Multicomponent adsorption kinetics of hydrocarbons onto activated carbon: effect of adsorption equilibrium equations

Modeling Bisolute Adsorption of Aromatic Compounds Based on Adsorbed Solution Theories

A large number of organic contaminants are commonly found in industrial and municipal wastewaters. For proper unit design to remove contaminant mixtures by adsorption, multicomponent adsorption equilibrium models are necessary. The present work examined the applicability of Ideal Adsorbed Solution Theory (IAST), a prevailing thermodynamic model, and its derivatives, i.e., Segregated IAST (SIAST) and Real Adsorbed Solution Theory (RAST), to bisolute adsorption of organic compounds onto a hyper-cross-linked polystyrene resin, MN200. Both IAST and SIAST were found to be less accurate in fitting the experimental bisolute adsorption isotherms than RAST. RAST incorporated with an empirical four-parameter equation developed in this work can fit the adsorbed phase activity coefficients, γ_i, better than RAST combined with the Wilson equation or the Nonrandom two-liquid (NRTL) model. Moreover, two polyparameter linear free energy relationships were developed for the adsorption of a number of solutes at low concentrations in the presence of a major contaminant (4-methylphenol or nitrobenzene). Results show that these relationships have a great potential in predicting γ_i of solutes when the adsorbed amounts are dominated by a major contaminant. To the best of our knowledge, this is the first study predicting γ_i for bisolute adsorption based on molecular descriptors. Overall, our findings have proved a major step forward to accurately modeling multisolute adsorption equilibrium.

Tracing the origins of transient overshoots for binary mixture diffusion in microporous crystalline materials

Due to thermodynamic coupling overshoots in the loading of the more mobile species are observed during transient uptake.