应用穆斯堡尔(Mössbauer)谱学方法研究Fe+++, Fe++与胡敏酸结合的性质

本文应用穆斯堡尔谱学方法,研究了在不同pH条件下Fe⁺⁺⁺,Fe⁺⁺与胡敏酸结合的性质。计算机拟合的pH3.0⁵⁷Fe-胡敏酸络合物泥浆的穆斯堡尔谱和参数表明,三对四极双峰(图1,AA',BB',CC')是合理的。在pH3.0 Fe⁺⁺⁺以高自旋态存在,它和胡敏酸的结合多于一种环境类型。在pH1.0的⁵⁷Fe-胡敏酸络合物中,观察到了Fe⁺⁺⁺的穆斯堡尔谱信号,但没有Fe⁺⁺的信号,在这个样品离心分离出的液体部分检测到了加入量的59.7%的铁,表明在pH1.0时相当数量的Fe⁺⁺⁺被胡敏酸还原成Fe⁺⁺,Fe⁺⁺并不与胡敏酸牢固结合。在30伏电析过的⁵⁷Fe-胡敏酸络合物样品中(pH2.8)出现了Fe⁺⁺⁺,Fe⁺⁺的穆斯堡尔谱,这一结果指示出,在电析过程中由于⁵⁷Fe⁺⁺⁺-胡敏酸络合物悬浮液pH的降低,一部分Fe⁺⁺⁺还原成Fe⁺⁺,在pH2.8相当数量的Fe⁺⁺与胡敏酸牢固结合。根据在80K记录的穆斯堡尔谱,在pH1—3的范围出现了磁有序成份,但在室温记录的穆斯堡尔谱没有磁分裂。

STUDY ON THE NATURE OF Fe3+ AND Fe2+ BOUND WITH HUMIC ACID BY MÖSSBAUER SPECTROSCOPIC METHOD

The Mössbauer spectra at ambient temperature and 80 K of ⁵⁷Fe-humic acid complexes,of which were centrifuged or electrodialyzed,were recorded respectively,and the nature of Fe³⁺,Fe²⁺ bound with humic acid at different pH values was studied.The Mössbauer spectra and parameters of ⁵⁷Fe-humic acid slurry at pH 3 fitted by computer show that three doublets(Fig.1 AA',BB",CC') are reasonable.The Fe³⁺ in the humic acid at pH 3.0 occurs in more than one type of enviroment and high spin forms.The Mussbauer spectrum signal for Fe³⁺ was observed but not for Fe²⁺ in the ⁵⁷Fe-humic acid at pH 1.0.59% of iron doped was detected in the decantate at pH 1.0.It showed that considerable proportion of Fe³⁺ was reduced to Fe²⁺ by humic acid at pH 1.0,but no Fe²⁺ bound with humic acid strongly.The Mössbauer spectra for Fe³⁺,Fe²⁺ were found in the ⁵⁷Fe-humic acid samples (pH 2.8) which were electrodialyzed at 30 V.This indicates that a part of Fe³⁺ is reduced to Fe²⁺.Owing to the decrease of pH of ⁵⁷Fe-humic acid complexes suspension in the process of electrodialysis,considerable proportion of Fe²⁺ was bound with humic acid at pH 2.8 strongly.According to Mössbauer spectra recorded at 80 K,there is evidence for magneticallyordered component in the range of the pH 1-3 but no evidence for that at ambient temperature.