USE OF THE 2ND DERIVATIVE OF TG CURVES FOR INVESTIGATION OF THE EXCHANGED INTERLAYER CATION IN MONTMORILLONITE

Various catian-exchanged montmorillanites (Li+, Na+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Cu2+, Ag+, Cd2+, Hg2+, Al3+, Pb2+ and NH4+) were prepared from calcium montmorillonite and their properties were studied by mea ns of X-ray diffraction and thermal analysis. The two methods give inf ormation on the cation exchange in the interlayer space only. X-ray di ffraction studies at room temperature are mainly suitable for estimati on of the exchange of cations of different valencies. At 500 degrees C , when the structure is completely collapsed, the d value of montmoril lonite depends on the non-hydrated ionic radius of the interlayer cati on, but the measurement interval Is limited for-fine interpretation. T he thermoanalytical method is suitable for a better distinction of dif ferent exchangeable cations of higher hydration energy on the basis of the DTG or DDTG curve.