Pietro P. Falciglia

Stabilisation/solidification of Radionuclides Polluted Soils: a Novel Analytical Approach for the Assessment of the γ-radiation Shielding Capacity

Soil contamination caused by γ-radiation emitter radionuclides is a serious problem worldwide. Cementbased Stabilisation/solidification (S/S) could represent an optimal choice to treat radionuclides polluted soils due to the possibility to shield the γ-radiation emitted by contaminant. In order to better planning the treatment procedures, a novel analytical approach has been developed and applied in order to assess the γ-radiation shielding (γRS) of cylindrical S/S treated bodies taking into account the shielding properties of materials used in S/S treatment, all the parameters related to nuclear processes involved and the interaction between radiation and matter. Calculations were compared with γRS values obtained by bench-scale experimental activities. For experiments a soil spiked by thorium oxide (ThO2) was stabilised/solidified using different binder mixture of Portland cement and barite aggregates at different soil:binder ratios and tested for its γ-radiation shielding properties. Results obtained showed that the presence of the barite aggregates mixed with cement gives a significant containment of the γ-radiation possibly representing an optimal choice to S/S treat low level radionuclides polluted soil. Furthermore, a good correspondence between analytical and experimental data was observed making the proposed analytical approach a potential suitable tool to great simplify the estimation of γ-radiation shielding properties of several binders-materials-radionuclides S/S systems.

Development of a performance threshold approach for identifying the management options for stabilisation/solidification of lead polluted soils

AbstractTwo soils spiked with lead at different rates were stabilised/solidified using Portland cement and fly ash at different soil:binder ratios, and tested for their setting time, unconfined compressive strength, leachability and durability. A performance threshold approach was used in order to identify optimal management options for the products of the S/S treatment. Results show that soil texture, percentage of binders and lead concentration play an important part in the treatment, significantly influencing the performance of the resulting products in terms of curing, compressive strength and durability. Pb soil concentrations higher than 15000 mg kg−1 were found to heavily reduce the applicability of the treatment requiring the maximum amount of binder in order to satisfy the performance criteria. The performance of sandy soils was shown to be limited by setting time and UCS features due to the retardation of the hydration reactions and also by its leaching behaviour, whereas for silt-clayey soils t...

Performance study and influence of radiation emission energy and soil contamination level on γ-radiation shielding of stabilised/solidified radionuclide-polluted soils

This work focuses on the stabilisation/solidification (S/S) of radionuclide-polluted soils at different (232)Th 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.

Effectiveness of water saving devices and educational programs in urban buildings

In this study different water saving measures (structural and non-structural) were implemented in different urban buildings. A monitoring program of water consumption was carried out to verify and compare the effectiveness of high-efficiency plumbing fixtures and educational programs in different types of buildings (two residential houses, two Middle Schools and two Sport Centres) located in a drought experienced region (Sicily, Italy). In all cases, relevant water conservation percentages were achieved with prominent values in public buildings. The highest water conservation (up to 60%) was observed in two Middle Schools, where a large amount of water was wasted. Overall, the structural measures led to high water conservation, while the educational programs did not always improve the water saving effectiveness. These results highlight that in some urban areas the awareness of water conservation is not well established and large volumes of water are wasted, especially in public buildings, due to faulty plumbing fixtures. Governments and Environmental Agencies should promote with more effort water saving measures in order to support green building policy and global sustainability.Ferrous catalyzed persulfate oxidation of dissolved aniline was investigated in aqueous systems under a variety of ferrous ion concentrations and temperature. Result showed that the addition of ferrous ions accelerated the degradation of aniline by persulfate. For the thermally activated persulfate oxidation experiment, the optimum persulfate/aniline concentration ratio at 30˚C was at 5.4 mM or 20/1. This ratio gave the highest aniline removal of 45%. For the ferrous ion catalyzed persulfate oxidation experiment, there was marginal difference in the result for the various ferrous ion/oxidant molar ratios. Thus, another series of experiment was conducted to determine the optimum ratio and a ferrous ion/persulfate molar ratio of 1.25/1 showed the highest removal efficiency.

Environmental Life Cycle Assessment of marine sediment decontamination by citric acid enhanced-microwave heating

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).

Removal of Hg from Real Polluted Sediments Using Enhanced-EK Decontamination: Verification of Experimental Methods and Batch-Test Preliminary Results

The aim of the research is to apply a biosurfactant-enhanced-EK technology to marine sediment contaminated by high level of Hg. In this work, data from batch-tests using different novel biosurfactant agents were reported. In addition, a dedicated EK bench-scale apparatus was designed and carried out. Technical test was also performed to evaluate the optimal operating features of the EK bench-scale apparatus, assessing the influence of applied voltage and treatment time on the current intensity and electroosmotic flow. Batch experiments were conducted using two sugar esters as biosurfactants and EDTA salt at different concentrations. Results showed that the maximum extraction efficiency was observed for the biosurfactant Olimpicon GC (15%), for which the Hg extraction was shown to be 3.6-fold higher than for 0.2 M EDTA. From technical tests, the observed reduction of current intensity and electroosmotic flow with time highlights the necessity of using conditioning agents during the treatment. Data demonstrates also the good working features of the experimental apparatus. Preliminary results show that EK treatment jointly with biosurfactants such as sugar esters could be a better choice for the remediation of Hg-polluted sediments. The results obtained are of scientific and practical interest and can be used for further researches.

Microwave Heating-Mediated Remediation of Hydrocarbon-Polluted Soils: Theoretical Background and Techno-Economic Considerations

Massive amounts of soil and water have been contaminated with hydrocarbon compounds, including fuel and petrochemical products, because of economic and industrial activities. Several chemical-physical or biologic treatments have been studied to remediate hydrocarbon-polluted soils; however, these alternatives may be ineffective, expensive or too lengthy. Otherwise, ex situ conventional thermal desorption was successfully applied to remove organic contaminants, presenting excellent removal values in a very short time but requiring high energy and costs. Microwaves (MW) are a part of the electromagnetic spectrum occurring in the frequency range of 300 MHz–300 GHz, and recently, their application has been identified as a potential tool for hydrocarbon-polluted soil remediation. Compared to other remediation methods, MW heating has advantages including simplicity, safety, flexibility and cost-effectiveness since it offers the potential to significantly reduce treatment times, risk of contamination and costs due to the direct interaction of microwaves with the soil and its ability to overcome heat and mass transfer limitations. In conventional heating systems, the energy is transferred through conduction, convection and radiation, while in MW heating, energy is supplied directly to soil by molecular interaction with the electromagnetic field generated. Therefore, the components of the soil are heated individually and instantaneously, overcoming limits imposed by material heat transfer properties. Literature studies have shown that MW remediation has the potential to remove polar and semipolar organic pollutants from soil. The key factor of the remediation process is represented by the mechanism due to a partial dissipation of the electromagnetic field energy and its conversion into heat, avoiding the limitations of conductive heating phenomena of conventional thermal desorption treatment. This chapter discusses the theoretical background including MW heating process and the related techno-economic features for ex situ full-scale applications in remediation activities of hydrocarbon contaminants.

Chapter 12 – Reclamation of Sites Impacted by Mining Activities: Stabilization/Solidification of 232Th-Contaminated Soils

The radioactive waste produced by mining activities contains a series of long-lived radionuclides, such as uranium (U), radium (Ra), and thorium (Th) isotopes. These radionuclides are considered to be TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials) due to their high concentration in the mining byproducts. Their indiscriminate and improper disposal increases the risk of soil and groundwater contamination. According to the Environmental Protection Agency (EPA), among TENORM, 232 thorium ( 232 Th) is the primary source of contamination at the superfund sites, due to extraction activities. 232 Th, as a soil pollutant, presents both a chemical and radiological hazard, and risks connected to 232 Th exposure are increased by its γ-ray emission capacity. Very limited techniques are present in the literature to remediate 232 Th-contaminated soils, but the cement-based stabilization/solidification (S/S) technique has been shown to be a perfect choice for this purpose. S/S has three main advantages: (i) it is well established as an efficient and cost-effective treatment, (ii) it has high versatility, and (iii) it produces no waste or contaminated wastewater that needs landfill disposal. In addition, employing of high-density binder/materials with γ-radiation shielding properties represents a key factor in remedial activities of radionuclide-polluted soils. In this work, we report the theoretical background including the S/S process and recent related scientific and technoeconomic development for the S/S application in reclamation activities of 232 Th-contaminated soils from mining activities.