Adsorption of organic compounds and water vapor on activated carbon: Equilibria and fixed-bed humidity steps

Adsorption equilibrium and fixed-bed adsorption dynamics are the two major parts investigated experimentally and theoretically in this research.; In the first part, the Virial Excess Mixing Coefficient (VEMC) model was developed to describe nonideal multicomponent adsorption equilibrium. It treats a real adsorbed solution as an ideal adsorbed solution with an excess surface mixing correction. A new model was developed to describe pure water vapor adsorption equilibrium on activated carbon with higher accuracy than other models published to date. Another new model was developed to extend a single adsorption isotherm at one specific temperature to an adsorption isotherm family at multiple temperatures with a small number of parameters. Adsorption equilibria were measured for methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and toluene as pure components and binary mixtures with water vapor on BPL carbon. The experimental data were analyzed using the VEMC and the Virial Mixture Coefficient (VMC) models.; In the second part, fixed-bed breakthrough behavior was measured and investigated for pure water, single organics, and binary organic mixtures under humidity steps. Pure water adsorption kinetics was studied. A new model was developed to describe the water adsorbed-phase mass transfer coefficient as a function of water loading. A new algorithm was developed to optimize the system parameters in fixed-bed simulation by combining an ODE solver with a least-squares solver. For organic fixed-bed adsorption under humidity steps, the effects of organic chemical properties (e.g., hydrophilicity and volatility), concentration and molecular interactions on breakthrough curves were examined. A general mathematical model and a computer program were developed to simulate the fixed-bed dynamics. Predicted behavior is in good agreement with the experiments in time, trend, extent, and shape of breakthrough curves. The applicability and efficiency of regenerating an adsorption bed by humidity desorption were also evaluated. Humidity increases are effective in removing light components, particularly light hydrophobic components, from a bed of activated carbon. These components are typically design-limiting for trace contaminant control systems.