Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604
O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).
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Item Acesso aberto (Open Access) Síntese e caracterização de hidróxidos duplos lamelares para uso no tratamento de águas contaminadas por metais pesados(Universidade Federal do Pará, 2009-03-25) GRANA, Reinaldo José de Aguiar; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568Layered double hydroxides (LDHs) are synthetic compounds obtained by the coprecipitation method with mineralogical structure similar to the mineral hydrotalcite. The LDHs presents octahedral layers containing combinations of one or more bivalent and trivalent metals by means of isomorphic substitution and a interlayer space containing water molecules and one or more anions intercalated. In this work the LDHs were synthesized by the coprecipitation method at variable pH. LDHs containing íons Mg2+ and Al3+ with the chloride anion intercalated. Molar rations were used between diand trivalent metals of (2,0), (2,5) and (3,0). After the syntheses, the samples were hydrothermally treated at 100°C and 80°C to evaluat e the temperature effect on the structure and morphology of synthesized LDHs. The new compounds characterization was made by the X ray diffraction that allowed to calculate the values of basal spacing between 7,68 to 7,79, values compatible with the existent in the natural hydrotalcites. The thermogravimetric analyses showed that synthetic LDHs presents two decomposition stages, interpreted as the losses of water of the interlayer space and removal of hydroxyl groups of the main layer. All the synthetic compounds showed similarity in the thermal behavior. The infrared spectroscopy analyses showed absorption vibrations at around 3477-3500 cm-1 and 1369cm-1, interpreted as being hydroxyl and intercalated water respectively. The superficial areas of the synthesized samples were obtained by BET method and they varied from 16,48 to 24,13 m2.g-1. The main diameters of the pores were obtained by BJH method and they allowed to characterize the synthetic LDHs as mesopores according the classification adopted by IUPAC. The unitary cell parameters were calculated by the Debye-Scherrer equation, using the basal spacing of the reflections (006) and (110) obtained from diffractograms with values for "a " varying from 3,04 to 3,05 Å and " c " varying from 22,96 to 23,33Å. The crystals morphology crystals and the pore distribution were obtained by scanning electron micrographs, that show images of crystals similar to the clayminerals, forming small pseudo-hexagonal plates with main size between 0,5 to 1,0 mm, that to group. To evaluate the application of those compounds in the wastewater treatment contaminated by heavy metals, adsorption tests were made for the Cu and Pb metals and the results showed a high adsorption rate, confirming the efficiency of HDL for the metallic ions removal in the water.