The temperature dependence of slow desorption kinetics of organic compounds from sediments
At various temperatures, desorption kinetics were measured of some chlorobenzenes, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from one lab-contaminated and one field-contaminated sediment. The desorption technique employed was extraction with solid Tenax TA beads in separation funnels. A first-order model with three sediment compartments turned out to describe properly the observed desorption behavior. Apart from a rapidly desorbing fraction, two slowly desorbing sediment fractions were distinguished, one desorbing with a rate constant of about 10{sup {minus}3} h{sup {minus}1} and one with rate constants approximately 10--30 times lower. Rates of slow desorption increased strongly with increasing temperature; the resulting activation enthalpies appeared to be 50--60 kJ-mol{sup {minus}1} for the lab-contaminated sediment and 40--50 kJ-mol{sup {minus}1} for the field-contaminated one, respectively. The activation enthalpies for desorption were approximately constant for all compounds studied. The magnitudes of the observed activation energies for slow desorption are in agreement with a diffusion process. However, the exact nature of this diffusion (intra-organic matter diffusion or micropore diffusion) could not be identified. Because slow desorption is much faster at elevated temperatures, the measurement of high temperature desorption kinetics can provide information on long-term desorption kinetics and, probably, on the feasibility of bioremediation of aged contaminants.
- OSTI ID:
- 442873
- Report Number(s):
- CONF-961149--
- Country of Publication:
- United States
- Language:
- English
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