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| Author(s): |
Mauricio Alves de Melo Junior
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Química |
| Defense date: | 2013-07-05 |
| Examining board members: |
Claudio Airoldi;
Liliane Magalhães Nunes;
Benedito dos Santos Lima Neto;
Ana Flávia Nogueira;
Yoshitaka Gushikem
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| Advisor: | Claudio Airoldi |
| Abstract | |
This thesis reports the syntheses of hybrid mesoporous sílicas, through the functionalization of SBA-15, and cobalt and nickel phyllosilicates functionalized with organic macrocycles containing basic sites for the sorption of the toxic metallic ions Pb, Cd and Cu. SBA-15 and magnesium phyllosilicates were also modified with organic chains containing different amounts of sulfur atoms to be applied to the sorption of complex ions of gold and platinum group metals. This is done in the aim of optimizing the conditions adopted in the extraction of these precious metals from their ores. The materials with pendant organic macrocycles were formed through successive reactions on the surfaces with different organic molecules possessing nitrogen, oxygen and sulfur basic centers. The characterization techniques confirmed the formation of mesoporous and layered structures, showing the presence of pendant organic chains with the desired functional groups. The hybrids functionalized with macrocycles were effective in the sorption of toxic metals, with high sorption capacities for Pb when the solids are functionalized with macrocycles containing sulfur atoms. Whereas the sorption capacities of all materials were improved with the increase of basic centers amounts. These sorption capacities were even improved after the macrocycles formation. The sorption of precious metals complexes were effective in all cases, especially for tetrachloroaurate and tetrachloropalladate, which presented high sorption values. Exceptional values were also acquired in the sorption of aurothiosulfate complex by the magnesium phyllosilicate functionalized with thiol groups. The calorimetric titrations of toxic metals with the matrices containing organic macrocycles indicated favorable processes for the interaction between the basic centers and the cations in aqueous solution, due to negative values of Gibbs energy, in a spontaneous process. The results also indicated positive values of entropy. The values of enthalpy showed that all the metal/basic centers interactions at the solid/liquid interface are exothermic (AU) | |