An experimental method was described to calibrate the depth of interaction (DOI) of high-energy <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-ray in large-size thick ...pixel CdZnTe detector. The experimental results indicated that the ratio of the cathode and anode amplitude strongly showed linear relationship with the DOI of incidence <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-rays and the detector. The correlation coefficients were optimized. Based on the experimental calibration of DOI, the photoelectric effect signals from the depth range where the energy resolution and the photopeak location are high were screened out to draw the energy spectrum. In this way, the energy resolution of the CdZnTe pixel detector was improved to 0.707% for 137 Cs@662 keV. Further combined with the anode rise time, the electron mobility of CdZnTe in 2-D (1 mm accuracy) and 3-D (2 mm <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 2 mm <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 1 mm accuracy) scales was calculated. At different pixel positions and depths in CdZnTe detector, the electron mobility varies between 1000 and 1150 cm 2 /(<inline-formula> <tex-math notation="LaTeX">\text{V}\cdot \text{s} </tex-math></inline-formula>).
In this study, graphene oxide was synthesized, characterized and applied for cesium removal from aqueous solution. The effect of various parameters, including adsorbent dosage (0.05–0.2 g L−1), pH ...(3–9) and ionic strength (NaNO3 0.001–0.1 mo L−1) on adsorption capacity, as well as its adsorption kinetics, isotherms, thermodynamics and mechanism were investigated. The experimental results indicated that the adsorption of cesium (I) by the graphene oxide was an exothermic, pH- and ionic strength-dependent process. The pseudo second-order kinetic model and the Langmuir model fitted this process well, and the adsorption capacity was calculated to be 95.46 mg g−1. According to the analytical results of XRD, FTIR, and XPS, the adsorption mechanism for cesium ions should be attributed to the oxygen-containing functional groups of the graphene oxide.
•Graphene oxide (GO) was synthesized, characterized, and applied for cesium removal.•The effect of various parameters on adsorption capacity was examined.•Cs adsorption by GO was an exothermic, pH- and ionic strength-dependent process.•The adsorption of cesium was attributed to the O-containing functional groups.
Aiming at radioactive cesium waste treatment, this work report a low-temperature immobilization method to convert Cs-polluted waste into pollucite. Results reveal that pollucite can be synthesized ...over a wide range of Cs content (36.5–53.2 wt.%) at 500 °C via the CsOH-Zeolite 4A-Silica gel system. The synthesized pollucite is composed of lamellar particles (0.8–2.5 μm) along with the agglomerates of small particles (0.1–0.3 μm) and Cs, Al, Si, O elements distribute uniformly on surface. Cs content and chemical stability analysis indicate 99.24% of Cs are immobilized and the leaching rate of Cs is on the order of 10
–3
g/(m
2
·d).
Graphical abstract
Floodplain wetlands in agricultural river basins provide critical ecosystem services such as nutrient retention, flood mitigation, carbon sequestration and ecological habitats and are a key component ...of a nature‐based solution approach to restoration. In the context of the global challenge to reducing impact increasingly intensive food production on downstream ecosystems, restoration of wetlands in river floodplains offers a practical means for downstream retention and mitigation of P flux from upstream agricultural land. Data on short term, flood event related, accretion rates are, however, difficult to acquire via conventional monitoring yet such information is essential for restoration planning and scenario testing. Here, we evaluate a promising approach that applies naturally‐occurring short‐lived fallout radionuclide (FRN) 7Be as a tracer to quantify sediment and, by association, particulate phosphorus retention rates in restored floodplain wetlands. Following a series of major inundation events, a restored floodplain unit was sampled to determine 7Be inventories of the floodplain relative to an undisturbed reference site. This was undertaken in conjunction with direct measurement of sedimentation as an independent check of FRN results. Accretion rates up to 27 kg m−2 were recorded using 7Be for recent deposition events compared to a longer term annual average rate of ca. 6 kg m−2 derived from 137Cs measurements. While accretion rates varied spatially and temporally, there was excellent coherence between FRN‐based measurements and direct measurements once rigorous correction for particle size effects on tracer properties had been undertaken. The study demonstrates the important contribution that FRN technology can make to support wetland management and restoration initiatives and the essential need for a systems thinking approach across the soil‐sediment continuum. Such decision support tools will become increasingly important in the 21st century with growing anthropogenic pressure on aquatic ecosystems related to upstream food production, and implementation of more nature‐based solutions such as restored wetlands to counteract these pressures.
Schematic representation of particulate phosphorus storage in floodplain sediment.
•Studies on adsorption removal of cesium from water are reviewed.•Minerals, biosorbents, and synthesized composites were used as adsorbents.•Demonstration tests were reported to highlight the points ...raised.•Feasibility of using Prussian blue (PB) for large scale application is discussed.
Radiocesium (Cs) removal from waters becomes an emerging issue after the Fukushima Daiichi Nuclear Power Plant Disaster, during which a total of approximately 3.3×1016Bq Cs was released to contaminate the environment. This mini-review provided a summary on literature works to develop efficient adsorbent for removing Cs from waters. Adsorbent made of raw and modified minerals, composites particles, and biosorbents that are highly specific to Cs in the presence of other alkali and alkali earth metals were summarized. Development of Prussian blue (PB) nanoparticles on Cs removal and its potential use in drinking waterworks was discussed. This review is a unique report for adsorption removal of Cs from contaminated waters.
Molecular dynamics (MD) simulation was conducted to obtain the interfacial behavior of cesium (Cs
+
) extraction by functionalized carbon nanotubes (CNTs). The present study explores the extraction ...mechanism of Cs
+
with functional groups such as OCH(CH
3
)
2
, and CONH
2
-based CNTs. The results display that adsorption capacity is improved significantly using a surface modification of a single-walled carbon nanotube (SWCNT) with isopropoxide and amide functional groups. The studies investigate the separation of Cs
+
in the presence of functionalized CNTs from the ionic liquid (IL) - water biphasic systems. It has been found that CNT with OCH(CH
3
)
2
functional group is highly efficient for Cs
+
extraction as compared to the CONH
2
group and bare CNT. The higher interaction energy between Cs
+
and CNT with OCH(CH
3
)
2
functional group (˗84.41 kcal/mol) was observed at the interface when compared with bare CNT (˗4.34 kcal/mol). In general, the order of Cs
+
ion adsorption capacity on the CNT surface is CNT - OCH(CH
3
)
2
> CNT - CONH
2
> bare CNT. The current study offers quantitative data and insights into the extraction of metal ions with functionalized CNTs, which may be highly helpful for future technological exploration of the many nano-adsorbent-based investigations.
Nuclear accidents such as the events at the Fukushima Daiichi nuclear power plant in 2011 require a rapid response to minimise contaminant release. Self-propelling shuttles functionalised with ...Prussian blue are developed for radioactive caesium (Cs) removal from aqueous phases during accident and emergency scenarios. The Marangoni effect provides thrust to the shuttle
via
ethanol diffusion from an infused hydrogel housed in the shuttle, achieving self-motion for 20-30 minutes with a peak velocity of 1.2 cm s
−1
. Cs adsorption efficiency by the self-propelling shuttles (83.9%) was comparable after 30 minutes to stirred systems containing a dormant shuttle (85.6%), indicating that the self-propelling property is effective. A maximum loading capacity was estimated at 106 mg g
−1
(Langmuir, adj.
R
2
- 0.99) based on adsorption isotherms, with pseudo-second-order kinetics (
R
2
= 0.98) best describing the rate-limiting adsorption step as chemisorption. Cs adsorption and subsequent recovery of the shuttles enabled the effective removal of
137
Cs from solution (91%).
Self-propelling shuttles for radioactive caesium adsorption.
Buenos Aires Province coastline is a populated area visited yearly by millions of tourists. However, the radioactivity baseline data of the sand has not been reported yet, and, therefore, the ...external dose rate received by tourists and inhabitants is also unknown. This work is a study of the natural (
238
U,
232
Th and
40
K) and anthropogenic (
137
Cs) radionuclides activity, an analysis of the sand mineralogy, and the correlations between activity values and sand properties, still unclear in regions belonging to no high background radiation areas. Activity values have been determined on the three Holocene geomorphological units of the region, from Punta Rasa to Santa Teresita (30 km coast). The
238
U,
232
Th and
40
K activities vary between 9 and 16 Bq/kg, 14 and 25 Bq/kg and 497 and 647 Bq/kg, respectively. These results indicate that Buenos Aires Province coastline is not a high background radiation area, related to the sediments sources (coastal cliff, Patagonian sediments, and the Andean volcanoes), which contain relatively low concentrations of radionuclide bearing minerals. Significant and positive correlations were found between the three natural radionuclides, contrary to high background radiation areas, where
40
K activity does not correlate to those of
238
U and
232
Th. After separating sand in two fractions by means of a permanent magnet, called black and brown fractions, the major activity of the three radionuclides were observed in the former, as well as a higher amount of feldspar, magnetite/maghemite, and ilmenite. Pearson correlation coefficient determined between magnetite plus ilmenite content and the activity of the three radionuclides seems indicate the inclusion of these radionuclides on that Fe compounds, without discarding the inclusion of
40
K on feldspar.
137
Cs was not detected in the sand or the deeper clayey layers, but it was found on clay samples collected from the discharge zone of the region, indicating the relevance of horizontal groundwater flow. External dose rate determined across the studied area was 38 ± 2 nGy/h, which is lower than the external dose determined for other regions of Buenos Aires Province and the mean worldwide value. From the dosimetric point of view, the seashore of Buenos Aires Province is a safe area.
Ejecta from the explosion of massive stars (core-collapse supernovae) make an important contribution to dust in the interstellar medium. However, dust formation around supernovae is not a simple ...process, with the formation of several components over time. In particular, the exact timing is a matter of debate. Here, we demonstrate that the isotopic composition of barium in supernova grains that survived in primitive meteorites constitutes a potential chronometer. For a subset of supernova silicon carbide grains (X1 grains), the Ba isotopes indicate that they formed at roughly the same time, and that, at this time, a substantial fraction of the freshly produced unstable 137Cs (half-life 30 yr) had already decayed into 137Ba. Application to the 137Cs/137Ba system of nucleosynthesis models that replicate the abundance patterns of stable neutron capture isotopes in these grains indicates a surprisingly late (∼20 yr) timescale for condensation, a conclusion that naturally rests on the reliability of these models.
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