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The thermal stability (60°C, 80°C, 100°C), antioxidant activity, and ultraviolet C light (UV-C) stability of standard polyphenols solutions (catechin, gallic acid, and vanillic acid) and of vegetal extracts from spruce bark and grape seeds were investigated. Exposure of the standard solutions and vegetal extracts to high temperatures revealed that phenolic compounds were also relatively stable (degradations ranged from 15 % to 30 % after 4 h of exposure). The highest antioxidant activity was obtained for ascorbic acid and gallic acid followed by catechin and caffeic acid and the grape seeds. The results show that, after 3 h of UV-C exposure, approximately 40 % of vanillic acid, 50 % of gallic acid, and 83 % of catechin were removed. Similar degradation rates were observed for vegetal extracts, with the exception of the degradation of catechin (40 %) from grape seeds. In addition, the photo-oxidation of polyphenols in the presence of food constituents such as citric acid, ascorbic acid, sodium chloride, and sodium nitrate was assessed.

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This study aims to highlight discrepancies between experimental and simulation linked to the mechanisms of Mo and V adsorption onto ferrihydrite (FHY) nanoparticles. We have measured adsorption capacities and uptake efficiencies and then fitted and compared these with outputs from various geochemical and adsorption models that were run as a function of pH, surface area (SA) and ferrihydrite particles size distributions. Our results revealed that the experimental data for the Mo system could be fitted very well, but this was not the case for the V system, when a model default value for the SA of FHY of 600 m2 g−1 was used. The discrepancy in the results for the V system can be explained by the lack of specific V species and/or associated constants in databases and variation in software versions, which change the outputted chemical species. Our comparative results also confirm that any experimental variables used as modelling inputs need to be checked carefully prior to any modelling exercises.