Electron scavenger-assisted photocatalytic degradation of amido black 10B dye with Mn₃O₄ nanotubes : A response surface methodology study with central composite design

In this present work, visible-light-sensitive Mn₃O₄ photocatalyst has been synthesized using a simple hydrothermal route and the photocatalyst has been characterized by XRD, FT-IR, UV-vis DRS and SEM-EDX techniques. These studies show the formation of Mn₃O₄ nanotubes assembled into fused rod-like structures with good crystallinity and an optical bandgap of 1.81 eV. The photocatalytic performance of Mn₃O₄ in the absence and presence of electron scavenger (ES) such as peroxomonosulfate (PMS), peroxodisulfate (PDS) and hydrogen peroxide (HP) has also been analyzed in detail. The results reveal that merely 25% photodegradation efficiency is achieved by Mn₃O₄ photocatalysis. However, the photodegradation efficiency is significantly amplified up to 80% by Mn₃O₄ photocatalysis in the presence of PDS as an ES. Mn₃O₄ with PDS exhibits higher photodegradation efficiency than PMS and HP. The possible mechanisms of dye degradation by the photocatalyst in the absence and presence of electron scavengers and the significance of the obtained results are discussed. To identify the effects of experimental factors involved in photocatalytic degradation of amido black 10B dye, a response surface methodology (RSM) based on central composite design (CCD) has been employed. The factors that most significantly affect the degradation process are identified as the choice of electron scavenger, amount of photocatalyst added, and the irradiation time. A quadratic model has been developed based on the RSM analysis and has been found effective in predicting the degradation performance.