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

Wang, Na, Jia, Daqing, Jin, Yaoyao, Sun, Sheng-Peng, Ke, Qiang
Environmental science and pollution research international 2017 v.24 no.21 pp. 17598-17605
EDTA (chelating agent), chelating agents, citrates, groundwater, hydrogen peroxide, hydroxyl radicals, isopropyl alcohol, magnetite, nitrilotriacetic acid, pH, phytic acid, remediation, sand, trichloroethylene
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.