The Kinetics and Mechanism of Lead (II) Adsorption in Different Types of Contactor by Powderized Rhizopus Oligosporus
The effect of sorption conditions on the rate and capacity of lead uptake by powderized biomass of Rhizopus oligosporus was first carried out in shake flask experiments. Lead sorption by Rhizopus oligosporus was also investigated in different types of contactor such as stirred tank bioreactor, ai...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1998
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/8396/1/FSMB_1998_17_A.pdf |
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| Summary: | The effect of sorption conditions on the rate and capacity of lead uptake
by powderized biomass of Rhizopus oligosporus was first carried out in shake
flask experiments. Lead sorption by Rhizopus oligosporus was also investigated
in different types of contactor such as stirred tank bioreactor, airlift fennenter and
packed-bed column. The experimental data of lead adsorption in different sorption
conditions (pH, temperature, solution viscosity, lead and biomass concentration)
and different operating variables of the contactor (agitation speed and air flow rate)
were analysed using Langmuir and Freundlich sorption isotherm models. The
mechanism of lead uptake by the cell was examined using TEM micrograph,
EDXA and FTIR photoacoustic. The experimental data of lead sorption by Rhizopus oligosporus fitted well
to Langmuir and Freundlich sorption isotherm models, indicating that the sorption
was similar to that for ion-exchange resin. This means that the sorption is a single
layer metal adsorption which occured as a molecular surface coverage. This
assumption was confirmed by the examination of lead sorption using TEM
micrograph, EDXA and FTIR photoacoustic, which showed that during sorption
most of lead was adsorbed on the surface of cell.From shake flask experiment, it was found that the biomass concentration
and initial solution pH optima for lead sorption at initial lead concentration
ranging from 50-200 mglL was 0.5 g/L and pH 5, respectively. In term of the
ratio of initial lead concentration to biomass concentration, the optimum value for
lead sorption was 750 mg/g. In all types of contactor investigated, maximum lead
uptake capacity increased with increasing temperature and drastically decreased
with increasing solution viscosity. Lead adsorption kinetic parameters values,
calculated using Langmuir and Freundlich models, were significantly varied with
sorption condition. Intraparticle diffusion rate constant (Kp) and equilibrium
adsorption rate (Kₐ decreased with increasing solution viscosity, while diffusion
coefficient (D) increased with increasing solution viscosity. On the other hand,
D was decreased with increasing temperature while Kad was not significantly
different at different temperatures. When 5 L stirred tank bioreactor was used as
a contactor, the highest lead uptake capacity was obtained at agitation speed
ranging from 50-150 rpm (Re = 3,900 - 11,700). On the other hand, the optimum air tlowrate for lead sorption in 2 L airlift fermenter was obtained at 2 vvm.
Increased in the degree of turbulence as created by increased in degree of agitation
(stirred tank bioreactor) and air flowrate (airlift fermenter), significantly reduced
Kad and D but has no effect on Kp-
The maximum lead uptake capacity obtained in shake flask, stirred tank
bioreactor and airlift fermenter at optimum sorption conditions was 126, 79 and
74 mglg, respectively. Absolute removal of lead ions from solution was achieved
when fixed packed-bed column was used as a contactor. However, the maximum
lead uptake capacity (24 mg/g) was 3 times lower than that obtained in stirred
tank bioreactor or an airlift fermenter. |
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