Peretyazhko T, Zachara J M, Heald S M, Kukkadapu R K, Liu C, Plymale A E, Resch C T
Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
Environ Sci Technol. 2008 Aug 1;42(15):5499-506. doi: 10.1021/es8003156.
Under oxic conditions, Tc exists as the soluble, weakly sorbing pertechnetate [TcO4-] anion. The reduced form of technetium, Tc(IV), is stable in anoxic environments and is sparingly soluble as TcO2 x nH2O(s). Here we investigate the heterogeneous reduction of Tc(VII) by Fe(II) adsorbed on Al (hydr)oxides [diaspore (alpha-AlOOH) and corundum (alpha-Al2O3)]. Experiments were performed to study the kinetics of Tc(VII) reduction, examine changes in Fe surface speciation during Tc(VII) reduction (Mössbauer spectroscopy), and identify the nature of Tc(IV)-containing reaction products (X-ray absorption spectroscopy). We found that Tc(VII) was completely reduced by adsorbed Fe(II) within 11 (diaspore suspension) and 4 days (corundum suspension). Mössbauer measurements revealed thatthe Fe(II) signal became less intense with Tc(VII) reduction and was accompanied by an increase in the intensity of the Fe(III) doublet and magnetically ordered Fe(III) sextet signals. Tc-EXAFS spectroscopy revealed that the final heterogeneous redox product on corundum was similar to Tc(IV) oxyhydroxide, TcO2 x nH2O.
在有氧条件下，锝以可溶的、吸附性较弱的高锝酸根[TcO4-]阴离子形式存在。锝的还原态Tc(IV)在缺氧环境中稳定，且以TcO2·nH2O(s)的形式微溶。在此，我们研究了吸附在铝（氢）氧化物[水铝石（α-AlOOH）和刚玉（α-Al2O3）]上的Fe(II)对Tc(VII)的非均相还原作用。进行了实验以研究Tc(VII)还原的动力学，考察Tc(VII)还原过程中Fe表面形态的变化（穆斯堡尔光谱），并确定含Tc(IV)反应产物的性质（X射线吸收光谱）。我们发现，吸附的Fe(II)在11天（水铝石悬浮液）和4天（刚玉悬浮液）内将Tc(VII)完全还原。穆斯堡尔测量表明，随着Tc(VII)的还原，Fe(II)信号强度减弱，同时伴随着Fe(III)双峰和磁有序Fe(III)六重峰信号强度的增加。Tc-EXAFS光谱显示，刚玉上最终的非均相氧化还原产物类似于氢氧化锝Tc(IV)，即TcO2·nH2O。
