Henry's Law Constants of Polychlorinated Biphenyl Congeners and Their Variation with Temperature

Abstract

The Henry's law constants for 26 polychlorinated biphenyl (PCB) congeners were measured using a gas-stripping apparatus at five environmentally relevant temperatures between (4 and 31) °C. The Henry's law constants ranged between (0.079 ± 0.003) Pa·m3·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195) at 4 °C and (308 ± 29) Pa·m3·mol-1 for 2,2‘,3,3‘,4,5‘,6,6‘-octachlorobiphenyl (IUPAC congener #201) at 31 °C. The temperature dependence of each PCB congener's Henry's law constant was modeled to calculate the enthalpy and entropy of the phase change between the gaseous and dissolved phases. For many PCB congeners, this study reports the first experimentally measured temperature variations of their Henry's law constants. The enthalpies of phase change (ΔHH) ranged between (14.5 ± 3.4) kJ·mol-1 for 2,2‘,4,6,6‘-pentachlorobiphenyl (IUPAC congener #104) and (167 ± 13) kJ·mol-1 for 2,2‘,3,3‘,4,4‘,5,6-octachlorobiphenyl (IUPAC congener #195). These data can be used to predict PCB congener Henry's law values within the experimental temperature range within a relative standard error of less than 10%.