红外光谱法及单晶X衍射法研究Fe(Ⅲ)水解形态分布

采用Fe-Ferron逐时络合比色法研究了聚铁絮凝剂中不同pH值的Fe(a)，Fe(b)，Fe(c)的稳定性。结果表明，Fe(b)不稳定，10～15 d后全部转化为Fe(c)，Fe(c)的含量经10～15 d后趋于稳定，Fe(a)的含量10 d后也趋于稳定。采用常温长时间结晶法从Fe(Ⅲ)-SO2-₄水溶液中制备出了单晶，并用红外光谱法及单晶X射线衍射法研究了所得单晶的结构。研究显示，从低pH值(pH 0.5左右)的Fe(Ⅲ)溶液中所得单晶中没有Fe—OH—Fe基团、Fe—OH基团、Fe的二聚羟基络合基团，仅为Fe(Ⅲ)离子形态的单晶，以氨水为碱化剂时其单晶化学式为Fe(H₂O)₆ (SO₄)₂NH₄·6H₂O。采用常温长时间结晶法，随水分的不断蒸发，不同初始pH值及不同碱化剂的Fe(Ⅲ)溶液一般都在pH 0.5左右结晶，还由于铁盐水解形态不稳定等原因引起。在低pH值下难以得到Fe(Ⅲ)的羟基络合物或聚合体单晶。实验研究显示，在絮凝剂水解形态研究中，红外光谱法、单晶X射线衍射法均有良好的应用前景。

Study on the Hydrolysis Distribution of Ferric Saline by Infrared Spectrophotometry and Single Crystal X-Ray Diffraction Method

The hydrolytic stability of Fe(a), Fe(b) and Fe(c) in different pH values of poly-ferric-flocculants was studied by using Fe-ferron time by time complexation colorimetry. The research results showed that Fe(b) was unstable, and all Fe(b) was transformed to Fe(c) after 10-15 d placement. The content of Fe(c) tended towards stability after 10-15 d. Also, the content of Fe(a) tended towards stability after 10 d. The single crystal was synthesized by the method of direct crystallization in Fe(Ⅲ)-SO2-₄ water solution at normal temperature and its structure characteristic was studied by single crystal X ray diffraction method and IR (infrared spectrophotometry). The research results showed that there was no group of Fe—OH—Fe, Fe—OH and binary ferric complexed with two hydroxyl groups in the single crystal synthesized from the ferric aqueous solution in low pH(pH was about 0.5). The form of Fe in single crystal was all Fe(Ⅲ). The chemical formula of the single crystal was Fe(H₂O)₆(SO₄)₂NH₄·6H₂O when the ammonia water was used as the alkalinizing agent. One reason was that with the evaporation of water, these single crystals were synthesized at pH 0.5 despite of different initial pH and different initial alkalinizing agents. Another reason was that the hydrolysis distribution of ferric saline was unstable. Therefore, it was not easy to obtain the single crystal of Fe(Ⅲ)-hydroxy complexes or Fe(Ⅲ)-polymer at low pH value. The study showed that infrared spectrophotometry and single crystal X ray diffraction method have a good prospect in the research on hydrolysis distribution of flocculants.