Affiliations: Department of Environmental Sciences, Zhejiang
University, Hangzhou 310028, China | Department of Urban and Environmental Sciences, Peking
University, Beijing 100871, China
Abstract: The thermodynamic behavior of organic contaminants in soils is
essential to develop remediation technologies and assess risk from alternative
technologies. Thermodynamics of phenanthrene partition into four solids (three
soils and a bentonite) from water were investigated. The thermodynamics
parameters (ΔH, ΔG°, ΔS°,) were calculated according
to experimental data. The total sorption heats of phenanthrene to solids from
water ranged from −7.93 to −17.1 kJ/mol, which were less exothermic
than the condensation heat of phenanthrene-solid (i.e., −18.6 k J/mol).
The partition heats of phenanthrene dissolved into solid organic matter ranged
from 23.1 to 32.2 kJ/mol, which were less endothermic than the aqueous
dissolved heat of phenanthrene (i.e., 40.2 kJ/mol), and were more endothermic
than the fusion heat of phenanthrene-solid (i.e., 18.6 kJ/mol). The standard
free energy changes, ΔG°, are all negative which suggested that
phenanthrene sorption into solid was a spontaneous process. The positive values
of standard entropy changes, ΔS°, show a gain in entropy for the
transfer of phenanthrene at the stated standard state. Due to
solubility-enhancement of phenanthrene, the partition coefficients normalized
by organic carbon contents decrease with increasing system temperature (i.e.,
In K_{&infty;} = −0.284 In S +9.82 (n =4,
r^2 = 0.992)). The solubility of phenanthrene in solid
organic matter increased with increasing temperatures. Transports of
phenanthrene in different latitude locations and seasons would be predicted
according to its sorption thermodynamics behavior.
