Effect of the flow rate on the measurement of adsorption data by dynamic frontal analysis

Journal Article · Sat Jan 01 04:00:00 EST 2005 · Journal of Chromatography A

DOI:https://doi.org/10.1016/j.chroma.2004.08.129· OSTI ID:978120

Gritti, Fabrice ^[1]; Guiochon, Georges A ^[2]

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1. University of Tennessee, Knoxville (UTK)
2. ORNL

The adsorption data of propyl benzoate were acquired by frontal analysis (FA) on a Symmetry-C{sub 18} column, using a mixture of methanol (65%, v/v) and water as the mobile phase, at three different flow rates, 0.5, 1.0 and 2.0 mL/min. The exact flow rates F{sub v} were measured by collecting the mobile phase in volumetric glasses ({delta}F{sub v}/F{sub v} {le} 0.2%). The extra-column volumes and the column hold-up volume were accurately measured at each flow rate by tracer injections. The detailed effect of the flow rate on the value of the amount adsorbed was investigated. The best isotherm model accounting for the adsorption data was the same BET isotherm model at all three flow rates. Only slight differences (always less than 5%) were found between the three different sets of isotherm parameters (saturation capacity, q{sub S}, equilibrium constant on the adsorbent, b{sub S} and equilibrium constant on successive layers of propyl benzoate, b{sub L}). The reproducibility of the same isotherm parameters measured by the inverse method (IM) is less satisfactory, leading to R.S.D.s of up to 10%. A flow rate increase is systematically accompanied by a slight increase of the amount adsorbed. This phenomenon is consistent with the influence of the pressure on the equilibrium constant of adsorption due to the difference between the partial molar volumes of the solute and the adsorbate. The larger average pressure along the column that is required to achieve a larger flow rate causes a larger amount of solute to be adsorbed on the column at equilibrium. This result comforts the high sensitivity and versatility of the FA method for isotherm determination under any kind of situation.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 978120
• Journal Information: Journal of Chromatography A, Journal Name: Journal of Chromatography A Journal Issue: 0 Vol. 1069
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
ADSORPTION
CAPACITY
FLOW RATE
ISOTHERMS
METHANOL
MIXTURES
SATURATION
SENSITIVITY
SOLUTES
WATER