J. G. P. Espínola

Kinetic study of the decomposition of hydrogen peroxide catalysed by Co(II) acetylacetonate supported on a silica-propylpiperazine matrix

Abstract The catalytic decomposition of hydrogen peroxide by Co(II) acetylacetonate supported on a propylpiperazine-silica matrix (Co(II)(acac)-PPS) was studied in aqueous media. The results showed that the reaction was first order in H2O2. It was found that the reaction eate was pH dependent with a maximum at around pH = 8. Activation parameters were determined in the temperature range 30–45°C. The low value obtained for the activation energy is in accordance with the proposed free-radical mechanism.

Isotherm data of Fe3+, Cr3+ and Co2+ adsorved on surface of silica-propylpiperazinedithiocarbamato

Abstract The silylant agent chloropropyltrimetoxysilane immobilized on silica gel reacts with piperazine, followed by another reaction with carbon disulfide in the presence of sodium hydroxide, to produce a new matrix sodium propylpiperazinedithiocarbamato silica. The basic centres of the resulting surface complexes are the Cr3+, Fe3+ and Co2+ cations from aqueous solution. The adsorbed isotherms for cations were adjusted to fit Giles models. The isotherm for Cr3+ could be classified as L2, while those for Fe3+ and Co2+ fitted the subgroup 2 of C class. The isotherm data show that the capacity of the final carbamate surface to chemisorb Fe3+ and Co2+ is only one third that observed for Cr3+.