Efficient activation of percarbonate by metal-free carbonylated activated carbon for green groundwater remediation: Performance, mechanism, applicability, and environmental implications

Sodium percarbonate (SPC)-based advanced oxidation processes (AOPs) hold great promise for in-situ groundwater remediation. However, most existing studies have focused on the metal-carbon composite activation systems, facing the risk of secondary pollution from metal ion leaching. Herein, this study innovatively prepared metal-free carbonylated activated carbon (CAC) by regulating the conversion of oxygen-containing functional groups on carbon materials to activate SPC efficiently. The results showed that the removal of 1-naphthoic acid (1-NA) by the CAC/SPC system reached 100.0 % within 60 min, with k_obs of 0.5188 min⁻¹, which was 6.84–11.85 times higher than that without carbonyl-modified carbon materials. Mechanistic studies revealed that the abundant carbonyl and graphitic carbon-like structures in CAC could activate SPC and promote 1-NA degradation through synergistic reactive oxygen species (¹O₂ > CO₃•^– > •OH) and electron transfer processes. The static/dynamic groundwater simulation experiments confirmed that the system maintained efficient degradation performance under a wide range of pH (3–10), complex inorganic anions (Cl⁻, HPO₄²⁻), and coexisting organics (humic acid, surfactant), showing strong adaptability to real groundwater environments. Moreover, the CAC/SPC system exhibited universal degradation of phenol (100.0 %), sulfamethoxazole (83.5 %), and carbamazepine (65.3 %), further highlighting its application potential. Notably, the CAC/SPC system was environmentally safe: the toxicity of degradation products was obviously lower than 1-NA; the carbon leaching of CAC (1.2 mg L⁻¹) was much lower than from other carbon materials (68.5–80.9 mg L⁻¹), and there was no risk of metal ions leaching; the pH (around 7.6) buffering of SPC degradation products (CO₃²⁻/HCO₃⁻) prevented acidification of groundwater. This study provides an efficient, safe, and adaptable green technology solution for the remediation of organic contaminated groundwater.