Enhancement in trichloroethylene dechlorination by mixed particles of iron–iron disulfide or iron–iron sulfide

A column test was carried out to clarify the effect of the mixed particles of iron (Fe) and iron disulfide (FeS₂) or iron sulfide (FeS) on the trichloroethylene (TCE) degradation rate and compared with a reported batch test. The TCE degradation rate of the mixed particles of Fe and FeS₂ was faster than the laminar packing of Fe and FeS₂. The TCE degradation rate proceeded at the first-order reaction and had a peak value at the mass ratio of Fe/FeS₂ = 7/3 and Fe/FeS = 3/7, and they showed the same trend as the batch test. The rate constant of Fe/FeS₂ and Fe/FeS based on unit surface area remained constant for the mixing ratio of Fe to FeS₂ or FeS, and 6.1 and 1.3 times larger than single component of Fe, respectively. The surface chemical reaction of TCE on the Fe/FeS₂ and Fe/FeS particles was the rate determining step and the mass transfer steps did not affect the reaction rate. Chloride ion, ethylene and ethane were detected from the treated solution and off-gas due to the TCE degradation, and the pH value increased with the increase in the TCE degradation rate until pH ≒ 10.