Enhanced Fenton-like degradation of TCE in sand suspensions with magnetite by NTA/EDTA at circumneutral pH

Abstract

The present study investigated the degradation of trichloroethylene (TCE) in sand suspensions by Fenton-like reaction with magnetite (Fe₃O₄) in the presence of various chelators at circumneutral pH. The results showed that ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) greatly improved the rate of TCE degradation, while [S,S]-ethylenediaminedisuccinic acid (s,s-EDDS), malonate, citrate, and phytic acid (IP6) have minimal effects on TCE degradation. Quenching tests suggested that TCE was mainly degraded by hydroxyl radical (HO^·) attack, with about 90% inhibition on TCE degradation by the addition of HO^· scavenger 2-propanol. The presence of 0.1–0.5% Fe₃O₄/sand (w/w) contributed to 40% increase in TCE degradation rates. In particular, the use of chelators can avoid high concentrations of H₂O₂ required for the Fenton-like reaction with Fe₃O₄, and moreover improve the stoichiometric efficiencies of TCE degradation to H₂O₂ consumption. The suitable concentrations of chelators (EDTA and NTA) and H₂O₂ were suggested to be 0.5 and 20 mM, respectively. Under the given conditions, degradation rate constants of TCE were obtained at 0.360 h⁻¹ with EDTA and 0.526 h⁻¹ with NTA, respectively. Enhanced degradation of TCE and decreased usage of H₂O₂ in this investigation suggested that Fenton-like reaction of Fe₃O₄ together with NTA (or EDTA) may be a promising process for remediation of TCE-contaminated groundwater.

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