1,721,000 research outputs found
Ozone-based electrochemical advanced oxidation processes
No full textNovel processes have recently been developed that provide for the enhancement of ozonation through combination with electrochemical treatments. These are processes that can be included among those defined as advanced oxidation processes as they proceed via electrogeneration of highly oxidizing radical species. These processes are generally carried out by sparging ozone in both divided and undivided electrochemical cells in order to promote its decomposition through different mechanisms, depending on the electrode materials adopted, and in some cases still debated. This mini review presents the most recent advances in the field of electrochemically assisted ozonation. In particular, the first section is focused on the process known as electroperoxone (EP) where the ozone decomposition is enhanced by the adoption of carbon-based cathodes, due to the electrogeneration of hydrogen peroxide, while the second section is focused on the process that implies ozonation in a cell adopting metal-based cathodes
Enhanced degradation of paracetamol by combining UV with electrogenerated hydrogen peroxide and ozone
No full textThe in-situ production of highly oxidizing species represents a sustainable approach for the treatment of unregulated emerging contaminants. In this article, we investigate the UV induced degradation and mineralization of paracetamol that represents one of the most frequently prescribed and sold drugs worldwide. In particular, this work compares two advanced oxidation processes based on photolysis of electrogenerated hydrogen peroxide (H2O2), and ozone (O3). The H2O2 electrosynthesis has been performed via oxygen reduction on gas diffusion electrodes (GDE). To maximize the efficiency of the treatments, the effect of the main operative parameters such as reagent concentration, pH, current density and UV irradiance has been discussed. The results show that, due to the synergistic effect, paracetamol undergoes rapid degradation and extensive mineralization. The comparison of the cost-effectiveness of the treatments, in terms of energy consumption, is also provided
Entrapped zinc oxide and titania nanoparticles in calcium alginate beads for the removal of Methylene Blue (MB). Adsorption properties and photocatalytic stability
Full text linkIn this work, zinc oxide (ZnO) and titania (TiO2) nanoparticles were entrapped in calcium alginate (Ca-Alg) beads to form a composite photocatalytic adsorbent material. The adsorption and photocatalytic properties of ZnO and TiO2 Ca-Alg beads were investigated for different amount of encapsulated nanoparticles. In particular, 2% w/w, 5% w/w, 7% w/w of ZnO and 2% w/w, 5% w/w, 10% w/w of TiO2 calcium alginate beads were synthetized and Methylene Blue (MB) was selected as target pollutant. Adsorption batch test revealed the existence of a maximum removal percentage of MB (at equilibrium conditions) according to the nanoparticles concentration: 54% and 40% of MB removal was obtained for 2% w/w of ZnO and 5% w/w of TiO2 respectively. Moreover, it was also observed that the kinetic of the process improves increasing the amount of nanoparticles in the beads. The pseudo-first-order kinetic model was used for fitting and it reproduces very well the behavior of experimental data. Photocatalytic batch tests revealed that, in the range of time analysed, negligible photocatalytic activity was recorded for ZnO Ca-Alg beads, while an intense photocatalytic activity was observed for TiO2 Ca-Alg beads. In the latter case the stability of the alginate structure was compromised as detected by a spectrophotometric analysis
An Innovative and Easy Method for Iron-Doped Titania Synthesis
Full text linkIn this work, photocatalytically active titanium oxide nanoparticles were synthesized for the treatment of contaminated water under visible light. Various Ag, Sr and Fe-based synthesis and doping techniques (mainly hydrothermal and sol-gel methods) were performed. Adsorptive and photocatalytic properties were studied by testing in batch mode for the decontaminating a synthetic methylene blue solution (used as a model contaminant) using a simple 13 W LED bulb as the light source. The best material in terms of both activity (high removal kinetics) and simplicity of synthesis was found to be titanium oxide doped with Fe via "solid-state"method. This method enabled the synthesis of titania nanoparticles about 70 nanometers in size with Fe3+ effectively substituting titanium atoms (Ti4+) in the crystalline bulk of titania. The pseudo-first-order kinetic model was found to represent the behavior of the experimental data
Experimental study of rheological characteristics of bentonite-based drilling fluids
No full textBentonite and polymer-based drilling slurries are widely used in numerous geotechnical applications such as Slurry Shield TBM tunnelling, MicroTunnelling, Horizontal Directional Drilling and other trenchless technologies, piles and diaphragms constructions. In all cases, the rheological characteristics of the fluids must be correctly adjusted to ensure the stability of the excavation, proper lubrication and transportability of the excavated material. To date, there are several international standards and many best practices, empirical abacuses and indications for the definition of rheological properties of drilling fluids. However, there is often a lack of correlation between the results of different tests or measurements that can be carried out in laboratories using rheometers, viscometers and other sensitive and accurate equipment, and the rapid measurements that are widely used on site. The study presented in this paper involves the systematic performance of laboratory tests and rapid measurements on a natural bentonite used in the construction of tunnels and other underground works. The aim is to provide a broad overview of the rheological characteristics of drilling fluids prepared at different bentonite dosages, a series of correlations between the results of laboratory tests carried out using different mixing speed and mixing time. The results of the study support a better selection of the correct properties during drilling, an informed choice of the most appropriate measuring instruments and a more accurate measurement and control of the rheological properties of drilling fluids
Electrochemically assisted decomposition of ozone for degradation and mineralization of Diuron
No full textIn this work, we explore the possibility of enhancing the ozonation of a solution of Diuron by combination with electrochemical processes. To this aim, the ozonation was performed in a membrane free electrolyzer where a reticulated vitreous carbon (RVC) and a stainless steel (SS) cathode have been alternatively tested and compared. The effect of pH, current density and ozone flow on degradation and mineralization of Diuron has been investigated. The involvement of radical species has been verified by means of test conducted with selective scavenging agents. The results show that both cathodes can promote the decomposition of ozone and therefore the degradation of Diuron. The use of scavengers has shown that the removal of Diuron is driven by means of radical species. Depending on the adopted materials, different mechanisms occur and different operating conditions are required. In particular, the use of a carbon-based cathode implies the production of hydrogen peroxide and therefore the occurrence of an Electro-peroxone process, which is favored at alkaline pH and low current values. On the other hand, the adoption of a metal cathode, whose efficiency is highly promoted by acidic pH and high currents, implies the direct reduction of ozone with the production of hydroxyl radicals
Effect of ZnO-decorated electrospun veils on the damage tolerance of CFRP laminates
No full textIn this work, multifunctional carbon fiber reinforced polymer (CFRP) laminates were manufactured by interleaving electrospun veils decorated with ZnO nanorods (NRs) (CFRP_NY_ZnO). The laminates were tested under dynamic (low velocity impact at 5.0 J and 7.5 J) and quasi-static (pre- and post-impact four-point bending tests) loading conditions. The delamination resistance of CFRP_NY_ZnO was compared with those of CFRP (without veils) and CFRP_NY (with four non-decorated veils) laminates. At 5.0 J, ZnO NRs enhanced the delamination resistance (the lowest delaminated area was around 232.3 ± 38.7 mm2) due to additional energy consuming mechanisms. When the impact energy was increased (7.5 J), the debonding of ZnO NRs from the nanofibers was promoted and a rapid failure propagation was observed (increase in delaminated area of about 27% with respect to CFRP_NY). In quasi-static condition, ZnO NRs proved to be effective in increasing flexural strength (914.4 MPa (±18.8 MPa)) and modulus (83.6 GPa (±0.3 GPa)) of the laminate with respect to CFRP and CFRP_NY and in preventing laminate stiffness losses even after impacts at 5.0 J and 7.5 J
Soil Biocementation via Enzyme Induced Carbonate Precipitation (EICP) Method Employing Soybeans as a Source of Cheap Enzyme
Full text linkIn this work, the soil improvement technique via Enzyme Induced Carbonate Precipitation (EICP) was investigated by employing, as an alternative to expensive pure enzymes, enzymes extracted from agro-food wastes (tomato, apple, and soybean) such that the process is economically viable and fully embraces the concept of the circular economy. The feasibility of the process was evaluated by monitoring calcium carbonate precipitation in a sand sample. The effect of selected operative parameters was investigated during the injection into different grain size sand samples. The optimal operating conditions in terms of sand grain size, temperature, Urea/Calcium concentration were found. Results demonstrated the effectiveness of this alternative solution for EICP method in term of acquired material strength and the possibility to operate sand consolidation through an economically sustainable process
Surface modification of basalt fibres with ZnO nanorods and its effect on thermal and mechanical properties of pla-based composites
Full text linkThe composites based on basalt fibres and poly(lactic acid) (PLA) show promising applications in biomedical and automotive fields, but their mechanical performance is still largely hindered by poor interfacial properties. Zinc oxide nanorods have been successfully used to tune the PLA/basalt fibre interface by growing them on commercially available basalt fabrics. The hierarchical fibres significantly enhanced the mechanical properties of PLA-based composites, especially their flexural strength and stiffness. These values are 26% and 22% higher than those of unmodified basalt/PLA composites, and 24% and 34% higher than those of glass/PLA composites used as a baseline. The increase in tensile and flexural properties hinges on the mechanical interlocking action promoted by ZnO nanorods and on the creation of a compact transcrystallinity structure. A degradation of PLA matrix was detected but it was positively counteracted by the better interfacial stress transfer. This study offers a novel approach for modifying the fibre–matrix interface of biocomposites intended for high-performance applications
Circular economy and reuse of excavated materials from TBM excavations
No full textThe management of excavated materials is one of the major issues for tunnelling projects from environmental, logistical, administrative and economical point of views. Despite the extreme importance of the topic and the huge volumes of materials produced in the context of major works, the excavated materials are too often considered as a waste and therefore their reuse is not a widely established practice. Webuild and GEEG have launched a research activity aimed at developing an integrated management system for excavated soils that involved numerous real tunnelling projects in Italy and abroad and a relevant number of different reuse modality, from the most common, as the morphological re-profiling, up to innovative uses with high added value. This paper, after a general introduction to the topic, intends to provide an overall description of the WE CYCLE Project and an update of the experimental evidences collected on the applicability of several methods of reuse of different soil typologies
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