Abstract The development of ceramic membranes for the most diverse separation processes has gained high visibility, mainly due to their better performance in harsh environments in comparison to polymeric materials. Among the different techniques used to prepare tubular ceramic membranes, the centrifugal casting (CC) is interesting for obtaining highly homogeneous structures, essential for gas separations. This study assessed the influence of two sintering temperatures (1450 and 1500 °C) of alumina membranes prepared by CC on the membrane morphology and on the permeation of helium, nitrogen and oxygen gases. The membranes were characterized by their morphology, apparent porosity, and gas permeation. The results indicated that the sintering temperature is a fundamental parameter for controlling membrane properties, an increase of only 50 °C led to a tenfold decrease in the gas permeate flux, indicating densification of membrane porous structure. This was in accordance with the results observed in the membrane micrographs and the apparent porosity.

The efficiency of the application of a chemically-modified activated carbon surface was investigated. The purpose of this study was to examine the effect of treatment with CaCl2 solution at a concentration of 2000 mg.L-1 on the sorption of nitrate ions from aqueous solutions in successive sorption/t reatment cycles. The sorbent was initially subjected to chemical treatment with CaCl2 and subsequently to the sorption process. Nine sorption cycles were performed. The concentrations of nitrate ions in the solution were measured by UV-Vis spectrophotometry before and after sorption. The results show that treatment with CaCl2 caused a significant increase in the percentage removal for each treatment step, reaching a removal rate of 80% of nitrate in the solution after nine cycles.

The objective of this work is to investigate the production of hydrogen as an energy source by means of the reaction of aluminum with water. This reaction only occurs in the presence of NaOH and KOH, which behave as catalysts. The main advantages of using aluminum for indirect energy storage are: recyclability, non-toxicity and easiness to shape. Alkali concentrations varying from 1 to 3 mol.L-1 were applied to different metallic samples, either foil (0.02 mm thick) or plates (0.5 and 1 mm thick), and reaction temperatures between 295 and 345 K were tested. The results show that the reaction is strongly influenced by temperature, alkali concentration and metal shape. NaOH commonly promotes faster reactions and higher real yields than KOH.