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Isosteric heats of sorption and desorption of phenanthrene in soils and carbonaceous materials.

Environmental pollution (Barking, Essex : 1987) (2013-02-02)
Guohui Wang, Peter Grathwohl
ABSTRACT

Isosteric heats (ΔH) of sorption/desorption of phenanthrene were determined for carbonaceous materials (Pahokee peat, lignite, and high-volatile bituminous coal) and two soils based on reported equilibrium sorption/desorption isotherms at four different temperatures (4, 20, 46 and 77 °C). In addition, ΔH for desorption of native phenanthrene was determined to elucidate the "aging" effect by equilibrating samples with water at six temperatures (20, 40, 53, 61, 73, and 86 °C). Isosteric heats decreased with increasing solute concentration and were in a range of 19-35 kJ mol(-1). Values higher than the heat of octanol-water phase transfer for phenanthrene (19 kJ mol(-1)) imply that both partitioning and adsorption processes are involved for these materials, where the sorptive contributions from both processes were estimated based on the phenanthrene thermodynamic data. Moreover, on the basis of ΔH values of desorption, release of native and spiked phenanthrene from our samples was similar.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Phenanthrene, 98%
Sigma-Aldrich
Phenanthrene, sublimed grade, ≥99.5%
Supelco
Phenanthrene, analytical standard, for environmental analysis
Supelco
Phenanthrene, certified reference material, TraceCERT®
Supelco
Phenanthrene solution, certified reference material, 5000 μg/mL in methanol