Abstract
Saccharomyces cerevisiae yeast was entrapped in alginate for the recovery of copper ions from aqueous solution, in which both yeast and alginate could take metal ions. The Freundlich isotherm had been shown to be successful in describing biosorption and a linear biosorption was assumed when the equilibrium copper ion concentration in the fluid was lower than 1 mg/l. The biosorption isotherm was found to be independent of the immobilized yeast densities ranging from 6 to 17 percent. A mathematical model describing the mass transport along with the biosorption was developed with the main assumptions that the inner diffusion with constant diffusivity was the rate limiting step of the biosorption process and the pore solution locally equilibrated with the adjacent biosorbent (both yeast and alginate). This model has theoretical advantages over the formerly proposed Shrinkage Core Model and Linear Adsorption Model. Effective diffusion coefficients of copper ion in immobilized yeast beads using the model developed were found to be independent of the immobilized yeast densities ranging from 6 to 17 percent. The average result was 2.22×10−5 cm2/s.
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Abbreviations
- C :
-
Copper concentration in the pore of the bead (mg/l)
- C 0 :
-
Initial concentration of copper ion in the reactor (mg/l)
- C b :
-
Copper concentration in the bulk solution (mg/l)
- C ∞ :
-
Final (equilibrium) concentration of free copper in solution (mg/l)
- C 0 :
-
Average copper binding site density of immobilized yeast beads based on biosorption isotherm (mg/l)
- D e :
-
Effective diffusivity of copper ion in the immobilized yeast bead (cm2/s)
- i :
-
Grid point corresponding tor axis
- j :
-
Grid point corresponding tot axis
- m :
-
Grid dimension int axis
- N :
-
Number of immobilized yeast beads in the reactor
- n :
-
Grid dimension inr axis
- Q :
-
Copper concentration in the biomass (mg/g dry mass)
- R :
-
Average radius of the immobilized yeast beads (cm)
- r :
-
Distance from the center of a bead (cm)
- T :
-
Experiment period, (sec)
- t :
-
Time (sec)
- V :
-
Volume of copper ion solution except beads in the reactor (ml)
- X :
-
Dimensionless concentration (C 0−C)/(C 0−C ∞)
- ∈:
-
Apparent immobilized yeast bead porosity
- ρ:
-
Apparent biomass density (g dry mass/l)
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Lu, Y., Wilkins, E. A mathematical model for the biosorption of copper on immobilized yeast in alginate. Environ Model Assess 1, 159–169 (1996). https://doi.org/10.1007/BF01874903
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DOI: https://doi.org/10.1007/BF01874903