不同因素影响下Fe(Ⅲ)水解中和法制备FeOOH矿相的光谱分析

羟基氧化铁(FeOOH)作为重金属等污染物的吸附材料倍受关注，但不同因素作用下形成的FeOOH产物矿相、结构性质的差异及其对环境功能的影响，却少有报道。采用X射线衍射仪，红外光谱仪，扫描电子显微镜和激光粒度分析仪，系统考察了Fe(Ⅲ)溶液水解中和形成FeOOH时，不同作用因素如铁盐种类、pH和温度等对产物矿相的影响。结果表明，pH 8条件下，Fe(Ⅲ)溶液水解产物均为二线水铁矿(Fe₅HO₈·4H₂O);随着pH升高，Fe₅HO₈·4H₂O会向α-FeOOH相转化。Cl-和NO-₃离子的存在分别有利于β-FeOOH和α-FeOOH的形成;SO2-₄会阻碍Fe₅HO₈·4H₂O向α-FeOOH相转化;Fe2+存在时，会促进Fe₅HO₈·4H₂O向α-FeOOH相转化。加热陈化，可促进Fe₅HO₈·4H₂O转化为α-FeOOH，且利于良好结晶α-FeOOH的形成。但pH≤5，富含Cl-的Fe(Ⅲ)溶液加热水解利于β-FeOOH的生成。不同因素影响下形成的FeOOH，在矿相、表面基团、颗粒形貌和粒径大小上存在一定的差异。

Spectral Analysis of FeOOH Prepared Through Hydrolysis and Neutralization of Ferric Solutions under Different Conditions

In the present work, the iron oxyhydroxides were prepared by hydrolysis and neutralization of ferric ion from FeCl3, Fe(NO3)3 and Fe2(SO4)3 salts, under the conditions of various pH values and aging for about 6 days at 60 ℃. These iron minerals were identified and characterized using X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). In addition, particle size distributions of FeOOH suspension were also determined by LS-230 model laser grainsize analyzer. Results showed that ferrihydrite formed in the ferric solutions containing Cl-, NO-3 and SO2-4 at pH values of 8 and 10. It was testified that the presence of Cl- was favorable for the formation of akaganéite. Meanwhile, the poor crystalline goethite phase was observed to be formed in FeCl3 or Fe(NO3)3 solution, but not be formed in Fe2(SO4)3 solution at pH 12. It indicated that the presence of SO2-4 obviously inhibited the formation of goethite. However, the goethite phase formed in Fe2(SO4)3 solution with addition of ferrous ion, indicating that ferrous ion could promote the formation of goethite in SO2-4-rich solution. In addition, it was usually easy for the crystalline goethite to be transformed from the above generated ferrihydrite precipitates by aging at 60 ℃. Furthermore, the phase of akaganéite also was obtained in the Cl--rich acid (pH≤5) solution by aging at 60 ℃. In conclusion, the prepared FeOOH samples show some differences in their properties such as the phase, surface properties, morphology structures and particle size.