Bruna Fonseca

Treatment of chromium(VI) solutions in a pilot-scale bioreactor through a biofilm of Arthrobacter viscosus supported on GAC

The aim of this work is to evaluate the applicability of a biofilm to the removal of chromium in solution, at a pilot scale. The effect of the initial concentration of metal on the biosorption behavior of an Arthrobacter viscosus biofilm supported on granular activated carbon, in batch and column essays was also analyzed. Six isotherm equations have been tested in the present study. The best fit was obtained with the Freundlich model. It was observed that as the initial chromium concentration increases, the uptake increases too, but the removal percentage decreases, with values between 95.20% (C(0)=5mg/l) and 38.28% (C(0)=1000 mg/l). The batch adsorption studies were used to develop a pilot bioreactor able to remove chromium from aqueous solutions. Data obtained in a pilot-scale reactor showed an average removal percentage of 99.9%, during the first 30 days, for the initial concentration of 10mg/l and an average removal percentage of 72%, for the same period and for the initial concentration of 100mg/l. Uptake values of 11.35 mg/g and 14.55 mg/g were obtained, respectively, for the initial concentration of 10 and 100mg/l. The results obtained are very promising and encourage the utilization of this biofilm in environmental applications.

Modelling of the Cr(VI) transport in typical soils of the North of Portugal

Adsorption of hexavalent chromium [Cr(VI)] onto a loamy sand soil was studied using batch and steady flow tests with contaminant solutions at pH 2, 5 and 7. In all the cases the adsorption of Cr(VI) decreased with increasing pH. The hexavalent chromium speciation and its presence as different oxyanions, according to the solution pH, were the main variables affecting the adsorption process. The influence of the ratio soil/solution concentration was also studied in flow systems at pH 2. Chromium retention increased with the increasing of its concentration in the influent solution. A two-site adsorption model was fitted to the breakthrough curves of hexavalent chromium solutions in order to estimate the Freundlich (k(F)) and Langmuir (S(max)) adsorption parameters, using CXTFIT code. These values were compared to those determined by batch tests and it was concluded that batch tests tended to underestimate these parameters. Nevertheless, they followed the same trend as the parameters determined in opened system, even when the pH of the initial solution was modified.