Assessments of Water Sorption Methods to Determine Soil’s Specific Surface Area

AbstractA soil’s specific surface area (SSA) is commonly determined by two conventional methods: adsorption isotherms using nitrogen gas with interpretation through the Brunauer-Emmet-Teller (BET) equation, and ethylene glycol monomethyl ether (EGME) adsorption. The SSA so obtained may possess sever...

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Bibliographic Details
Published in:Journal of geotechnical and geoenvironmental engineering 2021-08, Vol.147 (8)
Main Authors: Zhou, Baochun, Lu, Ning
Format: Article
Language:English
Subjects:
Adsorption
Dimensions
Ethylene glycol
Interlayers
Isotherms
Labour
Mechanical properties
Methods
Moisture content
Nitrogen
Soil
Soil classification
Soil mechanics
Soil swelling
Soil water
Sorption
Specific surface
Surface area
Surface chemistry
Technical Papers
Water vapor
Water vapour
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Summary:AbstractA soil’s specific surface area (SSA) is commonly determined by two conventional methods: adsorption isotherms using nitrogen gas with interpretation through the Brunauer-Emmet-Teller (BET) equation, and ethylene glycol monomethyl ether (EGME) adsorption. The SSA so obtained may possess several drawbacks: (1) it does not directly reflect the SSA for soil-water interaction, (2) nitrogen sorption applies only to external mineral surface area and does not account for intracrystalline (expandable mineral interlayer) surface area, and (3) the EGME method is labor- and time-intensive. Recently, several water vapor adsorption SSA methods have emerged with improved capability to quantify SSA and directly probe soil-water interactions. Here the authors systematically assess the paradigms of non-water-based methods and water-based methods for their suitability to quantify soil’s SSA through a wide spectrum of soils. Independent adsorption isotherms using water vapor, EGME, and nitrogen gas for a variety of soils are measured and considered together with existing data from the literature to comparatively assess the methods. Among the water-based sorption methods, the augmented BET (A-BET) method compares consistently well with the non-water-based paradigm (EGME method). The A-BET method is superior to the other SSA methods as it can quantify and separate a soil’s external SSA (particle surface) and internal SSA (intracrystalline surface), thus providing a new dimension to understanding the role of soil-water retention in soil classification, swelling, collapsing, multiphysics flow, and mechanical behavior.
ISSN:1090-0241
1943-5606
DOI:10.1061/(ASCE)GT.1943-5606.0002579