Roberto Bagatin

Hydrophobic Meshes for Oil Spill Recovery Devices

Widespread use of petrochemicals often leads to accidental releases in aquatic environments, occasionally with disastrous results. We have developed a hydrophobic and oleophilic mesh that separates oil from water continuously in situ via capillary action, providing a means of recovering spilt oil from surface waters. Steel mesh is dip-coated in a xylene solution of low-density polyethylene, creating a hydrophobic surface with tunable roughness and opening size. The hydrophobic mesh allows oil to pass through the openings while preventing the concomitant passage of water. A bench-top prototype demonstrated the efficacy of such an oil recovery device and allowed us to quantify the factors governing the ability of the mesh to separate oil and water. Preliminary data analysis suggested that the oleophilic openings behave somewhat like capillary tubes: the oil flux is inversely proportional to oil viscosity, and directly proportional to the size of the mesh openings. An unpinned meniscus model was found to predict the water intrusion pressure successfully, which increased as the opening size decreased. The trade-off between water intrusion and oil flow rate suggests an optimal pore size for given oil properties and sea conditions.

Competitive adsorption of VOCs from binary aqueous mixtures on zeolite ZSM-5

Adsorption equilibria of methyl tert-butyl ether (MTBE)/toluene (TOL), and 1,2-dichloroethane (DCE)/MTBE binary mixtures in aqueous solution on ZSM-5 were measured over a wide range of concentrations. In comparison with the single-component data, the loading of all of the three compounds was reduced in the presence of a second component in the mixture. The binary system was described by a competitive dual site Langmuir adsorption isotherm. The model was chosen on the basis of the results obtained from X-ray diffraction studies of the adsorbent material loaded with equimolar binary mixtures. Rietveld structure refinements provide information about the relative position of molecules inside the structure after TOL-MTBE and DCE-MTBE mixture adsorption. The short intermolecular distances between the adsorption sites of MTBE, DCE and TOL inside the zeolite framework clearly prevent the simultaneous occupancy of one site by more than one component, when these compounds are adsorbed from binary mixtures.

Removal of emerging organic contaminants from aqueous systems: adsorption and location of methyl-tertiary-butyl-ether on synthetic ferrierite

Abstract This study reports on experimental results concerning methyl-tert-butyl-ether (MTBE, C5H12O) adsorption from water into the pores of siliceous zeolite ferrierite (FER) by combining powder X-ray diffraction analyses and chromatography techniques. Rietveld structure refinement (Immm space group) highlighted the presence of two crystallographically independent MTBE sites located in the 10-ring channel parallel to the [001] direction (MTBE1) and in the ferrierite cage (MTBE2), respectively. On the whole, Rietveld refinement revealed clearly the incorporation of ~1.8 MTBE molecules per unit cell, in very good agreement with the weight loss given by thermogravimetric analyses, and saturation capacity as determined by adsorption isotherms. Rapid kinetics combined with good adsorption suggests that FER can be used beneficially as an adsorbent medium in removing this emerging organic contaminant from water.

Influence of water on the retention of methyl tertiary-butyl ether by high silica ZSM-5 and Y zeolites: a multidisciplinary study on the adsorption from liquid and gas phase

Ambient temperature adsorption isotherms have been determined for methyl tert-butyl ether (MTBE) in aqueous solutions on high silica ZSM-5 and Y zeolites which differ from each other in framework topology and pore window apertures. The comparison of their adsorption properties was performed to evaluate the importance of the competitive interference of water with pore size. The adsorption Henrys constants for MTBE decrease with an increase in the zeolite pore size, indicating that confinement of the adsorbate in the zeolite pores is a driving force for adsorption. On the contrary, the saturation capacity increases with an increase in the adsorbent pore size (i.e. about 95 and 250 mg g−1 for ZSM-5 and Y, respectively). These data were confirmed from Rietveld refinement, that clearly revealed the incorporation of about 8 and 32 MTBE molecules per ZSM-5 and Y unit cell respectively. X-ray diffraction and IR spectroscopy indicate that significant clustering of the guest molecules (i.e. water and MTBE) occurs in the two investigated zeolites during adsorption from both the liquid and gas phase. The clusters originate from hydrogen bonding between MTBE and water molecules and their interaction with zeolite lead to framework flexibility for both zeolites. However, the framework deformation in Y is more evident than in ZSM-5 and occurs with a change of the real symmetry. These findings could have an impact on the adsorption, separation and catalytic use of zeolites for oxygenate compounds.

Assisted phytoremediation of a multi-contaminated soil: Investigation on arsenic and lead combined mobilization and removal

The removal of contaminants from an earthy matrix by phytoremediation requires the selection of appropriate plant species and a suitable strategy to be effective. In order to set up an assisted phytoremediation intervention related to a disused industrial site affected by an arsenic and lead complex contamination, an extensive experimental investigation on micro and mesocosm scale has been conducted. Particular attention was given to the choice of plant species: using crop plants (Lupinus albus, Helianthus annuus and Brassica juncea) a series of parallel test campaigns have been realized to investigate different scenarios for the reclamation. With regard to the arsenic contamination, which is certainly the most worrying, the possibility of employing a hyper-accumulator species (Pteris vittata) has also been investigated, highlighting advantages and difficulties associated with such an approach. The application of various mobilizing agents in different concentrations was tested, in order to maximize the extraction efficiency of plants in respect of both contaminants, showing the necessity of a chemically assisted approach to promote their uptake and translocation in the shoots. Phosphate addition appears to produce the desired results, positively affecting As phyto-extraction for both hyper-accumulator and crop plants, while minimizing its toxic effects at the investigated concentrations. With regard to Pb, although tests with EDDS have been encouraging, EDTA should be preferred at present due to lower uncertainties about its effectiveness. The performed tests also improved the addition of mobilizing agents, allowing the simultaneous removal of the two metals despite their great diversity (which in general discourages such approach), with significant saving of time and an obvious improvement of the overall process.

Multivariate comparison of reverse osmosis and nanofiltration membranes through tree cluster analysis

AbstractExperimental trials are usually needed to integrate information reported on data sheets in order to properly drive membrane choice. It results in data-sets where each membrane is characterised by several performance descriptors. Multivariate data-mining (i.e. chemometrics) effectiveness in analysing such data-sets has been demonstrated through the comparison of seven commercial membranes. Each membrane was represented as an object described by 15 features got from trials with different single-component test solutions. Tree cluster analysis based on Ward amalgamation method was employed for multivariate data mining. The algorithm progressively grouped the membranes in clusters, adopting the Euclidean distance in the 15-dimensional feature space as a measure of similarity. Thus, a graphical output consisting into a similarity tree representing the membrane taxonomy was obtained. A restricted number of membranes, selected as representatives of each identified cluster, underwent to further experiments...