摘要
稀释0.5mol/L Fe(NO_3)_3母液,制成二组0.001mol/L Fe(NO_3)_3,溶液,每组分成5等份,于每份溶液中分别加入不同量的NaOH,使溶液的NaOH/Fe,分子比为0、1.0、1.8、2.7、3.1,然后在70℃烘箱中水解。制备二组试样的主要区别是母液稀释水的最初温度不同,但其最终形成的氧化铁在颗粒大小,结晶度以及显微形貌等方面有明显差别。Ⅰ组试样是用70℃水稀释制备而成,1天后其反应产物呈无定形的非晶物质,在70℃老化很短时间后,便转变成结晶好的针铁矿和赤铁矿。Ⅱ组试样是用室温水(25℃)制备。在整个实验期间,其水解产物具有轮廓明显的小圆球状微晶氧化铁,即使在老化248天后仍属结晶差的针铁矿和赤铁矿,只能用高功率转靶的X射线衍射仪才能反映其特征衍射峰,鉴定其组成。试验结果表明:制备试样时,水的温度对最初水解产物的性质起关键作用,而最初产物的特性对溶液中再溶解再结晶的速率起着重要作用。
Two series of 0.001 M Fe(NO_3)_3 solutions, having NaOH/Fe molar ratios ranging from 0 to 3.1, were prepared by diluting a 0.5 mol/L Fe(NO_3)_3 stock solution with water and then hydrolyzed at 70℃. The preparation differed only in the initial temperature of the water for dilution, but the final products were very different in particle size, morphology and crystallinity. In Series Ⅰ solutions, prepared with 70℃ water the reaction products were amorphous, structureless masses initially, but became well crystallized goethite and/or hematite in the shape of rods or plates shortly after being aged at 70℃. In Series Ⅱ solutions, prepared with room temperature water, the hydrolyzed products were tiny spheres having a well-defined outline and homogeneous size throughout the experimentation. They were very poorly crystallized goethite and/or hematite even after 248 d of aging at 70℃ and could be detected only with a high power Rigaku rotating anode x-ray diffractometer. The results suggested that the temperature of water for solution preparation plays a key role in the size and nature of the initial hydrolytic product which, in turn, plays a key role in the rate of redissolution and recrystallization.
出处
《土壤学报》
CAS
CSCD
北大核心
1989年第1期9-15,共7页
Acta Pedologica Sinica
