|Tipo di tesi||Tesi di dottorato di ricerca|
|Titolo||Reazioni alle interfacce solido/liquido e solido/gas tra fillosilicati 1:1 e 2:1, complessi del Fe(III), Cu(II) e composti solforati|
|Titolo in inglese||Reactions at the solid/liquid and solid/gas interfaces between 1:1 and 2:1 phyllosilicates, complexes of Fe (III), Cu(II) and sulphur compounds|
|Settore scientifico disciplinare||GEO/06 - MINERALOGIA|
|Corso di studi||Scuola di D.R. in MODELLISTICA, SIMULAZIONE COMPUTAZIONALE E CARATTERIZZAZIONE MULTISCALA PER LE SCIENZE DEI MATERIALI E DELLA VITA|
|Data inizio appello||2016-03-04|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
I minerali argillosi, in particolare le smectiti a strati 2:1, che sono caratterizzate da una elevata capacità di scambio cationico e proprietà di assorbimento derivanti dalla debolezza dei legami nella regione dell’interstrato, sono particolarmente adatte ad ospitare molecole capaci di conferire proprietà peculiari alle strutture risultanti.
Clay minerals, in particular 2:1 layer smectites which are characterized by high cation exchange capacity and swelling properties deriving from the weak bonding in the interlayer region, are particularly suited to host, in the interlayer, molecules able to confer peculiar properties to the resulting structures. Several literature report that organic and inorganic chemical species with specific and rationally designed properties have been immobilized inside the interlayers of expandable phyllosilicates generating a wide range of clay-functionalized species, nowadays increasingly exploited in the field of environmental mineralogy to capture pollutants. During the PhD research work we have studied the immobilization of metal ion complexes onto natural phyllosilicates with the aim to design and build hybrid materials being able to entrap gaseous compounds at the solid/gas interface and to act as heterogeneous catalysts at the solid/liquid interface. In particular we characterized the hybrid materials resulting from the interaction between a standard montmorillonite and a standard kaolinite with some phenanthroline complexes of Fe(III) and Cu(II). Later we tested some other phyllosilicates such as sepiolite and a synthetic tobermorite. We solved the novel structure of the Fe-phenantroline complex as well. DR UV-Vis, elemental analysis, TGA-MSEGA, temperature-controlled XRPD, single crystal XRD, EXAFS techniques, and temperature dependence magnetic susceptibility measurements were used to characterize the structural properties of the new and hybrid materials. Actually, the complex was found to be a good candidate for building an hybrid material with novel heterogeneous catalytic and gas-compound capturing capabilities. The fact that each iron ion in the complex coordinates three weakly linked water molecules suggested that one or more of these molecules could be easily removed in proper conditions, leaving free coordination positions on the iron available for the interaction with a substrate. In particular we tested the ability of the complex immobilized on montmorillonite to catalyze the oxidation of organic substrates by means of hydrogen peroxide. The presence of a bridged oxygen atom between the two iron atoms in μ-oxo Fe+3phenanthroline complexes destabilizes the structure and thereby opens the way to fragmentation and/or interaction with other molecules. This feature made the complex, once immobilized on a solid support, being able to interact with high-iron-affinity gaseous compounds. Hence we investigated the uncommon capability of a solid phase system (i.e., montmorillonite-Fe3+Phen complex), to catch sulphur compounds, in particular thiols and H2S, from gas phase. We also studied the ability of the novel hybrid material to entrap gaseous aromatic compounds due to their stacking interactions with the phenanthroline aromatic rings present in the immobilized complex. We characterized the hybrid material after each exposure to the different gas phases in order to investigate any changing on its structure. Finally we tested the ability of the new hybrid layered silicates to capture heavy metal ions from water solution. The enhanced CEC led to think about a specific interaction between the metal ions and the intercalated complex. A modeling of the crystal lattice structure of the complex was performed and we compared its structural and physical-chemical properties generated by atomistic calculations with the ones obtained by experimental work. The resulting optimization of the molecular structure of the hydrated Fe complex, allowed us to compute a simple model of the intercalation of the complex into the montmorillonite interlayer space.