Ana Paula de Oliveira

Application of high resolution X-ray emission spectroscopy on the study of Cr ion adsorption by activated carbon.

In this work granular activated carbon has been chosen as an absorbent in order to investigate the Cr(VI) reduced by adsorption experiments. Several batch chromium-sorption experiments were carried out using 0.25 g of granular activated carbon in 50 mL aqueous solution containing approximately 70 and 140 mg L(-1) of Cr(VI) and Cr(III), respectively. Cr-Kbeta fluorescence spectra of Cr adsorbed in a carbon matrix and Cr reference materials were measured using a high-resolution Johann-type spectrometer. Based on evidence from the Cr-Kb satellite lines, the Cr(VI) reduction process has actually happened during metal adsorption by the activated carbon.

Assessment of the banana pseudostem as a low-cost biosorbent for the removal of reactive blue 5G dye.

In this work, the removal of reactive blue 5G (RB5G) dye using the drying biomass of banana pseudostem (BPS) was investigated. The characterization of BPS particles was performed. Improvement in the RB5G dye removal performance at the following sorption conditions was evidenced: pH 1, 30°C sorption temperature and 40 rpm shaking, regardless of the particle size range. Kinetic RB5G dye sorption data obtained at better conditions fit well in an Elovich model. A combined Langmuir–BET isotherm model provides a good representation of the RB5G dye equilibrium sorption data, which shows the evidence of a physical sorption process on the BPS surface. Based on the results, the removal of RB5G dye molecules by BPS is based on a physical sorption process.

Potential of Salvinia auriculata biomass as biosorbent of the Cr(III): directed chemical treatment, modeling and sorption mechanism study

ABSTRACT In this work, the mechanism of the Cr(III) sorption by Salvinia auriculata biosorbent was studied in two stages. To understand the influence of the sorption parameters on the Cr(III) uptake, preliminary tests were performed. First, S. auriculata biomass was separately treated with base and acid solutions. Second, acid and base treatment of samples was performed based on the knowledge data base of our group. It was achieved a higher Cr(III) sorption capacity above 15 mg g-1 as associated to an increase of the micro-pores specific area and biosorbent volume. The obtained kinetic data of raw and treated biosorbents were well described by the intra-particle diffusion model. In this model, Cr(III) adsorption onto treated biomass is progressively improved with appearing of different mass transfer zones from out layer up to micro-porous layers. The equilibrium data of raw biomass were best described by the Langmuir isotherm, whereas the equilibrium data of the treated biomass were best fit by a combination of both Langmuir and Dubinin–Radushkevich isotherms. At low concentrations the adsorption most likely occurred on the outer monolayer, as proposed by the Langmuir model, followed by the adsorption on the micro-porous layers, as validated by the Dubinin–Radushkevich isotherm.