Determination of cation exchange capacity of clay minerals by potentiometric titration using divalent cation electrodes

Abstract

This paper will demonstrate the use of divalent cation electrodes on the determination of cation exchange capacity (c.e.c.) of clay minerals. Potentiometric titration was carried out for Coclay A 90 Wyoming bentonite, Na-montmorillonite and illite-bearing shale. Ion exchanges between MgBa, CaBa, CuBa and ZnBa were studied by titrating the barium saturated soil suspension with MgSO 4, CaSO 4, CuSO 4 or ZnSO 4 solution. The c.e.c. values are different for each exchange pair. The results obtained by the potentiometric titration will be compared with those determined by conductometric titration. The potentiometric titration is fast and simple. It measures the free ion activity and has the possibility of making automated and in situ ion determination.