Mechanical, fatigue and wear properties of sintered Carbon Nanotube-based functionally graded materials

Tese de Doutoramento Engenharia Mecânica

Production and characterization of ZrCN-Ag coatings deposited by mganetron sputtering

Tese de Doutoramento (Programa doutoral em Engenharia de Materiais)

Influence of different activated carbons on Ochratoxin A decrease in wines

The presence of mycotoxins in foodstuff is a matter of concern for food safety. Wines can also be contaminated with these toxicants. Several authors have demonstrated the presence of mycotoxins in wine, especially ochratoxin A (OTA) [1]. As these toxicants can never be completely removed from the food chain, many countries have defined levels in food in order to attend health concerns. The maximum acceptable level of OTA in wines is 2.0 µg/kg according to the Commission regulation No. 1881/2006 [2]. Although, higher levels of OTA have been detected in several wine samples. In order to reduce OTA to safer levels, several oenological products can be used in wine; including activated carbons, as shown in previous experiments. Regarding this, the aim of present study was to evaluate the effectiveness of several activated carbons for reducing the amount of OTA present in white and red wines as well as to evaluate their effect on wines physicochemical characteristics. Wine samples were artificially supplemented with OTA at a final concentration of 10.0 µg/L. The different activated carbons were applied at the concentration recommended by the manufacturer in order to evaluate their efficiency in reducing OTA levels. A mixture composed by gelatine, bentonite and activated carbon reduced 80% of OTA concentration in white wine. The same mixture was however less efficient in red wine, achieving only a reduction of 55%. Thereafter, the effect of activated carbon was evaluated in a red wine, achieving reductions of 66%. Considering these results more assays are being performed with other commercial activated carbons, in order to evaluate their efficiency. These results may provide valuable information for winemakers. Knowing the effect of commercial activated carbons they may choose most appropriate products to remove OTA, thus enhancing wine safety and quality.

Effect of different carbon materials as electron shuttles in the anaerobic biotransformation of nitroanilines

Aromatic amines resulted from azo dyes biotransformation under anaerobic conditions are generally recalcitrant to further anaerobic degradation. The catalytic effect of carbon materials (CM) on the reduction of azo dyes is known and has been confirmed in this work by increasing 3-fold the biological reduction rate of Mordant Yellow 1 (MY1). The resulting m-nitroaniline (m-NoA) was further degraded to m-phenylenediamine (m-Phe) only in the presence of CM. The use of CM to degraded anaerobically aromatic amines resulted from azo dye reduction was never reported before. In the sequence, we studied the effect of different CM on the bioreduction of o-, m- and p-NoA. Three microporous activated carbons with different surface chemistry, original (AC0), chemical oxidized with HNO3 (ACHNO3) and thermal treated (ACH2), and three mesoporous carbons, xerogels (CXA and CXB) and nanotubes (CNT) were assessed. In the absence of CM, NoA were only partially reduced to the corresponding Phe, whereas in the presence of CM, more than 90% was converted to the corresponding Phe. ACH2 and AC0 were the best electron shuttles, increasing the rates up to 8-fold. In 24h, the biological treatment of NoA and MY1 with AC0, decreased up to 88% the toxicity towards a methanogenic consortium, as compared to the non-treated solutions. This article is protected by copyright. All rights reserved