Modeling of activated carbon and coal gasification char adsorbents in single-solute and bisolute systems
A mathematical model of fixed-bed adsorption was able to predict the bed response to a sustained step change in influent concentration. The model was employed to compare the performance of different adsorbants in the removal of organics from water and to analyze factors that affect desorption. Three species, 3,5-dimethylphenol (DMP), 3,5-dichlorophenol (DCP) and rhodamine 6G (R6G), were the single solutes studied, and the two phenols were also examined as a mixture. Four activated carbons and a coal gasifiction char were the adsorbents studied. Several single-solute and bisolute column experiments were conducted to provide data for model verification; the model predicted not only adsorption, but also desorption that resulted from a step change in influent concentration and from competition. The pretreatment of one of the carbons with free chlorine reduced the capacity, surface diffusivity and film transfer coefficient for the DMP. The model was used to compare the adsorbents in the removal of DMP, R6G and the bisolute mixture, and equilibrium capacity was found to have a greater influence than kinetics on fixed-bed performance. From single-solute model predictions of desorption due to a reduction in influent concentration, it was determined that lower initial effluent concentrations resulted when the mass transfer coefficients, capacity, isotherm slope and bed length were decreased and the flow rate and adsorbent particle size were increased. Simulations of bisolute adsorption demonstrated that mass transfer resistance reduced the chromatographic overshoot of the weakly adsorbed species. Finally, it was observed that, under conditions approximating a drinking water plant, the time during which the effluent concentration of a desorbed species was higher than the influent concentration was significant (on the order of weeks) whether a reduced influent concentration or competition was responsible for the desorption.
- OSTI ID:
- 5580888
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACTIVATED CARBON
SORPTIVE PROPERTIES
CHARS
PHENOLS
ADSORPTION
ADSORBENTS
DESORPTION
MATHEMATICAL MODELS
PERFORMANCE
REMOVAL
RHODAMINES
WASTE WATER
XYLENOLS
AMINES
AROMATICS
CARBON
CARBOXYLIC ACIDS
DYES
ELEMENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
LIQUID WASTES
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXYGEN COMPOUNDS
PYROLYSIS PRODUCTS
REAGENTS
SORPTION
SURFACE PROPERTIES
WASTES
WATER
520200* - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)