Chemistry Letters, Vol.37, No.11, 1110-1111, 2008
A Convenient Procedure for the Acidic Activation of Mineral Bentonite: An Environmentally Friendly Method for the Preparation of Bleaching Earths
Refluxing montmorillonite-containing raw bentonite ((Na,Ca)(0.33)(Al,Mg)(2)Si4O10(OH)(2)) in aq HNO3, then neutralizing it with NH3 produces NH4NO3-containing NH4-bentonite. The NH4NO3 intercalated can be eliminated as a gaseous product (N2O and H2O) by heating at 400 degrees C, and the deammoniation and dehydroxylation process of the preactivated bentonite leads to formation of bleaching earth (H-x(Al,Mg)(2-y)Si4O10-(OH)(2)).