STUDY OF DIQUAT AND PARAQUAT SORPTION BY LAYERED SILICATES WITH EXPANDING STRUCTURAL CELLS

A complex study of the sorption of double-charged organic cations of d iquat and paraquat by Na-and Ca-forms of montmorillonite and vermiculi te and desorption of inorganic Na+ and Ca2+ cations showed evidence of a superequivalent amount of sorption of organic cations in Na-vermicu lite-paraquat and Na-montmorillonite-diquat (or paraquat) systems. It is shown that this effect is due to the equimolar sorption of a part ( 10-12%) of diquat and paraquat in the form of single-charged cations, which is caused by incommensurate distances between positively charged nitrogen atoms of the organic cations and the centers of single-charg ed negative ions in the silicate layer. It is also demonstrated that c ommensurate (incommensurate) distances lead to higher (lower) selectiv ity of the layered silicate with respect to double-charged organic cat ions. The selectivity of montmorillonite with respect to diquat and pa raquat is higher as compared to that of vermiculite. The structure of orgamonineral complexes is discussed.