Determination of exchangeable potassium by electroultrafiltration
1994
Cumakov, A. | Cicel, B. | Hrnciarova, K. | Smrcok, L. (Slovenska Akademia Vied, Bratislava (Slovak Republic). Ustav Anorganickej Chemie)
The results of experimental tests of bonding strength of potassium on montmorillonite using electroultrafiltration and possibility of distinguishing between adsorbed, exchangeable, fixed and structural K+ are reported. Fine fraction of Jelsovsky Potok bentonite (Slovakia) containing montmorillonite was used potassium oxide content in monoionic K-saturated material was 4.2 %. The applied Grimme's method allows calculation of theoretically extractable amount of potassium (dm) and the half-time of its extraction (t0.5). Coincidence of measured and calculated data was tested using the Durbin-Watson coefficient (D-W). Substantial change of D-W coefficient in increasing voltage-series provides additional information at the end of extraction of one subfraction of exchangeable potassium (KEX) and the start of the next one. Up to 36 % of KEX can be extracted at room temperature and voltages over 300 V. Majority of KEX (26.6 %) was extracted at 50 V. Comparison of desorption parameters (dm, t0.5 and D-W) yielded 3 to 4 subfractions of KEX extracteable at rooom temperature. At 80 degrees C and 50 V all KEX extractable at room temperature enters in the solution. At higer voltages, especially at 150 and 200 V, the remaining 64 % of KEX was extracted. At 300, 350 and 400 V approximately 3 % of KEX remained fixed in the structure of montmorillonite.
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