Makki Rabih, Al-Ghoul Mazen, Sultan Rabih
Department of Chemistry, American University of Beirut, P.O. Box 11-0236, 1107 2020 Riad El Solh, Beirut, Lebanon.
J Phys Chem A. 2009 May 28;113(21):6049-57. doi: 10.1021/jp8087226.
In this paper, we studied the dynamics of a CaCO3 precipitate deposition pulse in a thin, long tube connecting two reservoir sinks of coprecipitates. The pulse profile, as well as the time t(c) and distance x(c) of the first appearance of precipitate, is studied as a function of the initial concentration of CO(3)(2-) in the right reservoir, CO(3)(2-), and later as a function of an applied external electric field at different voltages. The time variations of the pulse location and the pH at the center of the tube are determined. The distance from the calcium chloride sink (x) at any fixed time decreases as CO(3)(2-) increases. The time evolution of the front location exhibits a crossover between an early time regime and a late time regime. The pH-time curve shows a marked resemblance with a sigmoid shape. At any time, the pH consistently increases with CO(3)(2-). In the presence of a constant electric field applied across the tube (fixed voltage), t(c) decreased with the field strength, whereas x(c) exhibited a correlated increase. Irregularities in the variation of distance with the applied voltage (at a fixed time) were noted. The pH experiences a slight increase with the applied voltage. The pulse width exhibits a nonlinear time dependence, of the form w = a + bt(1/6). The shape of the deposition pulse deviates from a Gaussian distribution. This study is of special interest in the experimental simulation and modeling of precipitate deposition and potential clogging in microcapillary channels.
在本文中，我们研究了在连接两个共沉淀物储库水槽的细长管中碳酸钙沉淀物沉积脉冲的动力学。研究了脉冲轮廓以及沉淀物首次出现的时间t(c)和距离x(c)作为右储库中CO(3)(2-)初始浓度CO(3)(2-)的函数，随后又研究了其作为不同电压下施加的外部电场的函数。确定了脉冲位置和管中心pH值随时间的变化。在任何固定时间，距氯化钙水槽的距离(x)随着CO(3)(2-)的增加而减小。前沿位置的时间演化在早期阶段和晚期阶段之间表现出交叉。pH-时间曲线呈现出明显的S形。在任何时候，pH值都随CO(3)(2-)持续增加。在管两端施加恒定电场（固定电压）的情况下，t(c)随场强减小，而x(c)则相应增加。注意到距离随施加电压（在固定时间）变化的不规则性。pH值随施加电压略有增加。脉冲宽度呈现出非线性时间依赖性，形式为w = a + bt(1/6)。沉积脉冲的形状偏离高斯分布。这项研究对于微毛细管通道中沉淀物沉积和潜在堵塞的实验模拟和建模具有特殊意义。
