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Russian Journal of Applied Chemistry, Vol. 76, No. 4, 2003, pp. 544!546. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 4, 2003,
Original Russian Text Copyright + 2003 by Simeonov, Minchev.
AND ION-EXCHANGE PROCESSES
Calculation and Control of Solid!Liquid Extraction
with Characteristic Function
E. B. Simeonov and A. D. Minchev
University of Chemical Technology and Metallurgy, Sofia, Bulgaria
Received July 8, 2002
Abstract-The kinetics of extraction of practically interesting vegetable raw materials: carsil (Silibium
marianum L.), amorpha (Amorpha fructicosa L.), and coriander (Coriandrum sativum L.), was studied ex-
perimentally. The results obtained were represented as a characteristic function. The optimal conditions of
the extraction process were studied.
The wide diversity of vegetable raw materials used
for solid-phase extraction, combined with the com-
plexity of mass transfer in the solid3liquid system,
leads to a number of methodological and mathemat-
ical difficulties in describing the extraction process.
To ensure versatility of extraction apparatus, it
is necessary not only to determine the extractor pa-
rameters, but also to control the process when chang-
ing the type of vegetable raw materials. This is pos-
sible with the use of the characteristic function. The
method is especially valuable in the case of processing
of a vegetable raw material characterized by a com-
plex mechanism of diffusion extraction [1, 2].
The characteristic function takes into account, in
an integral manner, specific structural features of the
solid phase and the amount of outer-diffusion resis-
tance. The function is derived from an experimental
kinetic curve c
= f(t) on the condition that the con-
is the same for all particles. The char-
acteristic function Q(g) is most easily found with the
use of kinetic curves obtained in the batch mode of
the process under ideal mixing conditions [3, 4].
The aim of the present study was to demonstrate
the applicability of the characteristic function to cal-
culations and control of the extraction process.
Three solid3liquid systems were studied:
System T, oC
Carsil3methanol (I) 30 0.02 7.5 889.80
Amorpha3petroleum 40 0.01 7.0 921.31
Coriander3petroleum 50 0.01 7.0 735.21
Note. x is the specific volume; n, the rate of worm rotation;
, the saturation concentration.
The experiments were carried out in a batch extrac-
tion apparatus under ideal mixing conditions. The in-
stants of sampling were varied, depending on a raw
material under study. It was established experimental-
ly that the process is limited by inner diffusion-
transport within pores of the solid phase. The outer-
diffusion resistance is virtually eliminated at the in-
dicated stirring rate.
The kinetics of extraction is described by the ex-
= A 3 B exp(3Ht), (1)
is the concentration of the component being
extracted in the liquid (kg m
); A, B, and H are con-
stants; t is the process duration (s).
For systems (I)3(III), respectively,
= 0.980 3 0.966exp(32.20 0 10
= 4.600 3 4.400exp(33.40 0 10
= 2.050 3 1.950exp(31.20 0 10
Figures 1a31c [respective Eqs. (2)3(4)] show the
experimental data obtained. In system (I), silimarine
(the solid phase contains silibine, silidianine, and
silichrytine, with the flavolignan complex having
general name silimarine) is extracted under the con-
ditions specified. The content of the complex was
analyzed by spectrophotometry. Silimarine is used in
manufacture of an important pharmaceutical product
Legalon (Carsil). In the case of system (II), the ex-
tracted solid phase contains isoflavonoids (or, more