Doehlert matrix-based optimization of degradation of Rhodamine B in a swirling flow photolytic reactor operated in recirculation mode

Textile industries produce extensive dye waste which if discharged into the freshwater bodies, can result in contamination and toxic effects on humans as well as ecosystem. Rhodamine B (RhB) is one of the major pollutants in textile wastewater and requires considerable attention for its remediation. The present study focuses on developing a novel design of a swirling flow photolytic oxidation reactor for large volume treatment of RhB dye. Degradation of Rh-B was studied at varying initial concentrations, variable quantities of Fenton’s reagent and hydrogen peroxide as additives, individually and in combination to achieve maximum efficacy. Further, the treatment efficacy of the reactor was optimized using surface response method based on Doehlert matrix with initial dye concentration (ppm), Fenton’s reagent (g) and pH as independent factors optimized to achieve maximum RhB degradation (%). The article also describes in detail about the design considerations and advantages of swirling flow photolytic reactor over classical UV/Fenton batch reactor setup. It highlights advantages of the design modifications along with catalytic oxidative reactions to achieve maximum dye degradation. The swirling flow photocatalytic reactor showed promising results especially for large volume degradation of RhB dye, while degradation percentage was significantly improved using the optimized parameters. When compared to the individual UV irradiation (25% degradation), the approach involving the combination i.e. UV with Fenton in the modified reactor, demonstrated degradation of RhB as high as up to 100%.