Eco-friendly oxidation of a reactive textile dye by CaO₂: effects of specific independent parameters

Textile wastewater containing dyes poses significant risks to the environment. Advanced oxidation processes (AOPs) effectively eliminate dyes by converting them into harmless substances. However, AOPs have drawbacks such as sludge formation, metal toxicity, and high cost. As an alternative to AOPs, calcium peroxide (CaO₂) offers an eco-friendly and potent oxidant for dye removal. Unlike certain AOPs that generate sludge, CaO₂ can be directly employed without resulting in sludge formation. This study examines the use of CaO₂ for oxidizing Reactive Black 5 (RB5) in textile wastewater without any activator. Various independent factors-pH, CaO₂ dosage, temperature, and certain anions-were investigated for their influence on the oxidation process. The effects of these factors on dye oxidation were analyzed using the Multiple Linear Regression Method (MLR). CaO₂ dosage was determined to be the most influential parameter for RB5 oxidation, while the optimal pH for oxidation with CaO₂ was found to be 10. The study determined that 0.5 g of CaO₂ achieved approximately 99% efficiency in oxidizing 100 mg/L of RB5. Additionally, the study revealed that the oxidation process is endothermic, with an activation energy (Ea) and standard enthalpy (ΔH°) for RB5 oxidation by CaO₂ determined as 31.135 kJ mol^-1 and 110.4 kJ mol^-1, respectively. The presence of anions decreased RB5 oxidation, with decreasing effectiveness observed in the order of PO₄^3-, SO₄^2-, HCO₃^-, Cl^-, CO₃^2-, and NO₃^-. Overall, this research highlights CaO₂ as an effective, easy-to-use, eco-friendly, and cost-efficient method for removing RB5 from textile wastewater.