Use of a reactive surface-diffusion model to describe apparent sorption-desorption hysteresis and abiotic degradation of lindane in a subsurface material

Abstract

Desorption hysteresis has been reported frequently in the literature, with several theories advanced to explain the cause of this phenomenon. Several of these theories hypothesize that desorption hysteresis is an experimental artifact. Batch experiments were performed to observe sorption-desorption and transformation of the solute lindane in systems that included a subsurface sand material. Results of these experiments were interpreted with a diffusion and reaction model. Methods were developed to isolate and determine model parameters from experimental data. Rates of dehydrochlorination were determined for lindane in solution and solid phases. A pseudo sorption-desorption equilibrium experiment was performed by allowing 720 h for attainment of sorption equilibrium and 384 h for attainment of equilibrium for each of three desorption steps-longer than most experiments of a similar nature have been allowed to equilibrate. The pseudoequilibrium data showed marked hysteresis. A surface-diffusion model, which accounted for solute degradation from the solution and solid phases, was calibrated with sorption rate data. The model was verified with desorption rate data. Model predictions of the pseudo sorption-desorption experiment showed that slow sorption-desorption rates explained most of the apparent hysteresis.

Long-term desorption behavior of uranium and neptunium in heterogeneous volcanic tuff materials /

“…To test this hypothesis, efforts have been made to compare the rate of solute uptake with solute desorption. An intraparticle diffusion model with parameters determined from uptake experiments was able to account for the majority of sorption hysteresis (Miller and Pedit 1992). Cunningham and Deitsch et al (2005) quantify sorption and desorption time scales for an organic contaminant onto four natural sorbents from the previous study above (Deitsch, Smith et al 2000) using temporal moment analysis.…”

The effect of equilibration time on desorption rate measurements with chlorinated alkenes and aquifer particles

“…These researchers have observed an increase in the residual fraction with increasing equilibration time, and ascribed these results (qualitatively) to intraparticle diffusion processes [12-141. A more recent study examined non-singularity between sorption and desorption behavior in a lindane-sand system, and interpreted the results using a reactive surface diffusion model [ I q . In that study, desorption data from an under-equilibrated sample was successfully simulated using an intraparticle diffusion model that accounted for an intraparticle concentration gradient (Figures 6 and 7 [16]) suggesting that a short-term method may be possible for determining desorption rates. The underlying assumption of this work, and of several related sorption rate studies [I-5], is that the sorption/ desorption rate in aquifer particles is governed by a pore diffusion mechanism.…”

Electrochemical Processes for In-situ Treatment of Contaminated Soils

“…Presently, sorption-desorption kinetic models can be generally categorized into several kinds based on the controlling mechanisms, such as first-order rate models, two-site rate models, pore-diffusion models, surface-diffusion models, or combined pore and surface-diffusion models (Miller and Pedit, 1992). Table 3.1 summaries some common sorption-desorption models have been developed.…”