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Recebido em 16/2/11; aceito em 12/9/11; publicado na web em 8/11/11 This paper reports the use of an electrode modified with poly(o-methoxyaniline) for detecting lithium ions. These ions are present in drugs used for treating bipolar disorder and that requires periodical monitoring of the concentration of lithium in blood serum. Poly(omethoxyaniline) was obtained electrochemically by cyclic voltammetry on the surface of a gold electrode. The results showed that the electrode modified with a conducting polymer responded to lithium ions in the concentration range of 1 x 10 -5 to 1 x 10 -4 mol L -1 . The results also confirmed that the performance of the modified electrode was comparable to that of the standard method (atomic emission spectrophotometry).

We studied the effect of drying temperature of sugarcane bagasse (SB) on sorption of reactive blue 5G (RB5G) dye to test whether SB is a suitable biosorbent for industrial dye removal. First we assessed a set of SB characteristics that could influence the sorption capacity of dried biomass. Kinetic drying of the SB biomass was measured at different drying temperatures, ranging from 30 o C to 80 o C. We used a static gravimetric method to perform equilibrium moisture sorption experiments at drying temperatures of 35-65 o C. In addition, we measured activation energy and net isosteric heat of sorption. SB biomass was characterized as a heterogeneous low-porous and hygroscopic material, with a series of functional groups on its surface. A Lewis thin-layer model best represented the kinetic drying data. In addition, moisture diffusion into the SB biomass was characterized by a rate-controlling step in the drying process. Equilibrium moisture sorption data showed the expected effects of temperature controlling the sorption capacity and a multilayer sorption process. A sigmoidal sorption isotherm data was best represented by a BET model. A high energy demand is required for moisture removal from biomass as suggested by the measured isosteric heat of moisture sorption. Drying temperature did not influence the RB5G adsorption capacity of bagasse, therefore any drying temperature in the range of 30 o C to 80 o C could be used to make this material feasible as an industrial adsorbent.

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Neste trabalho, foi avaliado o desempenho do carvão ativado na adsorção dos corantes azul turquesa QG e amarelo reativo 3R. Para tanto, foram obtidos dados experimentais da cinética e do equilíbrio de adsorção para cada corante individualmente. Os experimentos foram conduzidos em sistema batelada sob temperatura e agitação controlada. Para descrever o equilíbrio de adsorção foi utilizado o modelo de isoterma de Langmuir. Para descrever a cinética de adsorção foram utilizados modelos matemáticos baseados nos mecanismos de transferência de massa que ocorrem no processo de adsorção (difusão no filme externo, adsorção na superfície, difusão nos poros). Os dados experimentais de equilíbrio mostraram que o processo de adsorção dos corantes pelo carvão ativado é favorável, sendo que a isoterma de Langmuir descreveu satisfatoriamente o equilíbrio de adsorção dos sistemas investigados. Os dados experimentais da cinética de adsorção mostraram que o tempo de equilíbrio foi de 800 e 1200 min para os corantes azul e amarelo, respectivamente. Na descrição da cinética de adsorção, os três modelos testados representaram de forma eficiente o processo.