Reactive black 5 elimination via a Cu(ii)-induced sodium percarbonate process: Box–Behnken design, mechanism profiling, application performance and energy boosting†

Abstract

The utilization of sodium percarbonate (SPC, Na₂CO₃·1.5H₂O₂) as an alternative to H₂O₂ for degrading recalcitrant organics in advanced oxidation is emerging due to SPC's stability, safety, and pH adaptability. This study innovatively employed Cu(ii)-activated SPC to remove reactive black 5 (RB5), focusing on Box–Behnken design (BBD), mechanism profiling, application performance, and energy boosting. BBD and response surface methodology optimized conditions (2.592 mM Cu(ii), 0.022 mM SPC, pH 7.18) achieved 90.08% RB5 removal (R² = 0.9997, prediction error <1%), with the model showing strong predictive capability. Quenching experiments and liquid chromatography–mass spectrometry (LC–MS) revealed that ¹O₂, O₂˙⁻, and CO₃˙⁻ were the main active species in oxidizing RB5 through three possible pathways. Cl⁻, SO₄²⁻, NO₃⁻, and HCO₃⁻ (0.1–5.0 mM) contained in the ultrapure water did not inhibit RB5 removal in the Cu(ii)/SPC system, and the Cu(ii)/SPC could remove 76.1% of RB5 in industrial wastewater, demonstrating the potential for practical application of this system. The application of energy (heating, ultraviolet light, ultrasound) significantly improved the effectiveness of the Cu(ii)/SPC system in degrading RB5, thus these means can be used to assist in the activation of SPC in real dye wastewater treatment. This work provides theoretical and practical insights for SPC-based advanced oxidation processes.