Cation exchange capacity methodology II: A modified silver-thiourea method

被引:81
作者
Dohrmann, R. [1 ]
机构
[1] BGR, LBEG, D-30655 Hannover, Germany
关键词
CEC; exchangeable cations; modified silver-thiourea method; barium chloride method; ammonium acetate method; excess adsorption;
D O I
10.1016/j.clay.2006.02.009
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The silver-thiourea method for the determination of the cation exchange capacity (CEC) has been critically examined. The chemical instability of the exchange solution used causes silver sulphide precipitation on the walls of tubes resulting in a loss of the index cation. This produces misinterpretation and yields usually in an overestimation of the CEC. Furthermore, when expandable clay minerals are investigated excess adsorption occurs leading to unreliable CEC results dependent on solution/solid ratio and ionic strength of the exchange solution. A modified silver-thiourea method is proposed, which uses a chemically more stable exchange solution, eliminating silver sulphide precipitation and substantially lowering excess adsorption, which is abolished by additional washings. The results are comparable to the ammonium acetate method. (c) 2006 Elsevier B.V. All rights reserved.
引用
收藏
页码:38 / 46
页数:9
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