Concentration-dependent kinetics of pollutant desorption from soils.
نویسندگان
چکیده
Sorption-desorption kinetics play a major role in transport and bioavailability of pollutants in soils. Contaminant concentration is a potentially important factor controlling kinetics. A previous paper dealt with the effect of solute concentration on fractional uptake rates of phenanthrene and pyrene from a finite aqueous source. In this study we determined the effect of initial phenanthrene sorbed concentration (q(0)) on the fractional mass desorption rates from each of six soils to a zero-concentration solution, approximated by including a polymer adsorbent (Tenax) as a third-phase sink. The soils were preequilibrated with phenanthrene for 180 d. Consistent with theory, the fractional desorption rates determined by empirical curve fitting increased with q(0) provided the isotherm was nonlinear. After 500 to 600 d of desorption at the steepest possible concentration gradient, all soils retained a highly resistant fraction, which ranged from 4 to 31% of q(0), except for one soil at a high q(0). The highly resistant fraction decreased with increasing q(0), for nonlinear isotherm cases, but increased with q(0) for linear or nearly linear isotherm cases. Application of a nonlinear diffusion model, the dual-mode diffusion model (DMDM), to the nonresistant fraction gave reasonably good fits. The DMDM attributes the increase with concentration of the apparent diffusivity to a decrease in the proportion of sorbate occupying immobile sites (holes) in soil organic matter. The concentration-dependent term in the expression for the apparent diffusivity correlated with either of two indices that reflect the linearity of the sorption isotherm. Bunker C oil present in one soil acted as a partition domain. The findings of this study are consistent with heterogeneous models of soil organic matter, and indicate that concentration effects should be taken into account whenever desorption rate is important.
منابع مشابه
Desorption Kinetics of Heavy Metals (Lead, Zinc, and Nickel) Coexisted with Phenanthrene from a Natural High Buffering Soil
This work aims to investigate the competitive time-dependent desorption rate of heavy metals (lead, zinc, nickel) coexisting with phenanthrene from natural high buffering soil. Two non-ionic surfactants (Tween 80 and Brij 35) combined with disodium ethylene diamine tetraacetate salt (Na2-EDTA) were utilized as the reagents. The contaminants’ time-dependent desorption data was fitted with five k...
متن کاملBiodegradation Modeling of Nitrophenolic Pollutant in a Slurry Bubble Reactor
Biodegradation kinetics of 4-nitrophenol (PNP) in aqueous solution by a gram negative soil bacterium, Ralstoniaeutropha was firstly studied in a small scale batch reactor. The degradation of PNP was evaluated at initial PNP concentrations ranging from 3 mg/L to 14 mg/L. The rate of PNP consumption by the bacterium culture was modeled using Monod and Contois kinetics in batch condition. PNP degr...
متن کاملA WHAM-based kinetics model for Zn adsorption and desorption to soils.
A novel model has been developed to describe the kinetics of Zn adsorption and desorption to soils. The model incorporates the mechanistic-based equilibrium model WHAM (Windermere humic aqueous model) to account for the chemical variation during the reaction (e.g., pH and Zn2+ concentration), the heterogeneity of binding sites of soil organic matter (SOM), and the nonlinear binding of Zn to SOM...
متن کاملModeling Zn Adsorption and Desorption to Soils
The rate of reaction of trace metals between soils and solutions is important in predicting trace metal behavior as equilibrium may not be attained. Although chemical equilibrium models are commonly used for soil systems, there has been less progress in developing predictive kinetic models. Kinetics of Zn adsorption/desorption have been modeled based on the linear adsorption isotherm assumption...
متن کاملKinetics of copper desorption from soils as affected by different organic ligands
*Corresponding Author Email: [email protected] Tel.: +2 0359 04684; Fax: +2 0359 04684 ABSTRACT: Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behavior be understood. In this paper, the...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Environmental toxicology and chemistry
دوره 21 12 شماره
صفحات -
تاریخ انتشار 2002