A Convenient Procedure for the Acidic Activation of Mineral Bentonite: An Environmentally Friendly Method for the Preparation of Bleaching Earths

摘要

Refluxing montmorillonite-containing raw bentonite ((Na,Ca)_(0.33)(Al,Mg)2Si4O_(10)(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 °C, and the deammoniation and dehydroxylation process of the preactivated bentonite leads to formation of bleaching earth (H_x(Al,Mg)_(2-y)Si4O_(10)-(OH)2).