Maria Laura Santarelli

Graphite Nanoplatelets and Caenorhabditis elegans: Insights from an in Vivo Model

We evaluated the toxicity of graphite nanoplatelets (GNPs) in the model organism Caenorhabditis elegans. The GNPs resulted nontoxic by measuring longevity as well as reproductive capability end points. An imaging technique based on Fourier transform infrared spectroscopy (FT-IR) mapping was also developed to analyze the GNPs spatial distribution inside the nematodes. Conflicting reports on the in vitro antimicrobial properties of graphene-based nanomaterials prompted us to challenge the host-pathogen system C. elegans-Pseudomonas aeruginosa to assess these findings through an in vivo model.

Sulphur-extended asphalt: reaction kinetics of H2S evolution

Abstract The interest in sulphur-asphalt mixtures was especially high in the 1970s and 1980s. At present, there is concern about the behaviour of sulphur-extended asphalts (SEA) because of the problems that could arise during the recycling of old SEA pavements. This paper studies the kinetics of H 2 S evolution during the reaction of sulphur with asphalt; such a reaction starts well below 150°C, as previously stated. The activation energy and the reaction order are different for various types of material: for cracked bitumens the reaction order is 0.5, while for straight-run products it is higher and dependent on the type of bitumen. The results of the study suggest operating with great caution when heating SEA mixtures.

Dissociation Rate of THF-methane Hydrates

Abstract A number of papers and research projects suggest that stranded natural gas can be transported in a solid hydrate state at higher temperatures or lower pressures compared to conventional transportation systems (LNG and CNG). The self-preservation effect of methane hydrate can probably be improved by the use of a third component besides CH4 and water. Tetrahydrofuran (THF) is a promoter that greatly reduces the required formation pressures. In the present work the influence of THF on the decomposition kinetics of mixed THF-CH4 hydrates was studied to evaluate the THF stabilization effect. The experimental work, carried out with the help of a reaction calorimeter, has revealed that the dissociation rate of mixed THF hydrates is lower (on average by one order of magnitude) than that of simple methane hydrates. Mixed hydrates can also be stored for short periods at temperatures over 0°C. However, the best preservation conditions (among the experimented ones) are realized at −1°C and 3 MPa. (about 66 days required for complete dissociation).

Kinetic analysis of biomass pyrolysis using a double distributed activation energy model

Pyrolysis is a fundamental step in thermochemical processes of biomass materials, so a suitable kinetic model is an essential tool to predict the evolution of the resulting products of reaction. However, many difficulties arise in modeling this process step due to the very high number of the involved reactions. In this work, a new double-Gaussian distributed activation energy model was applied in fitting the experimental data of olive residue pyrolysis obtained by thermogravimetric analysis. 2-DAEM formulation considers two sets of parallel reactions occurring and sharing the same pre-exponential factor, but shows different distributions of the activation energy, described by two separate Gaussian distributions that, in turn, grasp the two pyrolysis steps with a high accuracy. Since it is well known that in fitting all the kinetic parameters the pre-exponential factor results highly correlated with the activation energy, the former parameter was separately estimated as a linear combination of the values obtained for the three main biomass components, cellulose, hemicellulose and lignin.

REACTION OF VISBREAKER BITUMENS WITH SULFUR

ABSTRACT The utilization of sulfur in bituminous binders started many years ago: a number of roads were paved in U.S. with SA (sulfur-asphalt) mixtures. Literature reports that, when mixing sulfur and asphalt, H2S evolution starts at temperatures higher than 150°C. By using thermal analysis techniques, the present paper shows that H2S evolution begins at about 130°C for most types of bitumens. Kinetics of reaction between sulfur and visbreaker bitumens were also studied: the reaction order with respect to sulfur is equal to 0.5 for the three visbreaker bitumens considered in this work.

Tea waste: A new adsorbent for the removal of reactive dyes from textile wastewater

Spent tea leaves (STL), a valueless waste produced during the manufacturing of tea beverages, were investigated as a potential low-cost adsorbent for the removal of the azo dyes Reactive Blue 19 (RB19), Reactive Red 120 (RR 120), Reactive Violet 5 (RV5) and Reactive Green 19 (R19) from wastewater. Untreated STL showed very low removal efficiency (< 7%), while a significant increase in dye adsorption was observed when they were thermally activated. Heating STL to 300 °C for 1 hour resulted in removal efficiencies ranging from 68.5 to 98.4%. Characterization of the waste by FTIR and TG/DTA indicated that major structural and/or chemical changes of the cellulose and hemicellulose components of STL occurred during heating.

Reaction of phosphoric acid with thermal residues and bitumens

ABSTRACT The purpose of the work was to study the effect of the addition of small quantities of phosphoric acid (or P2O5), on the physical and chemical behaviour of petroleum residues and bitumens. Phosphoric acid (and P2O5) reacts only with thermal products such as visbreaker (VB) residues and bitumens, and do not react with straight run (SR) products. The unstable constituents of VB residues, i.e. carbonaceous material and part of the asphaltenes, contain significant amounts of free radicals which easily share electrons with phosphorous. The resulting condensed particles are higher molecular wighht, polar material no longher soluble in the bitumen, and flocculate. This reaction confirms the presence of stable free radicals in thermal bitumens and residues, suggests a way to neutralize their destabilizing effect.

Effect of an enzymatic treatment with cellulase and mannanase on the structural properties of Nannochloropsis microalgae

The effects of an enzymatic treatment with cellulase and mannanase on the properties of marine microalgae Nannochloropsis sp. were investigated. The combined use of these enzymes synergistically promoted the recovery of lipids from the microalgae, increasing the extraction yield from 40.8 to over 73%. Untreated and enzymatically treated microalgae were characterized by chemical analysis and by TGA/DTG, FTIR, XRD and SEM. Significant changes were observed in the chemical composition and thermal behavior of the microalgae. The enzymatic treatment also resulted in an increase of the crystalline-to-amorphous cellulose ratio. SEM images revealed dramatic changes in cell morphology, extensive cell damage and release of intracellular material. Overall, the results obtained indicate that the enzymes used are capable of disrupting the microalgal cell wall and that a combination of common analytical techniques can be used to assess the enzyme-induced damage.

Dimensional variations of Roman masonry subjected to wetting-drying cycles

Abstract Many Roman monuments made of opus caementicium are subjected to wetting and drying phenomena caused by water or/and humidity from the ground. The action of water impregnation on the hypothetical dimensional changes in this Roman concrete has not been considered in the literature and no experimental data are available. The purpose of this work was the evaluation of the effect of wetting and drying cycles in a number of cores taken from an ancient Roman monument (Domus Tiberiana in the Palatine, Rome). The concrete samples were made of a pozzolanic mortar with large pieces of tuff, marble and bricks. In spite of some differences in their composition, the behaviour of the cores was similar and, generally, quite constant during the experimental cycles. On the average, the length variation was about 3–4%,or 3–4mm for each metre and, when related to high structural walls and monuments, the possible dimensional changes were quite impressive.

Effectiveness of Phosphocitrate as Salt Crystallization Inhibitor in Porous Materials: Case Study of the Roman Mosaic of Orpheus and the Beasts (Perugia, Italy)

Salt crystallization in porous materials constitutes one of the major causes of decay of buildings/archaeological sites in a wide range of environments. Desalination is among the most common methodologies of conservative treatment for salt decay. However, classic desalination techniques might be not suitable for long-term conservation. During the past decade interest has been an increasing towards crystallization inhibitors as a new means of controlling crystallization damage. This study deals with the first in-field application of an environment-friendly inhibitor system— phosphocitrate (PC). In particular, the case study of the Roman mosaic of Orpheus and the Beasts in Perugia (Italy) is presented. The inhibitor is completely soluble in water or alcohol, non-toxic, and easy to apply, thus enabling its use in accordance with the volatile organic compounds emission control and safety during the conservation works. Relevant samples from control and treated mosaic areas were collected and analyzed comparatively by means of Fourier transform-infrared spectroscopy, scanning electron microscopy, and energy dispersive spectrometry to study the potential of the inhibitor system in preventing/controlling salt damage in such archaeological site.