Nl. Dias et al., STUDY OF COPPER-COMPLEXES ADSORBED ON A SILICA-GEL SURFACE CHEMICALLY-MODIFIED WITH 2-AMINO-1,3,4-THIADIAZOLE, Colloids and surfaces. A, Physicochemical and engineering aspects, 141(2), 1998, pp. 181-187
The isotherms of adsorption of CuX2 (X=Cl-, Br-, ClO4-) by silica gel
chemically modified with 2-amino-1,3,4-thiadiazole were studied in ace
tone and ethanol solutions: at 298 K. The following equilibria constan
ts (in 1 mol(-1)) were determined: (a) CuCl2: 3.5 x 10(3) (ac), 2.0 x
10(3) (eth); (b) CuBr2: 2.8 x 10(3) (ac), 2.0 x 10(3) (eth); (c) Cu(Cl
O4)(2): 1.8 x 10(3) (ac), 1.0 x 10(3) (eth); ac = acetone, eth = ethan
ol. The electron spin resonance spectra of the surface complexes indic
ated a tetragonal distorted structure in the case of lower degrees of
metal loading on the chemically modified surface. The d-d electronic t
ransition spectra showed that for the ClO4-, complex, the peak of abso
rption did not change for any degree of metal loading, and for Cl- and
Br- complexes, the peak maxima shifted to a higher energy region with
a lower metal loading. (C) 1998 Elsevier Science B.V. All rights rese
rved.