extracted when pH ≤ 1.50, which was beneficial for effectively separating U(VI) and Th(IV) from La(III), Eu(III) and Yb(III). In the multi-stages stripping experiments, when the stripping stage number was 3, the effective separation could be achieved by using HCl and H2SO4, since the stripping efficiency reached 80.0% and 100.0% for Th(IV) and U(VI), respectively. Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(VI) and Th(IV) by chelation mechanism. The extraction of multi-elements indicated that U(VI) and Th(IV) could be well separated from the solution which contains all rare earth elements, and the extraction efficiencies of U(VI) and Th(IV) both were close to 100.0%. Based on the above experimental results, a flowchart for efficient separation of U(VI) and Th(IV) from rare earth elements was proposed.

Removal of antibiotics from aqueous solution by semiconductor photocatalysis has aroused much attention, yet developing high-performance visible-light-driven photocatalysts remains a huge challenge. Herein, red phosphorus/borocarbonitride (RP/BCN) heterojunction photocatalysts were fabricated by growing RP nanoparticles on BCN nanosheets through a vaporization–deposition method. A series of characterization techniques verified the formation of the heterojunction and the improved photo-electric properties. Benefiting from the strong optical absorption and effective photocarrier separation, the RP/BCN composites showed significantly enhanced photocatalytic activity towards tetracycline (TC) degradation. After 90 min of visible light illumination, a TC degradation ratio of 73.8% could be achieved over the optimized photocatalyst with an apparent rate constant of 0.0224 min−1, which was almost 7.5 and 13.2 folds higher than that of pristine RP and BCN, respectively. The possible degradation pathways of TC were illustrated by identifying the reaction intermediates using UPLC-MS analysis. Such improvement was ascribed to the formation of a type-II heterojunction with the intimate interfacial contact between RP and BCN, which greatly facilitated the spatial separation of photoinduced electron–hole pairs. Furthermore, the radical capturing experiments ascertained that the generated holes and superoxide radicals dominated TC degradation. Based on these results, a reasonable mechanism was proposed to depict the photocatalytic degradation of TC over RP/BCN heterojunction composites. This work is expected to pave the way for constructing high-efficiency BCN-based heterojunction photocatalysts towards environmental protection.

Radioactive Tc-99 released by nuclear accidents threatens the environment and human health due to its long half-life and strong transportability. A combined strategy synergizing topological construction and chemical modification was proposed for the synthesis of high-performance adsorbents for Re as an analogue to Tc. On the one hand, hierarchically mesoporous SiO2with a fibrous structure (F-SiO2), a peculiar topology integrating wrinkled open mesopores around 12 nm and on-wall mesopores around 3 nm, was adopted as the substrate of adsorbents. The larger mesopores can act as the superhighway for mass transfer, while the abundant smaller mesopores provide numerous adsorption sites. On the other hand, a series of dicationic pyridine (DCP) derivative groups (−Py+CnH2nN+Me3) were designed to functionalize F-SiO2for improving the adsorption performance toward ReO4–anions, the dominating form of Re in aqueous solution. Density functional theory (DFT) calculation combined with batch adsorption experiments revealed that the ReO4–adsorption on −Py+C5H10N+Me3was the most favorable when the length of the spacer between the two positively charged N atoms ranged from 2 to 7 carbons (n= 2–7). However, −Py+C5H10N+Me3exhibited a much slower adsorption rate than −Py+C2H4N+Me3. The stronger interaction between ReO4–and −Py+C5H10N+Me3suppresses the adsorbate diffusion. The two positive charges of −Py+C5H10N+Me3may be perpendicularly distributed, sterically hindering ReO4–transport in smaller mesopores. The longer and flexible carbon chains may be aggregated to form the hydrophobic region, repulsing the hydrated ReO4–anions. Therefore, the efficient and ultrafast Re adsorption was achieved by synergizing the unique topology of F-SiO2and functionalization by −Py+C2H4N+Me3with a shorter spacer and weaker affinity ReO4–. The detailed investigation demonstrated that −Py+C2H4N+Me3possessed exothermic adsorption nature, adequate radiation-resistance, and excellent reusability. Meanwhile, −Py+C5H10N+Me3exhibited stronger salinity tolerance and higher selectivity. The DCP groups are promising in decontamination of radioactive Tc, as they can meet specific requirements by manipulating the length of spacers.

The recovery of precious metals like palladium (Pd) from secondary resources has enormous economic benefits and is in favor of resource reuse. In this work, we prepared a high efficiency pyridine-functionalized reduced graphene oxide (rGO) adsorbent for selective separation of Pd(II) from simulated electronic waste leachate, by one-pot γ-ray radiation-induced simultaneous grafting polymerization (RIGP) of 4-vinylpyridine (4VP) from graphene oxide (GO) and reduction of GO. The poly(4-vinylpyridine)-grafted reduced graphene oxide (rGO-g-P4VP) exhibits fast adsorption kinetics and high maximum adsorption capacity. The adsorption capacity is 105 mg g–1in the first minute and reaches equilibrium within 120 min. The adsorption process follows the Langmuir model, from which the maximum adsorption capacity of Pd(II) is estimated to be 177 mg g–1. We also proved that the adsorption mechanism of Pd(II) on rGO-g-P4VP involves both ion exchange and coordination adsorption by XPS analysis. Most importantly, the loss of oxygen-containing groups due to reduction of GO not only facilitates the separation of adsorbent from aqueous solution but also reduces the electrostatic repulsion toward Pd(II)Cl42–in hydrochloric acid solution, leading to a higher adsorption selectivity of Pd(II) over some common metal cations in electronic waste including Fe(III), Cu(II), and Al(III) compared with poly(4-vinylpyridine)-grafted graphene oxide (GO-g-P4VP) prepared by atom transfer radical polymerization. Other precious metals like Pt(IV) and Au(III) can also be recovered easily and selectively by rGO-g-P4VP. This work demonstrates that rGO-g-P4VP prepared by the facile RIGP is a promising adsorbent for recovery of precious metals from secondary resources like electronic waste leachate.

This work presents the electrochemical properties of gadolinium (Gd), a significant rare earth element in spent nuclear fuel (SNF), in the LiClKCl eutectic. To explore thermodynamic properties of Gd at the liquid gallium (Ga) electrode, experiments were performed both on the inert tungsten (W) and liquid gallium (Ga) electrode at different temperatures in a range from 723 to 823 K, which show that the Gd metal can be oxidized to Gd (III) by exchanging of 3 electrons. Electrochemical techniques including cyclic voltammetry (CV), open circuit potential (OCP), potentiostatic electrolysis and galvanostatic electrolysis were utilized to detect the electrochemical behavior and evaluate standard apparent potential of the Gd(Ⅲ)/Gd couple, and EGd(Ⅲ)/Gd*=−3.456+6.2×10−4T(±0.046)(vsCl2/Cl−)is obtained. In addition, electromotive force (EMF) and coulometric titration were employed to calculate the activity and activity coefficient of Gd in metal Ga. After calculation, the activity is 1.791×10−15at 723 K and function of activity coefficient and temperature is lgγ=3.485−10927/T(±0.0875).

In order to promote the sustainable development of nuclear energy through thorium (Th(IV)) recycling, we synthesized SiO2-coated magnetic functional nanocomposites (SiO2@Fe3O4) that were modified with 2,9-diamide-1,10-phenanthroline (DAPhen) to serve as an adsorbent for Th(IV) removal. SiO2@Fe3O4-DAPhen showed effective Th(IV) adsorption in both weakly and strongly acidic solutions. Owing to its porous structure that facilitated rapid adsorption kinetics, equilibrium was achieved within 5 and 0.5 min at pH 3 and 1 mol L–1HNO3, respectively. In weakly acidic solutions, Th(IV) primarily formed chemical coordination bonds with DAPhen groups, while in strongly acidic solutions, the dominant interaction was electrostatic attraction. Density functional theory (DFT) calculations indicated that electrostatic attraction was weaker compared to chemical coordination, resulting in reduced diffusion resistance and consequently faster adsorption rates in strongly acidic solutions. Furthermore, SiO2@Fe3O4-DAPhen exhibited a high adsorption capacity for Th(IV); it removed Th(IV) through chelation and electrostatic attraction at pH 3 and 1 mol L–1HNO3, with maximum adsorption capacities of 833.3 and 1465.7 mg g–1, respectively. SiO2@Fe3O4-DAPhen also demonstrated excellent tolerance to salinity, adsorption selectivity, and radiation resistance, thereby highlighting its practical potential for Th(IV) removal in diverse contaminated water sources. Hence, SiO2@Fe3O4-DAPhen represents a promising choice for the rapid and efficient removal of Th(IV).

A comparative study using the pulse radiolysis technique was carried out to investigate transient absorption spectra and rate constants for the reactions of (•)OH and N(3)(•) with edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) and its four analogue compounds, 1,3-dimethyl-2-pyrazolin-5-one, 3-methyl-1-(pyridin-2-yl)-2-pyrazolin-5-one, 1-phenyl-3-trifluoromethyl-2-pyrazolin-5-one and 1-(4-chlorophenyl)-3-methyl-2-pyrazolin-5-one. The results showed that, unlike reaction mechanisms previously proposed, the phenyl group of edaravone played an important role in the reaction with (•)OH and OH adducts to the phenyl group were formed. Quantum chemical calculations also strongly supported this attribution and suggested that the most favorable site for attacks by (•)OH is the ortho position of the phenyl group. Moreover, the rate constants for the reactions of edaravone and its analogues towards (•)OH and N(3)(•) were about 8.0 × 10(9), and 4.0 × 10(9) dm(3) mol(-1) s(-1), respectively. Edaravone displayed higher reactivity compared to the others, in contrast to a previous report in which 3-methyl-1-(pyridin-2-yl)-2-pyrazolin-5-one showed the highest reactivity towards (•)OH.

The repair activities of silybin (SLB) and its analogues towards the oxidizing deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts are investigated by pulse radiolytic techniques. On pulse irradiation of nitrous oxide saturated 2.0 mM dGMP aqueous solution containing 0.1 mM silybin at neutral pH, the transient absorption spectrum of the dGMP hydroxyl radical adducts decreases with the formation of the phenoxyl radical of silybin within tens of microseconds, indicating that there is a repair reaction between the dGMP hydroxyl radical adduct and silybin. The rate constant of the repair reaction is calculated to be 1.0 x 10(9) M(-1)s(-1) for silybin. The repair activity of hesperetin (HESP), naringin (NAN) and naringenin (NAR) towards hydroxyl radical adducts of dGMP are also studied.

Time resolved laser photolysis was carried out to study the reaction of NO3 radical toward a series of organic phosphates tributylphosphate TBP and its analogues with different length of side alkyl groups such as CH3, C2H5, C3H7, CHCH32and C4H9in water, acetonitrile, and the mixtures of water and acetonitrile, respectively. For comparison, a similar investigation on SO4−radical was also conducted. The oxidation reaction of NO3 and SO4−radical with the phosphates was attributed to mainly an H-abstract reaction. The kinetics study shows that the rate constants of the reaction between the two radicals and phosphates increase remarkably with increasing of the length of the alkyl groups, e.g.in the case of NO3 radical in acetonitrile, the rate constant increases by almost 4 orders of magnitude from TMP –CH3 to TBP –C4H9. The composition of the solvent also greatly affects the reactivity but it exhibits an opposite effect of the two radicals, the rate constant of NO3 increases with the mole fraction of acetonitrile while that of SO4−decreases. The present study would be helpful for understanding the mechanism of deterioration of TBP in the Purex process.

Pulse radiolysis studies with aqueous benzophenone solutions were performed over the range 25–400 °C, including conditions beyond the critical point of water. The addition of e_aq− to benzophenone forms either ketyl anion in alkaline solutions or neutral ketyl radical in acidic/neutral solutions. Although both have an intense and sharp absorption band in the UV region and a weak but broad band in the visible region, their spectra are clearly different. The peak of the visible band is at 545 nm for the neutral ketyl radical and 610 nm for the anion at room temperature. With increasing temperature, the absorption peak of the ketyl radical shifts to a shorter wavelength while that of the anion shifts to a substantially longer wavelength. The decay of the ketyl radical is not monotonically temperature-dependent: its rate constant (2k/ɛ) increases with temperature up to 100 °C and then decreases at higher temperatures. The rate constant for the addition of e_aq− to benzophenone can be considered to be diffusion controlled and the Arrhenius plot can be fitted with a curved line. The temperature dependence of the rate constant for the reaction of e_aq− with proton was determined up to 400 °C by the competition method using benzophenone as the reference solute. It was also found that the addition of OH&z.rad; radical to benzophenone forms a transient species with a strong absorption band centered at 380 nm and the peak seems to be slightly blue-shifted with temperature. The decay of this species increases rapidly with temperature, indicating the enhanced conversion to stable products at high temperatures.

Reactions of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) with deoxyguanosine monophosphate (dGMP) hydroxyl radical adducts were investigated by pulse radiolysis technique. Edaravone was found to reduce the dGMP hydroxyl radical adducts through electron transfer reactions. The rate constants of the reactions were greater than 4 × 108 dm3 mol−1 s−1 and similar to those of the reactions of ascorbic acid, which is a representative antioxidant. Yields of single-strand breaks, base lesions, and abasic sites produced in pUC18 plasmid DNA by gamma ray irradiation in the presence of low concentrations (10–1000 μmol dm−3) of edaravone were also quantified, and the chemical repair activity of edaravone was estimated by a method recently developed by the authors. By comparing suppression efficiencies to the induction of each DNA lesion, it was found that base lesions and abasic sites were suppressed by the chemical repair activity of edaravone, although the suppression of single-strand breaks was not very effective. This phenomenon was attributed to the chemical repair activity of edaravone toward base lesions and abasic sites. However, the chemical repair activity of edaravone for base lesions was lower than that of ascorbic acid.