Dissolution behavior and dissolution mechanism of palygorskite in HCl solution*

Abstract

Abstract The 1 mol/L, 3 mol/L and 5 mol/L HC1 solutions were employed to leachtwo palygorskites with different trioctahedral contents in their crystal structure for different period of time. The results of the dissolution experiments show that the dissolution process could be divided into three steps, and that this dissolution behavior can be attributed to its higher Mg 2+ content, and is restricted by the extraction behavior of Si4+ . The preferential extraction for Mg2+ promotes the extraction behavior of Si4+ from Si-O framework. Because the Si4+ in the form of amorphous SiO2 is adsorbed onto the surface of palygorskite fibre, the reaction between palygorskite and acid is obstructed. With the elapsing of time, or the increasing of the acid concentration, the amorphous SiO2 flocculates, and then the channels of chemical reaction are reopened. The ratio value of Mg2+/(Fe3+Al3+) in leaching solution tends to a fixed value, showing that the acid attacks not only the surface but also the structural channels...