Hydration of γ-alumina in water and its effects on surface reactivity
Hydration of γ-alumina in water and its effects on surface reactivity
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DOI：
10.1021/la025651i
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发表时间：
2002-10-01
期刊：
影响因子：
3.9
通讯作者：
Fédoroff, M
中科院分区：
文献类型：
--
作者：
Lefèvre, G;Duc, M;Fédoroff, M
γ-氧化铝悬浮液在水中的稳定性已通过长期实验（1 天至 6 个月）进行了研究。使用几种补充方法来表征固体（酸碱滴定和溶解速率测量、X射线光电子能谱、X射线衍射、重量/差热分析、红外光谱和扫描电子显微镜）。 γ-氧化铝在吸附实验中被广泛用作模型氧化物，这主要归功于其高比表面积和其表面存在铝醇基团，它似乎逐渐转变为三羟铝石（β-Al(OH)(3)）。该转变的特征在于约4天的诱导期，对应于瞬时无定形水合相的形成，随后三羟铝石浓度增加，约2个月后趋于稳定。这种转变导致与质子反应的位点的表面密度急剧下降。热力学计算预测 γ-氧化铝的水合反应会产生更稳定的相（三羟铝石、三水铝石或勃铝石）。由于固体的表面反应性和吸附特性是控制水中元素传输的因素，因此在模拟吸附实验时有必要考虑固体的稳定性。这些因素对于长期预测放射性废物储存库周围屏障的有效性非常重要。
The stability of y-alumina suspensions in water has been investigated by long-duration experiments (1 day to 6 months). Several complementary methods were used to characterize the solid (acid-base titration and dissolution rate measurements, X-ray photoelectron spectroscopy, X-ray diffraction, gravimetric/differential thermal analysis, infrared spectroscopy, and scanning electron microscopy). It appears that y-alumina, which is widely used as a model oxide in sorption experiments, thanks mainly to its high specific surface area and to the presence of aluminol groups on its surface, is progressively transformed to bayerite (beta-Al(OH)(3)).' This transformation was characterized by an induction period of about 4 days, corresponding to the formation, of a transient amorphous hydrated phase, followed by an increase in the bayerite concentration, which levels off after about 2 months. This transformation results in a dramatic decrease in the surface density of sites reactive to protons. Thermodynamical calculations predict the hydration reaction of y-alumina leading to a more stable phase (bayerite, gibbsite, or boebmite). Since the surface reactivity and sorption properties of solids are factors controlling the transport of elements in water, it is necessary to take into account the stability of solids when modeling sorption experiments. These factors are important for the long-term prediction of the effectiveness of barriers placed around radioactive waste depositories.