Absorption of chlorinated VOCs in high-boiling solvents: Determination of Henry's law constants and infinite dilution activity coefficients

Three chlorinated VOCs of industrial significance were investigated in the low concentration domain (dichloromethane (DCM), tetrachlorethylene (TCE), and chlorobenzene (CB)), and using three solvents (di(2-ethylhexyl) phthalate (DEHP), di(2-ethylhexyl) adipate (DEHA), and tetraethylene glycol dimethyl ether (TEGDME)). The affinity of solvents toward a chlorinated VOC was studied by determining the Henry's law constant (infinite dilution activity coefficient) in the temperature range 30-70 degreesC. Three techniques were used for this purpose: headspace gas chromatography (HSGC), indirect, i.e., varying volume, headspace gas chromatography (IHSGC), and inert gas stripping (GS). The accuracies of the techniques were assessed and compared to one another. Generally, agreement between the three methods is good. The comparison was extended to literature data. The Henry's law constant measured with HSGC method were correlated as a function of temperature with an equation similar to the van't Hoff equation. For DCM, TEGDME appears as the most suitable solvent, with limiting activity coefficient near 0.20 at 30degreesC. DEHA has the greatest affinity toward TCE and CB, with activity coefficients at 0.69 for TCE and 0.57 for CB.