In this work, γ-ray shielding and Cs immobilisation performances of high-density magnetite (MG) and iron powder (IP) in Portland cement (PC) based-S/S treatment were investigated. Experimental ...results were elaborated using a γ-radiation shielding (γRS) index-based approach for assessing the effectiveness of in situ S/S of 137Cs-contaminated soils. Main results reveal that the replacement of PC by MG or IP (up to 50%) leads to a marked increase (up to about 4-fold) in the γ-ray shielding performance, whereas a further material addition decreases the S/S shielding performance. The highest γRS index of ∼26% (662 keV) was found in the case of IP addition (33.3%). The use of MG-mixes allows reaching slightly slower γRS index jointly with the highest Cs-immobilisation of 97.8%. In this case, calculation shows a maximum 137Cs-contamination level successfully treatable by in situ S/S up to ∼2.9 or ∼14.5 kBq kg−1 for the realistic or low probability scenario, respectively, highlighting the possibility to remediate a very wide range of real contamination. Findings show MG - PC S/S as the best choice and could provide a basis for decision-making of S/S remediation of 137Cs-contaminated sites.
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•We investigate the potentiality of novel high-density grouts for S/S of 137Cs-contaminated soils.•We assess contaminant immobilisation and γ-ray shielding effectiveness as γRS index.•We propose and apply a novel γRS-based approach for in situ effectiveness assessment.•Replacement of OPC by magnetite and iron powder increases γRS index and Cs-immobilisation.•Results highlight the possibility to remediate a very wide range of real 137Cs-contaminations.
This paper examines the application of cement (C)-barite (Ba) based-Stabilisation/Solidification (S/S) for the remediation of
Cs-contaminated soils, investigating the influence of soil: grout and C: ...Ba ratios on the shielding performance of the S/S mix assessed as gamma radiation shielding (γRS) index variation. Results from experiments were used to perform a novel approach and an economic analysis in order to calculate the effective dose reduction achievable by S/S and to assess the optimum quantities and costs of selected mixes, respectively. Gamma ray spectrometer measurements indicate that γRS index increases with increasing barite percentage up to a maximum level of 50%; however a further increase results in a worsening of the shielding performances. A maximum γRS variation of 46.5% was recorded with grout percentage increasing from 16.6 to 50%. At the photon energy of 662 keV (
Cs), the maximum grout amount results in the possibility to shield up to 24.1% of γ-rays emitted. The effective dose reduction achievable by the investigated S/S allows a maximum
Cs-soil contamination in the range 2.94-14.55 kBq kg
successfully treatable employing a soil: grout ratio of 1: 1 (C: Ba = 1:1). Technical data, jointly with economic analysis findings, make cement-barite based-S/S very competitive in cost-effectiveness and could provide a basis for decision-making of
Cs-contaminated site remediation.
This paper examines the application of cement (C)-barite (Ba) based-Stabilisation/Solidification (S/S) for the remediation of 137Cs-contaminated soils, investigating the influence of soil: grout and ...C: Ba ratios on the shielding performance of the S/S mix assessed as gamma radiation shielding (γRS) index variation. Results from experiments were used to perform a novel approach and an economic analysis in order to calculate the effective dose reduction achievable by S/S and to assess the optimum quantities and costs of selected mixes, respectively.
Gamma ray spectrometer measurements indicate that γRS index increases with increasing barite percentage up to a maximum level of 50%; however a further increase results in a worsening of the shielding performances. A maximum γRS variation of 46.5% was recorded with grout percentage increasing from 16.6 to 50%. At the photon energy of 662 keV (137Cs), the maximum grout amount results in the possibility to shield up to 24.1% of γ-rays emitted. The effective dose reduction achievable by the investigated S/S allows a maximum 137Cs-soil contamination in the range 2.94–14.55 kBq kg−1 successfully treatable employing a soil: grout ratio of 1: 1 (C: Ba = 1:1). Technical data, jointly with economic analysis findings, make cement-barite based-S/S very competitive in cost-effectiveness and could provide a basis for decision-making of 137Cs-contaminated site remediation.
•We investigate the influence of soil: cement: barite ratios on the γRS index variation.•We elaborate γRS index-based calculations to assess the effective dose variation achievable by S/S.•We assess optimum quantities and specific costs for the S/S of 137Cs-contaminated soils.•γRS is strictly linked to the S/S mix density and it increases with increasing barite percentage.•Experimental findings and techno-economic analysis are useful for real-scale S/S activity planning.
This study is aimed at investigating the levels of polyaromatic hydrocarbons and nitro-polyaromatic hydrocarbons in polluted urban soils and the potential application of microwave heating as ...decontamination treatment. The soil samples were collected from an area of 0.05 km
2
of Catania (Sicily, southern Italy) rural site. HPLC in fluorescence and electrochemical–fluorescence detection mode were used for selective separation, identification and quantification of pollutants in soil samples. A bench-scale microwave treatment was performed irradiating a contaminated soil using different operating powers for removing both kinds of contaminants. Results reveal that soil pollutant concentrations were sometimes higher than those found in other locations. Polyaromatic and nitro-polyaromatic hydrocarbon levels observed suggest a strong contribution from incomplete combustion of gasoline or other fuels also due to the vicinity to the airport. Many polyaromatic hydrocarbon derivatives are more carcinogenic than the initial contaminant form and may have toxicological significance, even if present at much lower concentrations than their parent compounds. Thus, the environmental levels of these pollutants need to be monitored and removed. Contaminant removals from simulated microwave remediation show that the treatment is effective. Results also showed that contaminant features, especially polarity, significantly influence the dielectric properties of the soil and thus the final temperature reachable during the heating processes and the contaminant removals.
Purpose
Localization and quali-quantitative characterization of radionuclide-contaminated soils are essential for healthcare and remediation activities. However, characterization activities are at ...the moment mainly based on very complex activities, generally dangerous for workers’ health. Unmanned aerial vehicles (UAVs) can be considered for this purpose, but the absence of data does not permit their use for a quantitative analysis. The main goal of this work is to obtain scientific information for successfully using UAVs in quali-quantitative characterization activities.
Materials and methods
The influence of the main flight UAV condition parameters on the detection efficiency and minimum detectable activity (MDA) concentration was assessed at lab-scale, considering
241
Am and
152
Eu as simulated soil contaminants. Obtained data were compared with reference to clearance levels. Specifically, the altitude (
h
) and inclination (
θ
) with respect to the soil surface of a small size γ-ray semiconductor CdTe detector and detection time were investigated as flight parameters.
h
and
θ
were adopted in the range 0–70 cm and 0°–60°, respectively.
Results and discussion
Main results reveal that in the case of
241
Am contamination, a duration time of about 13 and 20 min is required for an altitude of 60 and 70 cm, respectively, if an inclination of zero is considered, whereas inclinations higher than 15° lead to much longer times, up to 40 min. In the presence of
152
Eu, results reveal a more marked influence of the variables
h
and
θ
on the minimum detection time, with values higher for
241
Am. In terms of MDA, in the case of
241
Am, all the concentration values, with the exception of the highest
θ
investigated (60°), are below the Italian regulatory limit for altitudes lower than 35 cm and a detection time of 30 min. Higher
h
up to 50 cm can be considered, reducing the inclination up to 0°, whereas even higher altitudes make the detection of
241
Am not possible. On the other hand, for
152
Eu, the observed MDA values always make the contaminant detection possible.
Conclusions
All achievements and the calculated fitting parameters are useful preliminary data in the quantitative characterization of soil surface contamination, representing a valuable tool in knowing the soil surface γ-ray activity of
241
Am and
152
Eu for each given detected value. In general, obtained results will allow a better understanding of the technique limits and operating methods required for characterization activities by UAVs with vertical take-off and landing system.
This work aims to investigate the simultaneous mercury (Hg) and polycyclic aromatic hydrocarbons (PAHs) removal from seabed sediments by means of 2.45 GHz microwave irradiation with chemical ...enhancers. Decontamination kinetics were assessed applying Tween
®
80, methylglycinediacetic acid (MGDA) and citric acid as enhancers. Results clearly showed that sediment dielectric features allowed a large conversion of microwaves (MW) irradiated energy into temperature increase (405 °C within 7 min). The combined use of Tween
®
80 and MGDA in a 650 W MW irradiation treatment brought a final residual Hg concentration of 2.2 mg kg
−1
, whereas Tween
®
80 and citric acid allowed a residual concentration less than 1 mg kg
−1
(
R
= ~ 99%). Lower residual concentration was found also for total PAHs (< 1 mg kg
−1
) already after 1-min irradiation. Modelling revealed for all treatments that exponential decay has a very good fit with experimental points. For the unenhanced MW treatment, the decay rate (
k
) was 0.259. When Tween
®
80 and acid citric were contextually used, they brought an almost doubled k value of 0.493. The co-presence of PAHs decreased the Hg removal kinetic only without citric acid addiction. A simultaneous and very rapid Hg and PAHs total removal is very difficult to be achieved by other cleanup techniques, which operate in a selective way. Desorption parameters calculated are useful for Hg-PAH co-contamination removal kinetics prediction and for scaling-up studies that, at the moment, are essential to meet the great challenge of applying MW at the full scale.
Graphical abstract
Mt. Etna, the largest volcano in Europe, is periodically interested by intensive eruption activity sometimes causing environmental problems for the neighbouring urban areas such as Catania. The ...volcanic ash deposited on the roads is classified as waste (code 20 03 03 – municipal waste from European Waste Catalogue - EWC). In this work, with the aim to transform waste materials into useful product, two samples of ashes resulting from different explosive activities were treated by hydrothermal aging with distilled water and seawater. The results showed that the hydrothermal process determined mineralogical and magnetic changes in volcanic ashes. The data in fact indicated that X-type zeolite and sodalite were formed at 45, 60 and 70 °C of aging temperature. Moreover, magnetic characterization suggests an evolution of ferromagnetic materials to antiferromagnetic ones during zeolite formation. The presence of these new magnetic phases was responsible for the variety of magnetic behaviour. The applicability of obtained zeolite as novel adsorbent material in the field of water treatment was also evaluated. Batch adsorption experiments were carried to assert the adsorption capacity of novel synthetized zeolite in removing cesium ions from aqueous solutions thus confirming a possible End-of-Waste alternative.
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•Volcanic ash deposited on ground is classified as waste (European Waste Catalogue).•Volcanic ashes from different explosive activities of Etna are used to form zeolites.•Fe3O4 in raw ashes can be transformed in α-Fe2O3 during the zeolite synthesis.•Synthetic products show a variety of magnetic behaviour in zeolites.•Zeolites from volcanic ash can be used for Cs removal from aqueous solution.
This work focuses on the stabilisation/solidification (S/S) of radionuclide-polluted soils at different 232Th levels using Portland cement alone and with barite aggregates. The potential of S/S was ...assessed applying a full testing protocol and calculating γ-radiation shielding (γRS) index, that included the measurement of soil radioactivity before and after the S/S as a function of the emission energy and soil contamination level. The results indicate that setting processes are strongly dependent on the contaminant concentration, and for contamination level higher than 5%, setting time values longer than 72 h. The addition of barite aggregates to the cement gout leads to a slight improvement of the S/S performance in terms of durability and contaminant leaching but reduces the mechanical resistance of the treated soils samples. Barite addition also causes an increase in the γ-rays shielding properties of the S/S treatment up to about 20%. Gamma-ray measurements show that γRS strongly depends on the energy, and that the radioactivity with the contamination level was governed by a linear trend, while, γRS index does not depend on the radionuclide concentration. Results allow the calculated γRS values and those available from other experiments to be applied to hazard radioactive soil contaminations.
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•We assess the effects of 232Th contamination on performance of S/S treated soil.•We assess the γ-radiation shielding of the S/S materials as a function of energy.•We report a full testing protocol for assessing S/S resistance performance.•Emission energy influences the γ radiation shielding of the S/S.•Barite gives high γ-radiation shielding and low contaminant leaching.
•We investigate a glycerol enhanced-MW treatment of TPH-contaminated sediments.•Results revealed a strong passive ability of sediment in converting MW into heat.•Glycerol addition led to a strong ...increase in sediment MW absorbing ability.•Glycerol/MW resulted in an ultra-rapid (3min) and effective (>99%) decontamination.•No toxic by-products were generated during the remediation treatment.
In this study, a new enhanced MW heating treatment using glycerol was proposed and investigated in the remediation of marine sediments highly contaminated with hydrocarbons. The heating and contaminant removal performance of different treatments using varying glycerol doses were compared. The results showed that the addition of glycerol in sediments largely promoted the MW absorbing performance that corresponded to a large increase in temperature (up to∼120°C) with a maximum sediment temperature of 342°C. This allowed much faster contaminant removal kinetic to be obtained. A glycerol dose of 5% led to drastically lowered contaminant residual concentrations of 6454 (R=∼81%), 770 (R=∼98%) and 12 (R>99%) mgkg−1 after 3, 5 and 10min, respectively, demonstrating that∼5min were sufficient to reach the regulatory remediation target. A further dose increase (10%) led to a required time of 3min (R>99%), which corresponded to almost half of the MW energy required respect to the unenhanced MW. The main advantage of MW/glycerol treatment is the possibility to obtain a very rapid and effective decontamination process potentially reducing energy costs, also in the case of a very high initial hydrocarbon concentration, without producing additional by-products (respect to MW alone), which in some cases can be toxic. A comparison with other available clean-up alternatives revealed that literature does not report similar rapid and at the same time effective treatments for hydrocarbon-contaminated sediments.
