Importance of Mn(III) Availability on the Rate of Cr(III) Oxidation on δ-MnO2
Importance of Mn(III) Availability on the Rate of Cr(III) Oxidation on δ-MnO2
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DOI：
10.1021/es991462j
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发表时间：
2000-07
影响因子：
11.4
通讯作者：
P. Nico;R. Zasoski
中科院分区：
文献类型：
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作者：
P. Nico;R. Zasoski
Cr（III）氧化为Cr（VI）显著增加了其流动性和毒性，因此增加了其环境危害。研究了在不同焦磷酸盐浓度和pH值下，水钠锰矿（δ-MnO 2）悬浮液中Cr（III）的氧化速率。将已知与Mn（III）形成强络合物的焦磷酸盐加入悬浮液中以螯合可用的Mn（III），从而证明Mn（III）可用性对Cr（III）氧化速率的重要性。焦磷酸盐浓度为3 μmol/L，相当于约14%的氧化物表面位点络合，导致kobs减少45%以上。在0至7 μmol/L焦磷酸盐区域观察到速率显著降低。在浓度大于7 μmol/L时，额外的焦磷酸盐对反应速率几乎没有影响。在此基础上，建立了一个两反应途径模型，其中一个途径的速率与游离Mn（III）浓度成比例，该模型适用于实验。
The oxidation of Cr(III) to Cr(VI) significantly increases its mobility and toxicity and therefore its environmental hazard. The oxidation rate of aqueous Cr(III) in a suspension of δ-MnO2 (birnessite) was investigated at different pyrophosphate concentrations and pH values. Pyrophosphate, which is known to form strong complexes with Mn(III), was added to the suspension in order to sequester available Mn(III) and thereby demonstrate the importance of Mn(III) availability on the rate of Cr(III) oxidation. Pyrophosphate concentrations of 3 μmol/L, equivalent to approximately 14% oxide surface site complexation, resulted in a greater than 45% reduction in kobs. Dramatic rate reductions were observed in the 0 to 7 μmol/L pyrophosphate region. At concentrations greater than 7 μmol/L, additional pyrophosphate had little effect on the reaction rate. On the basis of experimental results a two reaction pathway model in which the rate of one pathway scales with free Mn(III) concentration was created and fit to expe...