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首页> 外文期刊>Environmental Science & Technology >Reductive Dechlorination of Carbon Tetrachloride in Aqueous Solutions Containing Ferrous and Copper Ions
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Reductive Dechlorination of Carbon Tetrachloride in Aqueous Solutions Containing Ferrous and Copper Ions

机译：含亚铁和铜离子的水溶液中四氯化碳的还原脱氯

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Fe(II) associated with iron-containing minerals has been shown to be a potential reductant in natural subsurface environments. While it is known that the surface-bound iron species has the capacity to dechlorinate various chlorinated compounds, the role of transition metals to act as catalysts with these iron species is of importance. We previously observed that the reduction of Cu(II) by Fe(II) associated with goethite enhanced the dechlorination efficiency of chlorinated compound. In this study, the reductive dechlorination of carbon tetrachloride (CCl{sub}4) by dissolved Fe(II) in the presence of Cu(II) ions was investigated to understand the synergistic effect of Fe(II) and Cu(II) on the dechlorination processes in homogeneous aqueous solutions. The dechlorination efficiency of CCU by Fe(II) increased with increasing Cu(II) concentrations over the range of 0.2 - 0.5 mM and then decreased at high Cu(II) concentrations. The efficiency and rate of CCI{sub}4 dechlorination also increased with increasing dissolved Fe(II) concentration in the presence of 0.5 mM Cu(II) at neutral pH. When the Fe(II)/Cu(li) ratio varied between 1 and 10, the pseudo-first-order rate constant (k{sub}(0bs)) increased 250-fold from 0.007 h{sup}(-1) at 0.5 mM Fe(II) to 1.754 h{sup}(-1) at 5 mM Fe(II). X-ray powder diffraction and scanning electron microscopy analyses showed that Cu(II) can react with Fe(II) to produce different morphologies of ferric oxides and subsequently accelerate the dechlorination rate of CCU at a high Fe(II) concentration. Amorphous ferrihydrite was observed when the stoichiometric Fe(II)/Cu(II) ratio was 1, while green rust, goethite, and magnetite were formed when the molar ratios of Fe(II)/Cu(II) reached 4-6. In addition, the dechlorination of CCU by dissolved Fe(II) is pH dependent. CCU can be dechlorinated by Fe-(II) over a wide range of pH values in the Cu(II)-amended solutions, and the k{sub}(obs) increased from 0.0057 h{sup}(-1) at pH 4.3 to 0.856 h{sup}(-1) at pH 8.5, which was 9-25 times greater than that in the absence of Cu(II) at pH 7-8.5. The high reactivity of dissolved Fe(II) on the dechlorination of CCU in the presence of Cu(II) under anoxic conditions may enhance our understanding of the role of Fe-(II) and the long-term reactivity of the zerovalent iron system in the dechlorination processes for chlorinated organic contaminants.
机译：与含铁矿物质相关的Fe（II）已被证明是天然地下环境中的潜在还原剂。虽然已知表面结合的铁物质具有对各种氯化化合物进行脱氯的能力，但是过渡金属在这些铁物质中充当催化剂的作用非常重要。我们先前观察到，与针铁矿结合的Fe（II）还原Cu（II）增强了氯化化合物的脱氯效率。在这项研究中，研究了溶解的Fe（II）在Cu（II）离子存在下对四氯化碳（CCl {sub} 4）的还原脱氯，以了解Fe（II）和Cu（II）的协同作用。在均质水溶液中进行脱氯过程。 Fe（II）对CCU的脱氯效率在0.2-0.5 mM范围内随Cu（II）浓度的增加而增加，然后在高Cu（II）浓度下降低。在中性pH下，存在0.5 mM Cu（II）时，随着溶解的Fe（II）浓度的增加，CCI {sub} 4脱氯的效率和速率也增加。当Fe（II）/ Cu（li）之比在1到10之间变化时，伪一级速率常数（k {sub}（0bs））从0.007 h {sup}（-1）在250倍增加了250倍。在5 mM Fe（II）时为0.5 mM Fe（II）至1.754 h {sup}（-1）。 X射线粉末衍射和扫描电子显微镜分析表明，Cu（II）可以与Fe（II）反应生成不同形态的三氧化二铁，并随后在高Fe（II）浓度下加速CCU的脱氯速度。当化学计量的Fe（II）/ Cu（II）比为1时，观察到非晶铁水铁矿，而当Fe（II）/ Cu（II）的摩尔比达到4-6时，形成生铁锈，针铁矿和磁铁矿。此外，溶解的Fe（II）对CCU的脱氯作用还取决于pH。在Cu（II）修饰的溶液中，可以在很宽的pH值范围内用Fe-（II）对CCU进行脱氯，并且在pH 4.3时，k {sub}（obs）从0.0057 h {sup}（-1）开始增加在pH 8.5时达到0.856 h {sup}（-1），比在pH 7-8.5时不存在Cu（II）时高9-25倍。溶解的Fe（II）在缺氧条件下在Cu（II）存在下对CCU脱氯的高反应性可能会增强我们对Fe-（II）的作用以及零价铁系统在水中的长期反应性的理解氯化有机污染物的脱氯过程。

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