Synthesis and characterization of inorganic-organic hybrid based on silicon: study of application as adsorbents, heterogeneous catalysts and modifiers for epoxy resins

Abstract

This project, with multidisciplinary characteristics, can be divided in three parts, according to the description as follows: In the first part, samples of materials based on silicon, as nanosilicates (POSS- Polyhedral oligomeric silsesquioxane), silicas gel and MCM-41, will be organofunctionalized with selected molecules, resulting, for example, the materials POSS-propil-ATD, MCM-41-propil-ATD and silica gel-propil-ATD (where ATD = 2-aminothiadiazole). The possible molecules with potencial application in the organofunctionalization process would be the ligand bis[2-(3,5-dimethyl-1-pirazolil)ethyl]amine, and/or 5-amino-1,3,4-thiadiazole-2-thiol, and/or thiosemicarbazide, and/or 4-amino-2-mercaptopyrimidine,etc. The samples of organofunctionalized silica gel, due to lesser cost of preparation when compared to other two precursor supports, they will be tested in the adsorption and removal of some endocrine disruptors (ED) and pharmacons from aqueous media, in order to obtain a large scale application in a conventional water treatment plant. The endocrine disruptors (ED) to be studied are from a class of pesticides, such as Paraquat, BHC, Dieldrin, Endosulfan-alpha, Endosulfan-beta, Endosulfan sulfate, Aldrin, heptachlor, DDT and/or others. The pharmacons to be studied are from a class of antibyotics, such as cefalexine, ciprofloxacin, ampicillin, amoxycillin and/or others. The results of adsorption will be compared with those obtained with activated carbon, conventionally used in the water treatment plant. The three functionalized supports will be also applied in the adsorption and preconcentration of the heavy metal ions As(III), and/or Cr(III), and/or Bi(III) and/or Fe(III), and/or others, from aqueous and ethanol solutions. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the solid adsorbent materiais, Cu(II) will be used as a probe to determine the geometrical arrangements of the ligands around the central metal ion by electronic and ESR techniques. The adsorption experiments will be performed using batchwise process and column chromatography process. In these studies it will be applied adsorption models for the mathematical description of adsorption equilibrium data, such as Langmuir, Freundlich, Temkin, Toth, Redlich-Peterson. The pseudofirst-order and pseudosecond-order kinetic models and/or others will be used to describe the kinetic data. The change of Gibbs energy, enthalpy, and entropy of adsorption will also be evaluated for the adsorption experiments. Also to be studied are the effects of solution pH, initial concentration, contact time, and temperature on the adsorption capacity. In the second part, the organofunctionalized materials prepared in the first step of this project will be coordenated to specific metallic centers, Mo(II) organometallic complexes derived from ([M(C3H5)(CO)2X(NCMe)2]) (M = Mo; X = Cl, Br, I) by substitution of the acetonitriles groups, in order to obtain new heterogeneous catalists more active and selectives for application in olefin oxidation reactions. This will allow obtaining, for example, catalysts as POSS-propyl-ATD-complex Mo, MCM-41-propyl-ATD-complex Mo e Sílica gel-propyl-ATD-complex Mo. The catalytic properties of the supported catalysts will be compared with those of the unsupported species. In the third part, to be compared are the fracture toughness (K1C) and Young modulus (E) mechanical properties of the epoxy thermosetting resins modified with nanoparticles of organofunctionalized POSS prepared in the first part of the project. The thermal properties, involving techniques as TGA, DSC, DMTA, and/or others will be studied, and coadjuvant agents in the formulation of the epoxy resin could be added. A study will also be of numerical modeling of some mechanical properties of the nanocomposites using a ANSYS® plataform (ANSYS® commercial software). (AU)