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Authors
Affiliations
1 Department of Food Technology of Biochemical Engineering, Jadavpur University, Calcutta 700 032, IN
Source
Journal of Surface Science and Technology, Vol 4, No 1 (1988), Pagination: 91-109
Abstract
The adsorption of proteins (bovine serum albumin and pepsin) and sodium carboxymethyl cellulose on the surface of barium sulphate particles has been measured at various ionic strengths, pH, temperatures and neutral salts. The adsorption isotherms appear to be similar to the Langmuir isotherm. In many cases, binding isotherms are found to be S-shaped at low range of solute concentration (cp). At high solute concentrations of the macromolecules, Γp appears to reach a constant value Γp - which becomes insensitive to further increase of cp. In the case of proteins, Γmp is found to be less than 1 mg per sq metre of barium sulphate whereas for NaCMC, this value may be greater than one. Based on Langmuir equation the maximum amount of adsorbate required Γlp to cover the surface of powdered barium sulphate has also been calculated, Γlp is always found to be higher than Γmp by twenty to forty percent depending on the ionic strength, pH and other solution parameters. The standard free energy changes (ΔG0 per gm of the adsorbent using appropriate reference states have been calculated by the appropriate equations and it has been found that the free energy values are in the same order of magnitude of Γmp so that the values correctly predict the maximum extent of adsorption. Adsorption of BSA on the mixture of barium sulphate and alumina in various proportions has shown that Γmp or Γlp calculated theoretically based on the addtively rule is always higher than those observed experimentally. From the variation of ΔG0 with temperature, the respective change in enthalpy(ΔHav0) and entropy (ΔGav0) for the adsorption processes heve been calculated and the results have been critically analysed.
Keywords
Thermodynamics, Adsorption solid/Liquid Interface, BSA, Pepsin, CMC, BaSO4, Al2O3