Abstract
Anthocyanins from maqui (Aristotelia chilensis) and blackberry (Rubus glaucus) were used as light harvesters to improve the photocatalytic activity of titanium dioxide in visible light. Anthocyanins from both species were obtained using high-frequency ultrasound-assisted liquid-liquid extraction with methanol. Mixtures of anthocyanins were developed to study their effectiveness in the visible light/TiO2 reaction for the oxidation of aniline blue. For this purpose, stainless-steel foams were covered with TiO2 and anthocyanin and characterized by SEM. Different samples were fabricated by varying the ratio of the two anthocyanins in the mixture (100, 75, 50, 25 and 0 vol% of maqui-anthocyanin (delphinidin)). The mixtures of 25 vol% anthocyanin from maqui and 75 vol% anthocyanin from blackberry had higher total anthocyanin content and better photocatalytic activity in visible light: degradation of aniline blue was 40% at pH 7, 56% at pH 3 and 95% at pH 3 with the injection of oxygen for 2 h in comparison with TiO2-foam/UV light, which yielded values of 13% at pH 7 and 73% at pH 3 with and without the addition of oxygen. Natural dyes that are low-cost and environmentally friendly substances are shown to be capable of improving the visible-light photocatalytic activity of TiO2.
Highlights
Wastewater treatment is a major concern to everyone, especially today, given the lack of water in many communities around the world
The total anthocyanin content obtained for each maqui-blackberry juice mixture and each fruit alone is in Table 1, in which the results are expressed as milligrams of cyanidin-3-glucoside equivalent per 100 g of fruit
The best results were obtained with the mixture containing 25 vol% maqui (Aristotelia chilensis) and 75 vol% blackberry due to an association effect of the anthocyanin from both fruits and high total anthocyanin content, determined by the ratio between delphinidin and cyanidin anthocyanin types
Summary
Wastewater treatment is a major concern to everyone, especially today, given the lack of water in many communities around the world. Aniline is an organic compound (C6 H5 NH2 ) formed by a benzene ring bonded to an amino group It has a characteristic lipid consistency, with a light-yellow tonality and moderate solubility in water. It can be oxidized in air, where it changes to a red-brown compound. Aniline is used in a large number of product fabrications, such as polyurethane foam, rubber, paints, dye, pharmaceuticals, pesticides and explosives. It is a by-product of petroleum, paper and coal processing fabrication [1], suggesting that it is abundant in water everywhere. Households are another source of aniline waste; for example, clothes with dye are Catalysts 2020, 10, 1245; doi:10.3390/catal10111245 www.mdpi.com/journal/catalysts
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