RESUMO
Ultrafine CeO2-δ nanopowder, prepared by a simple and cost-effective self-propagating room temperature synthesis method (SPRT), showed high adsorption capability for removal of different azo dyes. Batch type of adsorption experiments with fixed initial pH value were conducted for the removal of Reactive Orange 16 (RO16), Methyl Orange (MO), and Mordant Blue 9 (MB9). The equilibrium adsorption data were evaluated using Freundlich and Langmuir isotherm models. The Langmuir model slightly better describes isotherm data for RO16 and MO, whereas the Freundlich model was found to best fit the isotherm data for MB9 over the whole concentration range. The maximum adsorption capacities, determined from isotherm data for MO, MB9, and RO16 were 113, 101, and 91 mg g(-1) respectively. The adsorption process follows the pseudo-second-order kinetic model indicating the coexistence of chemisorption and physisorption. The mechanism of azo dye adsorption is also discussed.
RESUMO
Bentonite samples collected from vicinity of Petrovac and Aleksinac were treated with different sulfuric acid molarities. Acid attack dissolved the octahedral sheets by interlayer and edge attack. The effects of the H(2)SO(4) acid caused an exchange of Al(3+), Fe(3+) and Mg(2+) with H(+) ions leading to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheets promoted the dispersion of corresponding layers and formation of amorphous silicon. The activated bentonites, after the treatment of sulfuric acid, exhibited a lower cation-exchange capacity (CEC) and significant increase of specific surface area from 6 to 387 m(2) g(-1) (bentonite from Petrovac) and from 11 to 306 m(2) g(-1) (bentonite from Aleksinac). The acid reaction caused a splitting of particles within the octahedral sheet which led to an increase in specific surface area and decrease in CEC in both bentonites.