Schudel M, Behrens SH, Holthoff H, Kretzschmar R, Borkovec M
Swiss Federal Institute of Technology, ETH-ITO, Grabenstrasse 3, Schlieren, 8952, Switzerland
J Colloid Interface Sci. 1997 Dec 15;196(2):241-253. doi: 10.1006/jcis.1997.5207.
Measurements of absolute aggregation rate constants were performed for two samples of well-characterized spheroidal hematite particles with rather different surface morphology. At high ionic strength, the system is in the fast aggregation regime with pH independent rate constants around (1-4) x 10(-18) m3/s. At low ionic strengths, the rate constant is a function of pH and goes through a flat maximum around the point of zero charge (PZC) where fast aggregation conditions are reached. With increasing pH the rate constants increase gradually below the PZC while they decrease very rapidly above the PZC. Above the PZC the rate constants are rather well predicted by the classical DLVO theory. Below the PZC, however, it is necessary to assume a distribution in the surface potentials with a coefficient of variation around 30% to account for the observed behavior. In spite of the pronounced differences in the surface roughness of both hematite samples, their aggregation rate constants are rather similar. Copyright 1997 Academic Press.
对具有截然不同表面形态的两个特征明确的球状赤铁矿颗粒样品进行了绝对聚集速率常数的测量。在高离子强度下，体系处于快速聚集状态，pH无关的速率常数约为(1 - 4)×10⁻¹⁸立方米/秒。在低离子强度下，速率常数是pH的函数，在零电荷点（PZC）附近达到一个平缓的最大值，此时达到快速聚集条件。随着pH升高，速率常数在PZC以下逐渐增加，而在PZC以上则迅速下降。在PZC以上，速率常数可以很好地由经典的DLVO理论预测。然而，在PZC以下，有必要假设表面电位存在一个变异系数约为30%的分布，以解释观察到的行为。尽管两个赤铁矿样品的表面粗糙度存在明显差异，但它们的聚集速率常数相当相似。版权所有1997年学术出版社。
