Work

Understanding the limits of binary diffusion for enhanced clay barrier design

Year: 2024

Type: article

Abstract: Waste containment and isolation strategies often utilize bentonite as a buffer material due to its swelling capacity, sealing efficiency, low permeability, and limited diffusive transport. However, previous experimental studies of ionic diffusion through bentonite have shown discrepancies with binary diffusion assumptions. Meticulous experiments and complementary analyses reveal that the migration of preexisting ions in the medium enables the differential flux of diffusing anions and cations, while maintaining local electroneutrality in all cases. The separation between the cationic and anionic fronts is electrically tied to the motion of the preexisting ions and reflects the interplay between valence, concentration, and self-diffusion coefficients of the ions involved. Imposing binary diffusion conditions forces the faster anions to diffuse at the same rate as cations. Therefore, effective barriers to mitigate both cation and anion transport should have low surface charge and low excess salts to minimize the preexisting ionic concentration.

Source: PNAS Nexus

DOI: 10.1093/pnasnexus/pgae366

Authors: Jooyoung Im, J Carlos Santamarina

Institutions: King Abdullah University of Science and Technology, Georgia Institute of Technology

Language: English

Topic: Landfill Environmental Impact Studies

Subfield: Waste Management and Disposal

Field: Environmental Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,202

Funder: King Abdullah University of Science and Technology