Extraction of phenolic compounds from algerian Inula viscosa (L.) Aiton leaves: kinetic study and modeling

ABSTRACT

The present study provides the first data on the extraction kinetics of polyphenols from algerian Inula viscosa and aims to model the phenomenon of matter transfer involved.

Different models have been applied and evaluated for different conditions of temperature, solid to liquid ratio and stirring speed. The operating conditions affect the kinetic parameters as well as the mass transfer properties.

The diffusion coefficient values ranged from 2.25*10⁻¹² to 31.44*10⁻¹² m².s⁻¹. The Biot number vary from 45.37 to 92.35 which shows that internal mass transfer limits the extraction process. Activation energy (E_a) was found to be 25.22 KJ .mol⁻¹.

KEYWORDS:

• Inula viscosa (L.)
• phenolic compounds
• extraction
• kinetics
• modeling
• optimization

Nomenclature

a	=	Sphere radius
ap	=	Specific surface area (m2.m−3)
b	=	Dimensionless constant
C(eq)	=	Equilibrium concentration
Cl	=	The liquid phase concentration
Cs	=	The solid phase concentration
C(t)	=	Concentration at time t
C(∞)	=	Concentration at t →∞
${\text{C}}_{\infty }^{\text{d}}$	=	The equilibrium concentration for the diffusion part (g.L−1)
$C_{\mathrm{\infty }}^w$	=	The equilibrium concentration for the washing portion (g.L−1)
cal	=	Calculation
D	=	Diffusion coefficient (m2.s−1)
Deff	=	The effective diffusion coefficient (m2.s−1)
Ds	=	Coefficient of diffusion in the solid phase (m2.s−1)
DWM	=	Dry weight material (g)
D0	=	the Arrhenius constant (m2.s−1).
Ea	=	The activation energy (J.mol−1)
exp	=	Experience
F	=	The fraction of the rapidly released solute
(1-F)	=	The fraction of the solute released slowly
GAE	=	Gallic acid equivalent
H	=	Hydromodule (volume of solvent/mass of plant matter)(g.L−1)
k	=	The rate constant
k1	=	The first order rate constant describing the fast part (min−1)
k2	=	The first order rate constant describing the slow release fraction (min−1).
Ke	=	External mass transfer coefficient (m.min−1)
Kd	=	The diffusion rate constant (s−1)
Ke * ap	=	Mass volumetric mass transfer coefficient (min−1)
KD	=	Partitioning equilibrium = C solute (solid)/C solute (liquid)
K	=	Transport coefficient (m.s−1)
L	=	Mass transfer biot number
M(t)	=	Mass at time t (g)
M(∞)	=	Mass at t →∞ (g)
NRMSD	=	Normalized root mean square deviation = $\frac{RMSE}{\left(yca{l}_{max}\right)}$
R	=	Ideal gas constant (J.K−1.mol−1)
${\mathrm{R}}_0^{\mathrm{W}}$	=	washing diffusion model initial extraction rate
R2	=	Determination coefficient
RMSE	=	root mean square error = ${\left[\sum _{i=1}^n{(y_{cal}-y_{exp})}^2\right]}^{0.5}$
SSE	=	sum square error = $\left[\sum _{i=1}^n(y_{cal}-y_{exp}{)}^2\right]$
t	=	time
t1/2	=	The half-life (s)
x	=	the distance in the direction of diffusion
ycal	=	calculated yield
ycal max	=	maximum calculated yield
yexp	=	experimental yield

Acknowledgements

The authors gratefully acknowledge the Chemical Engineering Department (Algiers, Ecole Nationale Polytechnique) for their funding of this project, Mr Kamel Mezieche for providing the Inula viscosa samples and for language revision.