Study of copper complexes adsorbed on a silica gel surface chemically modified with 2-amino-1,3,4-thiadiazole

Abstract

The isotherms of adsorption of CuX 2 (X=Cl −, Br −, ClO − 4) by silica gel chemically modified with 2-amino-1,3,4-thiadiazole were studied in acetone and ethanol solutions, at 298 K. The following equilibria constants (in l mol −1) were determined: (a) CuCl 2: 3.5×10 3 (ac), 2.0×10 3 (eth); (b) CuBr 2: 2.8×10 3 (ac), 2.0×10 3 (eth); (c) Cu(ClO 4) 2: 1.8×10 3 (ac), 1.0×10 3 (eth); ac=acetone, eth=ethanol. The electron spin resonance spectra of the surface complexes indicated a tetragonal distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d–d electronic transition spectra showed that for the ClO − 4 complex, the peak of absorption 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.