Separation of fructose and glucose from date syrup using resin chromatographic method: Experimental data and mathematical modeling

Separation and Purification Technology 79 (2011) 72–78

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Separation of fructose and glucose from date syrup using resin chromatographic method: Experimental data and mathematical modeling A. Khosravanipour Mostafazadeh a,b, M. Sarshar a,∗, Sh. Javadian a, M.R. Zarefard c, Z. Amirifard Haghighi d a

Fars Engineering Research Center, Engineering Research Institute, Shiraz 71555-414, Iran National Elite Foundation, Tehran, Iran Food Research and Development Center, Agriculture and Agri-Food Canada, Quebec, Canada d Chemical Industries Group, Shiraz Girls’ Technical College, Shiraz, Iran b c

a r t i c l e

i n f o

Article history: Received 11 October 2010 Received in revised form 1 March 2011 Accepted 8 March 2011 Keywords: Cation-exchange resin Isotherm Breakthrough curves Sugars

a b s t r a c t In this work a series of experiments have been performed to study and simulate the separation of glucose and fructose as the most applicable sugars in the food industry. The objective of this work is understanding and modeling the behavior of these components in a chromatography column when they are introduced to the column as simple components, binary solutions, and also as the major species in date syrup. The column’s diameter and height are 3.5 cm and 15 cm respectively, and Purolite PCR642Ca, which is an acidic gel-type cation exchange resin (Ca2+ ), was used for the separation of sugars. Static method was applied to determine the equilibrium constants, and frontal (dynamic) analysis method was used to determine the mass transfer coefficients at two different temperatures of 30 and 60 ◦ C for single and multi-component mixtures for a solution with a sugar concentration of 70 g/L. The kinetic studies for the prediction of mass transfer coefficients were performed according to the breakthrough curves by a linear driving force approximation (LDF), while the adsorption isotherms were estimated by linear model. Adsorption equilibrium constants and mass transfer coefficients between fructose, glucose and solid resin were determine by optimization procedure. The results of the optimization and parameter estimation for synthetic sugar solutions were also applied for modeling the separation of sugars in date syrup. The predicted results of the real mixtures (date syrup) have a good agreement with the experimental data and show that both sugars can be separated successfully by this method. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Using chromatographic systems for the separation of sugars like fructose and glucose are very impressive and feasible methods. Date syrup is a very important and abundant fruit in the Middle-East and it can be a huge resource of sweeteners. Kinetics study of the separation of its sugars (containing fructose and glucose) to produce high fructose date syrup is the main objective of this work. The ingredients of date syrup depend on the type of date, but in general date syrup contains fructose, glucose, moisture and small amounts of sucrose, protein, pectin and calcium. Fructose is the sweetest natural sugar in the world and it is 30% sweeter than sucrose, while glucose has 70% of the sweetness of sucrose. In addition, fructose is more soluble than glucose in water. Most date sugars have an equal amount of fructose and glucose and

∗ Corresponding author. Tel.: +98 711 7201798; fax: +98 711 7203240. E-mail addresses: [email protected] (A. Khosravanipour Mostafazadeh), [email protected] (M. Sarshar). 1383-5866/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2011.03.014

a small portion of sucrose. Sucrose is made from one molecule of fructose and one molecule of glucose. Glucose and fructose have very similar structures and are hard to isolate. HFS90, HFS55, and HFS42 (on the basis of the fraction of fructose in syrup) are the typical high fructose syrup in the market, and are used extensively in the food and pharmaceutical industries. Fructose is preferred to glucose because it is sweeter than glucose and less can be used in the daily diet. Also, fructose is absorbed in human cells much better than glucose. In general, the mechanism and quality of the separation depends on several parameters such as the characteristics of the mixture and resin, but the most influencing parameters in the separation of the two mentioned components in their mixtures are the size exclusion and the ligand exchanged. In fact, gel-type calcinate resins make strong complexes with fructose rather than glucose. In most of the commercial methods, high fructose corn syrup (HFCS) is produced, and the aim of the present work is the production of high fructose date syrup (HFDS). Resin chromatographic method is a suitable method for the separation of fructose in sugar mixtures. The literature survey shows that there are many scientific researches on the separation of fructose and glucose by resin

A. Khosravanipour Mostafazadeh et al. / Separation and Purification Technology 79 (2011) 72–78

Nomenclature Ci Dax Ki kpi Pe q∗i q¯ i Rp t

v v0 z ε

Concentration of component i (g cm−3 ) Axial dispersion coefficient (cm3 min−1 ) Equilibrium constant Mass transfer coefficient for component i (min−1 ) Pecklet number Adsorbed concentration on solid phase in equilibrium with the concentration Ci (g cm−3 ) Concentration of component i on resin phase (g cm−3 ) Resin seed diameter (cm) Time (min) Interstitial velocity (cm min−1 ) Specific velocity (cm min−1 ) Axial coordinate (cm) Bed porosity

Subscripts i Component i out Outlet the column Superscripts cal Calculated exp Experimental Abbreviations LDF Linear driving force OF Objective function

chromatography, but to date, none have been reported by Purolite PCR642Ca. Nobre et al. [1] reported adsorption equilibrium constants of sugars by the use of potassium and sodium ion-exchange resins. Luz et al. [2] studied the separation of fructose and glucose of cashew apple and determined the kinetics and equilibrium parameters for the modeling of a chromatographic system using an experimental procedure for two different resins, Dowex Monosphere 99/Ca and Diaion UBK555. Pedruzzi et al. [3] reported equilibrium and sorption kinetics parameters for the mixtures of sugars by three gel type ion exchange resins charged with H+ , K+ and Ca2+ . Al Eid [4] investigated the experimental chromatographic separation of a mixture of fructose and glucose from date palm fruits using Dowex polystyrene cation exchange resin Ca2+ . Bubnik et al. [5] studied continuous counter-current chromatographic separation in sugar technology using an SMB (simulated moving bed) technique. Lee [6] simulated a moving bed, including Dowex resins of the Ca2+ form for separating glucose and fructose at high concentrations. Viard and Lameloise [7] modeled glucose–fructose separation in an ion exchange chromatographic system by determining equilibrium isotherms, kinetic and hydrodynamic parameters. Ho et al. [8] compared the separation of glucose and fructose mixture using zeolite and resin and concluded that these two types of adsorbent showed little difference in behavior at operating conditions, though the resin demonstrated a higher value of equilibrium separation parameter. Pansolli et al. [9] invented a continuous method for the separation of fructose and glucose using anion-exchange resins. Smith and Spriestersbach [10] studied the separation of d-fructose and d-glucose from invert sugar using cation exchange resin. Mowery [11] studied the experimental separation of d-fructose and d-glucose and determined distribution ratios and theoretical plates. In this work, the separation of the aforesaid sugars has been studied by determining the breakthrough curves in a chromato-

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graphic fixed bed column (low pressure liquid chromatography). The study deals with the application of a dynamic chromatographic system in sugar technology. Based on the experimental results, a model has been developed which is applicable in a wide range of operating conditions. 2. Model development The governing model is obtained by mass balance on a chromatography column, which is shown by the following partial differential equation: ∂2 C v ∂Ci (1 − ε) ∂q¯ i ∂Ci = Dax 2i − − ε ∂z ε ∂t ∂t ∂z

(1)

Derivatives of variants (Ci and q¯ i ) with respect to the independent parameters (t and z) are presented in the set of partial differential equations. The sugar concentration on the solid phase is also proportionate with the mass transfer coefficient according to the linear driving force approximation (LDF) model: ∂q¯ i = kpi (q∗i − q¯ i ) ∂t

(2)

The adsorption equilibrium isotherm is represented by the q∗i as a function of Ci . In this case, the linear equilibrium isotherm is as follows: q∗i = Ki Ci

(3)

where Ki is dimensionless equilibrium constant. By solving the model using the Danckwertz boundary conditions, the concentration of component i in the fluid phase is determined as a function of time and the column length. Boundary and initial conditions are given by Danckwertz equations: Ci = C0i +

εDax ∂Ci @z = 0 v ∂z

(4)

∂Ci = 0@z = l ∂z

(5)

t=0

Ci = 0

(6)

t=0

q¯ i = 0

(7)

Also, the boundary conditions of Dirichlet at the inlet of the column and Von Neumann at the exit of the column can be considered, but the most precise conditions are the Danckwertz conditions. The following suppositions were considered in the model: 1. Mass transfer mechanism follows linear driving force approximation (LDF) model. 2. According to the previous studies [2,3,7], only the internal mass transfer in the particles is taken into account and the external mass transfer is neglected. 3. Equilibrium sorption is described by linear equation. 4. Isothermal condition. 5. Constant flow rate and plug flow regime with axial dispersion. Although the axial dispersion can be neglected according to Cren et al. [12], it is considered in the model to provide higher accuracy. In this model, Ki and kpi should be obtained based on the experimental data. The next sections describe the method of determining these parameters. The model was solved by orthogonal collocation method for 30 time steps.

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Fig. 1. Adsorption isotherms of fructose at 60 ◦ C () and 30 ◦ C () (a), and glucose at 60 ◦ C () and 30 ◦ C () (b).

3. Experimental 3.1. Materials Purolite PCR642Ca ion exchange gel type resin was used in this work. The resin included a spherical bead and its polymer structure contained gel polystyrene crosslinked with divinylbenzene. Sulphonic acid was the functional group and Ca2+ was the ionic form. The typical mean size of the resin was 315 ␮m. Analytical grade glucose and fructose were purchased from Merck, and the date liquid sugar was purchased from Shahd Babe Pars (domestic) Company. Analysis of the date syrup showed that the total solid in the solution contains 49% fructose, 47% glucose and 4% other components like sucrose. 3.2. Experiments in chromatographic packed column A glass column with a 3 cm diameter and 15 cm length was filled with Purolite PCR642Ca ion exchange resin. The flow rate was fixed at 7 mL/min with the total sugar concentration 70 g/L for both single and multi-component sugar mixtures and 120 g/L for real mixtures. The experiments were carried out at two different temperatures of 30 and 60 ◦ C. The porosity of the bed was determined at 0.4 and Peclet number (Pe) was assumed vRp /Dax = 0.5 according to the experimental analysis. The axial dispersion can be calculated regarding the Peclet number. Dynamic analysis, namely the chromatographic method, was applied to determine breakthrough curves. The sugar solutions (synthetic or real mixtures) were injected into the column at a fixed flow rate, and the samples were taken after each 30 s and then analyzed. The experiments were carried on until the resins were saturated. De-ionized distillate water was used as an eluent, and the regeneration process was performed at the column with the water eluent at 36 mL flow rate during 13 min. Date syrup was pretreated before injection to the column. The pretreatment included dilution with De-ionized distillate water, demineralization using anionic and cationic resins, and pigment removal using activated carbon and filter press. 3.3. Static experiments for determining isotherms Static method (adsorption–desorption in batch mode) was used to determine the adsorption equilibrium isotherms. 50 mL (56 gr) of resin was poured into a 200 mL batch reactor, and 50 mL sugar solution was added to it. The mixture was then embedded in a water bath (Thermostated Water Bath, Fan Azma Gostar) and stirred with a mechanical stirrer (IKA RW-20) at 240 rpm at fixed tempera-

tures of 30 ± 0.1 and 60 ± 0.1 ◦ C. A concentration of 10–70 g L−1 was prepared and added to the reactor. The final concentration of the solution was determined after 100 min under agitation. The adsorbed sugar on the adsorbent was calculated by the mass balance. After each experiment, the resins were washed with the distilled water to regenerate the resin.

3.4. Sample analysis The samples were taken from the column exit and analyzed using two methods. The concentrations of mono sugar products were determined using a Refractometer, and the synthetic binary solutions and real mixtures were analyzed by Spectrophotometer (UNICO, UV-2100) and Enzymatic BioAnalysis, d-Glucose/d-Fructose UV-Test, Roche, R-Biopharm AG. The Spectrophotometer was operated at 340 nm wave length. Also, the samples from the static method were analyzed by Refractometer.

4. Results and discussions 4.1. Equilibrium adsorption isotherms The experimental data were fitted by linear function. As demonstrated in Fig. 1(a) and (b), the experimental data correlated well with the linear regression. The slope of each line distinguishes the K values. Fig. 1(a) shows the relationship between the concentration of sugar in the solution and on the solid phase for fructose at 30 and 60 ◦ C. Fig. 1(b) depicts the same feature, but for glucose. Linear equations and R-squared values for each series of experiments are shown in the figures. It is observed that the equations and R-squared values are in good agreement with the experimental data. The equilibrium isotherms at these circumstances are shown in Table 1. From the table it can be concluded that the K-values of the fructose are higher than those of the glucose, and their values decrease as the temperature increases. This means that the absorbed sugar declines by the rise in temperature.

Table 1 Mass transfer coefficients and equilibrium isotherms for fructose and glucose in the presence of ion exchange Ca2+ gel-type resin. Component

T (◦ C)

Ki

kpi (min−1 )

Fructose

30 60 30 60

0.55 0.48 0.35 0.31

0.92 1.11 1.41 1.60

Glucose

A. Khosravanipour Mostafazadeh et al. / Separation and Purification Technology 79 (2011) 72–78

a

Exp

7

8 Exp

7

Model

6

6

5

5

C (Brix)

C (Brix)

b

8

4 3

3 2

1

1 0

5

10

15

20

25

30

35

Model

4

2

0

0

40

0

5

10

20

25

30

8

8

d

Exp

7

Exp

7

6

Model

6

Model

C (Brix)

C (Brix)

15

Tim e (m in)

tim e (m in)

c

75

5 4

5 4

3

3

2

2

1

1 0

0 0

5

10

15

20

25

30

35

Tim e (m in)

0

5

10

15

20

25

30

Tim e (m in)

Fig. 2. Breakthrough curves for single component solutions of fructose at 30 ◦ C (a), glucose at 30 ◦ C (b), fructose at 60 ◦ C (c), and glucose at 60 ◦ C (d) (initial concentration C0 = 70 g L−1 (Brix = 7), and flow rate Q = 7 mL min−1 ). The solid line represents the model results and the pints show the experimental data.

4.2. Parameter estimation and mass transfer coefficients The mass transfer coefficients are determined using breakthrough curves by the optimization method. Parameter estimation is used to determine the values of the unknowns’ parameters (mass transfer coefficients) to predict the values achieved from the experimental data by the mathematical model. The objective function is defined as the sum of square differences (least square method) of the experimental and predicted sugar concentrations. The objective function is defined by Eq. (8).

OF =

N 

2 exp (Ci−out

cal − Ci−out )

(8)

i=1

The mass transfer coefficients and the equilibrium isotherms are shown in Table 1. According to the table, the internal mass transfer coefficient of glucose is higher than the mass transfer coefficients of fructose. Furthermore, the mass transfer coefficients increase by the rise in temperature. 4.3. Breakthrough curves The single sugar breakthrough curves of fructose and glucose are shown in Fig. 2. Optimized mass transfer coefficients were obtained according to theses profiles. Fig. 2(a) and (b) shows the experimental and simulated breakthrough curves of fructose and glucose at 30 ◦ C respectively, and Fig. 2(c) and (d) shows the same curves at 60 ◦ C. It is observed that the model predicts the breakthrough curves very well at these conditions. The mass transfer coefficient of glucose shows sharper breakthrough curves and decreases in saturation (end time) and break times.

Also, the breakthrough curves were measured for binary sugar solutions and leaned date syrup in order to check the ability of the model to forecast the multi component solutions, and to show the ability of the resin to separate the sugars. The parameters, which are determined from the experimental data of the single components, were applied to predict the behavior of the synthetic binary solution. The prediction is in good agreement with the experimental data. Fig. 3(a) illustrates the experimental and modeled dimensionless concentrations of the binary mixtures as a function of time (equal mass concentrations of each sugar) at 30 ◦ C, and Fig. 3(b) shows the total sugar concentration as a function of time as well. The same breakthrough curves at 60 ◦ C are shown in Fig. 4. The model predicts the binary solutions well, and the discrepancy of fructose and glucose concentrations confirms that these sugars can be separated by the resin chromatographic method. Fig. 5(a) and (b) demonstrates the outlet concentration of date syrup as a function of time at 30 ◦ C. The breakthrough curves of total soluble solid in the mixture, and also the summation of fructose and glucose, are shown in Fig. 5(a). Since the model predicts the behavior of the glucose and fructose solution, a small amount of solid such as sucrose cannot be predicted by the simulator. In addition, Fig. 5(b) exhibits the concentration of each component in the mixture. On the other hand, the model correlated well with the experimental data on fructose and glucose in the date syrup (Fig. 5(a) and (b)), though a small deviation can be observed due to the side effects of the other components such as sucrose. Generally, the presented model and estimated parameters are in good agreement with the experiments and are acceptable in the application, despite the slope of the breakthrough curve of the model being slightly higher than the experimental data. Fig. 6 shows the same results at 60 ◦ C. From this figure it can be concluded that, at

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A. Khosravanipour Mostafazadeh et al. / Separation and Purification Technology 79 (2011) 72–78

a

b

1.2

8 Exp

7

1

Model

Total sugar (Brix)

6

C/C0

0.8 0.6 0.4 Fructose (Model) Glucose (Model) Glucose (Exp) Fructose (Exp)

0.2

5 4 3 2 1 0

0 0

5

10

15

20

25

30

35

0

5

10

Time (min)

15

20

25

30

35

Time (min)

Fig. 3. Breakthrough curves for synthetic binary solution of glucose and fructose at 30 ◦ C (initial concentration of each sugar is equal to 35 g L−1 ).

a

b

1.2

8 Exp

7

Model

Total sugar (Brix)

1

C/C0

0.8 0.6 0.4 Fructose (Model) Glucose (Model) Fructose (Exp) Glucose (Exp)

0.2 0

0

5

10

15

20

25

30

6 5 4 3 2 1 0

35

0

5

10

Time (min)

15

20

25

30

35

Time (min)

Fig. 4. Breakthrough curves for synthetic binary solution of glucose and fructose at 60 ◦ C (initial concentration of each sugar is equal to 35 g L−1 ).

this temperature the model predicts well, even better than 30 ◦ C. In the first minutes the model slightly underestimates the real data, however, after that, overshooting is observed. Digression from the simulation results indicates that though the date syrup was purified, a small amount of chemical types in the date syrup may adsorb on resin. Totally, the results show the adsorption ability for date syrup is the same as the results of the synthetic solution. In spite of this fact, the mathematical model approaches the experimental data, and demonstrates that this separation method is appropriate and can be modeled.

To evaluate the contribution of this work the equilibria isotherms of fructose and glucose are compared with the other resins which have been research. As shown in Table 2, adsorption isotherms of fructose are 0.6, 0.63 for Dowex Monosphere 99/Ca gel type at 30 and 25 ◦ C respectively, 0.73 for Diaion UBK555 at 25 ◦ C, 0.8 for Dowex 50W-X8 at 30 ◦ C, 0.67 for Zerolit 225 SRC at 30 ◦ C, 0.88 for Duolite C204 at 29 ◦ C, while the adsorption isotherm of fructose for Purolite PCR642Ca is 0.55 at 30 ◦ C which means

b

a 14

1.2

12

1

10

0.8

8

C/C0

Brix

4.4. Comparison and contrast

6

0.6 0.4 Fructose (Model) Glucose (Model) Fructose (Exp) Glucose (Exp)

4 Model Fructose and Glucose Total sugar

2

0.2 0

0 0

5

10

15

20

time (min)

25

30

35

40

0

5

10

15

20

25

30

35

time (min)

Fig. 5. Breakthrough curves for treated date syrup (a) total sugar and (b) dimensionless fructose and glucose concentration at 30 ◦ C (total Brix at inlet of column is 12, and rate Q = 7 mL min−1 ).

A. Khosravanipour Mostafazadeh et al. / Separation and Purification Technology 79 (2011) 72–78

a 14

b

12

0.8

8

C/C0

Brix

1.2 1

10

6

0.6 Fructose (Model) Glucose (Model) Fructose (Exp) Glucose (Exp)

0.4

4 Total Brix Model Fructose and Glucose

2 0

77

0.2 0

0

5

10

15

20

25

30

35

0

time (min)

10

20

30

40

time (min)

Fig. 6. Breakthrough curves for processed date syrup (a) total sugar and (b) dimensionless fructose and glucose concentration at 60 ◦ C (total Brix at inlet of column is 12, and rate Q = 7 mL min−1 ).

fructose adsorption in Purolite PCR642Ca is lower than in mentioned resins. Also, adsorption isotherms of glucose are 0.28 and 0.29 for Dowex Monosphere 99/Ca gel type at 30 and 25 ◦ C respectively, 0.38 for Diaion UBK555 at 25 ◦ C, 0.3 for Dowex 50W-X8 at 30 ◦ C, 0.2 for Zerolit 225 SRC at 30 ◦ C, 0.5 for Duolite C204 at 29 ◦ C, but adsorption isotherm of glucose for Purolite PCR642Ca is 0.35

Table 2 Equilibrium isotherms and mass transfer coefficients of fructose and glucose by different resins. Resin type

T ( ◦ C)

Sugar type

kp (min−1 )

K

Dowex Monosphere 99/Ca [2]

25

Fructose

0.83

0.63

Diaion UBK555 [2]

25

Dowex Monosphere 88 Na Macroporous [1]

25

Glucose Fructose Glucose Fructose

1.34 0.83 1.40 –

0.29 0.73 0.38 1.266 [L kg−1 ]

Glucose Fructose Glucose Fructose

– – – –

0.923 [L kg−1 ] 0.794 [L kg−1 ] 0.645 [L kg−1 ] 0.852 [L kg−1 ]

Glucose Fructose Glucose Fructose

– – – –

0.793 [L kg−1 ] 0.763 [L kg−1 ] 0.671 [L kg−1 ] 0.60

Glucose Fructose Glucose Fructose Glucose Fructose Glucose Fructose Glucose Fructose Glucose Fructose Glucose Fructose

– – – – – – – – – – – – – –

0.28 0.8 0.3 0.67 0.2 0.49 0.2 0.88 0.5 0.67 0.5 0.468 0.374 0.47

Glucose Fructose Glucose Fructose

– – – –

0.245 0.805 [L kg−1 ] 0.746 [L kg−1 ] 0.685 [L kg−1 ]

Glucose Fructose Glucose Fructose

– – – –

0.420 [L kg−1 ] 0.792 [L kg−1 ] 0.729 [L kg−1 ] 0.758 [L kg−1 ]

Glucose

–

0.519 [L kg−1 ]

40 Dowex Monosphere 99 K/320 Gel type [1]

25

40 Dowex Monosphere 99/Ca Gel type [13]

30

Dowex 50W-X8 [14]

30

Zerolit 225 SRC 14 [15]

30 60

Duolite C204 [16]

29 70

Duolite C204F [17]

60

Dowex Monosphere 99/Ca [18]

70

Diaion UBK 530 [19]

60

Dowex Monosphere 99CA/320 [19]

60

Lewatit S 2568 [19]

60

Amberlite CR1320Ca [19]

60

at 30 ◦ C, and it shows that adsorption equilibrium isotherm of glucose in Purolite PCR642Ca is higher than Dowex Monosphere 99/Ca Gel type, Dowex 50W-X8, Zerolit 225 SRC and lower than Diaion UBK555, and Duolite C204. At 60 ◦ C, adsorption isotherms of fructose is equal to 0.49 for Zerolit 225 SRC and 0.468 for Duolite C204F, while this value is 0.48 for Purolite PCR642Ca. Also adsorption isotherms of glucose are equal to 0.2 for Zerolit 225 SRC and 0.374 for Duolite C204F, while this value is 0.31 for Purolite PCR642Ca. The adsorption isotherms of Dowex Monosphere 99 K/320 Gel type, Dowex Monosphere 88 Na Macroporous, Diaion UBK 530, Lewatit S 2568, and Amberlite CR1320Ca were reported with dimensions and cannot be compared here. Mass transfer coefficients are also compared among different resins. Mass transfer coefficient of fructose for Purolite PCR642Ca is 0.92 while 0.83 were reported for Dowex Monosphere 99/Ca and Diaion UBK555. Also Mass transfer coefficient of glucose is 1.41 for Purolite PCR642Ca, but this value was reported 1.34 and 1.40 for Dowex Monosphere 99/Ca and Diaion UBK555 respectively. Consequently, mass transfer coefficients of both species (glucose and fructose) relative to Purolite PCR642Ca are higher than those values relative to Dowex Monosphere 99/Ca and Diaion UBK555. Azevedo and Rodrigues [13] reported that it is possible to achieve a fructose purity more than 90% from 50% purity by use of Dowex Monosphere 99/Ca gel type, and Nikeghbal et al. [20] reported that the concentration of fructose gets to 92.5% starting from 49.2% purity in real date syrup using Purolite PCR642Ca.

5. Conclusion In this study the methodology of modeling the resin chromatographic column for separating fructose and glucose from date syrup was developed. A model that presented the behavior of dynamics of the column was derived from mass balances on the fluid and solid phase. The required mass transfer coefficients and equilibrium isotherms at two different temperatures were determined by the use of static and dynamic experimental studies, respectively. Adsorption kinetics was presented by LDF model and the equilibrium isotherms are also given by linear equation. The optimization results from the synthetic mono-component solution indicated an acceptable prediction of breakthrough curves of more complex sugar mixtures. Good agreement between the experimental and the simulated results was observed. The results showed that the fructose absorbed by the resin stronger than the glucose, and left the column later than the glucose. Therefore, a fructose-rich fraction can be obtained from date syrup for food industries applications by this method. The results are able to apply and provide basic data for research in the future studies of sugar chromatography technology.

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Acknowledgments The authors would like to thank the Office of the Basic Research of Industry and Mine, Ministry of Industries and Mines for the financial supports. References [1] C. Nobre, M.J. Santos, A. Dominguez, D. Torres, O. Rocha, A.M. Peres, I. Rocha, E.C. Ferreira, J.A. Teixeira, L.R. Rodrigues, Comparison of adsorption equilibrium of fructose, glucose and sucrose on potassium gel-type and macroporous sodium ion-exchange resins, Anal. Chim. Acta 654 (1) (2009) 71–76. [2] D.A. Luz, A.K.O. Rodrigues, F.R.C. Silva, A.E.B. Torres, C.L. Cavalcante Jr., E.S. Brito, D.C.S. Azevedo, Adsorptive separation of fructose and glucose from an agroindustrial waste of cashew industry, Bioresour. Technol. 99 (2008) 2455–2465. [3] I. Pedruzzi, E.A. Borges da Silva, A.E. Rodrigues, Selection of resins, equilibrium and sorption kinetics of lactobionic acid, fructose, lactose and sorbitol, Sep. Purif. Technol. 63 (2008) 600–611. [4] S.M. Al Eid, Chromatographic separation of fructose from date syrup, Int. J. Food Sci. Nutr. 57 (2006) 83–96. [5] Z. Bubnik, V. Pour, A. Gruberova, H. Starhova, A. Hinkova, P. Kadlec, Application of continuous chromatographic separation in sugar processing, J. Food Eng. 61 (2004) 509–513. [6] K.N. Lee, Continuous separation of glucose and fructose at high concentration using two-section simulated moving bed process, Korean J. Chem. Eng. 20 (3) (2003) 532–537. [7] V. Viard, M. Lameloise, Modelling glucose–fructose separation by adsorption chromatography on ion exchange resins, J. Food Eng. 17 (1992) 29–48. [8] C. Ho, C.B. Ching, D.M. Ruthven, A Comparative study of zeolite and resin adsorbents for the separation of fructose–glucose mixtures, Ind. Eng. Chem. Res. 26 (7) (1987) 1407–1412.

[9] Pansolli, Paolo, Barbaro, Aurelio, Maimone, Adriano, Valdiserri, Mario, Method and apparatus for the continuous separation of fructose from glucose starting from invert sugar or from isomerized glucose syrups, Document Type and Number: United States Patent 4,443,267 (1984). [10] F. Smith, D. Spriestersbach, The separation of d-glucose and d-fructose from invert sugar or sucrose, J. Am. Chem. Soc. 76 (16) (1954) 4191–4192. [11] J.R. Dwight Fay Mowery, Chromatographic adsorption. II. The separation of dglucose and d-fructose, J. Am. Chem. Soc. 73 (11) (1951) 5049–5052. [12] É.C. Cren, L.C. Filho, E.A. Silva, A.J.A. Meirelles, Breakthrough curves for oleic acid removal from ethanolic solutions using a strong anion exchange resin, Sep. Purif. Technol. 69 (2009) 1–6. [13] D.C.S. Azevedo, A. Rodrigues, SMB chromatography applied to the separation/purification of fructose from cashew apple juice, Braz. J. Chem. Eng. 17 (2000) 4–7. [14] Y.S. Ghim, H.N. Chang, Adsorption characteristics of glucose and fructose in ion-exchange resin columns, Ind. Eng. Chem. Fund. 21 (1982) 369. [15] C.B. Ching, D.M. Ruthven, Analysis of the performance of a simulated countercurrent chromatographic system from fructose–glucose separation, Can. J. Chem. Eng. 62 (1984) 398. [16] C.B. Ching, D.M. Ruthven, Experimental study of a simulated counter-current adsorption system—IV. Non-isothermal operation, Chem. Eng. Sci. 41 (1986) 3063. [17] V. Viard, M.L. Lameloise, Recents Progres en Genie des Procedes, vol. 8a, Lavoisier, Paris, 1989, p. 233. [18] M. Saska, S.J. Clarke, M.D. Wu, K. Iqbal, J. Chromatogr. 590 (1992) 147–151. [19] M. Gramblicka, M. Polakovic, Adsorption equilibria of glucose, fructose, sucrose, and fructooligosaccharides on cation exchange resins, J. Chem. Eng. Data 52 (2007) 345–350. [20] N. Nikeghbal, M. Sarshar, Sh. Javadian, M.R. Zarefard, Experimental study of fructose and glucose separation from date liquid sugar using chromatography method, in: The Second Conference of Separation Science and Engineering, 4–6 May, Kerman, Iran, 2010.