BENTONITE ASSISTED BIOPROCESS FOR 2-NITROPHENOL
REMOVAL FROM WASTEWATERS
B. Koumanova, Z. Kircheva
MODELLING OF SORPTION KINETICS BY BATCH
EXPERIMENTS UPTAKE CURVES FOR HEAVY METAL ION SORPTION ON NATURAL ZEOLITE
M. Kostova, I. Tsibranska, S. Nenov
KINETICS OF MULTISTAGE EXTRACTION FROM
VEGETABLE RAW MATERIALS
E. Simeonov, A. Mintchev
BENTONITE ASSISTED
BIOPROCESS FOR 2-NITROPHENOL REMOVAL FROM WASTEWATERS
B. Koumanova, Z. Kircheva
University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756
Sofia, Bulgaria
E-mail: vparvanova@hotmail.com
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Received 4 February 2003
Accepted 24 March 2003
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The effect of bentonite on the biotreatment of wastewater
containing 2-nitrophenol (2-NP) was studied. Two similar laboratory scale
bioreactors were used for the comparison of the conventional activated sludge
process with/without addition of bentonite. The aim of this addition was to
intensify the removal of 2-NP from the wastewater at aerobic conditions. Chemical
Oxygen Demand (COD) was determined for the evaluation of the processes.
The activated sludge was taken from a refinery wastewater treatment plant
because of its ability to decompose phenols. Preliminary adaptation to 2-NP
was carried out before experiments. Initial concentrations up to 40 mg/dm3
were used. It was established that the direct addition of bentonite to the
aerated activated sludge mixed liquor resulted in complete removal of 2-NP
at that accelerating the process by 50 %.
The contribution of the adsorption onto bentonite was investigated using model
aqueous solutions of 2-NP.
The comparative analysis on the studied processes demonstrated a synergistic
effect of adsorption of 2-NP on bentonite and assimilation by microorganisms.
Keywords: activated sludge process, biosorption, 2-nitrophenol, yellow
bentonite.
MODELLING
OF SORPTION KINETICS BY BATCH EXPERIMENTS UPTAKE CURVES FOR HEAVY METAL ION
SORPTION ON NATURAL ZEOLITE
I. THE MOMENT METHOD
M. Kostova, I. Tsibranska, S. Nenov
University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756
Sofia, Bulgaria
E-mail: miki@uctm.edu
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Received 13 June 2003
Accepted 1 July 2003
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A simple Model Equation based on the analogy between the
analytical solutions of the Linear Driving Force Model at linear and at strong
non-linear - "rectangular" equilibrium has been derived for the
uptake curve distribution at Langmuir type equilibrium.
The Model Equation includes the 1st absolute statistical moment of the uptake
curve as a synonymous quantitative measure for the sorption kinetics in batch
experiments.
In contrast to the breakthrough experiments, for which the curve dispersion
(2nd central statistical moment) and the mass transfer resistance are non-linearly
proportional, the 1st absolute statistical moment of an uptake curve is straight
proportional to the mass transfer resistance even for the non-linear Langmuir
type equilibrium. The influence of the non-linearity of the equilibrium condition
on the uptake curve distribution is manifested separately by the value of
the "end" equilibrium concentration Y? at given process parameters
- solid to liquid volume ratio, equilibrium constant and non-linearity factor.
The Model Equation has been found to agree very well with the "exact"
numerical solution of the Linear Driving Force Model as well as with the experimental
data, derived for lead ion sorption on natural clinoptilolite, which sorption
process was characterized by a relatively strong non-linear equilibrium relationship
and by a relatively low sorption kinetics especially at small particles, where
the mass transfer resistance was remarkably affected by the concentration.
Keywords: ion exchange, sorption, zeolite, heavy metal ions, mathematical
modeling.
KINETICS
OF MULTISTAGE EXTRACTION FROM VEGETABLE RAW MATERIALS
E. Simeonov, A. Mintchev
University of Chemical Technology and Metallurgy, 8 Kl. Ohridski, 1756
Sofia, Bulgaria
E-mail: evgeni@uctm.edu
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Received 3 April 2003
Accepted 18 April 2003
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Kinetic experiments have been carried out, under three-stage
led process of extraction according to the scheme crossed current, for two
solid-liquid systems. System I - tobacco leaves (Nicotiana tabacum L.) - water
and system II - geranium roots (Geranium macrorrhizum L.) - water. The solid
phase has been extracted three times and for each stage a fresh solvent has
been used. The experimental data have been received in a periodically stirred
vessel.
Kinetic curves for the three stages of extraction for the two investigated
systems have been received. Curves' type show, that there is a time interval
(first part of the curve) where the stage of extraction increases very rapidly
especially for the second and third stage of extraction. The main reason for
this is the increase of the internal porosity of the solid phase during the
extraction process. In support of the above stated are the received values
for after the first stage of extraction, which increase on average about 30
% for the investigated systems.
The experimentally received results give possibility to define the effective
diffusion coefficient for each stage using the Regular regime method.
Keywords: Solid-liquid extraction, extraction kinetics, internal porisity,
vegetables.
