Surface acidity constants of α-Al2O3 between 25 and 70°c
Surface acidity constants of α-Al2O3 between 25 and 70°c
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DOI：
10.1016/s0016-7037(99)00235-5
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发表时间：
1999-10
影响因子：
5
通讯作者：
W. Halter
中科院分区：
文献类型：
--
作者：
W. Halter
在25、30、40、50、60、70℃条件下进行电位滴定，研究了温度对刚玉吸附H+的影响。这些滴定用于测定表观酸度常数，由固有吸附常数和库仑项（Kiapp= Kiinte(−ΔZFΨ/RT)）在上述温度下的乘积给出。采用恒电容模型（CCM）确定了第一和第二固有酸度常数。这些常数和零电荷点随温度的逆变化呈线性变化。这些数据被用来确定质子吸附反应的热力学常数。在库仑项中，只有电容和表面电荷随温度变化，两者都是用不同温度下的滴定数据测定的。结果表明，电容的变化可以用水的介电常数随温度升高的变化来预测。在给定的pH值下，表面电荷随温度的变化可以用线性回归来预测。利用上述模型，可以在25 ~ 70℃甚至更高的温度下预测刚玉的表观酸度常数（包括化学和静电相互作用）。这些表观常数在这个温度范围内变化了几个数量级（主要是由于库仑项的变化），微小的温度变化可能对表面配合物的稳定性产生强烈的影响。
The effect of temperature on the adsorption of H+onto corundum was investigated experimentally by conducting potentiometric titrations at 25, 30, 40, 50, 60 and 70°C. These titrations were used to determine apparent acidity constants, given by the product of an intrinsic adsorption constant and a coulombic term (Kiapp= Kiinte(−ΔZFΨ/RT)) at the above temperatures. First and second intrinsic acidity constants were determined using a constant capacitance model (CCM). These constants and the point of zero charge change linearly with inverse temperature. These data were used to determine thermodynamic constants for the proton adsorption reactions. In the coulombic term, only the capacitance and the surface charge change with temperature and both were determined with the titration data at the various temperatures. Results show that the change in capacitance can be predicted with changes in the dielectric constant of water with increasing temperature. At a given pH, changes in the surface charge with temperature can, in turn, be predicted with a linear regression. With the above model, apparent acidity constants of corundum (including the chemical and electrostatic interactions) can be predicted for any temperatures between 25 and 70°C and possibly higher. These apparent constants change over several orders of magnitude in this temperature range (mainly due to a change in the coulombic term) and small temperature changes could have a strong influence on the stability of surface complexes.