Bioreduction of gold nanocolloids using Quercus infectoria ( Oliv ): UV-assisted cationic-anionic dye degradation

Water pollution is one of the biggest environmental problems that directly affect human beings. According to natural resources defense council (NRDC), it causes 1.8 million deaths in 2015 and each year, 1 billion people suffer from unsafe water. Dyes which are expelled by textile industry directly into water supply prevent light entering the ecosystem. Light absorption diminishes photosynthetic activity of algae and influences the food chain. The dyes being a potential carcinogen increase the risk of cancer. This study focuses on degradation of dyes using gold nanocolloids. Gold nanocolloids are synthesized in this experiment using green, bioreduction method. The precursor HAuCl 4 is prepared by dissolving gold and aqua regia. The precursor is reduced using Quercus infectoria ( Oliv ) gall extract which is rich in tannins. The optical, vibrational, structural, and morphological characterization is done for the colloidal gold. The obtained gold colloid is hence used to reduce methylene blue (MB) and methyl red (MR) dyes which could be used for studying degradation of dyes with large scale impact. In our work, we accomplished about 94% degradation of methylene blue (MB) into leucomethylene blue and 92% degradation of methyl red (MR) into reduced methyl red under 30 min. These results show that the gold nanocolloids exhibit good photocatalytic degradation comparing with previous literatures and the mechanism is elucidated and explained in this work.