Systematic errors in the measurement of adsorption isotherms by frontal analysis. Impact of the choice of column hold-up volume, range and density of the data points

Journal Article · Mon Aug 01 04:00:00 EDT 2005 · Journal of Chromatography A

DOI:https://doi.org/10.1016/j.chroma.2005.08.029· OSTI ID:989574

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

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

Besides the accuracy and the precision of the measurements of the data points, several important parameters affect the accuracy of the adsorption isotherms that are derived from the data acquired by frontal analysis (FA). The influence of these parameters is discussed. First, the effects of the width of the concentration range within which the adsorption data are measured and of the distribution of the data points in this range are investigated. Systematic elimination of parts of the data points before the calculation of the nonlinear regression of the data to the model illustrates the importance of the numbers of data points (1) within the linear range and (2) at high concentrations. The influence of the inaccuracy of the estimate of the column hold-up volume on each adsorption data point, on the selection of the isotherm model, and on the best estimates of the adsorption isotherm parameters is also stressed. Depending on the method used to measure it, the hold-up time can vary by more than 10%. The high concentration part of the adsorption isotherm is particularly sensitive to errors made on t{sub 0,exp} and as a result, when the isotherm follows bi-Langmuir isotherm behavior, the equilibrium constant of the low-energy sites may change by a factor 2. This study shows that the agreement between calculated and experimental overloaded band profiles is a necessary condition to validate the choice of an adsorption model and the calculation of its numerical parameters but that this condition is not sufficient.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 989574
• Journal Information: Journal of Chromatography A, Journal Name: Journal of Chromatography A Journal Issue: 2005 Vol. 1097; ISSN 0021-9673
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ADSORPTION ISOTHERMS
DATA ANALYSIS
DATA COVARIANCES
LIQUID COLUMN CHROMATOGRAPHY
MATHEMATICAL MODELS
adsorption isotherm
column hold-up volume
data acquisition
frontal analysis
isotherm modeling
overloaded band profiles
systematic errors