Immobilizing S-nZVI@LDO for simultaneous removal of PFOA and TCE co-contaminants from groundwater

The co-mingled plumes of chloroethenes and per- and polyfluoroalkyl substances (PFASs) raise a major challenge for groundwater remediation. This study is the first try to apply sulfidated nano zero-valent iron supported on calcined layered double oxides (S-nZVI@LDO) for simultaneous removal of trichloroethylene (TCE) and perfluorooctanoic acid (PFOA). Our findings revealed that 2 g/L S-nZVI@LDO simultaneously removed 73.3 % TCE and 37.8 % PFOA in pure water, with 49.5 % TCE degraded to less chlorinated products and 23.8 % adsorbed or unquantified transformation of C₃-C₆ hydrocarbons. Comparative experiments using individual and co-occurring TCE and PFOA revealed that co-existing PFOA and TCE minimally affected their respective removal efficiencies, highlighting S-nZVI@LDO's suitability for co-contaminant remediation. Furthermore, S-nZVI@LDO achieved optimal TCE and PFOA removal under acidic conditions, surpassing non-composite S-nZVI and LDO. Based on the characterization of S-nZVI@LDO, TCE removal involved reductive dechlorination and sorption via hydrophobic interactions, while PFOA removal was primarily driven by electrostatic interactions and hydrogen bonding. In real groundwater, S-nZVI@LDO achieved 58.2 % TCE and 33.7 % PFOA removal. Additionally, S-nZVI@LDO simultaneously removed nine different PFASs from a 12-PFASs mixture and demonstrated greater effectiveness for long-chain PFASs and their alternatives (e.g., GenX) owing to their hydrophobic nature. These findings highlight the potential of S-nZVI@LDO as an effective material for TCE-PFOA co-contaminated groundwater.