Coupling of Coagulation and Fenton-Like Oxidation for Decolorization of Congo Red Dye in Water

Azo dyes are widely utilized in a variety of industries, including food, cosmetics, and textiles. Removal of azo dyes from wastewater by the conventional biological process is challenging due to its toxicity. Alternative treatment technology is needed to remove the dye effectively and in a relatively short duration. The processing technology is expected to be able to reduce pollutant materials before they enter water bodies which are a source of agricultural irrigation. In this work, dye removal was studied in some physical and chemical processes, including coagulation (Coag.), Fenton-like oxidation (FLO), and its combination. Synthetic Congo Red (CR) solution was used as a contaminant model of dye wastewater. The assays were performed in a laboratory Jar-Test apparatus with varying FeCl₃ coagulant doses (20-30 mg/L), H₂O₂ doses (42-1,680 mg/L), and coupling mode (Coag.-FLO; FLO-Coag.; FLO/Coag.). The congo red decolorization up to 87% was observed in the coupling of Coag.-FLO process at 24 mg/L FeCl₃, 280 mg/L H₂O₂, pH⁸ (Coag.) and pH³ (FLO). Compared to the removal efficiency of the Coag. (color removal 45%) and FLO (color removal 62%) under selected circumstances. In addition to the higher CR removal, the coupling Coag.-FLO process showed potential cost saving due to less H₂O₂ dose and partially shift to coagulant.