Role of CTAB, and reactive radical species (HO and O2−) on the permanganate redox reaction

• Published in: Journal of molecular liquids Vol. 414; p. 126036
• Main Authors: Zaheer, Zoya, Bawazir, Wafa A., Youssef Ayed Al-Juhani, Atheer, Abdullah Hassan Abdullah, Thikra
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2024
• Subjects: Congo red; CTAB; Humic acid; Hydroxyl radical; Permanganate; Permanganate; Congo red; CTAB; Humic acid; Hydroxyl radical
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.126036

•Sulfuric acid enhanced the oxidative degradation of Congo red with permanganate.•Cationic surfactant solubilized the reactant into Stern-layer.•Humic acid accelerates oxidation rate of Congo red/MnO4− system.•Scavengers have no effect on the redox reaction. Permanganate-H2SO4 redox system was used to establish the role of cetyltrimethylammonium bromide (CTAB), and reactive radical species on the oxidative degradation of Congo red. The absorbance at 496 nm increases for ca. 6.0 min, and then decreases. Permanganate-Congo red redox reaction was very slow (degradation efficiency = 46 % in 180 min with kobs = 0.004 min−1 at 496 nm). The degradation efficiency was found to be 85 % in 6.0 min of reaction time with H2SO4. Congo red and permanganate interact with CTAB aggregates due to the electrostatic interactions. The decay of absorbance at 467 nm became very slow with increasing CTAB concentrations. The oxidative treatment of Congo red/MnO4− system follows first-, and complex – order kinetics with permanganate, and Congo red concentrations, respectively. The Congo red degradation efficiency remains unaffected with sodium pyrophosphate and sodium fluoride, which ruled out the possibility of Mn(III) formation as an oxidation state of manganese. Humic acid (HA) enhanced the degradation efficiency of Congo red/MnO4− system, and facilitated the in-situ formation of water soluble colloidal MnO2. The scavenger’s studies revealed that hydroxyl (HO), and superoxide (O2−) radicals were not the reactive species in the Congo red/ MnO4− redox system under our experimental conditions.