Imobilização de etilenimina, etilenossulfeto, 2- aminoetanotiol em silica gel - termodinamica das interações dos centros basicos nitrogenio e enxofre com cations em solução aquosa

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

The silylating agent 3-mercaptopropyltrimethoxysilane (MPTS) grafted onto silica gel was subsequently condensed with one molecule of ethylenimine (etn). In the homogeneous route, etn and MPTS reacted to yield 3-trimethoxypropylthioethylamine (MPTS), which was covalently anchored on silica gel. The dired reaction of silica and etn gave Sil(CH2CH2NH)4CH2CH2NH2 and its elemental nitrogen analysis showed 5.81 mmol per gram of silica. Ethylenesulfide (H2C)2S reacted with (CH3O)3Si(CH2)3NH2 forming a new silylating agent, which was anchored on silica surface through a sol-gel procedure. The compound 2-aminoethanothiol was immobilized on silica surface through a heterogeneous route, using (CH3O)3Si(CH2)3CI. The silylating agents and the modified silicas were caracterized by elemental analysis, infrared spectroscopy, NMR spectroscopy of H, C e Si, thermogravimetry and surface area. These modified organofunctionalized surfaces were able to adsorb divalent cloride and nitrate cations from aqueous solution. The adsorption was performed using a batchwise process and the maximum adsorption capacity followed the sequence Cu(ll) >Ni(ll) >Co(II). Through calorimetric titrations, the thermodinamic values of cation-basic centre interadions were obtained, with larger exothermic enthalpic values for copper nitrate. The calculated DG values indicated that the reactions are spontaneous and the entropy is also favourable for the majority of those systems.

ASSUNTO(S)

silica gel calorimetria termodinamica

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