Complementary: Green catalysis over red soil for pollutant removal

Abstract

Organic dyes from industrial wastewater pollute water tables. Here proposed solution for environmental control relies on pristine red soil for adsorption and oxidative degradation of methylene blue. Soil analysis comprised XRD, spectroscopic (FTIR and Raman) and microscopic (SEM/EDS) techniques, while spectrophotometry was applied for dye quantification. The dominant soil mineral is kaolinite while Fe homogeneous distribution is witnessed in the α- and γ-FeO(OH) form. Dye adsorption was monitored for both soil and kaolinite, with rising removal under basic conditions due to methylene blue transformation. Theoretical modelling enabled insight into dye orientation over goethite crystallographic planes and estimation of binding energy. Soil/Fenton reagent achieved a substantial 93 % dye removal. An optimal oxidant concentration in the Fenton system was 10 mM. We confirmed the excellent performance of pristine red soil samples as naturally occurring adsorbents and catalysts in Fenton oxidation of environmental pollutants.