COMPETITIVE ADSORPTION OF VOCS AND BOM - OXIC AND ANOXIC ENVIRONMENTS

The effect of the presence of molecular oxygen on the adsorption of vo latile organic compounds (VOCs) in distilled Milli-Q water and in wate r supplemented with background organic matter (BOM) is evaluated. Expe riments are conducted under conditions where molecular oxygen is prese nt in the test environment (oxic adsorption), and where oxygen is abse nt from the test environment (anoxic adsorption). Adsorption isotherms for tetrachloroethylene (PCE) and trichloroethylene (TCE) in Milli-Q water showed no impact of the presence of oxygen on their adsorption b ehavior, while adsorption isotherms for cis-1,2-dichloroethene (DCE) s howed higher capacities under oxic conditions. VOC adsorption isotherm s in BOM are conducted for three initial concentration sets of VOCs an d two initial concentration sets of BOM. VOC isotherms collected under oxic and anoxic conditions in water supplemented with BOM showed that by keeping the initial concentration ratio of VOCs to BOM constant, t he adsorption behavior of the VOC is very similar. VOC isotherms in BO M conducted under oxic conditions generally showed lower capacities th an the anoxic isotherms. The ideal adsorbed solution theory (IAST) suc cessfully predicted the VOCs anoxic adsorption isotherms in BOM. Howev er, the IAST model did not predict the VOCs oxic adsorption isotherms in BOM. Analysis of the data was conducted using the isotherm paramete rs of the VOCs in Milli-Q water, and correlation parameters using a fo ur fictive component approach for the BOM. The poor agreement between experimental data and model predictions obtained for the oxic isotherm s is attributed to the presence of molecular oxygen which promotes con glomeration of BOM on the surface of carbon.