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>Synergistic Effect of Copper Ion on the Reductive Dechlorination of Carbon Tetrachloride by Surface-Bound Fe(ll)Associated with Goethite
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Synergistic Effect of Copper Ion on the Reductive Dechlorination of Carbon Tetrachloride by Surface-Bound Fe(ll)Associated with Goethite
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机译：Synergistic Effect of Copper Ion on the Reductive Dechlorination of Carbon Tetrachloride by Surface-Bound Fe(ll)Associated with Goethite
The dechlorination of carbon tetrachloride ICT)by Felli)associated with goethite in the presence of transition metallons was investigated.X-ray photoelectron spectroscopy IXPS)and X-ray powder diffraction IXRPD)were used to characterize the chemical states and crystal phases of transition metals on solid phases.respectively.CT was dechlorinated to chloroform (CF)by 3 mM Felli)in 10 mM goethite 125.6 m~2 L~(-1))suspensions.The dechlorination followed pseudo-first-order kinetics,and a rate constant (k_(obs))of 0.036 ~(-1)was observed.Transition metal ions have different effects on CT dechlorination.The addition of Ni(II),Co(II),and Zn(II)lowered the k_(obs)for CT dechlorination,whereas the amendment of 0.5 mM Cull I)into the Felll)-Fe(lll)system significantly enhanced the efficiency and the rate of CT dechlorination.The k_(obs)for CT dechlorination with 0.5 mM Culll)was 1.175 h~(-1),which was 33 times greater than that without Cu(II).Also,the dechlorination of CT by surface-bound iron species is pH-dependent,and the rate constants increased from 0.008 h~(-1)at pH 4.0 to 1.175 h~(-1)at pH 7.0.When the solution contained Cu(ll)and Fe(II)without goethite,a reddish-yellow precipitate was formed,and the concentration of Fe(II)decreased with the increase in Cu(II)concentration.XPS and XRPD analyses suggested the possible presence of CU_2O and ferrihydrite in the precipitate.Small amounts of aqueous Cu(II)were also detected,reflecting the fact that Cu(II)was reduced to Cu(II)by Fe(II).A linear relationship between k_(obs)for CT dechlorination and the concentration of Cu(II)was observed when the amended Cu(II)concentration was lower than 0.5 mM.Moreover,the kobs for CT dechlorination was dependent on the Fe(II)concentration in the 0.5 mM Cu(II)-amended goethite system and followed a Langmuir-Hinshelwood relationship.These results clearly indicate that Fe(II)serves as the bulk reductant to reduce both CT and Cu(II).The resulting Cu(II)can further act as a catalyst to enhance the dechlorination rate of chlorinated hydrocarbons in iron-reducing environments.
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