Photocatalytic Activity of ZnO Nanoparticles from Pineapple Skin for Degradation of Congo Red Dye

The development of the cloth industry can trigger a large amount of liquid waste to be produced, which, of course, can pollute the environment without proper and effective processing. This fluid waste comes from the dyeing process and usually uses dyes made from azo compounds such as Congo Red (CR), where these compounds cannot be degraded naturally in the environment. For this reason, appropriate waste processing methods are needed that are capable of degrading dye waste produced by the industry, namely with photocatalysis. ZnO nanoparticles are semiconductor materials with the potential to be catalysts because of their high electron mobility, cheapness, and non-toxicity. These nanoparticles can be extracted using the green synthesis method with pineapple peel extract as a bio-reduction. The effectiveness of the photodegradation of the synthesized ZnO nanoparticles is altered by the mass of the catalyst and the duration of UV light irradiation. Catalyst masses of 5, 8, 10, 12, 20, and 30 mg were able to degrade CR dye with a concentration of 30 ppm, respectively 93.51, 93.87, 95.15, 96.15, 97.72, and 97.08 % after irradiation for 210 min. With the large percentage of dye photodegradation, the ZnO nanoparticles resulting from the research showed good photocatalytic activity, which could later be used to process liquid waste from the textile industry. HIGHLIGHTS The textile industry produces large amounts of liquid waste from the dyeing process, especially from azo compounds such as Congo Red (CR), which are difficult to degrade naturally in the environment. ZnO nanoparticles extracted using the green synthesis method with pineapple peel extract as a bio-reduction offer an environmentally friendly solution for processing liquid waste in the textile industry with a photocatalyst system. ZnO nanoparticles have good photocatalytic activity, especially in degrading Congo Red dye up to 97.72 % at a concentration of 30 ppm after 210 minutes of irradiation, depending on the mass of the catalyst. GRAPHICAL ABSTRACT