物理化学学报 >> 2010, Vol. 26 >> Issue (03): 552-560.doi: 10.3866/PKU.WHXB20100310

化学动力学和分子动态学 上一篇    下一篇

土壤颗粒表面电场作用下固-液界面Mg2+-K+与Ca2+-K+交换动力学的比较研究

李睿, 李航   

  1. 西南大学资源环境学院, 重庆 400716
  • 收稿日期:2009-09-30 修回日期:2009-11-18 发布日期:2010-03-03
  • 通讯作者: 李航 E-mail:hli22002@yahoo.com.cn

Comparison Study between Mg2+-K+ and Ca2+-K+ Exchange Kinetics under Electric Fields at the Solid-Liquid Interface of Soil

LI Rui, LI Hang   

  1. College of Resources and Environment, Southwest University, Chongqing 400716, P. R. China
  • Received:2009-09-30 Revised:2009-11-18 Published:2010-03-03
  • Contact: LI Hang E-mail:hli22002@yahoo.com.cn

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摘要：

通过恒流法研究了不同表面电场作用下Mg2+、Ca2+吸附动力学. 结果发现: (1)实验初期阶段是强静电力作用下的零级动力学过程和一定反应时间后的弱静电力作用下的一级动力学过程, 且零级速率过程和一级速率过程之间存在明显的转折点; (2)不同电解质构成中Ca2+的吸附速率明显快于Mg2+的, 平衡吸附量也大于Mg2+的, 且Ca2+在土壤颗粒表面的覆盖度比Mg2+在土壤颗粒表面的覆盖度高; (3)离子的相对有效电荷系数与土壤颗粒表面电场作用的不同是各体系中Ca2+、Mg2+吸附动力学有差别的根本原因; (4)根据离子吸附的理论模型可以分别计算出速率系数、平衡吸附量、离子在土壤颗粒表面的覆盖度以及固定液的体积, 这些参数可以定量评估土壤颗粒表面电场对离子吸附动力学的影响.

关键词: 固-液界面, 表面电场, 相对有效电荷系数, 离子吸附, 动力学

Abstract:

Comparison study between Mg2+ and Ca2+ adsorption kinetics, as influenced by different particle surface potentials, was investigated by the miscible displacement technique. In this study, important new features of ion adsorption were discovered. (1) The initial stage of experiment the adsorption process had zero-order kinetics because of strong adsorption. First-order kinetics then resulted because of weak adsorption and the transition point from zero-order to first-order kinetics was very sharp for each system. (2) At equivalent supporting electrolyte concentrations, the adsorption rate of Ca2+ is obviously faster than that of Mg2+，and the equilibrium adsorption capacity of Ca2+ is more than that of Mg2+. The coverage of Ca2+ on the solid soil particle's surface is also higher than that of Mg2+. (3) The differences between the relative effective charge coefficient and the surface electrochemical properties are the reason why the Ca2+, Mg2+ adsorption kinetics are different. (4) We also determined some important properties of the adsorbed ions such as the rate coefficients, the adsorption quantities, the surface coverage of the adsorbed ions and the distributed space in the fixed liquid film of the adsorbed ions. These parameters allow a future quantitative evaluation of the effects of different colloid surface potentials on the ion diffusion/adsorption kinetics.

Key words: Solid-liquid interface, Surface electric field, Relative effective charge coefficient, Ion adsorption, Kinetics