Synergistic Mechanisms Indigo Carmine Removal using Clay Rich Iron Coupled Ultrasound and Oxidant

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Background/Objectives: The coloured wastewater discharge from industrial sources cause harm to the human health due to these substance toxicities. Indigo dyes are among the most widely used in the dyeing process.This study is intended to achieve suitable approach to remove the dye using a catalytic method. Methods: The dye removal involves a natural catalyst and an oxidant coupled with ultrasound. Initially, the catalyst was characterized using analytical techniques, including Fluorescence and Diffractometer X-ray. Subsequently, the isotherm adsorption was modelled. Then, the degradation parameters optimization such as catalyst dose, dye concentration, PDS concentration and pH was investigated. To establish the involvement of SO4 •−, OH•, and HO2 •/O2 •− radicals in the degradation of IC, BQ, i-PrOH and t-BuOH, a scavenging test was performed using 100 mM of each product. Findings: The catalyst revealed the presence of quartz (SiO2), goethite (α-FeIIO(OH)), kaolinite (Al2Si2O5(OH)4) and (KAl2(AlSi3O10)(OH)2). Elemental chemical analysis demonstrated the presence of significant quantities of iron (48.98%) and silica (29.43%) in the sample. The adsorption phenomenon enabled the modelling of the isotherm, which demonstrated a perfect fit with the Langmuir model, and the determination of the adsorption kinetics, which are second-order. The subsequent analysis of degradation parameters indicated the following optimal conditions: The concentration of the catalyst (IC) was determined to be 30 µM, the dosage of the catalyst was established as 2 g/L, the concentration of the PS was measured to be 25 µM, and the pH was adjusted to 6.45. These conditions resulted in 61.35% degradation. The degradation mechanism demonstrated the involvement of various free radicals in the process, most notably sulfate (SO4 •−), hydroxyl (OH•) and superoxide (O2 •−). In conclusion, it was observed that the catalyst demonstrated a satisfactory catalytic capacity across a series of oxidation cycles, with this capacity being maintained until the fifth cycle. Novelty: The dye removal innovative process is involving a natural catalyst and an oxidant coupled with ultrasound. The implementation of this process is an effective approach for the dyes treatment in wastewater. Keywords: Indigo Carmine (IC), Peroxydisulfate (PS), Adsorption, Degradation, Innovative Oxidation Process