Wood Scott A, Tait C Drew, Janecky David R
Department of Geological Sciences, Box 443022, University of Idaho, Moscow, ID 83844-3022, USA.
Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Geochem Trans. 2002 Feb 26;3:31. doi: 10.1186/1467-4866-3-31. eCollection 2002.
The Raman spectra of thioarsenite and arsenite species in aqueous solution were obtained at room temperature. Solutions at constant ΣAs + ΣS of 0.1 and 0.5 mol kg were prepared with various ΣS/ΣAs ratios (0.1-9.0) and pH values (~7-13.2). Our data suggest that the speciation of As under the conditions investigated is more complicated than previously thought. The Raman measurements offer evidence for at least six separate S-bearing As species whose principal bands are centered near 365, 385, 390, 400, 415 and 420 cm. The data suggest that at least two different species may give rise to bands at 385 cm, bringing the probable minimum number of species to seven. Several additional species are possible but could not be resolved definitively. In general, the relative proportions of these species are dependent on total As concentration, ΣS/ΣAs ratio and pH. At very low ΣS/ΣAs ratios we also observe Raman bands attributable to the dissociation products of HAsO(aq). Although we were unable to assign precise stoichiometries for the various thioarsenite species, we were able to map out general pH and ΣS/ΣAs conditions under which the various thioarsenite and arsenite species are predominant. This study provides a basis for more detailed Raman spectroscopic and other types of investigations of the nature of thioarsenite species.
在室温下获得了水溶液中硫代亚砷酸盐和亚砷酸盐物种的拉曼光谱。制备了总砷（ΣAs）与总硫（ΣS）之和分别为0.1和0.5 mol/kg的溶液，其具有不同的ΣS/ΣAs比值（0.1 - 9.0）和pH值（约7 - 13.2）。我们的数据表明，在所研究的条件下砷的物种形成比之前认为的更为复杂。拉曼测量为至少六种不同的含硫砷物种提供了证据，其主要谱带集中在365、385、390、400、415和420 cm附近。数据表明，至少有两种不同的物种可能会在385 cm处产生谱带，这使得可能的物种最小数量达到七种。还可能存在其他几种物种，但无法明确分辨。一般来说，这些物种的相对比例取决于总砷浓度、ΣS/ΣAs比值和pH值。在非常低的ΣS/ΣAs比值下，我们还观察到了可归因于HAsO(aq)解离产物的拉曼谱带。尽管我们无法为各种硫代亚砷酸盐物种确定精确的化学计量，但我们能够描绘出各种硫代亚砷酸盐和亚砷酸盐物种占主导地位的一般pH值和ΣS/ΣAs条件。这项研究为更详细地研究硫代亚砷酸盐物种的性质提供了拉曼光谱和其他类型研究的基础。
