期刊名称：Journal of Materials and Environmental Science
印刷版ISSN：2028-2508
出版年度：2014
卷号：5
期号：5
页码：1541-1550
出版社：University of Mohammed Premier Oujda
摘要：The Clay fractions of five Moroccan vertisols (Chaouia, Gharb, Doukalla, Zair, and Sais) as well as a reference smectite (montmorillonite SWY-1) were Ca-saturated and dispersed in K + .Ca 2+ binary exchange solutions with constant ionic forces of 10 -2 at 25°C. Exchange isotherms established showed that K is preferentially adsorbed compared to Ca 2+ in all soil clays and the reference smectite. The clay fraction of the Ch-Chaouia soil, which is dominantly beidellitic, represents the highest affinity for K + . For all other soil clays, the values of the Vanselow (K V ) exchange selectivity coefficient, Gaines and Thomas (K GT ), and Gapon (K G ) were higher than 1. This corroborates the fact that clays fractions of vertisols dominated by smectites are highly selective to K + compared to Ca 2+ . The regression coefficient show that a two-site adsorption model predicts well the adsorption parameters α, K V1 , K V2 and N 0 . The site 1 (α) portion is more important in the Chaouia soil clay (α = 0.248) and the least in the Doukkala soil clay (α = 0.078). The selectivity coefficient of sites 1 (K V1 ) is less important for the reference Montmorillonite SWY-1 compared to all soil clays. For sites 2, the selectivity coefficients (K V2 ) are of less importance and vary from 1.77 (mole/l) -1 for SWY-1 to 12.54 (mole/l) -1 for the Chaouia soil clay. The equilibrium constants (Kéq) of the K-Ca exchange at 25°C are greater than 1. They are highest for the Chaouia clay and the lowest for the SWY-1 reference montmorillonite. For all clays, the standard free enthalpy (ΔG°) has negative values varying from -5 to 0 KJ/éq.
