Papers by Author: Paulo A.M. Mourão

Abstract: A carbon molecular sieve for the purification of a gas mixtures containing O2, N2 and CO2, CH4 was produced from a waste granulated PET by means of a single carbonisation step at 973 K. Activated carbon materials presenting good adsorption capacity and some selectivity for O2/N2 and CO2/CH4 were prepared from granulated PET and cork oak with pore mouth narrowing using CVD from benzene. The diffusion coefficients of O2, N2, CO2 and CH4 in these materials were calculated and are comparable to published values determined on Takeda 3A and on a carbon molecular sieve prepared from PET textile fibres by means of carbonisation and subsequent CVD with benzene. However, the selectivities were not quite as good as those given by Takeda 3A. However, taking into account that this is a first attempt at producing CMS from PET, the results are encouraging, and it is to be expected that further development of the experimental procedure will result in new materials with improved performance.

Abstract: Over the last decades the literature has shown the possibility of producing activated carbons (AC) from a wide variety of raw materials, and to use them as one of the most environment-friendly solutions for waste disposal [1]. Simultaneously, it has been shown that the adsorption of pollutants from different sources by activated carbons is one of the most efficient techniques for remediating or solving this kind of problem [2]. In this context, phenolic compounds represent one of the most important classes of pollutant present in the environment [3]. In this perspective, we present a study involving the production of AC from cork (Quercus suber L.), PEEK (polyetheretherketone) wastes or granulated recycled PET (polyethyleneterephthalate) and their applicability for the adsorption of phenolic compounds from the liquid phase. All samples were characterised in relation to their structural properties and chemical composition, by different techniques, including nitrogen adsorption at 77 K, elemental analysis (C, H, N, O and S) and point of zero charge (PZC). The activated carbons produced demonstrated high adsorption capacities both in the gas and liquid phase as exemplified by N2 and phenolic compounds adsorption experiments. Based on the structural and chemical properties, and on the kinetic and equilibrium studies of liquid phase adsorption, it is possible to conclude that it is the porous volume of the ACs that predominantly controls the process of phenolic compounds adsorption.

Abstract: Lysozyme and BSA were used, as model proteins of considerably different dimensions, in order to evaluate the influence of the distinct pore structural characteristics of three types of ordered mesoporous silica materials (MCF, SBA-15 and MCM-41) on protein adsorption. Characterisation by X ray diffraction and nitrogen adsorption at 77K revealed the typical pore structural features of each type of material. The maximum of the pore size distributions indicated that the width of the windows of MCF (2) (mesitylene/P123 of 2) was larger than the pore diameter of the unidirectional tubular pores of SBA-15. All the materials presented similar small external surface areas but high pore volumes, with that of MCF (2) being the highest. The adsorption of lysozyme at pH=8 increased in the order MCM-41<< SBA-15< MCF (2), and the uptakes were well above those of BSA at pH=5. Although BSA is not completely excluded from the mesopores of SBA-15 and MCF (2), as happens with MCM-41, the adsorption occurs to a very limited extent. The overall behaviour of these SBA-15 and MCF (2) samples was not significantly different and both revealed potential for the separation of these proteins.

Abstract: Activated carbons are materials extensively used to remove a variety of pollutants in different media. The porous structure, the surface chemistry and the type of adsorptive determine the potential of activated carbons as an adsorbent material. However, in a more global perspective it is necessary to consider other factors such as the economical viability of production and reuse. This last factor depends on the capacity of regeneration of the activated carbons after each application. Following this guideline, the objective of this work was to evaluate the capacity of regeneration of some specific activated carbons prepared from cork oak wastes, used in the adsorption of phenolic compounds in the liquid phase. Simultaneously, the performance of our carbons are compared with the behaviour of a commercial carbon (Norit SX plus). The experimental procedure consists in the adsorption of one phenolic compound, followed by the regeneration of the adsorbent, succeeding a series of adsorption/regeneration processes. The methods of regeneration used were simple washing with distilled water under magnetic stirring, washing with ultrasound and thermal regeneration under inert atmosphere. The performance of the activated carbons was strongly dependent on their nature and the regeneration method applied.

Abstract: Activated carbons (AC) were prepared from waste granulated Polyethyleneterephthalate (PET) by chemical activation with phosphoric acid, sodium hydroxide and potassium hydroxide. All AC were characterised by N2 adsorption at 77 K, and those prepared with H3PO4 had a narrow pore size around 0.8 nm, those prepared with NaOH had a larger pore size higher than 1.52 nm and those prepared with KOH presented a pore size varying between 0.66 and 1.58 nm. The results suggest that H3PO4 and NaOH are not the most suitable activating agents for preparing AC with a high pore volume from waste PET. The AC produced with KOH presented a very high porosity, which passed through a maximum of 0.75 cm3g-1, due to an enlargement of the small micropores with an increase of the carbonisation temperature.

Abstract: Activated carbons have been prepared by physical activation in CO2 of commercial byproduct kraft lignin (as received, after de-ashing and after impregnation with NaCl) and natural cork. The results obtained show that the presence of natural inorganic impurities increases the reactivity of cork and lignin significantly and also results in limiting values for the micropore volume and in widening of the micropore size. Pure de-ashed lignin is exceptionally non-reactive but allows microporous activated carbons to be obtained which have very narrow micropore widths of ~0.5-0.6nm. When the de-ashed lignin is impregnated with NaCl similar micropore volumes and widths can be obtained but in a considerably shorter time (~30min instead of ~8h) which would result in a considerable energy saving and is therefore a promising procedure for the production of microporous activated carbons from low-cost kraft lignin.