Ionicity of clay–cation bonds in relation to dispersive behavior of Mg and K soil clays as influenced by pH

Zhu, Yingcan ORCID: https://orcid.org/0000-0003-4087-0169 and Marchuk, Alla and Bennett, John McLean (2020) Ionicity of clay–cation bonds in relation to dispersive behavior of Mg and K soil clays as influenced by pH. Clays and Clay Minerals. pp. 1-13. ISSN 0009-8604


Abstract

The dispersive behavior dynamics of clay determine soil characteristics such as permeability and aggregate stability, and, consequently, crop productivity. Soil dispersion is heavily influenced by the ionicity of clay–cation bonds and has been shown to be related to the net negative charge and pH of the system. Little work has been done, however, which considers these factors together, especially for K and Mg clays. The objective of the present study was to investigate the effect of changing pH on the dispersive behavior of Mg and K homoionic clays, in comparison to Ca and Na clays under equivalent pH conditions. The clay fractions used here were extracted from three soils and have distinctly different mineralogies. These clays were treated to become homoionic with regard to Na, K, Ca, and Mg. Excess salts were removed by dialysis and pH was adjusted to 3, 4, 5, 6, 7, 8, 9, 10, and 11 for all clays, except Mg (pH range 3–7). Clay dispersion-flocculation dynamics were investigated, and the net negative charge, pH, electrical conductivity (EC), and turbidity were measured. Mg has a similar but less flocculative effect than Ca, while K has a similar but less dispersive effect than Na, under similar pH conditions. The dispersive behavior of Na, K, Mg, and Ca homoionic clays was correlated well with the ionicity of clay–cation bonds at equivalent pH, with the degree of clay dispersion being explained by the pH, EC, ionicity, ζ-potential, and mean particle size of the clay–cation system. A predictive model for dispersion was developed with its applicability and limitations discussed.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment - Centre for Sustainable Agricultural Systems (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment (1 Aug 2018 -)
Date Deposited: 04 Dec 2020 04:17
Last Modified: 10 Sep 2021 01:00
Uncontrolled Keywords: Clay dispersion; Clay mineralogy; Exchangeable cations; pH; Zeta potential
Fields of Research (2008): 05 Environmental Sciences > 0503 Soil Sciences > 050304 Soil Chemistry (excl. Carbon Sequestration Science)
05 Environmental Sciences > 0503 Soil Sciences > 050399 Soil Sciences not elsewhere classified
Fields of Research (2020): 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300299 Agriculture, land and farm management not elsewhere classified
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300210 Sustainable agricultural development
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9614 Soils > 961499 Soils not elsewhere classified
Socio-Economic Objectives (2020): 18 ENVIRONMENTAL MANAGEMENT > 1806 Terrestrial systems and management > 180605 Soils
Identification Number or DOI: https://doi.org/10.1007/s42860-020-00100-x
URI: http://eprints.usq.edu.au/id/eprint/40209

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