Stirring effect on kaolinite dissolution rate
Stirring effect on kaolinite dissolution rate
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搅拌对高岭石溶解速率的影响
DOI：
10.1016/s0016-7037(01)00686-x
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发表时间：
2001
影响因子：
5
通讯作者：
J. Ganor
中科院分区：
文献类型：
--
作者：
V. Metz;J. Ganor
在ph值为2 ~ 4，温度为25°C、50°C和70°C的条件下，采用搅拌式和非搅拌式反应器测量高岭石的溶解速率。结果表明，随着搅拌速度的增加，高岭石的溶解速率增加。搅拌作用是可逆的，即随着搅拌速度的减慢，溶解速率降低。搅拌速度对高岭石溶解速率的影响在25℃时大于50℃和70℃，pH为4时大于pH为2和3时。认为高岭石微粒是由搅拌引起的高岭石剥落或磨损形成的。这些非常细小的颗粒增加了活性表面积与比表面积的比值，从而提高了高岭石的溶解速率。细颗粒的产生和溶解之间的平衡解释了搅拌效果的可逆性以及温度和pH值的依赖性。由于搅拌对高岭石溶解速率的影响随温度和pH值的变化而变化，因此对活化能等动力学参数的测定也会受到搅拌的影响。因此，建议使用非搅拌反应容器进行矿物溶解和沉淀的动力学实验，至少对于表面可控的缓慢反应。
Experiments were carried out measuring kaolinite dissolution rates using stirred and nonstirred flow-through reactors at pHs 2 to 4 and temperatures of 25°C, 50°C, and 70°C. The results show an increase of kaolinite dissolution rate with increasing stirring speed. The stirring effect is reversible, i.e., as the stirring slows down the dissolution rate decreases. The effect of stirring speed on kaolinite dissolution rate is higher at 25°C than at 50°C and 70°C and at pH 4 than at pHs 2 and 3. It is suggested that fine kaolinite particles are formed as a result of stirring-induced spalling or abrasion of kaolinite. These very fine particles have an increased ratio of reactive surface area to specific surface area, which results in enhancement of kaolinite dissolution rate. A balance between production and dissolution of the fine particles explains both the reversibility and the temperature and pH dependence of the stirring effect. Since the stirring effect on kaolinite dissolution rate varies with temperature and pH, measurement of kinetic parameters such as activation energy may be influenced by stirring. Therefore, standard use of nonagitated reaction vessels for kinetic experiments of mineral dissolution and precipitation is recommended, at least for slow reactions that are surface controlled.