Dual-functional carboxymethyl-β-cyclodextrin for enhanced peroxydisulfate/Fe²⁺ removal of tetrachloroethylene in...

The removal of contaminants by peroxydisulfate (PDS)/Fe²⁺ system is a promising groundwater decontamination technology, while the non-recyclability of Fe²⁺ and the restricted mass transfer of contaminants in water limit the decontamination efficiency. Here, we developed carboxymethyl-β-cyclodextrin (CM-β-CD) to chelate Fe²⁺ coupled with enhancing the solubization of contaminants in groundwater for efficient decontamination. Results showed that a 4.60-fold enhancement in the perchloroethylene (PCE) degradation rate following the addition of 1 g/L CM-β-CD to the PDS/Fe²⁺ system. The ternary complex formed by CM-β-CD, Fe²⁺ and PCE was confirmed via ultraviolet absorption spectra and nuclear magnetic resonance hydrogen spectrum. Electron paramagnetic resonance, complemented by chemical probe and radical quenching experiments, identified singlet oxygen (¹O₂), high-valent iron (Fe(IV)), and hydroxyl radicals (^•OH) as the dominant reactive species in the PDS/Fe²⁺/CM-β-CD system, with relative contributions to PCE degradation quantified at 30.4%, 26.2%, and 18.1%, respectively. The presence of humic acid and common inorganic ions showed negligible effects on PCE degradation efficiency. The primary PCE degradation intermediate is dichloromethane, mediated by ¹O₂, Fe(IV), and •OH, with mineralization occurring via dechlorination pathways. This study developed an environmentally sustainable remediation strategy utilizing CM-β-CD as a dual-functional agent for simultaneous Fe²⁺ chelation and contaminant solubilization, enabling efficient groundwater decontamination.