Transport of rate-limited sorbing solutes in an aggregated porous medium: A multiprocess non-ideality approach

The purpose of this work is to investigate the transport of rate-limited sorbing solutes in a saturated, aggregated porous medium. Data obtained from miscible displacement experiments are used to examine the transport of solutes constrained by rate-limited sorption and mass transfer, to examine the synergistic effects of two non-ideality factors, and to test the capability of a multiprocess non-equilibrium (MPNE) model to simulate transport. The input parameters were obtained independently, allowing the model to be used in a predictive mode. The independent predictions obtained with the MPNE model provided very good descriptions of the experimental data for several organic solutes with different structures. The effects of multiple non-ideality factors controlling solute transport were explored, and flow interruption experiments provided additional evidence regarding the synergistic effects of rate-limited sorption and rate-limited mass transfer. Our analyses have shown quantitatively that both mass distribution and characteristic reaction time are important factors influencing transport. Solute characteristics controlled the degree to which each factor influenced transport behavior for a given porous medium. The velocity dependency of the mass-transfer and desorption rate coefficients and the resultant impact on solute transport were also examined.