The kinetic and hydrodynamic behaviour of a fixed-bed electrochemical reactor was studied in terms of current efficiency (CE) and energy efficiency (EE). In the kinetic experiments the effects of fixed bed thickness (L), current density (i) and initial concentration of copper (C0) were studied. In the hydrodynamic experiments the permeability (k) of the electrode and the coefficient for inertial forces (c) were also studied as functions of the applied current density. At low current densities and bed thicknesses greater than 1.0 cm, negative CE and EE were observed as a consequence of the dissolution of the porous matrix. At high current densities low CE and EE were observed and a powdery deposit was formed on the surface of the particles. From the results of the kinetic study bed thickness and the range of current densities employed in the hydrodynamic experiments were chosen. In these experiments the electrodeposition process continued until the whole electrode had been clogged and no more electrolyte could pass through it. The relationship between pressure drop and flow rate was well described by the Forchheimer equation. It was observed that the reduction in porosity due to copper electrodeposition causes the flow rate to decrease because of the decrease in electrode permeability, but it had no influence on current efficiency.

Dehydration of ethanol via adsorption using molecular sieves has recently been suggested as a promising alternative to the conventional separation methods for ethanol-water mixtures. 3A zeolites possess selective micropores whereon, due to the small size of their pores, the water molecules are adsorbed while the ethanol molecules are excluded. The scope of this work was, hence, the thermodynamic and kinetic study of ethanol-water adsorption on commercial zeolites of different origins, with the aim to select the best one. For the thermodynamic study, a thermostated bath was used at four different temperatures, where the data obtained by the static method could be correlated by means of a nonlinear isotherm. The kinetic data were obtained in a circulating finite liquid bath cell, where the effect of the temperature and of the mean diameter of the adsorbent particles on the rate of adsorption was studied. The results obtained in this way, expressed through uptake rate curves, showed that the adsorption rates were strongly dependent on the parameters studied. On comparing the adsorption rates among the adsorbents (commercial 3A zeolites), it could be concluded that, under the same operational conditions, exists a pronounced difference among them

Improving adsorptive processes demands a constant search for new adsorbents. In the specific case of ethanol-water separation, A zeolites are successfully being used. The use of nonconventional adsorbents to substitute zeolites, mainly starchy adsorbents in virtue of their known chemical affinity water, has recently been proposed. In this work a thermodynamic and kinetic study has been undertaken on the liquid phase adsorption of water from an ethanol-water mixture using manioc starch pellets as the adsorbent. The fundamental thermodynamic data were obtained by means of the static method, using a thermostated bath at four different temperatures (25, 40, 50 and 60° C), and could be correlated by means of a semi-empirical isotherm. The kinetic data, in turn, were obtained in a finite circulating liquid bath cell, enabling the construction of uptake rate curves, whereby the influence of temperature, interstitial velocity and adsorbent mean particle size on the adsorption rate was analyzed. The effective internal diffusivities at the experimental temperatures were estimated by a pore diffusion model and the results obtained were compared with those for commercial 3A zeolite