The mixing operation and design of agitated vessels for various chemical engineering applications... more The mixing operation and design of agitated vessels for various chemical engineering applications may still represent a challenge due to the complexity of hydrodynamic fields established inside the reaction system. Computational Fluid Dynamics (CFD) is considered a valuable tool for the investigation of the complex turbulent flow field proper of mechanically agitated vessel (MAV). The use of CFD may effectively support the process engineer for the selection of the most proper impeller/vessel geometry and operative conditions to achieve homogeneous and fully turbulent conditions. In this work, experimental tests and CFD simulations were performed to study the Cr(VI) removal efficiency through nano-hematite particles (nHP) in MAV. More in detail, some solutions of Cr(VI) were treated using lab-made nHP, produced by a spinning disk reactor, in labscale agitated vessel and the kinetic of the removal process was experimentally studied varying the reactor/impeller configuration (impeller geometry) and the impeller rotational velocity. The obtained results were interpreted according to a CFD model of the system hydrodynamic field based on the k- turbulent model whereas the kinetic data were fitted to a suitable mass transfer kinetic model.
Earth Pressure Balance (EPB) Tunnel Boring Machines (TBM) are currently the most widely used mach... more Earth Pressure Balance (EPB) Tunnel Boring Machines (TBM) are currently the most widely used machines to perform tunnel excavation, particularly in urban areas. This technology involves the injection of chemicals as conditioning mixtures, which commonly raises concerns limiting the reuse of soils after excavation. This study deals with the prospect of a simplified, rapid and replicable methodology for the evaluation of the biodegradability of these conditioning mixtures. For this purpose, the biodegradation of three commercial conditioning mixtures was investigated in closed bottle tests by investigating the effect of different mixtures dosages and two different inocula (soil humus and Bacillus Clausii). While using soil humus as inoculum, a comparative study of biodegradation of the three investigated mixtures was successfully carried out; in the case of Bacillus Clausii, it was not possible to make a comparison between the different formulations in a short time. The adoption of soil humus satisfied only the criteria of rapid test, while the Bacillus Clausii, as specific inoculum, can meet the criteria of replicable results. For this reason, in the second part of this experimental study, a rapid and replicable procedure was proposed and validated. A kinetic study of organic carbon removal was also carried out.
Environmental chemistry for a sustainable world, 2019
The use of photocatalysis in environmental remediation processes has become more important in the... more The use of photocatalysis in environmental remediation processes has become more important in the last decade, mainly due to the notable efforts made by researchers in this field. The photocatalytic process requires a semiconductor material (photocatalyst), usually a metal oxide, which can be activated through the energy transported by ultraviolet light or visible light waves. The activated photocatalyst generates active compounds, such as hydroxyl radicals and superoxide ion, able to degrade very recalcitrant and non-biodegradable compounds present on the catalyst surface or in the liquid medium. The efficiency of the pollutant removal process is affected by various factors related to the employed photocatalyst, such as mean dimension, size distribution, physical structure and energy required for the activation. The photocatalyst characteristics are strongly dependent on the production process, and several researchers have developed new intensified production processes that require particular equipment. In the present chapter, the production of nanostructured catalysts in a continuous Spinning Disk Reactor is discussed. The main features of Spinning Disk Reactor technology are reported and analysed, i.e. rotational velocity, disk diameter, disk surface material and roughness, focusing on the production of nanoparticles to be used in the photocatalytic application, in view of the process intensification of photocatalysis application in the field of environmental remediation. A general overview about process intensification and its application to chemical engineering is presented, and the advantages offered by Spinning Disk Reactor technology, in terms of an increase of process efficiency due to the misinformation of operative conditions in reactors, are illustrated. Basing on the Spinning Disk Reactor characteristics and operative conditions, nanoparticle production by Spinning Disk Reactor compared to conventional technologies and the current application of this technology to selected nanoparticles (titania, magnetite, MgO and hydroxyapatite), synthesis is discussed. Spinning Disk Reactor technology allows to produce active semiconductor particles, characterized by a mean size significantly below 100 nm and with a narrow unimodal distribution, improving the quality of these products in comparison with those produced through conventional processes and equipment. Finally, the application of vertical and horizontal Spinning Disk Reactor configuration to the degradation of refractory compounds by photocatalysis is reviewed, aiming at evaluating process efficiency and the produced nanoparticle characteristics, to assess the key parameters and the limiting factors of the technology.
During the last decades great attention has been payed at evaluating the feasibility of Cr(VI) re... more During the last decades great attention has been payed at evaluating the feasibility of Cr(VI) reduction in soil by nano zero valent iron (nZVI). An inhibitory effect on the Cr(VI) reduction by Fe 0 nanoparticles is generally shown in the presence of high level of heavy metals and natural organic matter in soil. Heavy metals in the environment can react with nZVI by redox reactions, precipitation/dissolution reactions, and adsorption/desorption phenomena. As a result of the presence of metals as Ni, Pb, a decrease in the rate of Cr(VI) reduction was observed. Hence, in the present study, experimental tests of Cr(VI) reduction by nZVI in the presence of selected heavy metals, such as nickel and lead, and in the presence of high level of organic matter, are presented and discussed. Results showed a decrease in the rate of Cr(VI) reduction in soil by nZVI (at a x25 stoichiometric excess) from 91% to 78%, 71% and 74% in the presence of Ni, Pb and both metals respectively. As regards the results of Cr(VI) reduction in the presence of organic matter, by using a reducing solution of nZVI (x25 stoichiometric excess) a decrease of Cr(VI) reduction yield from 91% to 12% was observed after 2 hours of treatment in a soil containing 35.71 g/kg of organic matter. Such low efficiency was attributed to the adsorption of organic matter onto Fe 0 nanoparticles surface, thus saturating the active reaction sites of Fe 0 nanoparticles. In addition, a significant reduction of the organic carbon in the treated soil was observed (up to 77.5%) caused by the degradation of organic matter and its dissolution in the liquid phase. A slight decrease of the total metal concentration in treated soil was also observed. Finally, kinetic tests show that Cr(VI) reduction using nZVI in the presence of a high concentration of organic compound obeyed a pseudo-zero-order kinetic model.
The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton pr... more The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton processes, by the addition of zero-valent iron nanoparticles (nZVI) as catalyzer. This study demonstrated that both methods could significantly reduce the organic content of the liquid extract from excavated soils. Operating parameters, such as pH and catalyzer/oxidant (w/w) ratio, were varied to investigate their influence on the Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) removal efficiency. In addition, Biochemical Oxygen Demand (BOD) was evaluated before and after the treatment. The optimal conditions found for conventional Fenton process were: H 2 O 2 /COD = 1 (w/w), Fe(II)/H 2 O 2 = 0.1 (w/w) and pH = 2.5, whereas for Heterogeneous Fenton were: H 2 O 2 /COD = 0.75 (w/w), nZVI/H 2 O 2 = 1.5 (w/w) and pH = 3. Heterogeneous Fenton resulted more efficient with respect to conventional Fenton, leading to a TOC and COD removal efficiency equal to 75.95 and 85.52%, respectively. The BOD 28 /COD ratio after Heterogeneous Fenton increased by about 200%, indicating the suitability of this oxidation process to achieve a biodegradability increase.
Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study... more Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study aimed to evaluate the Cr(VI) removal by zero valent iron nanoparticles (nZVI) reduction process and the impact of Cr(VI), nZVI and combined treatment with nZVI and Cr(VI) on tomato growth performance. To evaluate the Cr(VI) toxic effect on germination capability, seeds were exposed to increasing Cr(VI) concentrations up to 1000 mg L −1. The inhibition of seed germination and the decrease of hypocotyl and root length started from Cr(VI) 5 mg L −1. Under treatment with Cr(VI) + nZVI 5 mg L −1 , seed germination, hypocotyl and root length resulted significantly higher compared to Cr(VI) 5 mg L −1 treatment. The impact of only nZVI was investigated on chlorophyll and carotenoid in leaves; iron levels in leaves, roots, fruits and soil; carotenoid, fat-soluble vitamin and nicotianamine in mature fruits. A significant increase of leaf chlorophyll and carotenoids was observed after nZVI 5 mg L −1 treatment compared to controls. No significant variations were observed in carotenoids, fat-soluble vitamins and nicotianamine levels after treatment with nZVI 5 mg L −1 in mature fruits. For their ability to reduce Cr(VI) and to stimulate tomato growth, nZVI might to be considered as alternative for remediation purposes. According to the Agency for Toxic Substances and Disease Registry and the International Agency for Research on Cancer, chromium (Cr) has been ranked 7 th among the top 20 hazardous substances and no.1 carcinogen 1,2. Cr occurs in different oxidation states (−2 to + 6), but hexavalent chromate Cr(VI) and trivalent chromite Cr(III) forms are the most common and stable in the natural environment 3. Compared to Cr(III), Cr(VI) is highly mobile in soil, extremely toxic to living organisms with mutagenic, carcinogenic and teratogenic potential 4. On the other hand, Cr(III) is significantly less toxic and serves as an essential element in trace amounts. Environmental contamination of Cr(VI) is gaining increasing consideration worldwide due to its high levels in the water and soil deriving from natural and anthropogenic activities including industrial applications such as metallurgical, refractories and chemicals 3. The exposure to Cr(VI) can cause several serious diseases in nervous, kidney, hematopoietic and gastrointestinal systems of humans 5-7. Cr(VI) is also a toxic heavy metal for plants and it is harmful to their development and metabolism, interfering with plant growth, nutrient uptake and photosynthesis, inducing enhanced generation of reactive oxygen species, causing lipid peroxidation and altering the antioxidant activities 8. It is also important to stress that Cr uptake by crops and accumulation in edible plant parts organs with serious risks for consumer health 5,9. In order to remove Cr(VI) from soil and water and eventually reuse the reclaimed water for irrigation purposes, several methods have been researched and reviewed extensively. These include chemical reduction to Cr(III), solvent extraction, chelation and adsorption, among others 10-12. In recent years, zero valent iron
application for heavy metals recovery from polluted water: the combination of nano zero-valent ir... more application for heavy metals recovery from polluted water: the combination of nano zero-valent iron and carbon nanotubes. Competitive adsorption non-linear modeling, (2018),
Tunnelling and Underground Space Technology, Oct 1, 2019
During tunnel excavation with Tunnel Boring Machines (TBMs) and earth pressure balance (EPB) tech... more 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.
Hexavalent chromium, Cr(VI), still represents in several areas in Europe one of the groundwater p... more Hexavalent chromium, Cr(VI), still represents in several areas in Europe one of the groundwater pollutants of major concern, mainly due to its high toxicity, even enhanced by the synergic effect in the presence of other groundwater contaminants, such as nitrate. In this work, experimental tests of hexavalent chromium reduction in polluted groundwater in the presence of nitrate by nanoscale zero-valent iron (nZVI) particles are presented and discussed. The effect of nitrate on process mechanism was investigated and a kinetic model was proposed. nZVI produced by iron sulfate heptahydrate reduction with sodium borohydride was stabilized by carboxymethyl cellulose, and added to synthetic solutions at different nitrate contents. Results show that nitrate exerts an adverse effect on Cr(VI) reduction, depending on nZVI/Cr(VI) and Cr(VI)/NO 3 -ratio. Though hexavalent chromium reduction resulted slightly enhanced at low nitrate concentration (up to 1.5 nZVI/Cr(VI) molar ratio), as a consequence of the increase of the ionic strength of the solution, a significant decrease was observed at high nitrate level (up to a 25% at Cr(VI)/NO 3 -molar ratio equal to 1.2 with an nZVI/[Cr(VI) + NO 3 -] molar ratio equal to 1), due to the competitive effect in the reaction with nZVI. In both cases, experimental data were successfully fitted by a pseudo-first-order kinetic until iron surface passivation determined nanoparticles deactivation.
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the final Version of Record (VOR). This work is currently citable by using the Digital Object Identifier (DOI) given below. The final VoR will be published online in Early View as soon as possible and may be different to this Accepted Article as a result of editing. Readers should obtain the final VoR from the journal website shown below when it is published to ensure accuracy of information.
h i g h l i g h t s g r a p h i c a l a b s t r a c t nZVI particles presented a typical grain st... more h i g h l i g h t s g r a p h i c a l a b s t r a c t nZVI particles presented a typical grain structure of spherical shape. Grain model was successfully used for the interpretation of both mechanism and kinetics.
Chemical Engineering Research & Design, Jul 1, 2018
This study reports a comparison among Conventional Fenton oxidation (CF) and Heterogeneous Fenton... more This study reports a comparison among Conventional Fenton oxidation (CF) and Heterogeneous Fenton oxidation (HF) processes performed at large lab-scale on a Tannery Wastewater (TW). The heterogeneous Fenton process was carried out by using self labprepared nano zero-valent iron particles as solid catalyst. Two different catalyst/oxidant (Cat/Ox) (w/w) ratio were examined: a study on the pH solution influence on the process efficiency, monitoring the COD, TP, H2O2 and Cr(VI) variation over the reaction time was carried out. The process was conducted for 10 h in batch mode for the first 2 h, followed by 8 h in continuous mode.
The use of iron nanoparticles in the heterogeneous Fenton oxidation treatment of tannery wastewat... more The use of iron nanoparticles in the heterogeneous Fenton oxidation treatment of tannery wastewater was investigated. A comparison with the conventional oxidation process, involving Fe(II) addition was performed. The main operating parameters influence, such as pH, temperature and reagents amount, on total phenolic species, total organic compounds, Cr(VI) content and chemical oxygen demand reduction was investigated. Heterogeneous Fenton oxidation resulted more efficient and fast with respect to the conventional process, but a higher amount of iron was required in the process. In this case, the optimal conditions were assessed at H 2 O 2 / COD (w/w) = 0.5, nZVI/H 2 O 2 (w/w) = 0.75 and pH = 3, achieving a total Cr(VI) removal as well as a remarkable TOC, COD and phenols degradation efficiency (up to 70, 73 and 88%, respectively). The best results were obtained with the combination of the two processes, fixing the optimal conventional Fenton operating parameters (H 2 O 2 /COD (w/w) = 0.75, Fe(II)/H 2 O 2 (w/w) = 0.15 and pH = 2.5), adopting a nZVI/H 2 O 2 (w/w) ratio equal to 0.2. In such conditions, that also allowed to reduce the catalyst amount used with respect to the Heterogeneous Fenton process, a noticeable TOC, COD and phenols removal efficiency (81.15, 87.44 and 94.04%, respectively) was achieved. In addition, the iron sludge production of such combined process was close to that obtained in the conventional one.
TiO 2 -SiO 2 mixed oxides have been prepared by the sol-gel technique from tetrabutyl orthotitana... more TiO 2 -SiO 2 mixed oxides have been prepared by the sol-gel technique from tetrabutyl orthotitanate and tetraethyl orthosilicate. The prepared materials were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, nitrogen physisorption, Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS). The results indicate that the TiO 2 -SiO 2 mixed oxides have a large surface area and a nanoscale size. FT-IR spectra show that Ti atoms are bonded to silica by oxygen bridging atoms in Ti-O-Si bonds. The titanium valence states in TiO 2 -SiO 2 mixed oxides were investigated by XPS, and their spectra report the presence of Ti 2+ and Ti 3+ cations for high silica concentration, suggesting the formation of oxygen vacancies. The photocatalytic activity of the prepared materials has been evaluated for the photodegradation of methylene blue (MB). The mixed oxides were activated by means of a UV light source, and the concentration of MB was monitored by UV-Vis spectroscopy. The synthesized TiO 2 -SiO 2 shows significantly higher MB removal efficiency in comparison with that of the commercial TiO 2 Degussa, P25.
The use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation purposes is... more The use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation purposes is increasing every year. This trend is the result of an improved research in the framework of nanotechnologies that have led to the synthesis and the production of this material on larger scale, the high efficiency determined experimentally, and the possibility to employ the technology in situ. On the other hand, there are still some drawback as high production costs and the fate of used nZVI in the soil and groundwater. Nevertheless, it appears that the use of nZVI as a remediation process to soil and groundwater may soon qualify as a BAT.
Journal of Materials Science: Materials in Electronics, Jan 23, 2021
In the present paper, a novel composite Graphene–Gold (Gr–Au)/TiO 2 –SiO 2 photocatalyst was synt... more In the present paper, a novel composite Graphene–Gold (Gr–Au)/TiO 2 –SiO 2 photocatalyst was synthesized and tested for the removal of methylene blue and rhodamine B in water solutions. First, Gr–Au nanoparticle composite was synthesized by simultaneous reduction and deposition of Au nanoparticles on Gr surface. The photodegradation of methylene blue and rhodamine B in aqueous solutions was studied using various photocatalysts, including neat TiO 2 –SiO 2 , Gr/TiO 2 –SiO 2 and Gr–Au/TiO 2 –SiO 2 composites. The Gr weight ratio in this research is 2% in the Gr/TiO 2 –SiO 2 composites. Detailed characterization (field emission scanning electron microscope, Raman, Fourier transform infrared spectra and UV–vis absorbance spectroscopy) of such material was conducted. As a result, the uniform deposition of nanometer-sized Au NPs on the graphene sheets was observed. The Gr–Au/TiO 2 –SiO 2 exhibited excellent photocatalytic efficiency because of the reduction of electron–hole recombination. The Gr2%–Au0.1%/TiO 2 –SiO 2 composite had the highest photoactivity.
Fenton oxidation and Chromium recovery from Tannery wastewater by means of iron-based coated biom... more Fenton oxidation and Chromium recovery from Tannery wastewater by means of iron-based coated biomass as heterogeneous catalyst in fixed-bed columns,
In this work hexavalent chromium, Cr(VI), removal in aqueous solution by olive stones coated by z... more In this work hexavalent chromium, Cr(VI), removal in aqueous solution by olive stones coated by zero-valent iron and magnetite nanoparticles was investigated. The Cr(VI) removal test results showed that the coated biomass adsorption capacity significantly increased (2.54 and 4.11 mg Cr g -1 ) when compared to the uncoated one (1.48 mg Cr g -1 ). Optimal removal conditions were reached by fixing the operating parameter values for pH, mass concentration and contact time equal to 3, 2.5 g L -1 and 120 min for the uncoated and equal to 2, 1.5 g L -1 and 120 min for the coated biomasses, respectively. Both Cr(VI) and Cr(III) recovery, after 5 cycles of use, was investigated using different solvents and operative conditions (with and without sonication), showing that remarkable Cr recovery was possible using the more environmentally friendly washing procedure. A possible Cr(VI) removal mechanism will be here proposed and discussed, considering both reduction and adsorption contribution towards Cr(VI) removal in aqueous medium and capable to justify the obtained results.
Chinese Journal of Chemical Engineering, Mar 1, 2018
In this study the copper and lead adsorption efficiency onto banana peels powder was investigated... more In this study the copper and lead adsorption efficiency onto banana peels powder was investigated. The agro-industrial waste recovery represents one of the Circular Economy pillars. In the view of the synthesis of an environmentally friendly adsorbent material, the powder was used without any preliminary chemical or thermal activation, but only after simple washing, drying and grinding. The bio-adsorbent was characterized by the FTIR technique and tested in batch mode on synthetic aqueous solutions containing Pb and Cu in the range 10-90 mg•L-1. A selection of two (Langmuir, Freundlich) and three (Sips, Redlich-Peterson, Koble-Corrigan) parameter isotherm models was chosen to fit adsorption equilibrium data by non-linear regression procedure. The best fit isotherm model was selected relying on the error function with the lowest average percentage error (APE) value, among those characterized by the highest R 2 values. As expected, the three-parameter models are found to better represent both metals bio-adsorption, with APE and R 2 values always lower and higher, respectively, than the corresponding values obtained for the two-parameter models.
The mixing operation and design of agitated vessels for various chemical engineering applications... more The mixing operation and design of agitated vessels for various chemical engineering applications may still represent a challenge due to the complexity of hydrodynamic fields established inside the reaction system. Computational Fluid Dynamics (CFD) is considered a valuable tool for the investigation of the complex turbulent flow field proper of mechanically agitated vessel (MAV). The use of CFD may effectively support the process engineer for the selection of the most proper impeller/vessel geometry and operative conditions to achieve homogeneous and fully turbulent conditions. In this work, experimental tests and CFD simulations were performed to study the Cr(VI) removal efficiency through nano-hematite particles (nHP) in MAV. More in detail, some solutions of Cr(VI) were treated using lab-made nHP, produced by a spinning disk reactor, in labscale agitated vessel and the kinetic of the removal process was experimentally studied varying the reactor/impeller configuration (impeller geometry) and the impeller rotational velocity. The obtained results were interpreted according to a CFD model of the system hydrodynamic field based on the k- turbulent model whereas the kinetic data were fitted to a suitable mass transfer kinetic model.
Earth Pressure Balance (EPB) Tunnel Boring Machines (TBM) are currently the most widely used mach... more Earth Pressure Balance (EPB) Tunnel Boring Machines (TBM) are currently the most widely used machines to perform tunnel excavation, particularly in urban areas. This technology involves the injection of chemicals as conditioning mixtures, which commonly raises concerns limiting the reuse of soils after excavation. This study deals with the prospect of a simplified, rapid and replicable methodology for the evaluation of the biodegradability of these conditioning mixtures. For this purpose, the biodegradation of three commercial conditioning mixtures was investigated in closed bottle tests by investigating the effect of different mixtures dosages and two different inocula (soil humus and Bacillus Clausii). While using soil humus as inoculum, a comparative study of biodegradation of the three investigated mixtures was successfully carried out; in the case of Bacillus Clausii, it was not possible to make a comparison between the different formulations in a short time. The adoption of soil humus satisfied only the criteria of rapid test, while the Bacillus Clausii, as specific inoculum, can meet the criteria of replicable results. For this reason, in the second part of this experimental study, a rapid and replicable procedure was proposed and validated. A kinetic study of organic carbon removal was also carried out.
Environmental chemistry for a sustainable world, 2019
The use of photocatalysis in environmental remediation processes has become more important in the... more The use of photocatalysis in environmental remediation processes has become more important in the last decade, mainly due to the notable efforts made by researchers in this field. The photocatalytic process requires a semiconductor material (photocatalyst), usually a metal oxide, which can be activated through the energy transported by ultraviolet light or visible light waves. The activated photocatalyst generates active compounds, such as hydroxyl radicals and superoxide ion, able to degrade very recalcitrant and non-biodegradable compounds present on the catalyst surface or in the liquid medium. The efficiency of the pollutant removal process is affected by various factors related to the employed photocatalyst, such as mean dimension, size distribution, physical structure and energy required for the activation. The photocatalyst characteristics are strongly dependent on the production process, and several researchers have developed new intensified production processes that require particular equipment. In the present chapter, the production of nanostructured catalysts in a continuous Spinning Disk Reactor is discussed. The main features of Spinning Disk Reactor technology are reported and analysed, i.e. rotational velocity, disk diameter, disk surface material and roughness, focusing on the production of nanoparticles to be used in the photocatalytic application, in view of the process intensification of photocatalysis application in the field of environmental remediation. A general overview about process intensification and its application to chemical engineering is presented, and the advantages offered by Spinning Disk Reactor technology, in terms of an increase of process efficiency due to the misinformation of operative conditions in reactors, are illustrated. Basing on the Spinning Disk Reactor characteristics and operative conditions, nanoparticle production by Spinning Disk Reactor compared to conventional technologies and the current application of this technology to selected nanoparticles (titania, magnetite, MgO and hydroxyapatite), synthesis is discussed. Spinning Disk Reactor technology allows to produce active semiconductor particles, characterized by a mean size significantly below 100 nm and with a narrow unimodal distribution, improving the quality of these products in comparison with those produced through conventional processes and equipment. Finally, the application of vertical and horizontal Spinning Disk Reactor configuration to the degradation of refractory compounds by photocatalysis is reviewed, aiming at evaluating process efficiency and the produced nanoparticle characteristics, to assess the key parameters and the limiting factors of the technology.
During the last decades great attention has been payed at evaluating the feasibility of Cr(VI) re... more During the last decades great attention has been payed at evaluating the feasibility of Cr(VI) reduction in soil by nano zero valent iron (nZVI). An inhibitory effect on the Cr(VI) reduction by Fe 0 nanoparticles is generally shown in the presence of high level of heavy metals and natural organic matter in soil. Heavy metals in the environment can react with nZVI by redox reactions, precipitation/dissolution reactions, and adsorption/desorption phenomena. As a result of the presence of metals as Ni, Pb, a decrease in the rate of Cr(VI) reduction was observed. Hence, in the present study, experimental tests of Cr(VI) reduction by nZVI in the presence of selected heavy metals, such as nickel and lead, and in the presence of high level of organic matter, are presented and discussed. Results showed a decrease in the rate of Cr(VI) reduction in soil by nZVI (at a x25 stoichiometric excess) from 91% to 78%, 71% and 74% in the presence of Ni, Pb and both metals respectively. As regards the results of Cr(VI) reduction in the presence of organic matter, by using a reducing solution of nZVI (x25 stoichiometric excess) a decrease of Cr(VI) reduction yield from 91% to 12% was observed after 2 hours of treatment in a soil containing 35.71 g/kg of organic matter. Such low efficiency was attributed to the adsorption of organic matter onto Fe 0 nanoparticles surface, thus saturating the active reaction sites of Fe 0 nanoparticles. In addition, a significant reduction of the organic carbon in the treated soil was observed (up to 77.5%) caused by the degradation of organic matter and its dissolution in the liquid phase. A slight decrease of the total metal concentration in treated soil was also observed. Finally, kinetic tests show that Cr(VI) reduction using nZVI in the presence of a high concentration of organic compound obeyed a pseudo-zero-order kinetic model.
The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton pr... more The treatment of excavation by-products has been studied using Fenton and Heterogeneous Fenton processes, by the addition of zero-valent iron nanoparticles (nZVI) as catalyzer. This study demonstrated that both methods could significantly reduce the organic content of the liquid extract from excavated soils. Operating parameters, such as pH and catalyzer/oxidant (w/w) ratio, were varied to investigate their influence on the Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) removal efficiency. In addition, Biochemical Oxygen Demand (BOD) was evaluated before and after the treatment. The optimal conditions found for conventional Fenton process were: H 2 O 2 /COD = 1 (w/w), Fe(II)/H 2 O 2 = 0.1 (w/w) and pH = 2.5, whereas for Heterogeneous Fenton were: H 2 O 2 /COD = 0.75 (w/w), nZVI/H 2 O 2 = 1.5 (w/w) and pH = 3. Heterogeneous Fenton resulted more efficient with respect to conventional Fenton, leading to a TOC and COD removal efficiency equal to 75.95 and 85.52%, respectively. The BOD 28 /COD ratio after Heterogeneous Fenton increased by about 200%, indicating the suitability of this oxidation process to achieve a biodegradability increase.
Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study... more Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study aimed to evaluate the Cr(VI) removal by zero valent iron nanoparticles (nZVI) reduction process and the impact of Cr(VI), nZVI and combined treatment with nZVI and Cr(VI) on tomato growth performance. To evaluate the Cr(VI) toxic effect on germination capability, seeds were exposed to increasing Cr(VI) concentrations up to 1000 mg L −1. The inhibition of seed germination and the decrease of hypocotyl and root length started from Cr(VI) 5 mg L −1. Under treatment with Cr(VI) + nZVI 5 mg L −1 , seed germination, hypocotyl and root length resulted significantly higher compared to Cr(VI) 5 mg L −1 treatment. The impact of only nZVI was investigated on chlorophyll and carotenoid in leaves; iron levels in leaves, roots, fruits and soil; carotenoid, fat-soluble vitamin and nicotianamine in mature fruits. A significant increase of leaf chlorophyll and carotenoids was observed after nZVI 5 mg L −1 treatment compared to controls. No significant variations were observed in carotenoids, fat-soluble vitamins and nicotianamine levels after treatment with nZVI 5 mg L −1 in mature fruits. For their ability to reduce Cr(VI) and to stimulate tomato growth, nZVI might to be considered as alternative for remediation purposes. According to the Agency for Toxic Substances and Disease Registry and the International Agency for Research on Cancer, chromium (Cr) has been ranked 7 th among the top 20 hazardous substances and no.1 carcinogen 1,2. Cr occurs in different oxidation states (−2 to + 6), but hexavalent chromate Cr(VI) and trivalent chromite Cr(III) forms are the most common and stable in the natural environment 3. Compared to Cr(III), Cr(VI) is highly mobile in soil, extremely toxic to living organisms with mutagenic, carcinogenic and teratogenic potential 4. On the other hand, Cr(III) is significantly less toxic and serves as an essential element in trace amounts. Environmental contamination of Cr(VI) is gaining increasing consideration worldwide due to its high levels in the water and soil deriving from natural and anthropogenic activities including industrial applications such as metallurgical, refractories and chemicals 3. The exposure to Cr(VI) can cause several serious diseases in nervous, kidney, hematopoietic and gastrointestinal systems of humans 5-7. Cr(VI) is also a toxic heavy metal for plants and it is harmful to their development and metabolism, interfering with plant growth, nutrient uptake and photosynthesis, inducing enhanced generation of reactive oxygen species, causing lipid peroxidation and altering the antioxidant activities 8. It is also important to stress that Cr uptake by crops and accumulation in edible plant parts organs with serious risks for consumer health 5,9. In order to remove Cr(VI) from soil and water and eventually reuse the reclaimed water for irrigation purposes, several methods have been researched and reviewed extensively. These include chemical reduction to Cr(III), solvent extraction, chelation and adsorption, among others 10-12. In recent years, zero valent iron
application for heavy metals recovery from polluted water: the combination of nano zero-valent ir... more application for heavy metals recovery from polluted water: the combination of nano zero-valent iron and carbon nanotubes. Competitive adsorption non-linear modeling, (2018),
Tunnelling and Underground Space Technology, Oct 1, 2019
During tunnel excavation with Tunnel Boring Machines (TBMs) and earth pressure balance (EPB) tech... more 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.
Hexavalent chromium, Cr(VI), still represents in several areas in Europe one of the groundwater p... more Hexavalent chromium, Cr(VI), still represents in several areas in Europe one of the groundwater pollutants of major concern, mainly due to its high toxicity, even enhanced by the synergic effect in the presence of other groundwater contaminants, such as nitrate. In this work, experimental tests of hexavalent chromium reduction in polluted groundwater in the presence of nitrate by nanoscale zero-valent iron (nZVI) particles are presented and discussed. The effect of nitrate on process mechanism was investigated and a kinetic model was proposed. nZVI produced by iron sulfate heptahydrate reduction with sodium borohydride was stabilized by carboxymethyl cellulose, and added to synthetic solutions at different nitrate contents. Results show that nitrate exerts an adverse effect on Cr(VI) reduction, depending on nZVI/Cr(VI) and Cr(VI)/NO 3 -ratio. Though hexavalent chromium reduction resulted slightly enhanced at low nitrate concentration (up to 1.5 nZVI/Cr(VI) molar ratio), as a consequence of the increase of the ionic strength of the solution, a significant decrease was observed at high nitrate level (up to a 25% at Cr(VI)/NO 3 -molar ratio equal to 1.2 with an nZVI/[Cr(VI) + NO 3 -] molar ratio equal to 1), due to the competitive effect in the reaction with nZVI. In both cases, experimental data were successfully fitted by a pseudo-first-order kinetic until iron surface passivation determined nanoparticles deactivation.
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the final Version of Record (VOR). This work is currently citable by using the Digital Object Identifier (DOI) given below. The final VoR will be published online in Early View as soon as possible and may be different to this Accepted Article as a result of editing. Readers should obtain the final VoR from the journal website shown below when it is published to ensure accuracy of information.
h i g h l i g h t s g r a p h i c a l a b s t r a c t nZVI particles presented a typical grain st... more h i g h l i g h t s g r a p h i c a l a b s t r a c t nZVI particles presented a typical grain structure of spherical shape. Grain model was successfully used for the interpretation of both mechanism and kinetics.
Chemical Engineering Research & Design, Jul 1, 2018
This study reports a comparison among Conventional Fenton oxidation (CF) and Heterogeneous Fenton... more This study reports a comparison among Conventional Fenton oxidation (CF) and Heterogeneous Fenton oxidation (HF) processes performed at large lab-scale on a Tannery Wastewater (TW). The heterogeneous Fenton process was carried out by using self labprepared nano zero-valent iron particles as solid catalyst. Two different catalyst/oxidant (Cat/Ox) (w/w) ratio were examined: a study on the pH solution influence on the process efficiency, monitoring the COD, TP, H2O2 and Cr(VI) variation over the reaction time was carried out. The process was conducted for 10 h in batch mode for the first 2 h, followed by 8 h in continuous mode.
The use of iron nanoparticles in the heterogeneous Fenton oxidation treatment of tannery wastewat... more The use of iron nanoparticles in the heterogeneous Fenton oxidation treatment of tannery wastewater was investigated. A comparison with the conventional oxidation process, involving Fe(II) addition was performed. The main operating parameters influence, such as pH, temperature and reagents amount, on total phenolic species, total organic compounds, Cr(VI) content and chemical oxygen demand reduction was investigated. Heterogeneous Fenton oxidation resulted more efficient and fast with respect to the conventional process, but a higher amount of iron was required in the process. In this case, the optimal conditions were assessed at H 2 O 2 / COD (w/w) = 0.5, nZVI/H 2 O 2 (w/w) = 0.75 and pH = 3, achieving a total Cr(VI) removal as well as a remarkable TOC, COD and phenols degradation efficiency (up to 70, 73 and 88%, respectively). The best results were obtained with the combination of the two processes, fixing the optimal conventional Fenton operating parameters (H 2 O 2 /COD (w/w) = 0.75, Fe(II)/H 2 O 2 (w/w) = 0.15 and pH = 2.5), adopting a nZVI/H 2 O 2 (w/w) ratio equal to 0.2. In such conditions, that also allowed to reduce the catalyst amount used with respect to the Heterogeneous Fenton process, a noticeable TOC, COD and phenols removal efficiency (81.15, 87.44 and 94.04%, respectively) was achieved. In addition, the iron sludge production of such combined process was close to that obtained in the conventional one.
TiO 2 -SiO 2 mixed oxides have been prepared by the sol-gel technique from tetrabutyl orthotitana... more TiO 2 -SiO 2 mixed oxides have been prepared by the sol-gel technique from tetrabutyl orthotitanate and tetraethyl orthosilicate. The prepared materials were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, nitrogen physisorption, Fourier-transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS). The results indicate that the TiO 2 -SiO 2 mixed oxides have a large surface area and a nanoscale size. FT-IR spectra show that Ti atoms are bonded to silica by oxygen bridging atoms in Ti-O-Si bonds. The titanium valence states in TiO 2 -SiO 2 mixed oxides were investigated by XPS, and their spectra report the presence of Ti 2+ and Ti 3+ cations for high silica concentration, suggesting the formation of oxygen vacancies. The photocatalytic activity of the prepared materials has been evaluated for the photodegradation of methylene blue (MB). The mixed oxides were activated by means of a UV light source, and the concentration of MB was monitored by UV-Vis spectroscopy. The synthesized TiO 2 -SiO 2 shows significantly higher MB removal efficiency in comparison with that of the commercial TiO 2 Degussa, P25.
The use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation purposes is... more The use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation purposes is increasing every year. This trend is the result of an improved research in the framework of nanotechnologies that have led to the synthesis and the production of this material on larger scale, the high efficiency determined experimentally, and the possibility to employ the technology in situ. On the other hand, there are still some drawback as high production costs and the fate of used nZVI in the soil and groundwater. Nevertheless, it appears that the use of nZVI as a remediation process to soil and groundwater may soon qualify as a BAT.
Journal of Materials Science: Materials in Electronics, Jan 23, 2021
In the present paper, a novel composite Graphene–Gold (Gr–Au)/TiO 2 –SiO 2 photocatalyst was synt... more In the present paper, a novel composite Graphene–Gold (Gr–Au)/TiO 2 –SiO 2 photocatalyst was synthesized and tested for the removal of methylene blue and rhodamine B in water solutions. First, Gr–Au nanoparticle composite was synthesized by simultaneous reduction and deposition of Au nanoparticles on Gr surface. The photodegradation of methylene blue and rhodamine B in aqueous solutions was studied using various photocatalysts, including neat TiO 2 –SiO 2 , Gr/TiO 2 –SiO 2 and Gr–Au/TiO 2 –SiO 2 composites. The Gr weight ratio in this research is 2% in the Gr/TiO 2 –SiO 2 composites. Detailed characterization (field emission scanning electron microscope, Raman, Fourier transform infrared spectra and UV–vis absorbance spectroscopy) of such material was conducted. As a result, the uniform deposition of nanometer-sized Au NPs on the graphene sheets was observed. The Gr–Au/TiO 2 –SiO 2 exhibited excellent photocatalytic efficiency because of the reduction of electron–hole recombination. The Gr2%–Au0.1%/TiO 2 –SiO 2 composite had the highest photoactivity.
Fenton oxidation and Chromium recovery from Tannery wastewater by means of iron-based coated biom... more Fenton oxidation and Chromium recovery from Tannery wastewater by means of iron-based coated biomass as heterogeneous catalyst in fixed-bed columns,
In this work hexavalent chromium, Cr(VI), removal in aqueous solution by olive stones coated by z... more In this work hexavalent chromium, Cr(VI), removal in aqueous solution by olive stones coated by zero-valent iron and magnetite nanoparticles was investigated. The Cr(VI) removal test results showed that the coated biomass adsorption capacity significantly increased (2.54 and 4.11 mg Cr g -1 ) when compared to the uncoated one (1.48 mg Cr g -1 ). Optimal removal conditions were reached by fixing the operating parameter values for pH, mass concentration and contact time equal to 3, 2.5 g L -1 and 120 min for the uncoated and equal to 2, 1.5 g L -1 and 120 min for the coated biomasses, respectively. Both Cr(VI) and Cr(III) recovery, after 5 cycles of use, was investigated using different solvents and operative conditions (with and without sonication), showing that remarkable Cr recovery was possible using the more environmentally friendly washing procedure. A possible Cr(VI) removal mechanism will be here proposed and discussed, considering both reduction and adsorption contribution towards Cr(VI) removal in aqueous medium and capable to justify the obtained results.
Chinese Journal of Chemical Engineering, Mar 1, 2018
In this study the copper and lead adsorption efficiency onto banana peels powder was investigated... more In this study the copper and lead adsorption efficiency onto banana peels powder was investigated. The agro-industrial waste recovery represents one of the Circular Economy pillars. In the view of the synthesis of an environmentally friendly adsorbent material, the powder was used without any preliminary chemical or thermal activation, but only after simple washing, drying and grinding. The bio-adsorbent was characterized by the FTIR technique and tested in batch mode on synthetic aqueous solutions containing Pb and Cu in the range 10-90 mg•L-1. A selection of two (Langmuir, Freundlich) and three (Sips, Redlich-Peterson, Koble-Corrigan) parameter isotherm models was chosen to fit adsorption equilibrium data by non-linear regression procedure. The best fit isotherm model was selected relying on the error function with the lowest average percentage error (APE) value, among those characterized by the highest R 2 values. As expected, the three-parameter models are found to better represent both metals bio-adsorption, with APE and R 2 values always lower and higher, respectively, than the corresponding values obtained for the two-parameter models.
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