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An adsorption study of gelatin was performed from its aqueous solution onto the Fuller's earth surfaces at room temperature. The dynamics of the adsorption process were followed spectrophotometrically; and various adsorption and kinetic parameters, such as adsorption coefficient, rate constants for adsorption and desorption, and penetration rate constant, were evaluated. The adsorption was found to vary sensitively with pH variation and show minima in both the media, that is, in acidic and basic. It was also observed that the presence of anions reversed their impact on adsorbed amount at their high concentration. The effect of cations and temperature were also investigated.

The adsorption of poly(vinylpyrrolidone) (PVP) onto Fuller's earth surface was studied at fixed pH (4.2) and room temperature (27 ± 0.2°C). The kinetics of the adsorption process was monitored and various adsorption and kinetic parameters such as the adsorption coefficient, the rate constants for adsorption and desorption, the diffusion constant, and the penetration constant were evaluated. The effects of various experimental factors such as the pH and the presence of inorganic and organic anions or aliphatic alcohols were also studied on the adsorbed amounts of PVP. The role of temperature was also investigated and various thermodynamic parameters such as the standard Gibb's free energy, enthalpy, and entropy were also evaluated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2122–2133, 2000