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首页> 外文期刊>Environmental Science & Technology >Reduction of aqueous chromate by Fe(11)/Fe(111) carbonate green rust: Kinetic and mechanistic studies
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Reduction of aqueous chromate by Fe(11)/Fe(111) carbonate green rust: Kinetic and mechanistic studies

机译：Fe（11）/ Fe（111）碳酸盐绿锈对铬酸盐水溶液的还原：动力学和机理研究

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This work describes the heterogeneous reaction between Fell in carbonate green rust and aqueous chromate., in NaHCO3 solutions at 25 degreesC, and at pH values of 9.3-9.6. Evidence for reduction of Cr-VI to Cr-III and concomitant solid-state oxidation of lattice Fe-II to Fe-III was found from Fe-II titration and from structural analysis of the solids using FTIR, XRD, SEM, and XPS methods. Results indicate the formation of ferric oxyhydroxycarbonate and the concomitant precipitation of Cr-III monolayers at the surface of the iron compound that induce passivation effects and progressive rate limitations. The number of Cr-III monolayers formed at the completion of the reaction depends on {Fe-II}(t=0), the molar concentration of Fe-solid(II) at t = 0; on {n(o)}(t=0), the molar concentration of reaction sites present at the surface of the solid phase at t = 0; and on [Cr-VI](t=0), the molar concentration of Cr-VI at t = 0. Kinetic data were modeled using a model based on the formation of successive Cr-III monolayers, -(d[Cr-VI]/dt) = Sigma(1)(j)k(i)({S})[Cr-VI]({n(i-1) - {n(i)}) with k(i)({S}) (in s(-1) L mol(-1)), the rate coefficient of formation of Cr-III monolayer i, and {n(i)} and {n(i-1)}, the molar concentration of Cr-III precipitated in monolayer i and monolayer i - 1, respectively. Good matching curves were obtained with kinetic coefficients: k(1)({S}) = 5-8 x 10(-4), k(2)({S}) = 0.5-3 x 10(-5), and k(3)({S}) about 1.7 x 10(-6) s(-1) m(-2) L. The Cr-VI removal efficiency progressively decreases along with the accumulation of Cr-III monolayers at the surface of carbonate green rust particles. In the case of thick green rust particles resulting from the corrosion of iron in permeable reactive barriers, the quantity of Fe-II readily accessible for efficient Cr-VI removal should be rather low.
机译：这项工作描述了碳酸钠绿锈中的Fell与铬酸水溶液，在25℃，pH值为9.3-9.6的NaHCO3溶液之间的异质反应。通过Fe-II滴定以及使用FTIR，XRD，SEM和XPS方法对固体进行结构分析，发现了Cr-VI还原为Cr-III以及晶格状的Fe-II固态氧化为Fe-III的证据。 。结果表明，羟基羟基碳酸铁的形成以及铁化合物表面上Cr-III单层的伴随沉淀，这些沉淀诱导钝化作用和渐进速率限制。反应完成时形成的Cr-III单层的数量取决于{Fe-II}（t = 0），在t = 0时Fe-固体（II）的摩尔浓度；在{n（o）}（t ＝ 0）上，在t ＝ 0时存在于固相表面的反应位点的摩尔浓度；在[Cr-VI]（t = 0）上，t = 0时的Cr-VI摩尔浓度。使用基于连续形成的Cr-III单层-（d [Cr-VI ] / dt）= Sigma（1）（j）k（i）（{S}）[Cr-VI]（{n（i-1）-{n（i）}）且k（i）（{S }）（在s（-1）L mol（-1）中，Cr-III单层i的形成速率系数，{n（i）}和{n（i-1）}，其摩尔浓度） Cr-III分别在单层i和单层i-1中沉淀。使用动力学系数获得了良好的匹配曲线：k（1）（{S}）= 5-8 x 10（-4），k（2）（{S}）= 0.5-3 x 10（-5）和k（3）（{S}）约为1.7 x 10（-6）s（-1）m（-2）L。Cr-VI的去除效率随着Cr-III单层在金属表面的积累而逐渐降低。碳酸盐绿锈颗粒。如果铁在可渗透的反应性阻挡层中被腐蚀而产生了厚厚的生铁锈颗粒，那么为有效地去除Cr-VI而容易获得的Fe-II的含量应该相当低。

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