No abstract

ABSTRACT. The goal of this work was to study the adsorption equilibrium of ions Zn 2+ and Cd 2+ using bovine bone char in fixed bed columns. Dynamic tests were performed with upstream flow fixed bed column, at 30 o C and average particle diameter of 0.08 mm. Initially, the optimal operating flow rate was determined, which was 4 mL min.-1 for both metals. The dynamic isotherms, obtained by mass balance in the breakthrough curves, were fitted to the Langmuir and Freundlich models. Simulations of the dynamics of ion adsorption provided satisfactory results, wherein the mass transfer coefficient was directly affected by the inflow concentration of ions, within the range of the study.Keywords: equilibrium data, heavy metals, mathematical model. Estudo comparativo da adsorção dos íons cádmio e zinco no carvão ativado de osso bovino RESUMO. O objetivo deste trabalho foi estudar o equilíbrio de adsorção de íons Zn 2+e Cd 2+ usando carvão de osso bovino em colunas de leito fixo. Testes dinâmicos foram realizados com o fluxo ascendente em coluna de leito fixo, a 30°C e diâmetro médio de partícula de 0,08 mm. Inicialmente, a vazão ótima de trabalho foi determinada, sendo de 4 mL min.-1 para ambos os metais. As isotermas dinâmicas foram obtidas pelo balanço de massa nas curvas de ruptura, e foram ajustadas aos modelos de Langmuir e Freundlich. A simulação da dinâmica de adsorção forneceu resultados satisfatórios para ambos os íons, em que o coeficiente de transferência de massa foi diretamente afetado pela concentração inicial dos íons metálicos.Palavras-chave: dados de equilíbrio, metais pesados, modelo matemático.

We report here electron paramagnetic resonance (EPR) measurements at 9 and 34 GHz, and room temperature (T), in powder and single crystal samples of the ternary compounds of copper nitrate or copper chloride with glycine and 1,10-phenanthroline [Cu(Gly)(phen)(H 2 O)]•NO 3 •1.5H 2 O (1) and [Cu(Gly)(phen)Cl] 2 •7H 2 O (2). In compound 1, the copper ions are arranged in 1-D chains along one of the crystal axes connected by syn-anti carboxylate ligands, while in 2 the array is nearly 3-D and the connections involve H-bonds and stacking interactions. The angular variation of the squared g-factor and the line width were measured as a function of orientation of the magnetic field (B 0) in three orthogonal crystal planes. In both compounds we observed one resonance without hyperfine structure for any magnetic field orientation which we attribute to the collapse of the hyperfine coupling and of the resonances of two chemically identical but rotated coppers in the unit cell, produced by exchange interactions. We analyse the results in terms of the structures of the compounds and chemical paths connecting neighbour copper ions which support the exchange interactions between neighbour spins in the lattice. Considering the collapse of the EPR signals of rotated sites in the lattices we are able to set lower limits to the exchange interactions, which are supported by weak equatorialapical carboxylate bridges in 1, and by paths containing hydrogen bonds and aromatic π-π interactions in 2. Broadening due to dipole-dipole couplings and hyperfine interactions are strongly reduced by these exchange couplings and their role in the EPR line width is more difficult to recognize.