Iara R. Guimarães

Preparation of activated carbons from coffee husks utilizing FeCl3 and ZnCl2 as activating agents

Ferric chloride was used as a new activating agent, to obtain activated carbons (AC) from agro industrial waste (coffee husks). This material was compared with two samples from the same raw material: one of them activated by using the classical activating agent, zinc chloride, and the other, activated with a mixture of the two mentioned activating agents in the same mass proportion. The carbonaceous materials obtained after the activation process showed high specific surface areas (BET), with values higher than 900 m(2)g(-1). It is interesting to observe that the activation with FeCl(3) produces smaller pores compared to the activation with ZnCl(2). An important fact to emphasize in the use of FeCl(3) as activating agent is the activation temperature at 280 degrees C, which is clearly below to the temperature commonly employed for chemical or physical activation, as described in the bibliography. All the studied materials showed different behaviors in the adsorption of methylene blue dye and phenol from aqueous solutions.

Removal of organic dyes using Cr-containing activated carbon prepared from leather waste

In this work, hydrogen peroxide decomposition and oxidation of organics in aqueous medium were studied in the presence of activated carbon prepared from wet blue leather waste. The wet blue leather waste, after controlled pyrolysis under CO(2) flow, was transformed into chromium-containing activated carbons. The carbon with Cr showed high microporous surface area (up to 889 m(2)g(-1)). Moreover, the obtained carbon was impregnated with nanoparticles of chromium oxide from the wet blue leather. The chromium oxide was nanodispersed on the activated carbon, and the particle size increased with the activation time. It is proposed that these chromium species on the carbon can activate H(2)O(2) to generate HO radicals, which can lead to two competitive reactions, i.e. the hydrogen peroxide decomposition or the oxidation of organics in water. In fact, in this work we observed that activated carbon obtained from leather waste presented high removal of methylene blue dye combining the adsorption and oxidation processes.

Degradation of organic compounds in a fenton system based on chitosan/Fe0/Fe2O3 composites: a theoretical and experimental study

Chitosan is a polymer with interesting characteristics for use in catalysis, such as biocompatibility, high chemical reactivity and stability under various conditions. Seeking new applications, a new hybrid material was synthesized for use in the degradation of organic compound. A synthesis route proposed led to the formation of a material in the form of film. The characterization data indicated the presence of hematite, as well as metallic iron. In addition, a theoretical model for interaction of iron with chitosan was proposed. Molecular dynamics simulations indicate that non-Coulomb interactions modulate the adsorption process between reactive red dye and chitosan. The catalytic behavior of these hybrid materials was investigated for the H2O2 decomposition to O2 and the degradation of reactive red dye. The hybrid material showed high degradation capacity, confirming this material as an efficient heterogeneous Fenton catalysts.