HNO3 Medium Research Articles

Newly synthesised diglycolamide functionalised silica gel with terminal 2-ethylhexyl alkyl chain, Silica-DGA (2EH) having high ligand density for adsorption of trivalent actinide and lanthanide from acidic medium

A novel diglycolamide resin with 2-ethylhexyl terminal alkyl chain functionalised to silica gel was synthesised and characterised by ATR-FTIR, SEM, TG/DSC, &13C (CP/MAS) solid state NMR techniques. Effective functionalization of the organic ligand upon silica gel was confirmed from the two carbonyl stretching frequencies at 1735 cm−1 and 1619 cm−1 in the FTIR spectrum and carbonyl carbon atom signal at 170 ppm in 13C (CP/MAS) solid state NMR spectrum. Thermo gravimetric measurement showed 17.3 ± 0.2 % (W/W) weight loss corresponding to the ligand loading value of 425 µmol/g. The resin showed very high uptake of trivalent lanthanide and actinide ions from 4.0 M HNO3 medium and very low distribution of Cs & Sr; Kd ∼ 1.1×103 mL/g for Am(III), ∼ 1.41×103 mL/g for Eu(III), ∼2.5 mL/g for Sr and 1.53 mL/g for Cs. FTIR spectroscopic study of the Eu3+ adsorbed resin showed single carbonyl stretching frequency at 1654 cm−1, instead of the two carbonyl stretching frequencies in fresh silica-DGA(2EH) resin indicating complexation through carbonyl oxygen. Very low Kd of ∼1.2–5.1 mL/g for lanthanides/actinides from 4.0 M HNO3 containing water soluble DGA namely N, N, N, N, Tetraethyldiglycolamide (TEDGA) in the concentration range 0.3–0.1 M indicates 99 % back adsorption feasibility.

Modified Ordered Mesoporous Carbons for Cr(VI) Removal from Wastewater.

The pristine CMK-3 carbon was ozonized and then chemically modified by the Zr and Fe compounds. The synthesized carbonaceous materials were characterized with physicochemical methods. The obtained carbons had a high specific surface area (ca. 800 m2 g-1) and an acidic surface. The Cr(VI) adsorption properties of the oxidized and Zr/Fe-modified carbon were studied. The highest static adsorption capacity towards Cr(VI) ions was evaluated for Zr/Fe-modified carbon (50.1 mg g-1) at pHeq = 5.8 after 240 min. The Elovich and Freundlich theoretical models were well fitted to the Cr(VI) adsorption kinetic and isotherm data on the Zr/Fe-modified CMK-3-type carbon. The leading Cr(VI) adsorption mechanism acting on the Zr/Fe-modified carbon was probably based on the redox reactions between Cr(VI) and the carbonaceous surface. Electrostatic attraction and surface complexation processes could also occur during Cr(VI) adsorption in the studied system. The effect of the competitive anions on the concentration level, such as in the galvanic wastewater for Cr(VI) adsorption onto chemically modified carbon, was negligible. The HCl and HNO3 media were insufficient for the Zr/Fe-modified carbon regeneration after Cr(VI) adsorption. The Zr/Fe-modified carbon was successfully applied for the efficient (>90%) Cr(VI) removal from the model galvanic wastewater.

Synergistic shielding of copper from nitric acid corrosion: Unveiling the mechanisms through electrochemical, characterization, and computational insights with 2-Hydroxybenzaldehyde oxime

Schiff-base metallic complexes have garnered considerable attention due to their unique attributes and broad applications across various sectors. Among these, organic Schiff-type bases have emerged as effective agents for mitigating corrosion in challenging environments. This study employs a comprehensive approach to assess the efficiency of 2-Hydroxybenzaldehyde oxime (HOBAO) in preventing copper corrosion. Synthesis and characterization of the HOBAO compound were conducted using FTIR and NMR (1H and 13C) analyses, confirming successful production. The inhibition performance on copper was investigated in a 1 M HNO3 medium utilizing gravimetric, electrochemical impedance spectroscopy, and potentiodynamic polarization techniques. Our findings reveal that HOBAO, at a concentration of 300 ppm, significantly inhibits corrosion, achieving rates of 82.00 %, 93.30 %, and 91.80 % for weight loss, polarization, and EIS analyses, respectively. SEM, EDS, and UV investigations provide evidence of the inhibitor's adsorption onto the copper surface, resulting in a smoother and more uniform appearance with minimal damage. Theoretical and practical results were meticulously compared, demonstrating that HOBAO acts as a mixed-type inhibitor with heightened effectiveness at higher concentrations of 300 ppm. SEM observations offer compelling evidence of inhibitor molecules exhibiting robust resistance against HNO3 attacks at the metal boundaries. Molecular modeling, including DFT and MD simulation studies, further support these findings, suggesting that the oxygen heteroatoms of HOBAO serve as favorable sites for molecular adsorption onto the copper surface. In conclusion, our comprehensive findings highlight HOBAO's potential as a promising copper corrosion inhibitor, particularly in environments containing nitric acid.

Collaborative extraction of valuable components from saprolitic laterite ore through two-stage nitric acid leaching

Saprolitic laterite ore (SLO) is an important Ni resource that also contains high Mg and a small amount of Sc, but traditional extraction techniques cannot achieve the comprehensive utilization of valuable components, especially Mg and Sc. In this work, a new process was proposed to treat SLO through the application of an HNO3 medium. First, E-pH analysis showed that serpentine and part of iron oxide are easily destroyed, and Ni and Co embedded in silicate and Fe-bearing minerals can be also leached. Subsequently, Ni, Mg, Co, and Sc can be efficiently extracted under the HNO3 concentration of 240 g/L, 90 ℃, L/S of 5:1, 2 h, and 200 r/min. Relevant characterization confirmed that serpentine and goethite were almost completely dissolved after leaching. However, magnetite and its alteration intermediates have relatively stable properties and cannot be destroyed. To reduce acid consumption, the leach liquor was supplemented with HNO3 for two-stage leaching. Efficient extraction of valuable metals can be achieved again with the supplemented HNO3 concentration of 192 g/L. A two-stage leaching process can save 120 kg HNO3/t-ore. Finally, a technical route including two-stage HNO3 leaching, adding MgO to adjust pH, and pyrolysis of Mg(NO3)2 to regenerate HNO3 and MgO was suggested.

Toxicity of REEs, Th, and U: A Biodisponibility, Cytotoxicity, and Bioaccumulation Assessment in Marine Sediment.

In this work, bioaccessibility tests for rare earth elements (REEs), Th, and U in marine sediment were carried out, in addition to complementary tests for cytotoxicity and bioaccumulation for the elements La, Ce, Eu, and Gd. The evaluation of human health risk through dermal absorption and oral ingestion was performed using the hazard quotient (HQ). According to the gastric digestion simulation (SBET), it was observed that the elements Ce and Nd exhibited higher absorption capacities in the human body (> 2µgg-1). La and Sc presented intermediate concentrations (close to 1µgg-1), while the remaining elements displayed concentrations below 0.5µgg-1. In the gastrointestinal digestion extraction stage (PBET), all the elements maintained a similar absorption capacity to that observed in SBET, except for the absorption of Y which increased. The results of the bioaccumulation test conducted with fibroblast cells (L929) indicated that La and Eu had a 25% probability of intracellular accumulation. The cell viability test, with exposure to a standard REEs, Th, and U solution in 2% v v-1 HNO3 medium (until 100μgmL-1) and an aqueous solution of La2O3, Gd(NO3)3, Ce(NO3)3, and Eu2O3 (until 1000μgmL-1), did not demonstrate cytotoxic effects on fibroblast cells. Considering the ingestion hazard quotient (HQing) and dermal hazard quotient (HQderm) obtained, it was suggested that there is no significant risk of non-carcinogenic effects (< 1). However, they had higher HQing values compared to HQderm, indicating that REEs pose more significant risk to human health through oral ingestion absorption than dermal absorption.

Investigation on para‐aramid fiber‐reinforced poly‐ether ketone‐ketone high‐performance composite for ballistic application

AbstractThis investigation highlights the performance of high‐performance polymeric composite for ballistic application. Therefore, reinforcement of para‐aramid fiber in poly‐ether‐ketone‐ketone (PEKK) resin film has been made. The surface of PEKK and para‐aramid fiber was modified by low‐pressure plasma to enhance the surface energy of the polymeric film and reinforcement fiber. The polymeric composite was manufactured by compression molding with a pressure of 2 bar, temperature of 310°C with holding time of 15 min. Due to low‐pressure plasma treatment of PEKK film and para‐aramid fiber, the tensile strength of the composites increases considerably. In the accelerated aging test, the tensile specimens are dipped into concentrated HNO3 and NaOH medium for 15 days. It is observed that there is a decrease in tensile strength. The ultimate tensile strength (UTS) of the virgin specimen was compared to the environmentally aged for 15 days and in this case, also there was a decrease in tensile strength. Two types of composite panels were made (i) 25 layers of PEKK film with 24 layers of para‐aramid fabric and (ii) 45 layers of PEKK film with 44 layers of para‐aramid fabric with 15 mm × 15 mm. The composite panel was tested with four 9 mm handgun bullets fired from a distance of 5 meters with a speed of 430 m/s. In the case of 25 layers of PEKK film with 24 layers of para‐aramid fabric, the composite failed under ballistic test, however, in the case of 45 layers of PEKK film with 44 layers of para‐aramid fabric, the composite was successful under ballistic test.Highlights Film stacking method of PEKK and Aramid fiber. Ballistic composite panel with layers of PEKK and Aramid fiber. Enhancement of mechanical properties of the composite panel with plasma surface treatment. Ballistic testing of composite panel.

Multistage hydrometallurgical process for enhanced recovery and individual separation of Nd and Pr from NdFeB magnet scrap

This study introduces a multistage hydrometallurgical process designed for the recovery and individual separation of Nd and Pr from NdFeB magnet scrap. Following demagnetization, the magnet underwent crushing, grinding, and leaching using a sulfuric acid solution. The pH of the resultant leachate was subsequently adjusted to 1.2 using a NaOH solution, leading to the precipitation of Nd and Pr as sodium double sulfates. The produced double sulfate was then mixed with a saturated NaOH solution, resulting in the formation of rare earth hydroxide. The hydroxide was further decomposed into oxides (REO) after calcination at 500°C. The REO was dissolved in hydrochloric acid and nitric acid solutions to investigate the individual separation of Nd and Pr using the D2EHPA–TOA extractant system and compare the results with D2EHPA-only system. It was concluded that the extraction mechanism of D2EHPA–TOA system is highly dependent on the acidity of the solution, with TOA having a synergistic effect on the REE extraction when pH &gt; 3, and an antagonistic effect when pH ≤ 3. In terms of extraction efficiency, both extractant systems demonstrated efficiency levels exceeding 99% when the pH was ≥2, with similar behavior when extraction was performed in HCl and HNO3 media. Although both extractant systems yielded unsatisfactory outcomes in the separation of Nd and Pr, a marginal improvement was observed with the incorporation of TOA into the extractant system. This observation implies the potential of exploring analogous combinations in future studies.

Highly selective separation of tetravalent plutonium from complex system with novel phenylpyridine diamide ligands.

In this study, three phenylpyridine diamide ligands, namely, 2,2'-((pyridine-2,6-diylbis(3,1-phenylene))bis(oxy))bis(N,N-diethylacetamide) (PPEA, L1), 2,2'-((pyridine-2,6-diylbis(3,1-phenylene))bis(oxy))bis(N-ethyl-N-phenylacetamide) (PEPA, L2), and 2,2'-(((4-phenylpyridine-2,6-diyl)bis(3,1-phenylene))bis(oxy))bis(N,N-dioctylacetamide) (PPOA, L3), were synthesized and explored for the solvent extraction of Pu(iv) in a HNO3 medium using 1-(trifluoromethyl)-3-nitrobenzene as the diluent. The effects of HNO3 concentration, extractant concentration, and temperature on the Pu(iv) extraction efficiency were studied. All three extractants displayed high selectivity for Pu(iv) over other metals such as U(vi), Np(v), Am(iii), and various fission elements. At 3 M HNO3, the distribution ratio for Pu(iv) reached 27.18, in contrast to 1.11, 0.3, and 0.03 for U(vi), Np(v), Am(iii), respectively. Slope analysis and UV titration revealed the formation of 1 : 1 Pu(NO3)4/ligand complexes during extraction. The extraction reactions had negative Gibbs free energies, indicating the spontaneous nature of Pu(iv) extraction at room temperature. Furthermore, the extractants demonstrated good stripping ability and reusability, and their radiolytic stability was reasonable up to an absorbed dose of 100 kGy, underscoring their potential for practical applications. Overall, this study broadens our understanding of actinide-diamide ligand coordination and actinide chemistry during coordination, paving the way for the design and synthesis of new extractants.

Spent Foundry Sand (SFS)-Gum Arabic Admixed Concrete: X-Ray Diffraction, Microstructure, Acid and Sulphate Analysis

Concrete sustainability studies have opened opportunities in the use, and understanding of the characteristics, and performances of supplementary cementing materials (SCMs) using modern methods of investigation. The effect of spent foundry sand (SFS) with replacement levels of 10 and 20 % by wt. % of the fine aggregate (FA), 0.5 % dosage of gum Arabic (GA) on concrete, and its performance in acid and sulfate medium are presented. The investigations are carried out using crushed compressive strength test samples, prepared using a mix of 1: 3: 5, and cured for 28 days in water. The XRD analysis studied the crystalline and mineral phases of the concrete, the SEM-EDS analysis, the morphology (texture) and structural characteristics of the concrete samples, while the Acid and Sulphate analysis to understand the effects of these media on SFS-GA concrete. The results show that SFS and GA have acceptable characteristics for quality concrete. The XRD and SEM results show marked transformations in the crystalline and mineral phases, the morphology and structural characteristics of the hydration products of the concrete samples, because of the addition of GA and SFS, respectively. The performances of the concrete samples with GA and SFS, in the HNO3 medium show better performances than in the H2SO4 medium and better performances in Na2SO4 than in the MgSO4 medium with acceptable characteristics for quality concrete. The XRD and SEM results show marked transformations in the crystalline and mineral phases, the morphology and structural characteristics of the hydration products of the concrete samples, because of the addition of GA and SFS, respectively. The performances of the concrete samples with GA and SFS, in the HNO3 medium, show better performances than in the H2SO4 medium and better performances in Na2SO4 than in the MgSO4 medium

Corrosion and contamination study of nuclear plant steel in HNO3‑Based waste solution with Strontium under nuclear processing environment

Structural material like stainless steels (SS) was observed to be heavily contaminated by radioactive metal ions during the operation of radioactive liquid waste. Their safe, secure and environment friendly management is really challenging to nuclear industry. If the chemical behavior of steel corrosion could be determined, effective decontamination as well as successful decommissioning process could be planned. So far, in presence of radioactive metal ions, the severity of the steel corrosion, adsorption of Sr on steel surface under plant operating condition is unexplored. To study all these unexplored phenomena, experiments were carried out to understand the chemical behavior of contamination on SS304L under the exposure of Sr at 70 °C, since Sr is one high yield fission product, most heat emitting and long half-life. To explore the Sr adsorption behavior on plant structural materials (like SS), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/ EDX) analyses were carried out before and after the exposure under HNO3 medium at 70 °C for 3 months. The elemental compositions of the SS surface were determined before and after the exposure. To establish the Sr adsorption on SS metal X-ray elemental mapping of the exposed SS was carried out. The kinetics of the corrosion of the SS was measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). Grazing incidence X-ray diffraction (GI-XRD) analysis was carried out to identify possible formation of strontium chromate was observed. Finally we conclude the corrosion behavior and mechanism of contamination by Sr on SS.

Uptake behavior of arsenic and selenium with sulfur-based extraction chromatography resins in HCl and HNO3 media

Uptake behavior of arsenic and selenium with sulfur-based extraction chromatography resins in HCl and HNO3 media

Selective capture of uranium and zirconium from strong HNO3 solution by ethenylphosphonic acid copolymerized polymer

The nuclear fuel rod contains mainly uranium (U) as the fuel and zirconium (Zr) as the cladding material. Improper disposition of the dissolved solution of the exhausted fuel rod releases radioactive acidic aqueous solution, which is a waste of U and Zr resources and also poses a great threat to the environment and living beings. The present work aims to selectively capture U and Zr from a 4 mol/L HNO3 aqueous solution in the presence of competing ions including La, Zn, Cd, Gd, Ce, Sr, Mn, Cu and Ba. Trimethylolpropane trimethacrylate (TMPTMA) copolymerized with ethenylphosphonic acid (EPA). TMPTMA improved the mesoporous character and adsorption ability of the adsorbent towards U and Zr. The synthesized polymer adsorbent was characterized by SEM, EDS, FT-IR, TGA, XRD, BET, XPS, and NMR to study the adsorption. The results indicated that the EPA-POP-2 adsorbent showed considerable adsorption capacity towards U(VI) (374.1 mg g−1) and Zr(IV) (217.4 mg g−1) in a strong HNO3 medium. Langmuir isotherm model fitted well to the experimental data, indicating that the monolayer adsorption process was dominating. The fitted pseudo-second-order (PSO) model represents that the adsorption mechanism is chemisorption. XPS, FT-IR, and DFT calculation results revealed that this adsorption capacity towards U and Zr was because of the P = O ligands present in the adsorbent. Van’t Hoff graph for U and Zr were also drawn to calculate the enthalpy, entropy, and Gibb’s free energy of the reaction. The reusability test showed that the adsorption capacity of synthesized adsorbent was high enough towards the U and Zr even after five consecutive cycles of adsorption and desorption.

A new strategy for facile and rapid separation of astatine-211 from nitric acid medium

Developing fast and efficient separation avenues can promote either fundamental study or practical application of astatine-211(211At). This work presents a new solid-phase extraction (SPE) separation strategy based on functional resin for recovering 211At from the irradiated bismuth (Bi) target mildly and rapidly, without switching HNO3 medium into HCl system. Four functional resins containing acyl-resin, thioether, sulfonate- and sulfonate-groups had been prepared via Friedel-Crafts acylation and alkylation reactions successfully, and subsequently characterized by FTIR, EA, SEM etc. Acyl-resin from these functional materials have shown good retention towards 211At but low binding affinity to all possible metal impurities (Zn2+, Cu2+, Ga3+and Bi3+) in simulated separation experiments. Static batch sorption experiments indicate that the pseudo-second-order kinetic model is more suitable for describing the binding behavior of 211At on Acyl-resin. This reveals that chemisorption dominates the reaction between the target radionuclide and functional material. During several practical separations in medically-used scale, over 98.5 % of 211At can be well retained on SPE column with metal impurities removed in the process of loading target solution and removing non-target radionuclides. More importantly, 60.03 %∼79.05 % of 211At on the Acyl-resin SPE column is recoverable by NH2OH-NH3·H2O-CH3OH elution process, and over 60 % of the radioactivity distributes in volatile organic solvent (CH3OH). The whole SPE separation process can be completed within 20 min, giving 211At product with high radionuclidic purity (≥ 99 %), low metal impurities (Bi3+≤ 17.37 μg and Cu2+≤ 2.91 μg) and high radiolabeling availability. This work implies that acyl-groups can act as potential binding motifs not only for developing new 211At separation methods but also designing bifunctional conjugate agents for astatinated compounds based on coordination bonds.

Recycle graphite from spent lithium-ion batteries for H2O2 electrosynthesis.

On-site H2O2 synthesis via the two-electron route oxygen reduction reaction for environmental remediation is attractive. This work offers a novel strategy for both spent graphite recovery and H2O2 electrosynthesis catalyst preparation. The graphite is directly recycled from spent lithium-ion batteries to an H2O2 electrosynthesis catalyst. From the view of sustainable development and environmental protection, the H2O2 electrosynthesis catalyst prepared using spent graphite is eco-friendly and cost-efficient. The surface functional groups of the recycled graphite are finely tuned by the HNO3 medium to induce -COOH and C-O-C groups. The activated graphite exhibits high H2O2 activity and selectivity, compared to the raw spent graphite. The activated graphite can achieve an H2O2 Faradic efficiency of about 80%. The activated graphite has a good prospect for T-acid wastewater treatment as the H2O2 generation catalyst. Almost 92% of chemical oxygen demand can be removed.

Highly selective separation of plutonium using a mono-amide-based supported liquid membrane

ABSTRACT A monoamaide-functionalized supported liquid membrane was developed and employed for efficient and selective solid phase separation of Pu(IV). The membrane was prepared in a simple, one-pot process and was characterized for its homogeneity, stability and hydrophobicity. Various membrane parameters like sorption efficiency, sorption kinetics, sorption isotherm and equilibrium uptake capacity were studied for Pu(IV) in nitric acid medium. Langmuir and Freundlich isotherm models were employed for understanding the sorption mechanism of the membrane. Lagergren first-order kinetics and pseudo-second-order kinetics were applied to understand the plutonium sorption kinetics. The equilibrium sorption capacity of the membrane was found to be 27.18 mg g−1and the sorption kinetics followed a pseudo-second-order reaction with rate constants of 1.129 g mg−1 min−1 for Pu(IV). Stripping of Pu from the membrane was also studied to check the regeneration and reusability of the supported liquid membrane. The membrane was found to be very selective toward Pu(IV) in 4 M HNO3 medium, with separation factors 42 and 75 with respect to Am(III) and U(VI), respectively.

Utilizing deep eutectic solvent for facile, selective and sustainable sequestration of plutonium

In the recent surge of green and cheap energy for future generation; nuclear industry is going to play a pivotal role and reprocessing of nuclear fuel through safe and systematic approach is the key. In that direction recent literature has shown that there is lack of better and improved methods towards efficient extraction of highly radiotoxic and hazardous plutonium from nuclear waste. Herein, we have utilized a greener and cost effective indigenously synthesized deep eutectic solvent (DES) for the selective extraction of plutonium from (Am, Pu, U) waste. The maximum D value achieved for Pu was 67.42 at 5 mol L−1 HNO3 media and the equilibrium uptake capacity was found to be 107.28 ± 5 μg of Pu/g of C12DES. This was followed by solidified floating organic drop micro-extraction (SFODME) technique for its quantification. High radiation stability of this DES (upto 750 kGy) highlighted its great potential in nuclear fuel reprocessing. Several other reprocess parameters were studied and optimized such as DES volume, alkyl chain length attached to hydrogen bond acceptor (HBA), actinide concentration and speciation and its acidity to achieve best extraction of plutonium ion form the waste stream. Regeneration capability and reusability of the DES employing stripping agents gave encouraging results as 95% of Pu could be stripped in a single cycle using 1 M hydroxylamine hydrochloride as the stripping agent. The developed method was applied for recovery and quantification of Pu from real samples, viz. (U,Pu) Carbide fuel solution, radioactive research waste and synthetic dissolver solution. We believe this work is a way forward in resolving a variety of issues that exist in health physics and reprocessing laboratories of nuclear installation pertaining to selective and efficient extraction of Pu (IV).

Unfolding the extraction and coordination behaviors of trivalent lanthanides by two novel cyclohexyl o-oxydiamides ligands

In this work, two cyclohexyl o-oxydiamides ligands: 2,2′-(cyclohexane-1,2-diylbis(oxy))bis(N,N-dioctylacetamide)(L1: Octy-CDA) and 2,2′-(cyclohexane-1,2-diylbis(oxy))bis(N,N-bis(2-ethylhexyl)acetamide) (L2: 2-ethylhexyl-CDA) have been synthesized to study the extraction and coordination behaviors with trivalent lanthanides in HNO3 media. The extractability of ligands increases with the atomic number of lanthanides increasing. The straight alkyl chain demonstrated better extraction ability than the branched chain, which was also most likely caused by the impact of steric hindrance effects. Coordination chemistry studies were evaluated through slope analysis, ultraviolet–visible spectroscopy, nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, Fourier transform infrared spectroscopy and fluorescence, and all the results indicating that lanthanides with the above ligands can form both 1:1 and 1:2 metal/ligand complexes during extraction, and two ligands are tetradentate ligands. Density functional theory (DFT) calculations shed light that the interaction between the carbonyl oxygen atom and Eu(III) in the ligand is much stronger than that of the ether-bonded oxygen atom, and the analysis of the bond-forming properties shows that the stability of the 1:2 complex is stronger than that of the 1:1 complex. This work enriched the coordination study of diamide with lanthanides, which is expected to improve our understanding of the chemical properties of lanthanides during coordination and provide new insight into the design and synthesis of novel ligands.

Efficient and selective removal cesium from strong acidic medium by novel butenyl-calix [4]-crown 6 functionalized millimeter-sized mesoporous carbon spheres sorbent: Experimental and theoretical study

Eliminating the radioactive Cesium from high level waste (HLW) is crucial to avoid the radioactive pollution. Herein, a novel carbon-based recognizable material, butenyl-calix [4]-crown 6 functionalized millimeter-sized mesoporous carbon spheres (ButC[4]C6/MMCs), was prepared via “interpenetrating functionalization” strategy to remove Cs(I) from strongly acidic solution. ButC[4]C6 supramolecular was incorporated into the channels of MMCs and polymerized to form cross-linked IPN structure. The morphology and microstructure of the final product were characterized by SEM, NMR, FT-IR, TG-DSG and N2 adsorption–desorption isotherms. The adsorption behaviors of Cs(I) onto ButC[4]C6/MMCs were systematically investigated. ButC[4]C6/MMCs displayed an astonishing adsorption capacity (55.22 mg g−1), high selectivity and reusability at a low dose (2.0 g L-1) under 3.0 M HNO3 medium. Pseudo-second-order kinetic model, Brouers-Sotolongo model and thermodynamic study revealed that the adsorption process is a spontaneous endothermic chemical and heterogeneous adsorption process. Theoretical study revealed that the Cs(I) was tightly fixed in the calixarene cavity via cation-π interaction. This work proposes an effective approach to selectively remove Cs(I) from HLW by skillfully coupling supramolecular recognizer with millimeter-sized porous material to address radioactive pollution issue.

A Novel Type of Tetradentate Dipyridyl-Derived Bis(pyrazole) Ligands for Highly Efficient and Selective Extraction of Am3+ Over Eu3+ From HNO3 Solution

ABSTRACT The extraction of Am3+ and Eu3+ with 6,6’-bis(5-alkyl-1H-pyrazol-3-yl)-2,2’-bipyridine (BPzBPy, alkyl = i-Bu, n-Bu, n-Oct) from HNO3 medium and the complexation of BPzBPy with Eu3+ were investigated. By using meta-nitrobenzotrifluoride (F-3) as a diluent, iBu-BPzBPy ligand in combination with 2-bromohexanoic acid was able to extract Am3+ over Eu3+ with the nature of significantly high efficiency, relatively fast extraction kinetics, and easy stripping. Slope analysis showed the formation of a 1:2 metal/ligand extraction species. The analyses of electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared (FT-IR) and time-resolved laser fluorescence spectrum (TRLFS) revealed that the composition of the extracted complex was [Eu(H2O)L2]A3 (L = ligand; HA = 2-bromohexanoic acid). The complexation of iBu-BPzBPy ligand with Eu3+ was an enthalpy-driven spontaneous, exothermic, and entropy-decreasing process. Besides, the complex stability constants were also obtained via UV–vis spectrophotometric titration. Combining the results of solvent extraction and complexation studies, a cation exchange extraction model was also proposed.

Simultaneously efficient adsorption and highly selective separation of U(VI) and Th(IV) by surface-functionalized lignin nanoparticles: A novel pH-dependent process.

The simultaneous removal and selective separation of U(VI) and Th(IV) via adsorption remain challenging due to their strong mobility, reactivity, and similar chemical properties. Thus, a surface-functioned lignin nanoparticle (AL-PEI) was synthesized to adsorb U(VI)/Th(IV) in a unitary system via a pH-dependent process. In alkaline solution, AL-PEI exhibited excellent adsorption performance, and the maximum adsorption capacities for U(VI) and Th(IV) reached 392 and 396mg/g, respectively. Discrepantly in acidic solution, the adsorption performance of AL-PEI for U(VI) could still reach a high capacity (332mg/g), whereas highly limited adsorption capacity (less than 40mg/g) for Th(IV) was obtained, and the separation factor of U(VI) from U(VI)-Th(IV) matrix significantly reached 6662 in 3M of the HNO3 medium. The simultaneously efficient adsorption in alkaline solution and highly selective separation performance in acidic solution of AL-PEI also showed excellent anti-ions interference capacities, high reusability, and strong stability. This study is the first to apply lignin fabricating radiation-resistant adsorbent material, and the adsorbent displays good performance for U(VI)/Th(IV) removal and selective separation via a novel pH-dependent process, which is important to the green and sustainable development of nuclear energy and environmental protection.