| Summary: | The present study investigated the degradation of an aqueous Allura Red AC (AR–AC) solution by activating hydrogen peroxide with bicarbonate using cobalt ion (Co<sup>2+</sup>) as the catalyst. Four independent variables (H<sub>2</sub>O<sub>2</sub>, NaHCO<sub>3</sub>, Co<sup>2+</sup>, and dye concentrations) were analyzed in the composite central design (CCD). AR–AC degradation was optimized using the response surface methodology (RSM). Under optimal degradation conditions (41.86 mg/L AR–AC, 5.58 mM H<sub>2</sub>O<sub>2</sub>, 2.00 mM NaHCO<sub>3</sub>, and 9.00 µM Co<sup>2+</sup>), decolorization > 99.86%, mineralization (CO<sub>2</sub> to conversion) of 12.99%, and total nitrogen removal of 51.97% were achieved. The predicted values for the three response variables were consistent with the experimental values, with determination coefficients (R<sup>2</sup>) greater than 0.9053. Because cobalt ions (Co<sup>2+</sup>) are a source of water pollution, after oxidation, these were adsorbed on sodium bentonite (Na–Bent), obtaining a final concentration of <0.01 mg/L. Bicarbonate-activated hydrogen peroxide is a potential technology for dye wastewater treatment that operates at an alkaline pH and at ambient temperature.
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