Chemisorption and thermodynamic data of the interaction between a chelate free acidic center with basic groups attached to grafted silicas.
The molecule 2-aminoethanethiol was added to the grafted silylant agent [(3-chlorosilylpropyl)trimethoxysilane] (cpts) onto silica gel(triple bond SilCl), obtaining a surface (triple bond SilSNH(2)) and giving 0.70 mmol g(-1) of nitrogen; the surface of silica was modified with [(3-mercaptosilylpropyl)trimethoxysilane] (mpts) with surface (triple bond SilSH), giving 0.78 mmol g(-1) of sulphur. Both matrices, (triple bond SilSNH(2)) and (triple bond SilSH), adsorb copper and cobalt acetylacetonates from ethanolic solution. Adsorption, using a batchwise process, showed that copper chelate was the most adsorbed. The interactions between the basic centers attached to organic chains of these modified silicas with the cations in the chelates Me(acac)(2) [M=Cu and Co] were followed through calorimetric titrations. Exothermic enthalpic results were obtained for the triple bond SilSNH(2) matrix. The spontaneity of these systems was reflected in negative free Gibbs energy and positive from entropic values.
Arakaki
Luiza N H
LN
Departamento de Química, CCEN, Universidade Federal da Paraíba, João Pessoa, Paraíba 58059-900, Brazil. arakaki@labpesq.quimica.ufpb.fr
de Sousa
Antonio N
AN
Espínola
José G P
JG
Oliveira
Severino F
SF
Airoldi
Claudio
C