Adsorptive Mechanism on Activated Carbon in the Liquid Phase. I. Free Energy Change for Adsorption of Organic Compounds from Aqueous Solution on Activated Carbon

Abstract

Abstract The adsorption isotherms, from aqueous solution onto activated carbon, have been determined for the 22 aliphatic monofunctional compounds; alcohols, carboxylic acids, ketones, ethers, esters, and aldehydes. The free energy change for the adsorption process has been calculated from the adsorption equilibrium constant at infinite dilution; a linear relationship exists between the free energy change and the number of carbon atoms in the solute. The free energy of adsorption has been divided into two contributions: the hydrocarbon and the functional group contribution. The free energy change for the adsorption process has been compared with the free energy change for the precipitation process from solution into the pure liquid solute. The free energy contribution per individual methylene group to the adsorption process shows an approximate agreement with that for the precipitation process indicating that the adsorption process of the hydrocarbon portion of the solute is analogous to the precipitation process. The free energy contribution of the functional group to the adsorption process is smaller than that for the precipitation process indicating that the functional group portion of the solute is not appreciably dehydrated in the adsorption phase.