Enhanced trichloroethylene degradation in groundwater: synergistic activation of persulfate by multivalent iron materials coupled with activated carbon

This study investigates the synergistic activation of persulfate (PS) by multivalent iron-based materials (ZVI, FeS, and FeS₂) in the presence of activated carbon (AC) for the efficient degradation of trichloroethylene (TCE). The incorporation of AC markedly accelerated TCE oxidation by enriching contaminants within its microenvironment and promoting reactive species (ROS) generation. The optimal PS/iron/TCE molar ratios with 0.5 g L^-1 AC were 20/10/3 for the PS/ZVI/TCE system and 20/60/3 for both PS/FeS/TCE and PS/FeS2/TCE systems. Scavenging and electron paramagnetic resonance (EPR) analyses identified hydroxyl radicals (HO^•), sulfate radicals (SO₄^-•), and singlet oxygen (¹O₂) as the dominant ROS responsible for TCE degradation. All three systems maintained over 90% removal efficiency across a wide pH range (3-9). Anion interference tests revealed that bicarbonate (HCO₃^-) strongly inhibited ROS formation, while other anions had minor effects. Experiments using actual groundwater confirmed the robustness of the AC-iron systems, which achieved efficient degradation of chlorinated alkenes, while exhibiting limited activity toward saturated chlorinated alkanes. Overall, this research highlights the synergistic role of AC and iron-based materials in PS activation and provides valuable insights into selective CHC degradation in a complex groundwater environment.