Annalisa Martucci

Removal of sulfonamide antibiotics from water: Evidence of adsorption into an organophilic zeolite Y by its structural modifications

Sulfonamide antibiotics are persistent pollutants of aquatic bodies, known to induce high levels of bacterial resistance. We investigated the adsorption of sulfadiazine, sulfamethazine, and sulfachloropyridazine sulfonamides into a highly dealuminated faujasite zeolite (Y) with cage window sizes comparable to sulfonamide dimensions. At maximal solubility the antibiotics were almost completely (>90%) and quickly (t<1min) removed from the water by zeolite. The maximal amount of sulfonamides adsorbed was 18-26% DW of dry zeolite weight, as evidenced by thermogravimetric analyses and accounted for about one antibiotic molecule per zeolitic cage. The presence of this organic inside the cage was revealed by unit cell parameter variations and structural deformations obtained by X-ray structure analyses carried out using the Rietveld method on exhausted zeolite. The most evident deformation effects were the lowering of the Fd-3m real symmetry in the parent zeolite to Fd-3 and the remarkable deformations which occurred in the 12-membered ring cage window after sulfadiazine or sulfachloropyridazine adsorption. After sulfamethazine adsorption, zeolite deformation caused a lowering in symmetry up to the monoclinic P2/m space group. The effective and irreversible adsorption of sulfonamides into organophylic Y zeolite makes this cheap and environmentally friendly material a suitable candidate for removing sulfonamides from water.

Crystal structure of zeolite omega, the synthetic counterpart of the natural zeolite mazzite

Abstract Rietveld refinement of the structure of synthetic zeolite omega |Na6.6TMA1.8(H2O)22.2|[Al8.4Si27.6O72]-MAZ, using high-resolution X-ray powder diffraction data, by Rietveld method, provided the missing evidence that this material has the same framework type (MAZ) as the natural mazzite. Its real symmetry is P63/mmc, the same as the topological one, where a=18.215 A, c=7.634 A. TMA molecules are located inside the gmelinite cage, with two possible orientations, which are symmetric with respect to the plane passing through the center and orthogonal to the threefold axis of the cage. Sodium cations are distributed over two sites: one, at the center of the 8-ring channel, hosts most of Na and is 8-fold coordinated to six framework oxygens and two water molecules, while the other, located along the axis of the 12-ring channel, coordinates nine H2O.

Location of Brønsted sites in D-ferrierite by neutron powder diffraction

Abstract Neutron Rietveld refinements of one natural mordenite (Si/Al=5.5) and two synthetic mordenites (Si/Al=5.6 and 10.0) in their deuterium form were performed in the Cmcm space group. Four Bronsted acid sites were recognized. One was on framework oxygen O6, heading toward the side pocket; another was on O9, heading toward the center of the eight-ring; the other two were on O5 and O10, pointing toward the center of the 12-ring. On the whole, about half of the acid sites vibrate in the 12-ring channel, and half in the smaller channels. The occupancy of these sites varies in the range 7–23%, and all the OD groups show regular site geometry. The concentration of Bronsted acid sites found is around 50–60% of that which would be expected on the basis of the aluminum content. This discrepancy is attributed to the dehydroxylation process occurring during calcination. Few other extraframework sites, with low occupancy and at large distances from the framework oxygen atoms, were found, and are attributed to reabsorbed H 2 O molecules.

Removal of sulfamethoxazole sulfonamide antibiotic from water by high silica zeolites: A study of the involved host-guest interactions by a combined structural, spectroscopic, and computational approach

Sulfonamide antibiotics are persistent pollutants present in surface and subsurface waters in both agricultural and urban environments. Sulfonamides are of particular concern in the environment because they are known to induce high levels of bacterial resistance. Adsorption of sulfamethoxazole sulfonamide antibiotic into three high silica zeolites (Y, mordenite, and ZSM-5) with pore opening sizes comparable to sulfamethoxazole dimensions is reported. Sulfamethoxazole was almost completely removed from water by zeolite Y and MOR in a few minutes. Adsorption onto ZSM-5 showed an increased kinetics with increasing temperature. Antibiotic sorption was largely irreversible with little antibiotic desorbed. Sulfamethoxazole incorporation and localization into the pore of each zeolite system was defined along with medium-weak and cooperative host-guest interactions in which water molecules play a certain role only in zeolite Y and mordenite.

Factors affecting drug adsorption on beta zeolites

The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO2/Al2O3 ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.

Location of Brønsted sites in D-mordenites by neutron powder diffraction

Abstract Neutron Rietveld refinements of one natural mordenite (Si/Al=5.5) and two synthetic mordenites (Si/Al=5.6 and 10.0) in their deuterium form were performed in the Cmcm space group. Four Bronsted acid sites were recognized. One was on framework oxygen O6, heading toward the side pocket; another was on O9, heading toward the center of the eight-ring; the other two were on O5 and O10, pointing toward the center of the 12-ring. On the whole, about half of the acid sites vibrate in the 12-ring channel, and half in the smaller channels. The occupancy of these sites varies in the range 7–23%, and all the OD groups show regular site geometry. The concentration of Bronsted acid sites found is around 50–60% of that which would be expected on the basis of the aluminum content. This discrepancy is attributed to the dehydroxylation process occurring during calcination. Few other extraframework sites, with low occupancy and at large distances from the framework oxygen atoms, were found, and are attributed to reabsorbed H 2 O molecules.

Dehydration dynamics of epistilbite by in situ time resolved synchrotron powder diffraction

The step by step thermal dehydration process of the zeolite epistilbite from Osilo (Sardinia, Italy), (Ba 0.01 Sr 0.03 K 0.08 Na 1.04 Ca 2.29 )[Al 5.80 Si 18.20 O 48 ]-15.8H 2 O, has been studied in situ by synchrotron radiation powder diffraction. The time-resolved experiment was performed using a translating imaging plate system. Rietveld refinements, based on the average C2/m epistilbite structure, were carried out on 26 consecutive powder patterns in the temperature range from 323 K to 791 K, the upper stability limit of epistilbite in our experiment. Three dehydration steps occur at about 370 K, 470 K and 573 K. The first step is mainly related to the loss of the H 2 O molecules in the W3 site not directly coordinated to extraframework cations (‘only hydrogen bonded’ water). In the intermediate region between step (a) and (b) epistilbite retains only about 14 water molecules, corresponding to those coordinated to Ca (and Na) ions. Gradual W3, W2, and W1 water losses in step (b) reduce the residual water to about 9 H 2 O molecules, which is retained up to step (c). This is the minimum water content to maintain the six-coordination of Ca 2+ ions. Further water expulsion leads to a first-order phase transition to a collapsed structure (epistilbite B), which has been refined in the C2/m space group. The deformation pattern of the T-O-T angles and the re-arrangement of the extraframework Ca (and Na) cations in epistilbite B suggest a remarkable control exerted by the Si, Al ordering on the thermal stability of epistilbite, whose structural breakdown occurs at very low temperature compared to the related mordenite and ferrierite structures.

A reexamination of the crystal structure of erionite

The crystal structure of a natural erionite from Nizhnyaya Tunguska, Siberia (schematic formula K 2 Ca 3.5 Al 9 Si 27 O 72 · 32H 2 O) has been refined to a residual wR of 0.044. The erionite framework can be described by a sequence AABAAC … of 6-membered rings of tetrahedra. The (Si, Al) distribution (24% of Al in T1 and 31% of Al in T2) is consistent with the strong disorder found in tetrahedral sites for all zeolites describable by a sequence of 6-rings. Erionite, as in the closely related zeolite offretite, shows a slight enrichment of Al in the single 6-ring. K is at the center of the cancrinite cage and coordinates 6 framework oxygen atoms. Ca atoms alternately occupy three sites, quite near each other, on the triad axis parallel to c , at the center of the erionite cage. Their coordination number varies between 6 and 9. The marked differences in T—O distances found between hydrated and dehydrated erionite are explained in terms of interactions between extraframework ions and framework oxygens.

Phase transformations and structural modifications induced by heating in microporous materials

Abstract The thermal behaviour of microporous materials is relevant both for their characterization and for their application, and varies dramatically from one material to another. This paper intends to give a picture of their behaviour and to highlight analogies and differences in these materials as a function of their chemistry and topology. The information on their response to heating and dehydration/calcinations, even if still scanty and sometimes controversial, shows that some materials undergo dehydration-induced decrease in volume which can be dramatic or very scarce as a function of the extraframework content. These changes in volume can be partially or completely irreversible if they involve structural modifications of the tetrahedral framework. It is to highlight that topological changes are always due to the so called “face sharing tetrahedral” process.

In situ time resolved synchrotron powder diffraction study of mordenite

The step by step thermal dehydration process of the zeolites mordenite from Pashan (Poona, India) (Na 3.51 K 0.14 Ca 1.89 Mg 0.09 Sr 0.01 )[Fe 3+ 0.03 Al 7.40 Si 40.53 O 96 ] · 27.26H 2 O, has been studied in situ by synchrotron powder diffraction. The time-resolved experiment was performed using a translating imaging plate system. The structure refinements by full profile Rietveld analysis were performed in the Cmcm space group in the temperature range from 25 to 830°C. The results of structure refinements indicate that the slight cell-volume contraction (∼ 1.9%) is related to the release of water molecules from the channels: above 375°C, the water loss lead to an enlargement of the 8-membered ring parallel to [010], which occurred by a flattening of T3-O9-T3 and T4-O4-T3 bridges. The dehydration process is reflected not only in the content of water molecules in the zeolite channel, but also in the temperature behaviour of the unit cell parameters. The cell parameters b and c decreased regularly as the temperature rose, whereas a decreased up to 400°C then increased up to 630°C, and finally decreased until the end of experiment. The removal of water molecules was accompanied by a spreading of the initial Ca sites into many positions bonded to the framework oxygens. The increased interaction with the framework oxygens of Ca sites was intimately related to the distortion of the 12-ring which is in turn related to the lengthening of the a cell parameter.