(309g) Gas and Volatile Organic Compound Partitioning in Aqueous Environments

The partitioning of methane between air and produced water from gas wells is a source of greenhouse gases. Hydrocarbon partitioning data are also needed to evaluate remediation measures for leaking gasoline tanks. In this work, we present a model based on dilute solution theory for the correlation and prediction of Henry's constants of organic solutes in aqueous salt solutions, and demonstrate the application of this model for methane partitioning from produced water, and aromatics partitioning from saline and non-saline groundwater. Model parameters for methane and water were first obtained from literature data for methane at 300 atm and temperatures between 50 and 250 C. Data at other pressures up to 1000 atm were then predicted with a Krichevsky-Kasarnovsky-type term added to the dilute solution relationship. It was possible to reliably predict methane Henry's constants in samples of simulated produced water containing up to 4 molal sodium chloride or up to 1 molal calcium chloride from 50 to 125 C and between 100 and 600 atm using the extended model. The partitioning of aromatics at ambient pressure in saline and non-saline groundwater was also studied using the same model. Henry's constants of gasoline constituents including toluene, ethylbenzene, o-xylene, methyl tert butyl ether (MTBE) and ethyl tert butyl ether (ETBE) were correlated using VOC + water data from the literature and from our own laboratory measurements. New data for ternary systems containing up to 1 molal sodium chloride over a temperature range of 40 to 70 C were measured and will be presented.