Solid-state nuclear magnetic resonance spectroscopy on synthetic ammonium/aluminum-saponites

Ammonium-saponite is hydrothermally grown at temperatures below 300 degrees C from a gel with an overall composition corresponding to (NH (sub 4) ) (sub 0.6) Mg (sub 3) Al (sub 0.6) Si (sub 3.4) O (sub 10) (OH) (sub 2) . Using (super 27) Al and (super 29) Si solid-state Magic Angle Spinning NMR techniques it is demonstrated that synthetic ammonium-saponites have a rather constant Si/Al (super IV) ratio ( nearly equal 5.5) and an Al (super IV) /Al (super VI) ratio that varies between 1.5 and 3.8. The above ratios are independent of the synthesis temperature, although an increasing amount of Si, N, and, to a lesser extent, Al are incorporated in an amorphous phase with increasing temperature. (super 27) Al MAS-NMR is unable to differentiate between Al at octahedral and Al (super 3+) at interlayer sites. CEC, XRD, and the inability to swell prove the Al (super VI) to be mainly on the interlayer sites. Based on the NH (sub 4) (super -) exchange capacity, X-ray fluorescence, (super 27) Al and (super 29) Si MAS-NMR, it is possible to calculate a relatively accurate structural formula.