NONEQUILIBRIUM SORPTION AND TRANSPORT OF NEUTRAL AND IONIZED CHLOROPHENOLS

For a series of chlorophenols sorption nonequilibrium was assessed by fitting a bicontinuum sorption model to breakthrough curves measured by miscible displacement techniques. A single log-log inverse relationship was observed between the desorption rate coefficient (k2, h-1) and the equilibrium sorption constant (K(p), mL/g) for all chlorophenols as well as for a series of chlorobenzenes. This suggests that approach to sorption equilibrium for neutral and ionized chlorophenols is constrained in a manner similar to that for nonpolar hydrophobic organic chemicals. For neutral pentachlorophenol (PCP), K(p) values decreased log-linearly with increasing volume fraction methanol (f(c)), with successful extrapolation of these data to aqueous systems. A log-linear relationship was observed between k2 and f(c) in good agreement with independent estimates. For a series of ionized chlorophenols, the fraction of instantaneous sorption domains (F) increased with increasing solute hydrophobicity, while F decreased with increasing f(c) for neutral PCP.