Multi-cation exchanges involved in cesium and potassium sorption mechanisms on vermiculite and micaceous structures

Abstract

Vermiculite and micaceous minerals are relevant Cs sorbent in soils and sediments. To understand Cs bioavailability in soils resulting from multi-cation exchanges, Cs sorption onto clay minerals have been carried out in batch experiments with solutions containing Ca 2+ , Mg 2+ and K + . A sequence between a vermiculite and various micaceous structures were achieved by conditioning a vermiculite at various amounts of K. Competing cation exchanges were investigated according to the concentration of Cs. The contribution of K on trace Cs desorption is probed by applying different concentrations of K on Cs-doped vermiculite and micaceous structures. Cs sorption isotherms at chemical equilibrium were combined with elemental mass balances in solution and structural analyses. Cs replace easily Mg 2+ > Ca 2+ and competes scarcely with K. Cs is strongly adsorbed on the various matrix and a K/Cs ratio about a thousand is required to remobilize Cs. Cs is exchangeable as long as the clay interlayer space remains open to Ca 2+ . However, excess of K, as well as Cs, in solution leads to the collapse of the interlayer spaces that locks the Cs into the structure. Once K and/or Cs collapse the interlayer space, the external sorption sites are then particularly involved in Cs sorption. Subsequently, Cs + exchanges preferentially with Ca 2+ rather than Mg 2+ . Mg 2+ is extruded from the interlayer space by Cs + and K + adsorption, excluded from short interlayer space and replaced by Ca 2+ as Cs + desorbs.

Isolation and molecular characterization of potassium-solubilizing bacteria from limestone mountain of Bahorok, Langkat District, Indonesia

“…exchangeable and nonexchangeable (Eguchi et al 2023). Exchangeable K is readily available to plants for immediate uptake, and it is held on to the surface of soil particles and can be easily exchanged with other cations (Brady et al 2008;Dubus et al 2023). Soil pH, cation exchangeable capacity, and soil texture significantly determine the amount of exchangeable K in the soil (Kome et al 2019).…”

“…The non-exchangeable K is tightly bound to soil minerals such as mica, feldspar, and clay minerals, making it unavailable for plant uptake. Its release into the soil solution is slow and limited due to its strong bonding, which restricts its contribution to plant nutrition (Dubus et al 2023). Plants absorb K ions present in soil solutions (Çalişkan dan Çalişkan 2019) but very few.…”

“…Another issue is that K can be trapped in clay minerals soil while competing with ammonium (Hernández et al 2021). Vermiculite and micaceous are types of clay minerals that function as a reservoir for K, as they have a solid attraction for K ions and can retain them effectively (Dubus et al 2023). Therefore, an alternative solution is necessary to overcome the issue of K bonding in the soil's sediment and clay minerals.…”