Die Bestimmung der effektiven Kationenaustauschkapazität von Gesteinen

The determination of the effective cation exchange capacity of rocks The extractable cations (1 N NH₄Cl) of broken, mortared, and ground rocks (Sandstone, Clay schist, Diabase, Alkali-Olivinbasalt) were determined using vibration extraction and percolation. These methods were evaluated by re-exchange experiments. In addition mineralogical components, specific surface and effective porosity of the rocks were determined. Al-silicates which are cation exchangers like Illite and Zeolite minerals were found in these rocks. Mortaring and grinding increased the specific surface and the exchange capacity of the rocks which have a low porosity (Clay schist and Basalt). For example, the CEC of broken Clay schist was 27 μmol_c g^?1 and increased to ≈ 40 μmol_c g^?1 after mortaring. The CEC of the rocks with a high porosity (Diabase and Sandstone) did not depend on the particle size. Therefore we assume, that inner parts of the broken rocks were reached by extraction. The CEC amounts to ≈ 50–80% of the sum of the cations, which could be extracted with NH₄Cl. This difference is probably due to the dissolution of salts. Mortaring and grinding increased the amount of cations derived from dissolving of salts. The results show, that rocks are of signficance not only for silicate weathering, but also for the cation exchange.