Highly efficient degradation of azo dye Orange G using laterite soil as catalyst under irradiation of non-thermal plasma

In this study, laterite soil containing various mineral oxides (e.g., Al2O3, Fe2O3 and TiO2), used as an alternative catalyst, was combined with gliding arc plasma treatment for Orange G (OG) degradation in aqueous solution. The results showed that the incorporation of laterite soil (as catalyst) in (OG solution exposed to plasma led to a significant degradation enhancement from 17% for plasma treatment alone to almost 100%. Compared with P25 TiO2, Fe2O3, and TiO2/Fe2O3 photocatalysts, the decolorization rate of OG can be increased from 56, 68 and 75% respectively to 100% after 60 min laterite-mediated plasma treatment. In the calcinated laterite, Fe2O3 was considered not only as TiO2 sensitizer due to its narrow band-gap but also as the heterogeneous Fenton catalyst. These synergistically enhanced the generation of the reactive species, i.e., 'OH, in the gliding arc plasma system and thus process efficiency for OG removal. Under optimized operating conditions, approximately 83% mineralization of OG solution was achieved within 60 min of treatment with the combined process. From the kinetics point of view, OG oxidation fitted with Langmuir-Hinshelwood model with the second-order rate constant (k(r)) and adsorption constant (K-s) of 5.74 mg min(-1) and 0.12 L mg(-1), respectively, suggesting that the reaction occurs at the catalyst surface. The catalyst was highly stable even after 5 consecutive cycles.