REU program, Summer 2000 Julie P. Caires, Washington State University

Determination of Henry’s Law constants of organic compounds through use of an analytical air stripper with structured packing. REU program, Summer 2000 Julie P. Caires, Washington State University Michiya Suzuki, University of Oklahoma Dr. Tohren Kibbey, University of Oklahoma

Air stripping Water to be treated Air containing organic vapors out • Packed column air stripping • Filled with porous packing material • Increased surface area of water on packing material allows organic compounds to volatilize into moving air • Effectiveness depends on Henry’s Law constant for the organic compound, liquid flow rate, gas flow rate, temperature, size of column, and properties of the packing material. Filled with packing material Air in Clean water out

Henry’s LawKH = Cg / Caq • Closed container filled with liquid containing an organic compound • Cg = concentration of organic compound in air above liquid • Caq = concentration of organic compound in liquid • Slope of line is KH, or Henry’s Law constant Cg Caq

The Stripping Factor (S) • S = (G * KH) / L • G = gas flow rate • L = liquid flow rate • KH = Henry’s Law constant

What happens when S > 1 • When S > 1 • The air stripper works efficiently • It is possible to achieve significant removal of organic compounds • Looking at the chart • Co = original concentration • C = final concentration • N = number of theoretical plates in the air stripper C Co N

What happens when S < 1 • When S < 1 • The efficiency plateaus at a certain point • Therefore • Fraction removed equals S • Only true when S < 1 • By knowing S, the fraction removed, and air and water flow rates, the value of Kh can be calculated C Co N

Preliminary experiments: • Temperature profiling at different G and L rates along the air stripping column • Large (5.2C) temperature drop • Necessary to build an air saturator • Determination of equilibration time • Used red food coloring • Preliminary data: 35 minutes, later extended to 1 hour

Experiments conducted: • Determining Henry’s law constant • Isopropanol (IPA) • Methyl tert-butyl ether (MTBE) • Determining effect of co-solubility on KH • MTBE added to different concentrations of IPA

Three G/L ratios: 160, 260, 360 Two concentrations: 770mg/L and 80mg/L Isopropanol (IPA) experiment: • Equilibration time: • 35 minutes initially • 10 minutes between samples

Run #1: Concentration: 500 mg/L Equilibration time: 35 minutes initially, 10 minutes between samples G/L ratios: 10, 20 Methyl-tert butyl ether (MTBE): • Run #2: • Concentration: 500 mg/L • Equilibration time: • 60 minutes initially, 20 minutes between samples • G/L ratio: 30

G/L ratio: 30 MTBE concentration: 500 mg/L 4 IPA concentrations: 10%, 20%, 35%, 50% The effect of IPA on MTBE: • Equilibration time: • 60 minutes initially • 20 minutes between samples

Conclusions: • Analytical air stripper is effective • With low volatility compounds • With 1 hour initial equilibration time • At higher G/L ratios • Effect of co-solvent (IPA) • Dramatic decrease in Henry’s law constant

Acknowledgments • NSF • Dr. Kibbey • Michiya Suzuki • Joe (for the air saturator setup idea) • University of Oklahoma

REU program, Summer 2000 Julie P. Caires, Washington State University