An Innovative and Easy Method for Iron-Doped Titania Synthesis

In 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

Soil Biocementation via Enzyme Induced Carbonate Precipitation (EICP) Method Employing Soybeans as a Source of Cheap Enzyme

In 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

The 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

Geopolymer Materials for Low-Pressure Injections in Coarse Grained Soil: Multiscale Approach to the Study of the Mechanical Behaviour and Environmental Impact

The term soil improvement is commonly referred to the modification of soil structure in order to obtain a material with better physical and mechanical properties such as strength, stiffness or permeability. With this purpose, one of the most commonly used applications, particularly in coarse-grained soils, is the low pressure injection of cementitious mixtures. In recent years, there has been a growing demand for solutions with limited environmental impact and limited CO2 emissions and, in this regard, the cement present in the injected grout is evidently the weak point of traditional solutions. In this work, the experimental study of geopolymer materials as a substitute of cement mixture for low-pressure injection for coarse-grained soils improvement is presented. The study started with a focus on the geopolymer fresh mixture properties (density, viscosity, horizontal ellipsis ) and the evolution over the time of the mechanical properties (compression and tensile strength and stiffness) comparing three different mix designs at three different monitoring temperatures. The same evaluations were repeated on sand samples injected with the different types of mixtures previously analyzed. For a selected mix design, a permeation test was carried out under controlled conditions to test the pumpability and effectiveness of geopolymer injection. Finally, to deepen the chemical interaction between the injected mixture and interstitial water, an injection test was carried out using a scaled model of a real injection system. The experimental study carried out was aimed both at the analysis of the characteristics of the geopolymer material and at its physical interaction with coarse-grained soil, passing through the measurement of the mechanical characteristics of the geopolymer material and of the solid sand skeleton mixed with geopolymers. Finally, the possible chemical interaction of the mixtures with groundwater was also evaluated in order to highlight any environmental issues. The results shown provide a preliminary but sufficiently broad picture of the behavior of geopolymer mixtures for low-pressure injection for coarse-grained soil improvement purposes both from physical-mechanical and chemical points of view

Ozone-based electrochemical advanced oxidation processes

Novel 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

Cr(VI) removal by chitosan-magnetite nano-composite in aqueous solution

The production of functionalized nano-composites represents an important research activity in the environmental remediation field. The use of iron-based nano-particles (IBNs) supported on bio-polymer matrix might lead to the development of active nano-materials characterized by a notable eco-compatibility. Chitosan is a biodegradable biopolymer that can be effectively used to produce active nano-composites with IBNs. In this study, a chitosan-magnetite nano-composite was produced in the laboratory and used in batch experimental tests for the removal of Hexavalent Chromium, Cr(VI), in aqueous solutions. Cr(VI) is considered one of the most toxic compounds present in the Mediterranean Area due to its carcinogenic and mutagenic characteristics, besides its notable solubility and mobility in the environment. The most effective way for the remediation of Cr(VI)-polluted groundwater is represented by the combination of chemical reduction and co-precipitation processes, generating Cr(III) species, characterized by very low toxicity and solubility in comparison to Cr(VI) ones. The synthesized nano-composite was used in batch lab-scale reactors and the kinetics of the process was studied varying the initial nano-composite concentration (0.25, 0.5, 0.75, 1 g/L) at fixed Cr(VI) initial concentration (20 mg/L). In addition, the initial pH influence on the Cr(VI) removal efficiency was analyzed in the range 3-7

Enhanced degradation of paracetamol by combining UV with electrogenerated hydrogen peroxide and ozone

The 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

In 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

Classification of foam and foaming products for EPB mechanized tunnelling based on half-life time

During tunnel excavation with Tunnel Boring Machines (TBMs) and earth pressure balance (EPB) technology, conditioning agents are commonly used to modify the physical and mechanical properties of soils so that they are appropriate for the application of the front-face support pressure during excavation. The consistency of the conditioned soil must be stable during the time necessary to advance and install the lining. Hence, a stability analysis of the injected foams is an important aspect. To assess the stability of a foam a classification is proposed based on the results of a standard foam generation procedure and on half-life tests using products from the main suppliers. A further classification of the foaming agents used according to their ability to produce a stable foam in terms of Foam Expansion Ratio is also proposed