Recent Progress in Functional Nanomaterials towards the Storage, Separation, and Removal of Tritium

Eco-friendly synthesis of rod-like hydroxyapatite on spherical carbon: A dual-function composite for selective cobalt removal and enhanced oxygen evolution reaction

The presence of cobalt ions (Co2 +) and radionuclides (60Co) in industrial and radioactive effluents pose serious threats to environmental ecosystems and human health. This paper presents the synthesis of dual-functional hydroxyapatite (HAp)-incorporated spherical carbon (SC) composite (HAp/SC) towards the selective adsorption of cobalt from wastewater and the utilization of the Co2+-adsorbed HAp/SC composite (Co2+- HAp/SC) as an electrocatalyst for the oxygen evolution reaction (OER). Herein, we prepared a series of HAp/SC composites by varying HAp weight percentages of 10 %, 20 %, 30 %, 40 %, and 50 %. Among the prepared composites, 20 wt% HAp/SC exhibited the highest Co2+ adsorption capacity of 111.03 mg g⁻1 which was higher than those of individual HAp and SC. The excellent Co2+ adsorption performance of 20 wt% HAp/SC composite might be due to the synergistic effects of phosphate groups in HAp, which selectively capture Co2+, along with large number of surface -OH and -COOH functional groups of SC through electrostatic, ion-exchange, and surface complexation mechanisms. Batch adsorption experimental data fit well with the Langmuir model (R2 = 0.97) suggesting monolayer adsorption of Co2+ onto the adsorption sites of HAp/SC. Also, the 20 wt% HAp/SC composite exhibited rapid Co2+ adsorption kinetics and effectively describing the pseudo-first-order model (R2 = 0.97) with a rate constant (k1) of 0.14893 min-1. Additionally, the Co2+-HAp/SC composite demonstrates potential as an electrocatalyst for the oxygen evolution reaction (OER), exhibiting an overpotential of 380 mV and a Tafel slope of 39.3 mV dec-1. This dual functionality suggests the HAp/SC composite for the cobalt removal, with the resulting product serving as an electrocatalyst for OER.

Construction of Pt─O Sites on Pt Nanoclusters in Silicalite-1 Zeolite for Efficient Catalytic Oxidation of Hydrogen Isotope Gases

The construction, use, and maintenance of tritium-related equipment will inevitably produce tritium-containing radioactive waste gas, and the production of efficient catalysts for tritium removal remains a difficult problem. Herein, silicalite-1 zeolite with entrapped Pt nanoclusters is skillfully post-oxidized at an appropriate temperature, building highly active Pt─O sites on the nanoclusters to achieve efficient oxidation of hydrogen isotopes at low temperatures. The designed Pt─O sites can directly participate in the oxidation reaction of hydrogen isotopes. Compared to the case without Pt─O sites, the presence of these sites significantly reduces the reaction energy barrier to 0.55 eV, enabling the catalyst to achieve a hydrogen conversion rate of 99% at a low temperature of 40 °C. Specifically, the O atoms consumed by the Pt─O sites in the reaction are replaced by O2 gas and this cycle repeats, which is consistent with the Mars-van Krevelen (M-K) theory. This ensures efficient catalytic oxidation of hydrogen isotopes, and provides an astonishingly high conversion rate of 99% in the nearly 34 days restart performance test. The results of this study provide insights into the strategic design of efficient catalysts for hydrogen isotope oxidation.

Poisoning Mechanism Map for Metal Hydride Hydrogen Storage Materials

The effective utilization of hydrogen storage materials (HSMs) is hindered by impurity gas poisoning, posing a significant challenge for large-scale applications. This study elucidates the poisoning mechanisms of various impurities gases (CO, CO2, O2, Ar, He, CH4, N2) on ZrCo, Pd, U and LaNi5. Impurities gases are categorized into active and inactive types based on their effecting behaviors and mechanisms on the hydrogenation of HSMs. During the hydrogenation process, active impurities chemically poison the hydrogenation reaction by limiting hydrogen absorption at interface, while inactive impurities physically hinder hydrogenation reaction by impeding hydrogen diffusion in hydrogen-impurity mixed gas. In situ Scanning Tunneling Microscope clarifies these behaviors, and a novel criterion based on hydrogen spontaneous dissociation energy is introduced to explain and predict impurity-substrate interaction characteristics. The novel findings of this work provide a comprehensive framework for designing long-lived HSMs with poisoning resistance, guiding the development of more resilient hydrogen storage systems.

Multivalent Pt/Ti3C2Tx Nanocomposite-Based Immunochromatographic Sensor for Colorimetric/Temperature/Pressure Trimodal Detection

Multimodal immunochromatographic sensors (ICSs) have acquired extensive attention since they not only provide reliable results by comparing the different output signals but also flexibly respond to various application environments. Herein, an ICS with triple signal outputs including colorimetry, temperature, and pressure was developed for sensitive detection of chlorothalonil. The multivalent Pt/Ti3C2Tx nanoparticles as signal tags were facilely synthesized by loading PtNPs onto single-layer Ti3C2Tx nanosheets with high surface area. The acquired Pt/Ti3C2TxNPs accelerated the rate-limiting step of the aerogenesis reaction of H2O2 for producing intensive pressure signals due to their significant catalase-mimic activity. Meanwhile, they showed desirable photothermal conversion efficiency in the near-infrared region for producing significant temperature signals. Furthermore, their deep color also allowed facile colorimetry by using the naked eye. Based on a competitive immunoassay, chlorothalonil was detected as a model analyte on this trimodal ICS platform. The detection limits for pressure, temperature, and colorimetric modes were 0.04, 0.09, and 5 ng mL-1, respectively. The recoveries for detecting chlorothalonil supplemented in Astragalus and Honeysuckle with pressure mode were 84.0-110% and 108-114%, respectively. Therefore, the ICS presented a portable, sensitive, accurate, and flexible multimodal strategy suitable for point-of-care testing.

Efficient sequestration of cesium ions using phosphoric acid-modified activated carbon fibers from aqueous solutions

In this study, acid-modified activated carbon fibers (ACF-Ps) were synthesized by phosphorylation. Three different types of ACF-based adsorbents functionalized with PO43-, P2O74-, or P3O105- ions, namely, ACF-P1, ACF-P2, and ACF-P3, were prepared by phosphorylating ACF with trisodium phosphate (Na3PO4), sodium dihydrogen pyrophosphate (Na2H2P2O5), and sodium tripolyphosphate (Na5P3O10), respectively, and utilized as adsorbents to remove cesium ions (Cs+) from aqueous solutions. Among the tested adsorbents, ACF-P3 exhibited the highest Cs+ adsorption capacity of 37.59 mg g-1 at 25 °C and pH 7 which is higher than that of ACF (5.634 mg g-1), ACF-P1 (19.38 mg g-1), and ACF-P2 (30.12 mg g-1) under the same experimental conditions. More importantly, the Cs+ removal efficiencies of ACF-P3 (82.90%), ACF-P2 (66.2%), ACF-P1 (34.2%) were 29.3-, 23.4-, and 12.11-fold higher than that of un-treated ACF (2.83%). The results suggested that the phosphorylation with Na5P3O10 is highly suitable for Cs+ adsorption which effectively functionalizes ACF with a greater number of phosphate functional groups. Adsorption and kinetic data well-fitted the Langmuir isotherm and pseudo-second-order model, respectively, which indicated the monolayer adsorption of Cs+ onto ACF-P1, ACF-P2, and ACF-P3 which were largely controlled by chemisorption. Overall, phosphoric acids containing different phosphate-based polyanions (PO43-, P2O74-, or P3O105-) enriched -OH and/or -COOH surface functional groups of ACF in addition to P-containing surface groups (PO, C-P-O, C-O-P, and P-O) and facilitated the Cs+ adsorption through surface complexation and electrostatic interactions.

Assessment of environmental impacts from authorized discharges of tritiated water from the Fukushima site to coastal and offshore regions

In August 2023, the long-planned discharging of radioactive wastewater from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) started after the confirmation of its feasibility and safety. As this water contains elevated amounts of tritium even after being diluted, a lot of resources have been invested in the monitoring of the Fukushima coastal region where the discharge outlet is located. We compare the first 3H surface activity concentrations from these measurements (up to the end of November 2023) with the available background values to evaluate a possible impact of the long-term discharging on humans and environmental levels of the radionuclide of interest in the same or nearby area. From our results, we can conclude that the joint effect of horizontal and vertical mixing has been significant enough to reduce tritium concentrations at the monitored locations in the region close to the FDNPP port two days after the end of the respective phase of the discharging beyond the detection limit of the applied analytical methods (∼0.3 Bq L-1) which is by five orders of magnitude lower than safety limit for drinking water set by the World Health Organization (WHO). Moreover, the distant correlation analysis showed that tritium concentrations at stations located further than 1.4 km were very close to pre-discharge levels (∼0.4 Bq L-1). We also estimated that the 3H activity concentration in the offshore Fukushima region would be elevated by 0.01 Bq L-1 at maximum over a year of continuous discharging, which is in concordance with the already published modeling papers and much less than the impact of the FDNPP accident in 2011.

Removal of tritiated water molecules by isotope exchange reaction between H2O vapor and tritium water

Developing a cost-effective method for separating and concentrating tritium water (HTO) from light water (H2O) without consuming additional energy is crucial for achieving reliable and safe nuclear fission and fusion energy technologies. However, this presents a significant challenge because of the difficulties in obtaining basic information, such as the chemical and physical properties of HTO molecules. Here, we investigate the isotope exchange reaction (IER) between HTO molecules in H2O solution and H2O vapor in the atmosphere. The reduction and purification rates of HTO-containing water were measured by varying the system conditions, such as temperature (20-50 °C) and humidity (50 %-90 %), under an equilibrium state between the liquid phase (water) and vapor phase (air). Our findings indicate that the concentration of HTO in the solution can be significantly reduced by increasing H2O vapor in the atmosphere. This result can be quantitatively explained by considering the entropy of mixing between the solution and vapor phases. The results obtained here provide both basic understanding on the exchange process between liquid- and vapor-water molecules and a passive technology for treating HTO-containing water.

Demonstration of tritium adsorption on graphene

In this work, we report on studies of graphene exposed to tritium gas in a controlled environment. The single layer graphene on a SiO2/Si substrate was exposed to 400 mbar of T2, for a total time of ∼55 h. The resistivity of the graphene sample was measured in situ during tritium exposure using the van der Pauw method. We found that the sheet resistance increases by three orders of magnitude during the exposure, suggesting significant chemisorption of tritium. After exposure, the samples were characterised ex situ via spatio-chemical mapping with a confocal Raman microscope, to study the effect of tritium on the graphene structure (tritiation yielding T-graphene), as well as the homogeneity of modifications across the whole area of the graphene film. The Raman spectra after tritium exposure were comparable to previously observed results in hydrogen-loading experiments, carried out by other groups. By thermal annealing we also could demonstrate, using Raman spectral analysis, that the structural changes were largely reversible. Considering all observations, we conclude that the graphene film was at least partially tritiated during the tritium exposure, and that the graphene film by and large withstands the bombardment by electrons from the β-decay of tritium, as well as by energetic primary and secondary ions.

Ultrasensitive Eu-Based MOF Luminescence Sensor for Clenbuterol Visible Recognition

Clenbuterol (CLB) as an illegal feed additive may cause a great security risk to food safety. However, convenient and efficient detection means for CLB in practical application remain a formidable challenge. Herein, a stable Eu-based organic framework {[H2N(CH3)2]2[Eu2(ttca)2]·H2O}n (compound 1) (H4ttca = [1,1':2',1″-terphenyl]-4,4',4″,5'-tetracarboxylic acid) has been harvested, exhibiting excellent chemical stability and thermal stability. Luminescence investigation reveals that compound 1 can sensitively and selectively detect CLB without being affected by different components from simulated serum and urine (limit detection: 22.7 nM). Furthermore, sensor 1 can also be applicable to CLB recognition in real swine feeds, presenting excellent anti-interference performance. The good cyclicity of compound 1 endows CLB determination with many advantages: low cost, high stability, and simplicity. Importantly, in view of the indication of the luminescence color (red to blue), test membranes were fabricated and employed for convenient and fast CLB detection, providing a valuable scheme for the visual monitoring of CLB in meat products. This work enriches rare earth metal compounds and luminescence sensor portfolios and breaks the concentration record (nM) for detecting CLB compared with reported complex materials, providing an effective monitoring platform for CLB visually.