硅钙石
黄铁矿
化学
电子转移
X射线光电子能谱
结晶学
硫黄
无机化学
矿物学
光化学
核磁共振
有机化学
物理
闪锌矿
作者
I. Uhlig,R. Szargan,H.W. Nesbitt,K. Laajalehto
标识
DOI:10.1016/s0169-4332(01)00283-5
摘要
The sulphur surface sites of pristine marcasite surfaces and their reactivity during initial air oxidation were investigated for the first time using synchrotron radiation excited photoelectron spectroscopy (SRXPS). Both S 2p and Fe 2p spectra were collected and compared to those of the polymorph pyrite. A new sulphur surface component is found additionally to the two known pyrite surface signals. Due to the non-isotropic character of the orthorhombic marcasite structure, its peak intensity depends strongly on the surface orientation. Its binding energy is close to the region of short-chained polysulphides. The signal is assigned to sulphur trimers produced by electron transfer between surface near sulphur dimers and S− formed after ruptures of SS bonds which results in S2− and S32−. In the cubic crystal arrangement of pyrite the stabilisation of S− to S2− is realised by an electron transfer from iron to sulphur only. A confirmation of this assumption is found in the Fe 2p spectra. The contribution of Fe3+ species — a result of the electron transfer process — is considerably less pronounced for marcasite. The mechanism of initial oxidation is different for marcasite and pyrite. The sulphur species responsible for the new spectroscopic component are the most reactive sites at the marcasite surface, while S2− is oxidised first in case of pyrite. The signals indicating the products of marcasite oxidation in the S 2p spectrum are less intense as expected from the intensity decreasing of the trimer peak. Therefore, an oxidation of sulphur trimers to elemental sulphur is assumed which could not be detected because of its volatility in the vacuum of the air lock system.
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