Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Università degli Studi di Cassino e del Lazio Meridionale

A study was performed to assess the sorption capacity of the phenoxy acid herbicide, MCPA, on two mesoporous oxides, Al(2)O(3) and Fe(2)O(3,) by using a batch equilibrium method. Effects of pH, contact time, initial concentration and sorbent dosage on the sorption of the herbicide were investigated. The collected data evidenced the greater sorption efficiency of Al(2)O(3) with respect to Fe(2)O(3). These results can be explained by considering the specific mesoporous structure of Al(2)O(3) together with the greater value of surface area. MCPA is assumed to be bound to Al(2)O(3) and Fe(2)O(3) by a combination of ionic and ion-dipole bonding. Both oxides present as sorbents for a fast and highly efficient removal of MCPA from contaminated waters. For the first time the possible use of mesoporous metal oxides to remove MCPA from contaminated wastewaters identifies these sorbents as suitable filters for the decontamination of point sources.

Sorption capacity of mesoporous metal oxides for the removal of MCPA from polluted waters.

Two mesoporous metal oxides, Al(2)O(3) and Fe(2)O(3), were evaluated as regards their ability to remove simazine, a highly persistent herbicide of s-triazines, using a batch equilibrium method. The effect of several experimental parameters such as pH, contact time, initial concentration and sorbent dosage on the sorption of the herbicide was investigated. The maximum sorption of simazine on Al(2)O(3) and Fe(2)O(3) was observed at pH 6.5 and 3.5, respectively. The different sorption capacities of the two oxides were explained considering a set of factors affecting the sorption process such as the surface area and the porosity. The kinetics of sorption on both oxides was described using a pseudo second-order model. The sorption of simazine on Fe(2)O(3) was faster in comparison to that observed on Al(2)O(3). It was shown that aluminum oxide can be regenerated by incineration, and consequently can be considered for industrial treatment systems designed to mitigate the pesticide pollution in the aquatic environments.

Decontamination of waters polluted with simazine by sorption on mesoporous metal oxides.

Removal of the agrochemical simazine from polluted waters through adsorption by zeolite Y in its protonic form was studied. The investigated parameters were: pH, time, initial simazine concentration and solid/liquid ratio. An iterative process of simazine removal from waters is proposed, featuring: (i) final agrochemical concentration well below 0.05 mg/dm(3), the maximum concentration allowed by Italian laws in wastewaters; (ii) regeneration of the adsorbent by a few minutes thermal treatment in air at about 500°C, which results in the combustion of simazine without damage of the adsorbent; (iii) destruction of the agrochemical compound by combustion.

Cyclic process of simazine removal from waters by adsorption on zeolite H-Y and its regeneration by thermal treatment.

High-aspect-ratio nanomaterials (HARN) (typically, single-walled carbon nanotubes (SWCNT) or multiwalled carbon nanotubes (MWCNT)) impair airway barrier function and are toxic to macrophages. Here, we assess the biological effects of nanotubes of imogolite (INT), a hydrated alumino-silicate [(OH)3Al2O3SiOH] occurring as single-walled NT, on murine macrophages and human airway epithelial cells. Cell viability was assessed with resazurin. RT-PCR was used to study the expression of Nos2 and Arg1, markers of classical or alternative macrophage activation, respectively, and nitrite concentration in the medium was determined to assess NO production. Epithelial barrier integrity was evaluated from the trans-epithelial electrical resistance (TEER). Potential genotoxicity of INT was assessed with comet and cytokinesis-block micronucleus cytome assays. Compared to MWCNT and SWCNT, INT caused much smaller effects on RAW264.7 and MH-S macrophage viability. The incubation of macrophages with INT at doses as high as 120 μg/cm(2) for 72 h did not alter either Nos2 or Arg1 expression nor did it increase NO production, whereas IL6 was induced in RAW264.7 cells but not in MH-S cells. INT did not show any genotoxic effect in RAW264.7 and A549 cells except for a decrease in DNA integrity observed in epithelial A549 cells after treatment with the highest dose (80 μg/cm(2)). No significant change in permeability was recorded in Calu-3 epithelial cell monolayers exposed to INT, whereas comparable doses of both SWCNT and MWCNT lowered TEER. Thus, in spite of their fibrous nature, INT appear not to be markedly toxic for in vitro models of lung-blood barrier cells.

Imogolite: an aluminosilicate nanotube endowed with low cytotoxicity and genotoxicity.

The hydrothermal synthesis of a nanosized cobalt doped aluminum phosphate CoAPO-5 (CoAPO-5-N) in a water-surfactant-organic solvent mixture (emulsion method) is reported, along with its physico-chemical characterization and comparison with a sample obtained by conventional synthesis (CoAPO-5-C). Both XRD (X-ray Diffraction) peak widths and FESEM (Field Emission Scanning Electron Microscopy) pictures of CoAPO-5-N are in agreement with a nanoscale structure, although the aggregation of nanoparticles occurred. EDX analysis shows a more homogeneous distribution of cobalt in CoAPO-5-N, not attainable by conventional synthesis. The specific surface area, as measured by nitrogen adsorption at 77 K, shows a limited increase in CoAPO-5-N (242 m(2) g(-1)) with respect to CoAPO-5-C (216 m(2) g(-1)), whereas the external surface area is almost tripled. Such a definite increase in the outer surface of CoAPO-5-N is also evidenced by the fourfold increase in the rate of a reaction only involving the exterior surface of particles, the light-driven oxidation of water by persulfate anions, as activated by the bulky Ru(bipy)3(2+) complex, unable to enter CoAPO-5 micropores. Two new features were also noted, adding to the knowledge of CoAPO-5 systems: (i) tetrahedral Co(3+) species may coordinate ammonia molecules, assuming an octahedral configuration, as determined by UV-vis spectroscopy; (ii) Co(2+) species in trigonal coordination occur, able to coordinate either CO molecules at a low temperature or ammonia (or water) at room temperature, as evidenced by IR and UV-vis spectroscopy, respectively.

Nanoparticles of CoAPO-5: synthesis and comparison with microcrystalline samples.

In this work, we studied the removal of simazine from both a model and well water by adsorption on two different adsorbents: zeolite H-Y and a porous silica made in the laboratory by using the sol-gel technique. The pH dependence of the adsorption process and the isotherms and pseudo-isotherms of adsorption were studied. Moreover, an iterative process of simazine removal from both the model and well water, which allowed us to bring the residual simazine concentration below the maximum concentration (0.05 mg L(-1)) of agrochemicals in wastewater to be released in surface waters or in sink allowed by Italian laws, was proposed. The results obtained were very interesting and the conclusions drawn from them partly differed from what could reasonably be expected.

Adsorption of simazine on zeolite H-Y and sol-gel technique manufactured porous silica: A comparative study in model and natural waters.

The simple means adopted for investigating H-Y zeolite acidity in water is the pH-dependence of the amount of a basic molecule adsorbed under isochoric conditions, a technique capable of yielding, under equilibrium conditions, an estimate of the pKa value of the involved acidic centres: the behaviour with temperature of adsorbed amounts yields instead some information on thermodynamics. Simazine (Sim, 2-chloro-4,6-bis(ethylamino)-s-triazine) was chosen as an adsorbate because its transverse dimension (7.5 Å) is close to the opening of the supercage in the faujasite structure of H-Y (7.4 Å). In short term measurements, Sim adsorption at 25 °C occurs only at the outer surface of H-Y particles. Two types of mildly acidic centres are present (with pKaca. 7 and ca. 8, respectively) and no strong one is observed. Previous adsorption of ammonia from the gas phase discriminates between the two. The former survives, and shows features common with the silanols of amorphous silica. The latter is suppressed: because of this and other features distinguishing this site from silanol species (e.g. the formation of dimeric Sim2H(+) species, favoured by coverage and unfavoured by temperatures of adsorption higher than ambient temperature) a candidate is an Al based site. We propose a Lewis centre coordinating a water molecule, exhibiting acidic properties. This acidic water molecule can be replaced by the stronger base ammonia, also depleting inner strong Brønsted sites. A mechanism for the generation of the two sites from surface Brønsted species is proposed. Long term adsorption measurements at 25 °C already show the onset of the interaction with inner strongly acidic Brønsted sites: because of its size, activation is required for Sim to pass the supercage openings and reach inner acidic sites. When adsorption is run at 40-50 °C, uptake is much larger and increases with temperature. Isochoric measurements suggest a pKa value of ca. 3 compatible with its marked acidic nature, although attainment of equilibrium conditions is questionable. Measurements at 60 °C (both isochors and DRIFT) show the onset of changes at the outer surface brought about by the presence of hot water. Control experiments run with USY (Ultra Stabilized zeolite Y), featuring wormholes and cavities rendering accessible internal sites, show the extensive involvement of internal Brønsted sites already at 25 °C.

The role of outer surface/inner bulk Brønsted acidic sites in the adsorption of a large basic molecule (simazine) on H-Y zeolite.

The removal of simazine from both pure water and solute-bearing well water was studied by adsorption on two solids: zeolite H-Y from the commercial Na form and porous silica tailored by the sol-gel technique. The pH dependence of the amount adsorbed in a closed system at constant total simazine content as well as the apparent isotherms of adsorption was measured in all four cases. The low ion content of natural water suffices to alter the adsorption features in the case of silica, but not with zeolite H-Y. Iteration of the adsorption process onto constant amounts of solid allowed bringing the residual simazine concentration below 0.05 mg/L, the value allowed by Italian laws in wastewaters.

Application of highly porous materials for simazine removal from aqueous solutions.

In recent years, there has been a renewed interest in the impact of turbulence on aquatic organisms. In response to this interest, a novel instrument has been constructed, TURBOGEN, that generates turbulence in water volumes up to 13 l. TURBOGEN is fully computer controlled, thus, allowing for a high level of reproducibility and for variations of the intensity and characteristics of turbulence during the experiment. The calibration tests, carried out by particle image velocimetry, showed TURBOGEN to be successful in generating isotropic turbulence at the typical relatively low levels of the marine environment. TURBOGEN and its sizing have been devised with the long-term scope of analyzing in detail the molecular responses of plankton to different mixing regimes, which is of great importance in both environmental and biotechnological processes.

Serena Esposito

Department of Civil and Mechanical Engineering

Università degli Studi di Cassino e del Lazio Meridionale

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

Serena Esposito

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Civil and Mechanical Engineering

Università degli Studi di Cassino e del Lazio Meridionale

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

Department of Civil and Mechanical Engineering