INTERACTION OF METHYL- AND ETHYL-AMMONIUM IONS AND PIPERIDINIUM IONS WITH SOILS

Abstract

We measured exchange equilibria between A+ (NH4+, AA+ = CH3NH3+, (CH3)2NH2+, (CH3)3NH+, (CH3)4N+, and (C2H5)4N+ and Pip+ = (CH2)5NH2+) and Ca2+ for eight soil and clay samples at pH 5.7 to 7.5 and at the total cation concentration of 0.10 N. The adsorption capacity for A+ is equal to or smaller than that for Ca2+, depending on the kind of ion-exchange materials, and is very much affected by their selectivity for A+. Smectite in bentonite showed high selectivities for large AA+ and Pip+, whereas smectite in a Red-Yellow Soil and halloysite in weathered andesite did not show these high selectivities for large AA+. Ando soils containing imogolite and allophane showed low to extremely low selectivities for large AA+ and Pip+, and humus in an Ando soil and a Chernozem soil showed low selectivities similarly for different AA+ and relatively high selectivity for Pip+. Generally, the high and low selectivity sites for A+ can be associated with constant and variable charge sites, respectively. In addition, the “coverup” by large A+ and its “exclusion” from the exchange sites can also affect its adsorption by the soil.