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•We develop and apply a computer code to describe in situ soil microwave irradiation.•We validate the model with lab-scale experimental data.•We assess the 2m-effects of 6d-microwave ...irradiation of a diesel-polluted soil.•The validated model is a powerful tool providing good predictions.•Results can be used to guide the design of in situ microwave treatments.
This work aims to obtain essential data for the in situ application of microwave (MW) heating for hydrocarbon-polluted soil remediation. For this purpose, lab-scale experiments were performed and a dedicated computer code was developed and applied to simulate the phenomena induced by a MW treatment. MW process was modelled by means of the mono-dimensional transient equations of energy taking into account the interaction between the electromagnetic field and soil and conductivity phenomena. The model was validated by comparison with results from lab-scale experiments.
Main results indicate that, after a MW irradiation of 6days, the electric field was reduced by about one third of its initial value at a distance of 60cm and, as a consequence, soil temperatures equal to and lower than 180°C were observed. Overall, the thermal effect of the MW treatment was observed to affect a maximum distance of about 120cm, and this allows the achievement of the contaminant removal in the range 50–99% for a maximum distance of 80cm from MW source.
Results are of scientific and practical interest and can be used to guide the design of in situ MW treatments. The proposed model provides good prediction of the experimental data and it can be applied to investigate further operating conditions (soil types, incident electric field applied, remediation time). It represents a powerful and suitable tool to predict the effectiveness of the MW techniques.
The potential ability of microwave heating (MWH) for the remediation of marine sediments affected by severe hydrocarbon (HC) contamination was investigated. Decontamination effectiveness and ...environmental sustainability through a comparative Life Cycle Assessment (LCA) were addressed. Main results revealed that the application of a 650-W MWH treatment resulted in a rapid (15min) HC removal. A citric acid (CA) dose of 0.1M led to enhanced-HC removals of 76.9, 96.5 and 99.7% after 5, 10 and 15min of MW irradiation, respectively. The increase in CA dose to 0.2M resulted in a shorter successful remediation time of 10min. The exponential kinetic model adopted showed a good correlation with the experimental data with R2 values in the 0.913–0.987 range. The nature of the MW treatment was shown to differently influence the HC fraction concentration after the irradiation process. Achieved HC removals in such a short remediation time are hardly possible by other clean-up techniques, making the studied treatment a potential excellent choice. Removal mechanisms, which allowed the enhanced-MWH to operate as a highly effective multi-step technique (pure thermal desorption+chemical washing), undoubtedly represent a key factor in the whole remediation process. The LCA highlighted that the MW technology is the most environmentally sustainable alternative for sediment decontamination applications, with a total damage, which was 75.74% lower than that associated with the EK (0.0503pt).
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•A citric acid enhanced-MW treatment of TPH-contaminated sediment was investigated.•The environmental sustainability of the treatment through a LCA study was assessed.•Citric acid/MW resulted in a very rapid and effective (>99%) decontamination.•Results revealed pure thermal desorption and chemical washing as removal mechanisms.•The LCA classified MW technology as the most effective sustainable alternative.
Purpose
Microwave heating (MWH) has been recently proposed as a high-performance technique for the remediation of soils contaminated with organic pollutants. However, despite MWH potential ...advantages, it is scarcely applied due to the lack of full-scale in situ detailed studies. In this work, the in situ MWH applicability for the remediation of hydrocarbon-polluted soils was assessed by means of a specific energy and economic analysis. Essential technical information has also been purchased.
Materials and methods
Energy and economic analysis was performed using data obtained from modelling for which a dedicated equation-based process computer code simulating MWH phenomena was adopted. Elaborations involved the assessment of the influence of soil texture and moisture as well as operating conditions (supplied power and time) on electric field penetration into the soils and soil temperature variation as a function of time and radial distance from the irradiation source.
Results and discussion
Main results reveal that sandy soils are more penetrable by MW irradiation with respect to clayey ones. The soil MW penetrability was also observed to increase with decreasing the soil moisture. This was in turn reflected in the soil temperature profiles. However, the major effect on MWH effectiveness is ascribable by the changing of the operating power. In fact, the use of magnetrons with powers lower than 3 kW does not ensure enough microwave penetration into the soil and, therefore, is not suitable for in situ activities, whereas the application of a power of 6 kW led to a maximum treatable radius of 145 cm. In terms of energy consumption, calculation showed that almost 3 days more are in general required to remediate clayey soils with respect to sandy ones. Consequently, the economic analysis revealed that energy costs for sandy soils are about 3 € t
−1
lower than those required for clayey soils. Furthermore, the application of a power of 6 instead of 3 kW results in a higher total energy cost, which, jointly with the higher soil volume treatable, leads to almost equal specific costs.
Conclusions
The comparison of calculated costs with those of other available clean-up technologies for hydrocarbon-contaminated soils shows that very short remediation times and energy costs obtained (18–27 € t
−1
) make in situ MWH a deliverable alternative to conventional thermal desorption or physical-chemical techniques.
PURPOSE: Microwave (MW) heating has been identified as a potential cost-effective technique to remediate hydrocarbon-polluted soils; however, the soil texture and properties could have a great impact ...on its full-scale treatment. In addition, very limited energy and economical data on MW treatment are available, and this lack makes its real application very limited. In this work, a first experimental phase was performed simulating a MW of several hydrocarbon-polluted soils. Obtained data were elaborated for a techno-economic analysis. MATERIALS AND METHODS: Four soil textures, corresponding to medium, fine silica sand (at different soil moistures), silt as silica flour and clay as kaolin, were artificially contaminated with diesel fuel and irradiated by MWs using a bench scale apparatus. Soil samples were treated applying four specific power values at different times. At the end, soil temperature was measured, whereas residual contaminant concentrations were measured and fitted considering and exponential decay kinetic model. Temperature data, as well as kinetic parameters obtained, were used for the techno-economic analysis. The changing of the internal electric field was calculated for all the soils and operating conditions, then considering initial contamination values ranging from 750 to 5000 mg kg⁻¹, the minimal remediation time, specific energy and costs for the remediation were assessed. RESULTS AND DISCUSSION: At low powers, MW effectiveness is limited by low soil moistures or fine soil textures due to a limitation of the electric field penetration, whereas when high powers are used soil properties have a limited effect. Remediation time, as a function of the initial contamination level, follows a linear trend, except for dry soils, for which an exponential trend was observed. For powers higher than 30 kW Kg⁻¹, remediation times lower than about 100 min are needed, for all the moisturized soils, in order to treat a contamination of 5000 mg kg⁻¹. The variation of soil moisture or soil texture results in the range 20–160 € ton⁻¹, and doubled costs are required for the treatment of clayey soils respect to sandy soils. CONCLUSIONS: The analysis performed suggests that soil layers lower than 70 cm should be considered for ex situ remediation. MW has been shown as a quick technique also for high hydrocarbon concentrations; however, for energy saving, the application of some powers should be avoid. Unmoisturized or fine texture soil treatment results in higher costs; however, a maximum cost of 160 € ton⁻¹ generally makes MW heating a quick and cost-effective ex situ technique.
•We investigate an enhanced-EK treatment of sediments contaminated with Hg and PAHs.•We use MGDA and non-ionic surfactant as novel enhancing agents (EA).•Results revealed a synergic action of EK and ...EA that led to high Hg and PAH removals.•Results provide basic scientific information on Hg-PAH-removal from marine sediments.•Obtained data are useful for future enhanced-EK and cost analysis studies.
Mercury (Hg) and Hg-PAH removal effectiveness of several electrokinetic (EK) decontamination treatments, including the combined use of eco-friendly enhancing agents, was investigated in this work as a potential remedial treatment of heavily contaminated marine sediments. After a 400-h EK treatment, main results revealed a very poor Hg mobilization without the use of an appropriate conditioning agent, mainly due to the strong Hg-bounds with carbonates, organic matter and sulphides, which were present at high concentrations. The use of EDTA as processing fluid resulted in a slight improvement of Hg removal (∼15%). A further increase in Hg removal rate of ∼39% can be achieved with methylglycinediacetic acid (MGDA) as anodic solution. The best Hg-removal of ∼71% was obtained by means of the simultaneous use of MGDA and Tween® 80 due to their synergistic action in remedial processes. The same type of treatment led to a slightly lower total Hg-removal of ∼67% when a shorter time of 240h was considered. In the case Hg and PAHs as sediment co-contaminants, results revealed a total PAH-removal of 59.45%. The co-presence of PAHs significantly affected the electric current circulating in the system and the electrosmotic values, leading to a reduction of about 5% in Hg removal respect to the case where PAHs were not present in the sediments. Nevertheless, the combined application of Tween® 80 and MGDA in enhanced-EK treatment allows the possibility to successfully remove both highly persistent Hg and PAHs from marine sediments with high removal percentages. Obtained data can be useful for further enhanced EK treatments of sediments contaminated with Hg and PAHs, as well as providing basic information for future cost analysis.
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•We investigate a novel hybrid MWH treatment of Hg-contaminated sediments.•Results revealed a strong passive ability of sediment in converting MW into heat.•Results showed a synergic ...action of thermal and washing-stripping processes.•Combined removal processes led to a very high Hg removal of ∼99%.•Results provide basic scientific information on Hg-removal from marine sediments.
The aim of this work was to investigate Hg removal ability of a novel microwave heating (MWH) treatment for marine sediment remediation enhanced by the application of several agents, biodegradable complexing agent (methylglycinediacetic acid, MGDA), surfactant (Tween® 80), and citric acid. Main results revealed that MWH allowed a very rapid heating (∼450°C in 7min) of the irradiated medium. However, without the addition of enhancing agents, a maximum Hg removal of ∼72% can be achieved. The application of MGDA led to a higher contaminant removal of ∼87% (residual concentration=5.4mgkg−1). For the treatment including the simultaneous addition of both chelating agent and surfactant, their synergetic action and stripping processes resulted in a very high Hg removal of ∼99% for an irradiation time of 7min, corresponding to a residual concentration of 0.56mgkg−1, which is lower than the Italian regulatory limit of 1mgkg−1. The use of citric acid resulted in a shortening of the removal kinetics, which allowed the successful application of a shorter remediation time of 5min. The observed strong passive ability of sediments to convert a microwave irradiation energy into a rapid and large temperature increase undoubtedly represents a key factor in the whole remediation process, making the studied treatment an excellent choice. Kinetic data are suitable for a preliminarily assessment of the effectiveness of clean-up activities, and as basis for future scaling-up studies on MWH of Hg-contaminated sediments.
Purpose
Diesel fuel represents a permanent source of soil pollution, and its removal is a key factor for human health. To address the limitations of conventional remediation techniques, microwave ...(MW) heating could be employed due to its great potentiality. This work presents the lab-scale experiments performed to study the potential of MW processing for diesel-polluted soils treatment and related modeling for the optimization of MW systems operating conditions.
Materials and methods
A sandy soil was artificially contaminated with diesel fuel, moisturized with different amounts of water content, and thermally treated by MW radiation using a lab-scale apparatus to investigate the effect of soil moisture on soil temperature profiles and contaminant removal kinetics. An operating power, ranging from 100 to 1,000 W, and treatment times of 5, 10, 18, 30, and 60 min were investigated. Contaminant residual concentration values were fitted using the first order kinetic model, and desorption parameters were calculated for each soil at different operating powers.
Results and discussion
Main results show that the operating power applied significantly influences the contaminant removal kinetics, and the moisture content in soil has a major effect on the final temperature reachable during MW heating. Minimal contaminant concentrations were achievable by applying powers higher than 600 W for a treatment time longer than 60 min. For remediation times shorter than 10 min, which result in a soil temperature of about 100 °C, the effect of the distillation process increases the contaminant removal, whereas for longer times, soil temperature is the main key factor in the remedial treatment.
Conclusions
MW thermal desorption of diesel-polluted soil was shown to be governed by pseudo-first-order kinetics, and it could be a better choice for remediation of diesel-polluted soils, compared to several biological, chemical–physical, or conventional thermal treatments, due to its excellent removal efficiency. The results obtained are of scientific and practical interest and represent a suitable tool to optimize the treatment operating conditions and to guide the design and the scale-up of MW treatments for full-scale remediation activities of diesel-polluted soils.
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•We investigated a combined MW-UV treatment for PAH-contaminated sediments.•Sediment and PAH dielectric properties resulted in a high ability to convert MWs into heat.•PAH-removal was ...higher than 85% after only 1-min MW irradiation.•UV light irradiation of condensate from the unenhanced MW was very effective.•Data demonstrated the concept of the combined MW-UV remediation treatment.
The aim of this work was to demonstrate the concept of a combined MW-UV-A treatment for the successful remediation of PAH-contaminated marine sediments and the successive photo-degradation of the generated vaporized organic compounds, entrapped in the exhaust gas line. The role of Tween 80 and citric acid as degradation enhancers was also investigated, considering variable MW/UV operating conditions and irradiation times. Main results revealed a very rapid sediment temperature increase during MW heating (up to ∼380 °C), due to the dielectric properties of both sediment minerals and adsorbed PAHs, which highlighted their great ability to passively convert MWs into heat and in turn allow a very effective PAH-decontamination. PAH removal was higher than 85% after 1-min MW irradiation mainly due to “selective heating” and contaminant stripping removal mechanisms. Longer times led to the total removal of the contaminants. The addition of enhancing agents showed an improvement of the MW performance in the order: MW < MW + Tween 80 < MW + Tween 80 + citric acid. UV light irradiation of condensate from the unenhanced MW treatment resulted in an effective PAH-photo-removal in 34 min, with maximum values in the range 80.0–98.9%. However, the presence of enhancers in the sediments before MW irradiation lowered the contaminant removals (56.0–91.7%) by UV-A. The fate of PAH and their by-(photo)-products during UV irradiation, suggested molecular bond breaking as further contaminant removal mechanism. Overall, obtained data demonstrated the concept of the combined MW-UV-A treatment and the critical role of the enhancers in the photo-degradation, which elected unenhanced MW as the best choice.
The Giant Cell tumor (GCT) is a benign, locally aggressive lesion that cause bone destruction and shows a malignant potential. It is a relatively common skeletal tumor that is therefore typically ...seen in young adults. Few cases are described in literature of GCT in the immature skeleton, and the metatarsal is an unusual location for a primary bone GCT, especially in pediatric age. Therefore, there are very few data reported regarding the management protocol of GCT in metatarsal bones. We report a case about the use of no vascularized fibular graft for an original Y-shaped reconstruction of the metatarsal bone after Giant Cell Tumor resection in a 9 years-old patient, and performed a literature review about metatarsal bone reconstruction in skeletally immature patient.
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•Study on magnetite nano-particles agglomeration and magnetic map generation.•Understand the dynamics of magnetite nano-particles under an external magnetic field.•Trajectories of the ...larger particles converge more rapidly towards the magnet.•A global particles’ removal of ∼ 90% was observed for aggregate diameters > 1.2 µm.•Obtained data are useful for scaling-up and pilot-scale future practical application.
In this work, a modelling and experimental study was performed to understand the dynamic behaviour of magnetite nano-particles (MNPs) released in a water flow when subjected to an external magnetic field. MNPs physical and magnetic properties and their tendency to form aggregates were also investigated. A mathematical model was developed and applied using MNPs characterization and 3-D field maps generated by OPERA software, considering different magnet bar dimensions and particle aggregate sizes. Model was run to assess the MNPs trajectories, and the capture efficiency of a 10-cm height permanent magnet bar placed on the upper wall of a bench-scale rectangular duct in which MNPs are injected.
Shorter MNPs trajectories were observed in the flow regions farther from the duct walls (lateral or bottom walls) where the frictional forces are lower. It is relevant to notice that the MNPs attraction is possible also in regions where the magnetic field is weak due to the high magnetic susceptibility of the system. MNP aggregate size significantly influences the particle dynamics with the trajectories of the larger particles converging more rapidly towards the magnet leading to their capture. However, this does not affect the global removal (∼90%) for aggregate diameters higher than 1.2 µm, demonstrating the general effectiveness of the investigated magnetic capture system, which is only partially influenced by the aggregate size variation. The comparison of modelled and experimental results shows the goodness of the developed model. Along with magnetic and aggregation studies and generated 3-D magnetic field maps, it represents a valid tool for future studies towards the development of practical applications for the magnetic removal of MNPs loaded by water contaminants.
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