Flow-Through and Batch Methods for Determining Calcium-Magnesium and Magnesium-Calcium Selectivity
- Tom M. DeSutter *a,
- Gary M. Pierzynskib and
- Luke R. Bakerb
Conducting binary-exchange experiments is a common way to identify cationic preferences of exchanger phases and the two most common approaches are the flow-through and batch methods. The objectives of this research were to provide the materials and methods for both flow-through and batch equilibration techniques and to compare Ca-Mg and Mg-Ca selectivity when using these two methods on a montmorillonitic soil. The methods were evaluated by comparing both the Gibbs free energy values (ΔGex) and selectivity diagrams derived from the flow-through and batch exchange reactions. The ΔGex values for the Ca-Mg reaction were 634 and 444 J mol−1 as determined by the flow-through and batch methods, respectively, indicating an exchanger preference for Ca. Exchanger preference for Ca was also evident in the Mg-Ca reaction with ΔGex values of −882 and −784 J mol−1 for the flow-through and batch methods, respectively. The flow-through and batch methods worked very well for determining cation selectivity and results indicate no significant differences existed between the two methods.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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