Charge Heterogeneity and the Calorimetry of K-Ca Exchange-Adsorption in Clays and Soils

• Main Author: O. Talibudeen
• Format: Article
• Language: English
• Published: Hindawi - SAGE Publishing 1984-09-01
• Series: Adsorption Science & Technology
• Online Access: https://doi.org/10.1177/026361748400100306

Current evidence for surface heterogeneity of the permanent negative charge in some soils and phyllosilicates, which is based on the thermodynamic interpretation of K-Ca exchange isotherms and on other methods, is summarized and reviewed. The relationship between differential heats of K-Ca exchange and K-saturation of the permanent negative charge in the phyllosilicates, especially the Smectites and the Kaolins, is described and related to their known interlayer expansion with ethylene glycol intercalation. From these descriptions, their surface charge heterogeneity and new definitions of ‘pure’ phyllosilicates, especially ‘pure’ montmorillonite and ‘pure’ kaolinite are inferred. The heterogeneity of cation-exchange sites in some English soils is compared with those of the 2:1 phyllosilicates. Differences in the ‘differential heat:fractional K saturation’ relationships between soil phyllosilicates before and after treatment with potassium salts and with farmyard manure illustrate the effects of such treatments on site heterogeneity.