Biomedical subjects

Michael A Malusis

Publications and source records attributed to Michael A Malusis.

3 recordsLinked to original sources

PubMed2004

Explicit and implicit coupling during solute transport through clay membrane barriers.

Simulations of salt (KCl) flux through a 1-m-thick clay membrane barrier (CMB) based on coupled solute transport theory are compared to simulated fluxes based on traditional advective-dispersive transport theory. The simulations are based on measured values for the effective salt-diffusion coefficient (Ds*) and chemico-osmotic efficiency coefficient (omega) for a bentonite-based barrier material subjected to KCl solutions. The results indicate that the exit salt flux is reduced due to both explicit coupling (hyperfiltration and chemico-osmotic counter-advection) and an implicit coupling effect resulting from the decrease in Ds* due to a decrease in the apparent tortuosity factor, tau a, with an increase in omega. Implicit coupling is shown to be more significant than explicit coupling for reducing and retarding salt flux through a CMB under diffusion-dominated conditions. Failure to account for the implicit coupling effect may result in unrealistic results, such as the existence of salt flux through a perfect (ideal) clay membrane (i.e., omega=1).

Adsorption↗

PubMed2002

Coupling effects during steady-state solute diffusion through a semipermeable clay membrane.

Two separate coupling effects are evaluated with respect to steady-state potassium chloride (KCl) diffusion through a bentonite-based geosynthetic clay liner (GCL) that behaves as a semipermeable membrane. Both of the coupling effects are correlated with measured chemico-osmotic efficiency coefficients, omega, that range from 0.14 to 0.63 for the GCL. The first coupling effect is an explicit (theoretical) salt-sieving effect expressed as a coupled effective salt diffusion coefficient, Domega*, that is lower than the true (uncoupled) effective salt diffusion coefficient, Ds*, because of the observed membrane behavior. However, the maximum difference between Domega* and Ds* based on measured chloride concentrations is relatively small (i.e., = 10%), and the difference decreases with decreasing omega (i.e., Domega* --> Ds* as omega --> 0). The second coupling effect is implicit (empirical) and is characterized by the measurement of concentration-dependent effective salt diffusion coefficients that results in an degrees 300% decrease in Ds* as omega increases from 0.14 to 0.63. The decrease in Ds* resulting from implicit coupling is attributed to solute exclusion described in terms of a restrictive tortuosity factor.

Aluminum Silicates↗

PubMed2002

Theory for reactive solute transport through clay membrane barriers.

The theoretical development for one-dimensional, coupled migration of solutes with different ionic mobilities through clay soils that behave as ion-restrictive membranes, referred to as clay membrane barriers (CMBs), is presented. The transport formulation is based on principles of irreversible thermodynamics and accounts explicitly for coupling effects of hyperfiltration (ultrafiltration) and chemico-osmotic counter-advection associated with clay membrane behavior in the absence of electrical current. Since, by definition, no solute can enter a "perfect" or "ideal" membrane, the concept of an implicit coupling effect, such that the effective salt-diffusion coefficient, Ds* approaches zero as the chemico-osmotic efficiency coefficient, omega approaches unity is introduced. The theoretical development also illustrates that, even in the absence of membrane behavior, traditional advective-dispersive transport theory based on a constant value of Ds* for the solutes may not be appropriate for simulating transient transport in reactive (ion exchanging) systems. This potential limitation is illustrated through simulations for solute mass flux involving the migration of a binary salt solution (KCl) through a clay barrier with exchange sites saturated with a single exchangeable cation (e.g., Na+) that enters the pore solution upon ion exchange with the salt cation (K+).

Aluminum Silicates↗