DOI: 10.3303/CET24109004 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 6 December 2023; Revised: 2 February 2024; Accepted: 2 April 2024 
Please cite this article as: Bertino A., Mazzeo L., Liberatore L., Della Posta S., Fanali C., Piemonte V., 2024, Polyphenols Recovery from 
Hazelnut Skin Wastes Through Extraction with a Water-ethanol Solvent Mixture: Equilibrium and Kinetic Studies, Chemical Engineering 
Transactions, 109, 19-24  DOI:10.3303/CET24109004 
  

 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 109, 2024 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.cetjournal.it 

Guest Editors: Leonardo Tognotti, Rubens Maciel Filho, Viatcheslav Kafarov 

Copyright © 2024, AIDIC Servizi S.r.l. 

ISBN 979-12-81206-09-0; ISSN 2283-9216 

Polyphenols Recovery from Hazelnut Skin Wastes through 

Extraction with a Water-Ethanol Solvent Mixture: Equilibrium 

and Kinetic Studies 

Alice Bertinoa,*, Leone Mazzeoa, Luca Liberatorea, Susanna Della Postab, Chiara 

Fanalib,Vincenzo Piemontea 

aFaculty of Science and technology for sustainable Development and One Health, Unit of Chemical-physics Fundamentals 

in Chemical Engineering, University Campus Bio-medico of Rome, Via Alvaro del Portillo, 21, 00128 Rome, Italy; 
bFaculty of Science and technology for sustainable Development and One Health, Unit of Food and Nutrition Sciences, 

University Campus Bio-medico of Rome, Via Alvaro del Portillo, 21, 00128 Rome, Italy;  

alice.bertino@unicampus.it 

This study delves into the principles of the Circular Economy by focusing on the extraction of polyphenols from 

hazelnut skin wastes. The project’s innovation lies in the pioneering use of a 50% vol/vol water-ethanol mixture 

as a solvent for polyphenol extraction, within a custom batch set-up. The primary objective was to explore both 

equilibrium and kinetic aspects of this novel system. Initial experiments involved maintaining the solvent at 70°C 

for six hours to reach equilibrium, while varying solid/liquid ratios from 0.16 to 50 g/L. A fitting of the experimental 

data with an equilibrium modelling revealed values of 𝑞𝑡𝑜𝑡 = 0.255 g/g and 𝑘 = 0.0092 L/g as the total amount 

of extractable polyphenols and the solid-liquid linear isotherm partition coefficient, respectively. Furthermore, 

kinetics of the extraction process was investigated across three different solid-liquid ratios (0.54, 1.00 and 2.00 

g/L). Concentration measurements at different time intervals were fitted with the Linear Driving Force (LDF) 

kinetic model, allowing for the estimation of the LDF mass transfer coefficient 𝑎𝑘𝐿𝐷𝐹 for each solid-liquid dosage. 

Notably, the thermodynamic and kinetic parameters derived in this study are unique, since they are specifically 

tailored to the utilization of a 50% vol/vol water-ethanol mixture as polyphenol extraction solvent. This research 

underscores the potential of utilizing such solvent mixtures in polyphenol extraction from biomass wastes, 

thereby contributing to the advancement of sustainable practices within the Circular Economy framework.  

1. Introduction 

In the current historical context, the application of the traditional linear model based on the “take-make-use-

dispose” principle has become unsustainable, especially in light of exponential population growth. In opposition 

to this linear approach, the Circular Economy represents a production paradigm designed to maximize the 

lifespan of products and transform production waste into valuable resources. In this regard, hazelnut skin, a 

byproduct resulting from various food industry processes, demonstrates considerable potential. Hazelnuts are 

mainly cultivated in Turkey and Italy, with costs ranging from 2.12 to 2.52 euros/kg for the Turkish product 

(GİRESUN) and from 9.90 to 11.10 euros/kg for the Italian variant (Camera Di Commercio Cuneo) in 2019. 

Hazelnut skin, accounting for approximately 2wt% of the fruit, is a rich source of polyphenols, organic 

compounds which are highly valued by the industry for their strong antioxidant power. As reported by Silva and 

Pogačnik (2020), this property plays a vital role in preventing and treating diseases associated to oxidative 

stress and inflammation, including cancer, cardiovascular and neurodegenerative pathologies, metabolic 

syndrome and type 2 diabetes.  

Hence, by extracting polyphenols from discarded hazelnut skins using a liquid solvent, they can be profitably 

supplied to the industry. To illustrate the market potential, the quantity of extracted polyphenols reached 16,380 

tons in 2015 (Adebooye et al., 2018). Among the solvents traditionally applied to the extraction of organic 

compounds from vegetable matrices, exclusively water, ethanol, and water-ethanol mixtures are known for 

19



being fully green, safe, and non-toxic. Natural Green Eutectic Solvents (NADES) are also emerging as promising 

green solvents in recent years (Fanali et al., 2021). 

In this work, various extraction tests were performed at different solid/liquid ratios in a batch set-up using 50% 

vol/vol water-ethanol mixture at 70 °C as solvent.  

The scopes of this paper are the following:  

• to study the equilibrium of the polyphenols extraction from hazelnut skins at 70 °C, in order to estimate the 

thermodynamic parameters; in particular, the solid-liquid partition coefficient 𝑘 of the linear isotherm and 

the total extractable mass of polyphenols 𝑞𝑡𝑜𝑡 were evaluated from a fitting of experimental equilibrium data.  

• to investigate the kinetics of the extraction process; in particular, a fitting of experimental kinetic data with 

the Linear Driving Force (LDF) model allowed for the estimation of the product between the overall mass 

transfer coefficient and the specific surface area made available by the solid matrix referred to the liquid 

volume 𝑎𝐾𝐿𝐷𝐹. 

The paper’s results were compared with the outcomes of our previous works, which explored the extraction of 

polyphenols from the same solid matrix and using water (Bertino et al., 2023) and NADES (Mazzeo et al., 2023) 

as solvents.  

2. Materials and Methods 

2.1 Solid preparation 

Extraction tests were conducted on hazelnut skins samples obtained from a local company which employs 

hazelnuts to create food items. Before the experiments, the solid matrix was ground and sieved in order to 

obtain a solid particle size < 0.5 mm. 

2.2 Experimental set-up 

Extraction runs were performed in a batch set-up consisting of glass Laboratory bottles of 0.2 L filled with 

measured amounts of liquid solvent and solid matrix under constant stirring (300 rpm). The bottles were 

appropriately sealed to avoid solvent loss and placed in a thermostatic bath set at 70 °C. In accordance with 

our previous works, this temperature was selected as it is sufficiently elevated to facilitate extraction without 

promoting thermal degradation of phenolic compounds, which occurs at 80 °C (Antony & Farid, 2022).  

2.3 Experimental tests 

A total of 18 tests were carried out by varying the solid mass and the liquid volume, and consequently the solid-

liquid ratio 𝛼 (Table 1). Tests 1.1-1.15 focused on studying the system’s equilibrium within the 𝛼 range of 0.16 

to 50 g/L, while the last three tests, designated as 2.1-2.3, were dedicated to investigating the system’s kinetic 

within the 𝛼 range of 0.54 to 2 g/L. Thus, the maximum solid-liquid ratio tested was 50 g/L, as attempts to exceed 

this value in batch mode proved challenging due to excessive solid presence, impeding uniform liquid mixing.  

Table 1: Experimental conditions (T=70 °C). Tests 1.1-1.15 = Equilibrium runs; Tests 2.1-2.3 = Kinetic runs. 

Test  𝛼 (g/L) 𝑀𝑆 (g) 𝑉𝐿 (L) 

1.1 0.16 0.008 0.050 

1.2 0.31 0.016 0.050 

1.3 0.62 0.031 0.050 

1.4 1.24 0.062 0.050 

1.5 2.50 0.125 0.025 

1.6 5.00 0.125 0.025 

1.7 10 0.250 0.025 

1.8 15 0.375 0.025 

1.9 20 0.500 0.025 

1.10 25 0.625 0.025 

1.11 30 0.750 0.025 

1.12 35 0.825 0.025 

1.13 40 1.000 0.025 

1.14 45 1.125 0.025 

1.15 50 1.250 0.025 

2.1 0.54 0.081 0.150 

2.2 1.00 0.150 0.150 

2.3 2.00 0.300 0.150 

20



Equilibrium runs (tests 1.1-1.15) lasted for 6 h, which was evaluated from preliminary tests (data not shown) to 

be enough time for the system to reach equilibrium conditions. At the end of each test, the supernatant of the 

extracted solutions was analyzed as described in Section 2.4.   

During kinetic runs (tests 2.1-2.3), samples of the liquid supernatants were collected at fixed time intervals and 

then analyzed as described in Section 2.4 in order to determine the extraction kinetic curve. In particular, for 

each run, 9 total samples were collected at 0, 15, 30, 60, 90, 120, 150, 180 and 210 min. To ensure that the 

error introduced by removing a portion of the liquid during each sampling (leading to a gradual increase in the 

solid-liquid 𝛼 throughout the test) remains below 1%, the following inequality should be satisfied: 

(𝑛𝑖 − 1)𝑉𝑖

𝑉𝐿
<  0.01 (1) 

where 𝑛𝑖 and 𝑉𝑖 are the number and the volume of samples collected during each kinetic run, respectively, and 

𝑉𝐿 is the volume of liquid solvent loaded at the beginning of the test. Being 𝑛𝑖 = 9 and 𝑉𝐿 = 0.15 L, the use of 

volume samples equal to 𝑉𝑖 = 150 µL allowed Eq. 1 to be automatically respected. Each test was repeated at 

least two times to assure the reproducibility of the results. 

2.4 Analyticals 

The concentration of polyphenols in the liquid samples obtained from experimental tests was measured using 

the Folin-Ciocalteau (F-C) assay, which involves the oxidation of phenolic compounds. The specific analytical 

procedure is detailed by Everette et al. (2010). In summary, 20 µL of each experimental sample were combined 

with 1580 µL of distilled water and 100 µL of Folin-Ciocalteu’s reagent (C10H5NaO5S), sourced from Sigma 

Aldrich (Milan, Italy), without further purification. The mixture was stirred and placed in the dark for 8 min. 

Subsequently, 300 µL of an aqueous solution containing 20% w/w of sodium carbonate (Na2CO3) was added 

and the mixture was returned to darkness for 2 h. Finally, 200 µL of the prepared sample was transferred to a 

Greiner 96 flat transparent microplate. The absorbance of the sample was measured using the Infinite M200 

PRO Tecan microplate spectrophotometer (Tecan Trading AG, Switzerland) at 765 nm. The concentration was 

determined by interpolating the result on a calibration curve achieved by measuring the absorbance of solutions 

with known gallic acid compositions, serving as the analytical standard. Therefore, the concentration of 

polyphenols was expressed in terms of equivalent Gallic Acid. 

3. Results  

3.1 Equilibrium studies  

A global mass balance can be used to describe the extraction system at any time, and in particular when 

equilibrium is reached: 

𝑞𝑡𝑜𝑡 − 𝑞𝑒  =  
𝑉𝐿

𝑀𝑆
𝐶𝑒 =  

𝐶𝑒

𝛼
 (2) 

where 𝑞𝑡𝑜𝑡 is the total amount of extractable polyphenols per mass of solid matrix, 𝐶𝑒 and 𝑞𝑒 are the experimental 

equilibrium data of polyphenols in liquid and solid phases, respectively, 𝑉𝐿 and 𝑀𝑆 are the liquid solvent volume 

and the solid mass loaded at the beginning of the test, respectively, and 𝛼 is the solid-liquid ratio.  

The link between 𝑞𝑒 and 𝐶𝑒 at at 70 °C was expressed by a linear equilibrium isotherm as follows: 

𝑞𝑒 = 𝑘𝐶𝑒  (3) 

where 𝑘 is the linear partition coefficient, that gives information on how the polyphenols are distributed in the 

two solid and liquid phases at equilibrium.  

The system composed by Eq. 2 and Eq. 3 was solved to obtain the final equilibrium model, relating 𝐶𝑒 to 𝛼: 

𝐶𝑒  =  
𝑞𝑡𝑜𝑡

1
𝛼

+ 𝑘
 

(4) 

The latter expression was directly adopted to estimate both 𝑞𝑡𝑜𝑡 and 𝑘 with a fitting of the experimental 

equilibrium data 𝐶𝑒 obtained by varying the solid-liquid ratio 𝛼 within the tests 1.1-1.15. A graphical 

representation of the fitting is provided in Figure 1. It is worth noting that the trend of the 𝐶𝑒 data in Figure 1 is 

consistent with the use of a linear isotherm. This is particularly evident in Figure 1b, where a zoom on low 

concentration values is shown. 

 

21



  
Figure 1: Equilibrium Ce versus 𝛼 data at 70 °C (tests 1.1-1.15) fitting with equilibrium model (Eq. 4); 

(a): Fitting, (b): Fitting (zoom in) 

 

The fitting yielded values of 𝑞𝑡𝑜𝑡 = 0.255 g/g and 𝑘 = 0.0092 L/g. The 𝑞𝑡𝑜𝑡 result is consistent with the outcomes 

of our previous works. In particular, the total amounts of extractable polyphenols per mass of solid matrix 

obtained using water and NADES were 𝑞𝑡𝑜𝑡 = 0.114 g/g (Bertino et al., 2023) and 𝑞𝑡𝑜𝑡 = 0.470 g/g (Mazzeo et 

al., 2023), respectively.  

3.2 Kinetic studies 

The experimental results of the three kinetic runs (tests 2.1-2.3) are reported in Table 2. 

Table 2: Experimental data (concentrations 𝐶 of polyphenols in liquid solvent) for the kinetic tests 2.1-2.3 

(T=70 °C; Test 2.1: 𝛼 = 0.54 g/L, Test 2.2: 𝛼 = 1 g/L, Test 2.3: 𝛼 = 2 g/L). 

Time 𝑡 

(min) 

𝐶 (g/L) from test 2.1 𝐶 (g/L) from test 2.2 𝐶 (g/L) from test 2.3 

0 0.130 0.169 0.250 

15 0.132 0.218 0.304 

30 0.136 0.232 0.351 

60 0.138 0.231 0.418 

90 0.142 0.242 0.497 

120 0.140 0.229 0.483 

150 0.143 0.243 0.512 

180 0.145 0.234 0.520 

210 0.141 0.233 0.521 

 

It is worth noting that the initial concentration of polyphenols in liquid solvent (at 𝑡 = 0) is different from zero. In 

fact, during experimental tests, as soon as the solid was brought into contact with the solvent, a release of 

phenolic compounds was immediately evidenced by a rapid coloration of the liquid. 

The experimental data of Table 2 were then fitted with the corresponding theoretical predictions provided by the 

Linear Driving Force (LDF) Model. The aim of the fitting was to obtain the product between the global mass 

transfer coefficient and the specific surface area made available by the solid matrix referred to the liquid volume 

𝑎𝐾𝐿𝐷𝐹. In the LDF model, the mass balance equation for the liquid phase is (Bucić-Kojić et al., 2013): 

𝑑𝐶

𝑑𝑡
 =  𝑎𝐾𝐿𝐷𝐹(𝐶∗ − 𝐶) =  𝑎𝐾𝐿𝐷𝐹 (

𝑞

𝑘
− 𝐶) = 𝑎𝐾𝐿𝐷𝐹 [

𝑞𝑡𝑜𝑡

𝑘
− (1 +

1

𝛼𝑘
) 𝐶]         (5) 

where 𝑎𝐾𝐿𝐷𝐹 accounts for two resistances in series: the resistance offered by the liquid film according to the film 

theory and the hypothetical linear resistance offered by a film inside the solid where the 𝑞 gradient is considered 

to be concentrated. In Eq. 5, the theoretical liquid concentration 𝐶∗ in equilibrium with the solid phase was 

expressed with the linear Eq. 3. Finally, the variable 𝑞 was eliminated using the global mass balance provided 

by Eq. 2, evaluated at a generic time 𝑡. By integrating Eq. 5 with the initial condition 𝐶(𝑡 = 0) = 𝐶0, the following 

prediction of 𝐶 over time was obtained:  

0

2

4

6

8

10

0 10 20 30 40 50

C
e

 (
g

/L
)

α (g/L)

(a) 

Equilibrium
data

Equilibrium
model

0

0.1

0.2

0.3

0.4

0.5

0 0.5 1 1.5

C
e

 (
g

/L
)

α (g/L)

(b) 

Equilibrium
data

Equilibrium
model

22



𝐶(𝑡)  =  
𝛼𝑞𝑡𝑜𝑡

1 + 𝛼𝑘
[1 − (1 − 𝐶0 (

1 + 𝛼𝑘

𝛼𝑞𝑡𝑜𝑡
)) 𝑒𝑥𝑝 (−

1 + 𝛼𝑘

𝛼𝑘
𝑎𝐾𝐿𝐷𝐹𝑡)] (6) 

where 𝛼 and 𝐶0 are the solid-liquid ratio and the initial polyphenol concentration in liquid for the specific test 

under consideration, respectively, and the thermodynamic parameters 𝑞𝑡𝑜𝑡 and 𝑘 are taken from Section 3.1.  

The predicted concentration 𝐶 provided by the LDF Model, as described by Eq. 6, was used to fit the 

experimental data 𝐶 obtained from the three runs 2.1-2.3. In particular, a graphical representation of the fitting 

is provided in Figure 2. The good agreement between the experimental data and the model predictions shows 

the efficacy of the LDF model in describing the kinetic behaviour of the system.  

 

 

Figure 2: Kinetic curve of 𝐶 versus 𝑡 data fitted with the LDF kinetic model (Eq. 6). 

These results shows that the process is very fast, reaching a plateau within the first hour. This is in line with 

what we observed in our previous experimental studies regarding polyphenols extraction with water and NADES 

(Bertino et al., 2023; Mazzeo et al., 2023). Finally, the 𝑎𝐾𝐿𝐷𝐹 values estimated for each run are reported in Table 

3. It is possible to observe that the 𝑎𝐾𝐿𝐷𝐹 values increase accordingly to the increase in the solid-liquid ratio 

which is well-known to be proportionally related to the specific surface area.  

Table 3: Estimated 𝑎𝐾𝐿𝐷𝐹 values for the various kinetic runs 2.1-2.3.  

Test  𝛼 (g/L) 𝑎𝐾𝐿𝐷𝐹  (1/s) 

2.1 0.54 0.00030 

2.2 1.00 0.00037 

2.3 2.00 0.00039 

4. Conclusions 

This article is part of a research line focusing on evaluating the efficacy of different green solvents for extracting 

polyphenols from waste hazelnut skins. Specifically, it explores the feasibility of using a 50% vol/vol water-

ethanol mixture. Experimental tests were conducted in a batch set-up, varying the solid-liquid ratio from 0.16 to 

50 g/L while maintaining a constant temperature of 70°C, to investigate both equilibrium and kinetic aspects. 

Equilibrium tests lasted 6 hours to ensure reaching equilibrium conditions, and an equilibrium model combining 

global mass balance and a linear equilibrium isotherm was employed. Experimental equilibrium data were fitted 

with the model, yielding 𝑞𝑡𝑜𝑡 = 0.255 g/g and 𝑘 = 0.0092 L/g as the total amount of extractable polyphenols in 

solid mass of hazelnut skins and the linear partition coefficient, respectively. By comparing the 𝑞𝑡𝑜𝑡 value 

obtained in this paper with the values presented in our previous works, it is worth noting that the 50% vol/vol 

water-ethanol mixture has a higher extraction efficiency than water (𝑞𝑡𝑜𝑡 = 0.114 g/g, (Bertino et al., 2023)), but 

a lower extraction efficiency than NADES (𝑞𝑡𝑜𝑡 = 0.470 g/g, (Mazzeo et al., 2023)). However, the higher viscosity 

of NADES makes it less suitable for plant-use scale.  

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0 50 100 150 200

C
 (

g
/L

)

t (min)

2.00 g/L

1.00 g/L

0.54 g/L

LDF kinetic model

23



Kinetic runs involved collecting liquid samples at fixed intervals, with results fitted to the Linear Driving Force 

Model to estimate the LDF mass transfer coefficient, showing an increase with solid-liquid ratio. Rapid extraction 

reaching maximum polyphenol concentration within the first hour was consistent with our previous findings. 

Future research will involve investigating the application of water-ethanol mixtures in a continuous set-up, 

enabling an expansion of the investigated solid-liquid ratios range. Moreover, employing a closed-loop fixed bed 

set-up will enable precise calculation of total extractable mass of polyphenols, allowing for a comparison with 

the 𝑞𝑡𝑜𝑡 value fitted in this paper. Finally, ongoing research will delve into exploring diverse water-ethanol 

mixtures with varying %vol compositions. Nevertheless, it is important to highlight that the particular 50% vol/vol 

water-ethanol mixture employed in this study has already proven to be an effective solution for recovering 

polyphenols from hazelnut skins.  

 

Nomenclature

𝑎𝐾𝐿𝐷𝐹 – Linear Driving Force mass transfer 

coefficient, 1/s 

𝐶 – concentration of polyphenols in solvent, g/L 

𝐶∗ – theoretical concentration of polyphenols in 

solvent in equilibrium with solid, g/L 

𝐶𝑒 – equilibrium concentration of polyphenols in 

solvent, g/L 

𝐶0 – concentration of polyphenols in solvent at 𝑡 = 

0, g/L 

𝑘 – linear partition coefficient, L/g 

𝑀𝑆 – mass of solid matrix, g 

𝑛𝑖 – number of samples collected during each 

kinetic run, - 

𝑞 – concentration of polyphenols in solid mass of 

hazelnut skins, g/g 

𝑞𝑒 – equilibrium concentration polyphenols in solid 

mass of hazelnut skins, g/g 

𝑞𝑡𝑜𝑡 – total amount of extractable polyphenols in 

solid mass of hazelnut skins, g/g 

𝑡 – time, min 

𝑉𝑖 – volume of each sample collected during 

kinetic runs, µL 

𝑉𝐿 – volume of liquid solvent, L 

𝛼 – solid-liquid ratio , g/L

References 

Adebooye, O. C., Alashi, A. M., & Aluko, R. E. (2018). A brief review on emerging trends in global polyphenol 

research. In Journal of Food Biochemistry (Vol. 42, Issue 4). Blackwell Publishing Ltd. 

https://doi.org/10.1111/jfbc.12519 
Antony, A., & Farid, M. (2022). Effect of Temperatures on Polyphenols during Extraction. In Applied Sciences 

(Vol. 12, Issue 4). MDPI. https://doi.org/10.3390/app12042107 

Bertino, A., Mazzeo, L., Gallo, V., Posta, S. Della, Fanali, C., & Piemonte, V. (2023). Polyphenols Extraction 

from Hazelnut Skin Using Water as Solvent: Equilibrium Studies and Quantification of the Total 

Extractable Polyphenols. Chemical Engineering Transactions, 102, 55–60. 

https://doi.org/10.3303/CET23102010 

Bucić-Kojić, A., Sovová, H., Planinić, M., & Tomas, S. (2013). Temperature-dependent kinetics of grape seed 

phenolic compounds extraction: Experiment and model. Food Chemistry, 136(3–4), 1136–1140. 

https://doi.org/10.1016/j.foodchem.2012.09.087 

Camera di Commercio Cuneo. (n.d.). http://www.cuneoprezzi.it/ingrosso/ALIMENTARI/index?category=35 

Everette, J. D., Bryant, Q. M., Green, A. M., Abbey, Y. A., Wangila, G. W., & Walker, R. B. (2010). Thorough 

Study of Reactivity of Various Compound Classes toward the Folin - Ciocalteu Reagent. Journal of 

Agricultural and Food Chemistry, 58, 8139–8144. https://doi.org/10.1021/jf1005935 

Fanali, C., Gallo, V., Della Posta, S., Dugo, L., Mazzeo, L., Cocchi, M., Piemonte, V., & De Gara, L. (2021). 

Choline Chloride – Lactic Acid-Based NADES As an Extraction Medium in a Response Surface 

Methodology-Optimized Method for the Extraction of Phenolic Compounds from Hazelnut Skin. 

Molecules, 26(2652), 1–15. 

GİRESUN. (n.d.). http://www.giresuntb.org.tr/EN/statistic.php 

Mazzeo, L., Bertino, A., De Paola, L., Gallo, V., Della Posta, S., Fanali, C., & Piemonte, V. (2023). Equilibrium 

and fixed-bed kinetics study on hazelnut skin polyphenols extraction using choline chloride –lactic acid-

based NADES and water as solvents. Separation and Purification Technology, 327. 

https://doi.org/10.1016/j.seppur.2023.124896 

 Silva, R. F. M., & Pogačnik, L. (2020). Polyphenols from Food and Natural Products: Neuroprotection and 

Safety. Antioxidants, 9(61), 1–13.  

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	Polyphenols Recovery from Hazelnut Skin Wastes through Extraction with a Water-Ethanol Solvent Mixture: Equilibrium and Kinetic Studies