Treatment of cationic red X-GRL in high-salt printing and dyeing wastewater by an electrocatalytic ozonation system: treatment efficiency and degradation mechanism

High salt concentrations in printing and dyeing wastewaters significantly influence pollutant removal. The function of the electrocatalytic ozonation (MgMn _<i>x</i> O _<i>y</i> -GAC/EP) system in removing pollutants from high-salt printing and dyeing wastewater was investigated. Under high NaCl concentration, the H₂O₂ yield in the electrochemical system was maintained at approximately 53 mg L^-1. Under optimal treatment conditions, the degradation efficiency of cationic red X-GRL in the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system reached 100% within 16 min, and the mineralization efficiency achieved 90.8% within 60 min. The specific energy consumption of the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system was 0.027 kW h per gCOD. The SF of the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system was 13.04, indicating that MgMn _<i>x</i> O _<i>y</i> -GAC, EO and O₃ had a remarkable synergistic effect in the removal of cationic red X-GRL. The existence of ˙OH, ˙Cl, ˙O₂ ^- and ¹O₂ in the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system was demonstrated by quenching and electron paramagnetic resonance experiments. Based on these outcomes, the degradation mechanism of cationic red X-GRL in the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system under high salt conditions was proposed, which was the action mechanism of multiple free radicals mainly dominated by ˙O₂ ^- and ¹O₂. After repeated experiments, the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system accomplished a COD removal efficiency of 84%, which signified its relatively high stability. The MgMn _<i>x</i> O _<i>y</i> -GAC/EP system achieved a COD removal efficiency of approximately 86% for diverse pollutants. Overall, this study revealed that the MgMn _<i>x</i> O _<i>y</i> -GAC/EP system has novel prospects for the treatment of organic pollutants in high-salt wastewater.