Study On Adsorption Of Heavy Metal Ions To Palygorskite And Kinetics Of Acid-dissolution Of Palygorskite

Palygorskite is a chain-layer magnesium-aluminum silicate. Since it was discovered in the 19th century, few attention has been paid on the adsorption mechanism of heavy metal ions to the mineral and kinetics of acid-dissolution of palygorskite.Systematic study was carried out on adsorption properties of palygorskite, which was prepared from Guanshan palygorskite clay, and the mechanism was discussed on the basis of surface complexity theory. With a comparison to adsorption of metal ions to montmorillonite and study on acid-dissolution of palygorskite, a better understanding was obtained on aqueous interaction between palygorskite and metal ions.The results indicate the adsorption mechanism is not only adsorption but hydrolysis and precipitation of metal ions, mineral dissolution, crystal growth, co-precipitation of heavy metal ions and extracted ions from the mineral, etc. Induced hydrolysis and precipitation of metal ions by mineral-water interaction is an important interfacial interaction.The leaching rate of each octahedral cation depends on mineral cation concentration, reation rate and diffusion rate.The kinetics of acid-dissolution of palygorskite can be represented by the interface reaction model. For Fe3+ and Mg2+, the relation between leaching rate (X) and reaction time (t) can be both described as 1- (1- X)1/3 = K't and the apparent activation energies are 51.8kJ/mol and 46.8kJ/mol, respectively; for Al3+, the relation between leaching rate (X) and reaction time (t) can be described as 1-3(1-Z)2/3 +2(1-X) -K't and the apparent activation energy is 39.0kJ/mol.