Sorption and sequestration of hydroxylated aromatic compounds in natural geosorbents

The role of oxidative coupling on the equilibrium sorption-desorption and extractability (sequestration) of hydoxylated aromatic compounds, i.e., phenol, o-cresol, and p-chlorophenol, in natural sorbents comprised of different types of organic matter was studied. Almost total extractability of all three contaminants was observed on Lachine shale and Wagner II soil, comprised of geologically older kerogen soil organic matters. Addition of mineral catalysts to peat resulted in significant sequestration. With the exception of Canadian Peat, in which sequestration was not observed, non-linear isotherms were observed in all systems. Decreased capacity factor (Freundlich K_F) from sorption to desorption isotherm was observed in all systems in which cross coupling was significant while a small increase in K_F was apparent in the remaining systems. Slight increase in K_F from sorption to desorption isotherms was also observed with non-reactive compounds, e.g., phenanthrene in different soil types. Model simulations for the sorption and desorption of 4-chlorophenol in Lachine shale and Fox Forest soil revealed that although the Dual Reactive Domain Model (DRDM) and Freundlich models described well the data, DRDM described better the shale isotherms, where sequestration was not observed. The Freundlich model described better the Forest isotherms compared to DRDM, where oxidative coupling reactions controlled the sorption-desorption behavior of HAC.