RESUMO
The sorptive removal of hexavalent chromium from aqueous solutions by calcined Mg-Al-CO(3) hydrotalcite was investigated in a batch mode. The influence of agitation speed, solution pH, initial chromium concentration, sorbent concentration and temperature has been tested in kinetic runs. Three kinetic models have been evaluated to fit the experimental data: the pseudo-first order, the modified-second order and the Elovich equation. It was shown that the first-order model could best describe the sorption kinetics. A Freundlich isotherm was used to fit equilibrium experiments. Hydrotalcite presents a sorption capacity of approximately 120 mg Cr/g, under the investigated experimental conditions. The calculated activation energy for process studied was around 40 kJ/mol.
Assuntos
Hidróxido de Alumínio/química , Antiácidos/química , Carcinógenos Ambientais/química , Cromo/química , Hidróxido de Magnésio/química , Modelos Teóricos , Adsorção , Carcinógenos Ambientais/isolamento & purificação , Cromo/isolamento & purificação , Cinética , TemperaturaRESUMO
Biosorption using suspended non-living biomass, and flotation (for consequent solid/liquid separation of the metal-loaded biomass) have been studied in the laboratory as a possible combined process, for the removal of toxic metals (i.e., cadmium) from dilute aqueous solutions. The various parameters of the process were investigated in depth, including re-use of biosorbent. A filter aid (contained in the biomass industrial waste used) was found not really to interfere. Zeta-potential measurements of the aforementioned system were also carried out. Promising results were obtained during continuous-flow experiments. A flotation residence time of 4 min was achieved. Metal removal and suspended biomass recovery were generally over 95%.