Mathematical Modeling of Sorption Phenomena in Heterogeneous Systems. (Volumes I and II) (Adsorption, Mathematical Modeling).

Abstract

There is mounting evidence of the ubiquitous presence of potentially toxic organic chemicals in surface waters and groundwaters. Conventional water and wastewater treatment processes are often ineffective at removing these organics compounds. Adsorption of organics by activated carbon is a technology which is capable of removing most of organic priority pollutants from water. The effectiveness of activated carbon technology is dependent on many variables operative within a given treatment system. The application of mathematical models which forecast the impact of these variables provides a means of designing reliable treatment systems for the removal of hazardous compounds. The focus of this work is to formulate a conceptual and mathematical modeling framework which more accurately depicts the physical nature of adsorbents with poly-disperse pore structures, such as activated carbon. The dual particle-diffusion (DPD) model developed in this research provides a more accurate prediction of the adsorption phenomena to facilitate the design and operation of fixed-bed adsorption systems. Four versions of the DPD model have been formulated for porous adsorbents in batch reactors and fixed-bed systems using waters containing single and multiple solutes. In addition, the microcolumn or short-bed adsorber technique, developed and verified by Weber and Liu for single component systems has been modified to provide a more accurate and practical approach to the determination of mass transport parameters for multicomponent systems. Validations and experimental verifications were performed on all versions of the DPD model described herein. The DPD versions of the MADAM model agree well with the experimental data obtained from both batch reactors and fixed-bed adsorbers using phenol, para-chlorophenol, and para-nitrophenol solutes. The fixed-bed adsorber model was less adequate for prediction of experimental data obtained using para-bromophenol as the solute. Experiments with combinations of the above solutes as well as para-toluene(sodium)sulfonate, and dodecylbenzene(sodium)sulfonate indicate that multicomponent DPD models can also accurately predict adsorption phenomena in mixed-solute systems. The DPD models provide more accurate predictions than homogeneous surface diffusion models because the latter cannot precisely account for competitive interactions between solutes with widely different adsorption capacities.