Design of a New Catalyst, Manganese(III) Complex, for the Oxidative Degradation of Azo Dye Molecules in Water Using Hydrogen Peroxide

In the current work, chloro(<i>meso</i>-tetrakis(phenyl)porphyrin) manganese(III) [Mn(TPP)Cl] was synthesized following two steps: the preparation of <i>meso</i>-tetraphenylporphyrin (H_⁠2TPP) and the insertion of manganese into the free porphyrin H₂TPP. The compounds were characterized using SEM, FT-IR, UV, TGA/DTA, and XRD analyses. Manganese(III) <i>meso</i>-porphyrins exhibited hyper-type electronic spectra with a half-vacant metal orbital with symmetry, such as [dπ:dxz and dyz]. The thermal behavior of [Mn(TPP)(Cl)] changed (three-step degradation process) compared to the initial H₂TPP (one-step degradation process), confirming the insertion of manganese into the core of the free porphyrin H₂TPP. Furthermore, [Mn(TPP)Cl] was used to degrade calmagite (an azo dye) using H₂O₂ as an oxidant. The effects of dye concentration, reaction time, H₂O₂ dose, and temperature were investigated. The azo dye solution was completely degraded in the presence of [Mn(TPP)(Cl)]/H₂O₂ at pH = 6, temperature = 20 °C, C₀ = 30 mg/L, and H₂O₂ = 40 mL/L. The computed low activation energy (Ea = 10.55 Kj/mol) demonstrated the efficiency of the proposed catalytic system for the azo dye degradation. Overall, based on the synthesis process and the excellent catalytic results, the prepared [Mn(TPP)Cl] could be used as an effective catalyst for the treatment of calmagite-contaminated effluents.