Variation of relative fraction of bound cations with time 1 0.2 0.4 0.6 0.8 1 Virgin 1/6d-1/3d-1d-2d-4d-8d-16d-32d Elapsed Time (days) FIGURE 11A All cations DI 2 mM 50 mM 200 mM 0.8 0.6 K+ Na+ Ca2+ Mg2+ 0.4 0.2 5 10 15 20 25 Elapsed Time (days) FIGURE 11B Monovalent cations 30 35 DI 2 mM CaCl2 50 mM CaCl2 200 mM CaCl2 Virgin GCL fractions of K+ and Mg2+. The sodium in the bentonite is replaced increasingly with the calcium in the hydration solution with increasing CaCl2 concentration. The relative fraction of Na+ in the virgin GCL was 66%, which decreased to 9% for the GCL hydrated with the 200 mM CaCl2 solution for 32 days. The relative fraction of Ca2+ in the virgin GCL was 23%, which increased to 87% for the GCL hydrated with the 200 mM CaCl2 solution for 32 days. The amount of bound Ca2+ in the bentonite increased rapidly for the 200 mM CaCl2 solution followed by the 50 mM CaCl2 solution with negligible variations over time for the DI water and 2 mM CaCl2 solutions. Similarly, the amount of bound Na+ in the bentonite decreased rapidly for the 200 mM CaCl2 solution followed by the 50 mM CaCl2 solution with negligible variations over time for the DI water and 2 mM CaCl2 solutions. For the 200 mM CaCl2 solution, the maximum decrease in the relative fraction of Na+ was 14 percentage points and occurred for 1- and 2-day tests Elapsed Time (days) Elapsed Time (days) Elapsed Time (days) Elapsed Time (days) FIGURE 12 Variation of individual bound cation species with time GeosyntheticsMagazine.com 17 Mole Fraction in Exchange Complex Bound Cations (cmol+ /kg) Bound Cations (cmol+ /kg) Mole Fraction of Monovalent Cations, Xm Bound Cations (cmol+ /kg) Bound Cations (cmol+ /kg)http://www.GeosyntheticsMagazine.com