Clay mineralogy and cation exchange capacity of Brazilian soils from water contents determined by thermal analysis

• Published in: Thermochimica acta Vol. 413; no. 1-2; pp. 73 - 79
• Main Authors: Costa, Antonio Carlos S, Bigham, Jerry M, Tormena, Cássio A, Pintro, José Carlos
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 08-04-2004; Elsevier Science
• Subjects: 2:1 Clay minerals; CEC; Earth sciences; Earth, ocean, space; Exact sciences and technology; Gibbsite; Kaolinite; Mineralogy; Mineralogy: general, methodology, regional studies; Water content; Brazil; CEC; Kaolinite; 2:1 Clay minerals; Gibbsite; Water content; South America; oxides; kaolinite; cation exchange capacity; X-ray diffraction; mineralogy; clay; hydroxides; sedimentary rocks; Particle size distribution; gibbsite; differential thermal analysis; water content; clay minerals; sheet silicates; silicates; soils; clastic rocks; thermal analysis
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2003.10.009

The clay size fraction of subtropical soils is dominated by kaolinite, gibbsite, iron oxides, and small amounts of 2:1 clay minerals. Among these minerals, it is more difficult to quantify the presence of the 2:1 clay minerals where kaolinite is the dominant clay mineral present. Thermal analyses of 56 size clay size fractions, free of iron oxides, developed on magmatic rocks, were used to quantify the presence of expandable 2:1 clay minerals. The water content of the samples, measured in three different ranges of temperatures, gave significant (P<0.0001) linear correlations with the percentage of expandable 2:1 clay minerals and the cation exchange capacities of the whole soil materials. Water content can thus be used as a tool to estimate the quantity of 2:1 minerals in lieu of more complicated procedures.