2.4 Characteristic and activation of FPX66 and MN202 resins

FPX66 and MN202 resins were provided courtesy of Rohm & Haas aromatic and Purolite Ltd., respectively. The physicochemical characteristics of these resins are summarized in Table 3. FPX66 and MN202 resins were activated by using sodium


chlorite and washing with distilled water and then filtrating with a Buchner filter connected to a vacuum pump system. The filtrated resins were put into the beakers that already contained distilled water and the resulting solution was then left at constant stirring (70 rpm) for an hour. At the end of this procedure, the quantities of dissolved salts were evaluated through a digital conductivity meter. Since the results were not satisfactory, the new filtrations were made and the stirs were

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column…

The solutions were again measured at the end and the decreases in salt concen-

trations were revealed. Finally, the treated resins were put into others beaker containing 96% ethylic alcohol, and then the contents of the beakers were stirred (120 rpm) for an hour. After this procedure, the resins were filtrated and conserved

Lab-scale packed bed column experiments were carried out to evaluate the performance of the resin for the adsorption of phenolic compounds. In a typical procedure, the fixed-bed columns were made of Pyrex glass tubes of 1 or 2 cm inner diameter with 9.5 and 19.5 cm height respectively. The model column was packed with the adsorbent between glass wool and supported by inert glass beads as shown

The column performance adsorption onto resin was studied at different phenol concentrations of 200, 400 and 600 mg/L, bed height 9.5 and 19.5 cm and flow rate between 0.8–4.0 mL/min. The bed diameters and depths took were 10.0 and 19.5 cm (resin mass of 5.07 g), 2.0 and 19.5 cm (resin mass of 41.6 g), respectively. The influent of phenol solution was pumped in an upward mode with a peristaltic

The breakthrough curves showed the loading behaviour of phenol, tyrosol and hydroxytyrosol to be removed in a fixed bed. It is expressed in normalized concentration defined as the ratio of effluent solute concentration to inlet (feed) solute concentration (Cout/Cin), as a function of time or volume of effluent for a given

repeated, again for 60 minutes.

Schematic of the experimental setup in upward mode.

DOI: http://dx.doi.org/10.5772/intechopen.90087

in Figure 3.

Figure 3.

bed height [23].

87

in a distilled water environment ready for use.

2.5 Column adsorption and desorption experiments

pump in order to avoid channeling inside the column.

2.5.1 Performance indicators in a fixed-bed column

#### Table 2.

Characteristics of the membrane and the pretreatment of OMWW.


#### Table 3.

Physicochemical characteristics of the resins FPX 66 and MN202.

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column… DOI: http://dx.doi.org/10.5772/intechopen.90087

Figure 3. Schematic of the experimental setup in upward mode.

set at 20 1°C for all experiments [18, 19, 22]. The pretreatment processes aim to reduce TSS and organic matter by measuring the COD. The results obtained by the authors [18, 19, 22] are shown in Table 2 and are reported as a percentage of the reduction (Δ%). The adsorption step on polymeric resins is applied after the mem-

FPX66 and MN202 resins were provided courtesy of Rohm & Haas aromatic and Purolite Ltd., respectively. The physicochemical characteristics of these resins are summarized in Table 3. FPX66 and MN202 resins were activated by using sodium

bar] mw [L/hm<sup>2</sup>

COD TSS pH

Macroporous polystyrene cross-linked with divinylbenzene

/g

535 85 μm

d50, meso and macropores: 600–900 D50, micropores: 15

[g/L] Δ% [g/L] Δ% —

19.2 13.5 8.4 22.9 —

60–80% 50–60%

/g 825 m<sup>2</sup>

bar] Dp [nm] Pmax [bar]

brane treatment and obtaining the fraction of nanofiltration.

2.4 Characteristic and activation of FPX66 and MN202 resins

Stream Pretreatment of OMWW raw materials [18, 19, 22]

Characteristics of the membrane and the pretreatment of OMWW.

Matrix Macro-reticular aromatic

Surface area(2) ≥700 m<sup>2</sup>

Mean diameter Harmonic mean size

Physicochemical characteristics of the resins FPX 66 and MN202.

After centrifugation

Sorption in 2020s

Table 2.

Moisture holding capacity

Particle size • Uniformity coefficient(1) • Fine content(1) • Coarse beads(1)

Table 3.

86

Type Characteristic of membrane modules [18, 19, 22] Id mw [L/hm2

UF Osmonics model GM 16.3 4.8 2.0 16 NF Osmonics model DK 7.9 5.2 0.5 32 RO Osmonics model SC 2.7 2.6 < 0.1 65

Raww OMWW 32.4 — 33.0 — 5.2 After flocculation 22.2 31.5 10.9 66.9 3.1

After photocatalysis 16.5 14.1 5.2 38.1 —

Properties FPX66 MN202 Physical form White spherical beads White spherical beads

Shipping weight 680 g/L 655–685 g/L Specific gravity 1.015–1.025 1.04

Porosity(2) ≥1.4 cc/g 1–1.1 mL/g

0.600–0.750 mm

≤2.0 <0.300 mm:3.0% max >1.180 mm:5.0% max

polymer

chlorite and washing with distilled water and then filtrating with a Buchner filter connected to a vacuum pump system. The filtrated resins were put into the beakers that already contained distilled water and the resulting solution was then left at constant stirring (70 rpm) for an hour. At the end of this procedure, the quantities of dissolved salts were evaluated through a digital conductivity meter. Since the results were not satisfactory, the new filtrations were made and the stirs were repeated, again for 60 minutes.

The solutions were again measured at the end and the decreases in salt concentrations were revealed. Finally, the treated resins were put into others beaker containing 96% ethylic alcohol, and then the contents of the beakers were stirred (120 rpm) for an hour. After this procedure, the resins were filtrated and conserved in a distilled water environment ready for use.

#### 2.5 Column adsorption and desorption experiments

Lab-scale packed bed column experiments were carried out to evaluate the performance of the resin for the adsorption of phenolic compounds. In a typical procedure, the fixed-bed columns were made of Pyrex glass tubes of 1 or 2 cm inner diameter with 9.5 and 19.5 cm height respectively. The model column was packed with the adsorbent between glass wool and supported by inert glass beads as shown in Figure 3.

The column performance adsorption onto resin was studied at different phenol concentrations of 200, 400 and 600 mg/L, bed height 9.5 and 19.5 cm and flow rate between 0.8–4.0 mL/min. The bed diameters and depths took were 10.0 and 19.5 cm (resin mass of 5.07 g), 2.0 and 19.5 cm (resin mass of 41.6 g), respectively. The influent of phenol solution was pumped in an upward mode with a peristaltic pump in order to avoid channeling inside the column.

#### 2.5.1 Performance indicators in a fixed-bed column

The breakthrough curves showed the loading behaviour of phenol, tyrosol and hydroxytyrosol to be removed in a fixed bed. It is expressed in normalized concentration defined as the ratio of effluent solute concentration to inlet (feed) solute concentration (Cout/Cin), as a function of time or volume of effluent for a given bed height [23].

Effluent volume (Veff) can be calculated by the following relationship:

$$\mathbf{V}\_{\rm eff} = \mathbf{Q} \text{ t}\_{\rm total} \tag{1}$$

In respect to the breakthrough separation of phenol, tyrosol and HO-tyrosol in

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column…

A. Tyrosol solution with 100% purity is represented by Time (h) in which the outlet contains the only tyrosol since its breakpoint (B.T = Breakthrough time) as:

� � (9)

� � (10)

� � (12)

h i (13)

<sup>Q</sup> � kThCint (14)

<sup>100</sup>ð Þ¼ mL Q Timeð Þ 100% � Timeð Þ <sup>B</sup>:<sup>T</sup> � � (11)

ΔV100ð Þ¼ mL Q Timeð Þ 100% � Timeð Þ <sup>B</sup>:<sup>T</sup>

B. Tyrosol solution with 90% purity is represented by Time (h) in which the outlet contains the only tyrosol at 90% and phenol at 10% since its breakpoint

ΔV90ð Þ¼ mL Q Timeð Þ 90% � Timeð Þ <sup>B</sup>:<sup>T</sup>

C. In multi-component system OMWW NF concentrate, polyphenol solution with 100% purity (tyrosol and hydroxytyrosol) is represented by latest time (h) at which the outlet stream contains the target polyphenols of this study, that is tyrosol and hydroxytyrosol, at 100% purity towards phenol since their

D.Tyrosol+ Hydroxytyrosol solution with 90% purity is represented by Time (h) in which the outlet contains only tyrosol+ hydroxytyrosol at 90% and phenol

<sup>90</sup>ð Þ¼ mL Q Timeð Þ 90% � Timeð Þ <sup>B</sup>:<sup>T</sup>

The Thomas model is widely used in column performance modeling. Its derivation assumes Langmuir kinetics of adsorption–desorption and no axial dispersion. The expression for the Thomas model for adsorption column is given by [26]:

where kTh (mL/min/mg) a Thomas constant, qe (mg/g) the predicted adsorption capacity, m mass of adsorbent (g), Q influent flow rate (mL/min), Cin the initial concentration (mg/L), and Cout effluent concentration (mg/L). The linearization of

Yoon-Nelson model as other models did not require data about the characteristics

of the system such as well as the type of adsorbent and physical properties of

kThqeX Q

kThqeX

� � � kThCint

<sup>¼</sup> <sup>1</sup> 1 þ exp

at 10% since its breakpoint (B.T = Breakthrough time) as:

binary and in OMWW NF concentrate:

DOI: http://dx.doi.org/10.5772/intechopen.90087

(B.T = Breakthrough time) as:

breakpoint (B.T = Breakthrough time) as:

ΔV<sup>∗</sup>

ΔV<sup>∗</sup>

<sup>C</sup><sup>∗</sup> <sup>¼</sup> Cout Cin

the Thomas model was expressed in Eq. (14):

2.5.2.2 Yoon-Nelson (YN) model

adsorption bed.

89

TM <sup>¼</sup> ln <sup>C</sup><sup>∗</sup> ð Þ¼ � <sup>1</sup>

2.5.2 Breakthrough model studies

2.5.2.1 Thomas model

where Q and ttotal are the volumetric flow rate (mL/min) and the total flow time (min). The adsorption performance for a given bed mass is directly related to the number of bed volumes (BV) processed before the breakthrough point is reached [24]. The number of bed volumes treated before a breakthrough can be calculated as follows:

$$\text{BV} = \frac{\text{Volume of water treated at break through point (L)}}{\text{Volume of adsorption (L)}} \tag{2}$$

The rate for saturating the adsorbent during adsorption run was used to determine the regularity at which the adsorbent was replaced or regenerated. The adsorption exhaustion rate (AER), where low AER values imply the good performance of the bed was given by [23, 25] Eq. (3):

$$\text{AER} = \frac{\text{mass of adsorption } (\text{m}, (\text{g}))}{\text{Volume of water treated } (\text{L})} \tag{3}$$

The area under the breakthrough curve (A) calculated by integrating the plot of adsorbed concentration (Cad; mg/L) versus t (min) and used to find the total adsorbed phenol or tyrosol quantity (maximum column capacity). The total adsorbed phenol or tyrosol quantity (qtotal; mg) in the column for a given feed concentration and the flow rate was calculated as the following:

$$\mathbf{q}\_{\text{total}} = \frac{\mathbf{Q}\mathbf{A}}{1000} = \frac{\mathbf{Q}}{1000} \int\_{t=0}^{t=t\_{\text{total}}} \mathbf{c}\_{\text{ad}} \mathbf{d}t \tag{4}$$

The total amount of phenol or tyrosol in feed sent to column (mtotal; mg) is calculated by:

$$\mathbf{m}\_{\text{total}} = \frac{\mathbf{C}\_{\text{in}} \mathbf{Q}\_{\text{t}} \mathbf{t}\_{\text{total}}}{1000} \tag{5}$$

Equilibrium phenol/tyrosol uptake (qeq; mg/g) (or the maximum capacity of the column) in the column is defined as the total of solute adsorbed (qtotal) per g of adsorbent (X; g) at the end of total flow time, that is:

$$\mathbf{q}\_{\rm eq} = \frac{\mathbf{q}\_{\rm total}}{\mathbf{X}} \tag{6}$$

The column performance (Total removal percentage of solute) can be defined as the ratio of the total adsorbed quantity of phenol/tyrosol (qtotal) to the total amount sent to the column as follows:

$$\text{Column performance } (\%) = \frac{\mathbf{q}\_{\text{total}}}{\mathbf{m}\_{\text{total}}} \times \mathbf{100} \tag{7}$$

Unadsorbed phenol/tyrosol concentration at equilibrium in the column (Ceq; mg/L) can be defined by the following relationship:

$$\mathbf{C\_{eq}} = \frac{\mathbf{m\_{total}} - \mathbf{q\_{total}}}{\mathbf{V\_{eff}}} \times \mathbf{1000} \tag{8}$$

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column… DOI: http://dx.doi.org/10.5772/intechopen.90087

In respect to the breakthrough separation of phenol, tyrosol and HO-tyrosol in binary and in OMWW NF concentrate:

A. Tyrosol solution with 100% purity is represented by Time (h) in which the outlet contains the only tyrosol since its breakpoint (B.T = Breakthrough time) as:

$$
\Delta \mathbf{V}\_{100}(\mathbf{mL}) = \mathbf{Q} \left[ \mathbf{Time}\_{(100\%)} - \mathbf{Time}\_{(\mathbf{B.T})} \right] \tag{9}
$$

B. Tyrosol solution with 90% purity is represented by Time (h) in which the outlet contains the only tyrosol at 90% and phenol at 10% since its breakpoint (B.T = Breakthrough time) as:

$$
\Delta \mathbf{V}\_{90}(\mathbf{mL}) = \mathbf{Q} \left[ \mathbf{Time}\_{(9096)} - \mathbf{Time}\_{(\mathbf{B.T})} \right] \tag{10}
$$

C. In multi-component system OMWW NF concentrate, polyphenol solution with 100% purity (tyrosol and hydroxytyrosol) is represented by latest time (h) at which the outlet stream contains the target polyphenols of this study, that is tyrosol and hydroxytyrosol, at 100% purity towards phenol since their breakpoint (B.T = Breakthrough time) as:

$$
\Delta \mathbf{V}\_{100}^\*(\mathbf{mL}) \;= \mathbf{Q} \left[ \mathbf{Time}\_{(10096)} - \mathbf{Time}\_{(\mathbf{B.T})} \right] \tag{11}
$$

D.Tyrosol+ Hydroxytyrosol solution with 90% purity is represented by Time (h) in which the outlet contains only tyrosol+ hydroxytyrosol at 90% and phenol at 10% since its breakpoint (B.T = Breakthrough time) as:

$$
\Delta \mathbf{V}\_{90}^\*(\mathbf{mL}) = \mathbf{Q} \left[ \mathbf{Time}\_{(9096)} - \mathbf{Time}\_{(\mathbf{B.T})} \right] \tag{12}
$$

#### 2.5.2 Breakthrough model studies

#### 2.5.2.1 Thomas model

Effluent volume (Veff) can be calculated by the following relationship:

as follows:

Sorption in 2020s

calculated by:

88

sent to the column as follows:

where Q and ttotal are the volumetric flow rate (mL/min) and the total flow time (min). The adsorption performance for a given bed mass is directly related to the number of bed volumes (BV) processed before the breakthrough point is reached [24]. The number of bed volumes treated before a breakthrough can be calculated

BV <sup>¼</sup> Volume of water treated at breakthrough point Lð Þ

The rate for saturating the adsorbent during adsorption run was used to deter-

AER <sup>¼</sup> mass of adsorbent m, g ð Þ ð Þ

The area under the breakthrough curve (A) calculated by integrating the plot of

1000

<sup>t</sup><sup>¼</sup>ðttotal

t¼0

mine the regularity at which the adsorbent was replaced or regenerated. The adsorption exhaustion rate (AER), where low AER values imply the good perfor-

adsorbed concentration (Cad; mg/L) versus t (min) and used to find the total adsorbed phenol or tyrosol quantity (maximum column capacity). The total adsorbed phenol or tyrosol quantity (qtotal; mg) in the column for a given feed

<sup>1000</sup> <sup>¼</sup> <sup>Q</sup>

The total amount of phenol or tyrosol in feed sent to column (mtotal; mg) is

mtotal <sup>¼</sup> CinQ:ttotal

qeq <sup>¼</sup> qtotal

Column performance %ð Þ¼ qtotal

Ceq <sup>¼</sup> mtotal � qtotal Veff

The column performance (Total removal percentage of solute) can be defined as the ratio of the total adsorbed quantity of phenol/tyrosol (qtotal) to the total amount

Unadsorbed phenol/tyrosol concentration at equilibrium in the column (Ceq;

mtotal

Equilibrium phenol/tyrosol uptake (qeq; mg/g) (or the maximum capacity of the column) in the column is defined as the total of solute adsorbed (qtotal) per g of

concentration and the flow rate was calculated as the following:

qtotal <sup>¼</sup> QA

adsorbent (X; g) at the end of total flow time, that is:

mg/L) can be defined by the following relationship:

mance of the bed was given by [23, 25] Eq. (3):

Veff ¼ Q ttotal (1)

Volume of adsorbent Lð Þ (2)

Volume of water treated Lð Þ (3)

caddt (4)

<sup>1000</sup> (5)

<sup>X</sup> (6)

� 100 (7)

� 1000 (8)

The Thomas model is widely used in column performance modeling. Its derivation assumes Langmuir kinetics of adsorption–desorption and no axial dispersion. The expression for the Thomas model for adsorption column is given by [26]:

$$\mathbf{C}^\* = \frac{\mathbf{C}\_{\text{out}}}{\mathbf{C}\_{\text{in}}} = \frac{1}{\mathbf{1} + \exp\left[\left(\frac{k\_{\text{Th}}\mathbf{q}\_c\mathbf{X}}{\mathbf{Q}}\right) - \mathbf{k}\_{\text{Th}}\mathbf{C}\_{\text{in}}\mathbf{t}\right]}\tag{13}$$

where kTh (mL/min/mg) a Thomas constant, qe (mg/g) the predicted adsorption capacity, m mass of adsorbent (g), Q influent flow rate (mL/min), Cin the initial concentration (mg/L), and Cout effluent concentration (mg/L). The linearization of the Thomas model was expressed in Eq. (14):

$$\text{CTM} = \ln\left(\text{C}^\* - \mathbf{1}\right) = \frac{k\_{Th}q\_\epsilon \mathbf{X}}{Q} - k\_{Th}\mathbf{C}\_{in}\mathbf{t} \tag{14}$$

#### 2.5.2.2 Yoon-Nelson (YN) model

Yoon-Nelson model as other models did not require data about the characteristics of the system such as well as the type of adsorbent and physical properties of adsorption bed.

The YN was expressed as follows [27]:

$$\frac{\mathbf{C}\_{\text{out}}}{\mathbf{C}\_{\text{in}} - \mathbf{C}\_{\text{out}}} = \exp\left(k\_{\text{YN}}t - \tau k\_{\text{YN}}\right) \tag{15}$$

provided is the surface area of meso and macropores, and the volume of micropores. It enables the determination of the specific surface area of the micropores when coupled with the BET method. The accepted parameters for characterizing materials according to the diameter (d in nm) pores are: micropores (d < 2 nm);

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column…

The calculation method is based on the layout of the volume of gas adsorbed as a function of the thickness of the monomolecular film of the same gas. This diagram called thickness is subsequently used to evaluate quantitatively and qualitatively the porosity of the adsorbent. The film thickness is calculated by either equation

Pe <sup>þ</sup> <sup>0</sup>:034 !1=<sup>2</sup>

Pe <sup>þ</sup> <sup>0</sup>:034 !<sup>1</sup>=<sup>3</sup>

Micropores Volume ¼ ð Þ 0:001547 ∗ Y (22) Mesopores specific area ¼ 1547 ∗ α (23)

A ¼ BET specific area � Specific area of mesopores (24)

(20)

(21)

mesopores (2 < d < 50) macropores (50 < d < 7500) and megapores

<sup>t</sup> <sup>¼</sup> <sup>13</sup>:<sup>99</sup> log Po

2:303 ∗ log Po

By plotting the adsorbed volume according to the calculated thickness of the film, the intercept (Y) of this curve (t-plot) is converted to the volume of gas to liquid volume to provide micropores. The slope α of the linear section of the graph

The calculations also used to obtain the surface area A of the micropores as

The shapes of the curves and hysteresis provide information on the porosity of the material studied according to the classification proposed by isothermal [29] and modified by International Union of Pure and Applied Chemistry (IUPAC) [30].

The points of zero charge of FPX66 and MN202 resins were determined [31]. In

different flasks, 50 mL of NaNO3 0.1 mol/L was introduced and the pH of the solution was adjusted by using 1 mol/L NaOH or HCl to obtain a denoted pHi value between 2 and 12. One gram of activated resin was then introduced in each flasks, covered and allowed to rest for 48 hours during which they were manually stirred. At the end of the operation, the pH of the solution (pHf) was recorded. pHpzc were derived from the curve ΔpH = pHi � pHf = f (pHi) as the intercept of the abscissa

The determination of the recovery capacity by a mono-molecular layer of adsorbate (Vm) allows for the calculation of the specific surface. The number (Vm)

<sup>t</sup> <sup>¼</sup> <sup>3</sup>:<sup>54</sup> <sup>5</sup>

used to calculate the surface area of the mesopores and macropores. The

Halsey Eq. (20) that of Harkins and Jura Eq. (21) [28].

DOI: http://dx.doi.org/10.5772/intechopen.90087

corresponding formulas are given the following:

2.6.2 Determination of point of zero charge (PZC)

2.6.3 The specific surface area by the BET method

(7500 nm < d).

follows:

for resins.

91

where kYN (L/min) the rate constant and τ (min) the time required for 50% of adsorbate breakthrough. The linear form of YN model was expressed as follows:

$$\text{YN} = \ln \frac{\text{C}\_{out}}{\text{C}\_{in} - \text{C}\_{out}} = k\_{YN}t - \tau k\_{YN} \tag{16}$$

#### 2.5.2.3 Adams-Bohart (AB) model

Adams-Bohart model was based on the assumption that the rate of adsorption was proportional to the concentration of adsorbed species and the residual capacity of adsorbent. The AB model was used to describe the initial part of the breakthrough curve and expressed as [24]:

$$\mathbf{C}^\* = \frac{\mathbf{C}\_{\text{out}}}{\mathbf{C}\_{\text{in}}} = \exp\left(\mathbf{k}\_{\text{AB}}\mathbf{C}\_{\text{in}}\mathbf{t} - \mathbf{k}\_{\text{AB}}\mathbf{N}\_0 \frac{\mathbf{z}}{\mathbf{U}\_0}\right) \tag{17}$$

Where kAB (l/min.mg) is rate constant of Adams-Bohart model, z (cm) is the bed depth, N0 (mg/L) is maximum ion adsorption capacity per unit volume of the adsorbent column, and U0 (cm/min) is the linear velocity of influent solution. The linear form of Adams-Bohart model is expressed as follows:

$$\text{ABM} = \ln \text{C}^\* = k\_{AB}\text{C}\_{\text{in}}t - k\_{AB}N\_0 \frac{z}{U\_0} \tag{18}$$

#### 2.6 Characterization techniques

#### 2.6.1 Porosity and microporosity resins

#### 2.6.1.1 Mercury porosimetry

Penetration of a liquid in a capillary is related to the shape and dimensions of the capillary, and the surface tension of mercury and the pressure that is exerted on the latter. The relationship between the pressure and the pore radius in the case of a cylindrical pore is given by the following equation:

$$p.r = 2\gamma \cos \theta \tag{19}$$

where r: is the pore radius.

γ: mercury surface tension and equals to 480 mN.m�<sup>2</sup> . (Data Carlo Erba). θ: contact angle equal to 141.3 degrees (data Carlo Erba).

The measuring instrument used is the automatic mercury porosimetry 2000 Carlo Erba, it gives a distribution based pore volume and the cumulative volume per cent.

#### 2.6.1.2 Measurement of micropores by t-plot method (thickness plot)

This method is used to estimate the volume and the surface of the micropores, or to characterize the material from the point of view of their porosity. The data

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column… DOI: http://dx.doi.org/10.5772/intechopen.90087

provided is the surface area of meso and macropores, and the volume of micropores. It enables the determination of the specific surface area of the micropores when coupled with the BET method. The accepted parameters for characterizing materials according to the diameter (d in nm) pores are: micropores (d < 2 nm); mesopores (2 < d < 50) macropores (50 < d < 7500) and megapores (7500 nm < d).

The calculation method is based on the layout of the volume of gas adsorbed as a function of the thickness of the monomolecular film of the same gas. This diagram called thickness is subsequently used to evaluate quantitatively and qualitatively the porosity of the adsorbent. The film thickness is calculated by either equation Halsey Eq. (20) that of Harkins and Jura Eq. (21) [28].

$$t = \left(\frac{13.99}{\log\frac{P\_s}{P\_\epsilon} + 0.034}\right)^{1/2} \tag{20}$$

$$t = 3.54 \left( \frac{5}{2.303 \ast \log \frac{P\_o}{P\_\epsilon} + 0.034} \right)^{1/3} \tag{21}$$

By plotting the adsorbed volume according to the calculated thickness of the film, the intercept (Y) of this curve (t-plot) is converted to the volume of gas to liquid volume to provide micropores. The slope α of the linear section of the graph used to calculate the surface area of the mesopores and macropores. The corresponding formulas are given the following:

$$\text{Microprocess Volume} = (0.001547) \ast Y \tag{22}$$

$$\text{Mesopores specific area} = \mathbf{1547} \ast a \tag{23}$$

The calculations also used to obtain the surface area A of the micropores as follows:

$$A = \text{BET specific area} - \text{Specific area of mesopores} \tag{24}$$

The shapes of the curves and hysteresis provide information on the porosity of the material studied according to the classification proposed by isothermal [29] and modified by International Union of Pure and Applied Chemistry (IUPAC) [30].

#### 2.6.2 Determination of point of zero charge (PZC)

The points of zero charge of FPX66 and MN202 resins were determined [31]. In different flasks, 50 mL of NaNO3 0.1 mol/L was introduced and the pH of the solution was adjusted by using 1 mol/L NaOH or HCl to obtain a denoted pHi value between 2 and 12. One gram of activated resin was then introduced in each flasks, covered and allowed to rest for 48 hours during which they were manually stirred. At the end of the operation, the pH of the solution (pHf) was recorded. pHpzc were derived from the curve ΔpH = pHi � pHf = f (pHi) as the intercept of the abscissa for resins.

#### 2.6.3 The specific surface area by the BET method

The determination of the recovery capacity by a mono-molecular layer of adsorbate (Vm) allows for the calculation of the specific surface. The number (Vm)

The YN was expressed as follows [27]:

Sorption in 2020s

2.5.2.3 Adams-Bohart (AB) model

2.6 Characterization techniques

where r: is the pore radius.

per cent.

90

2.6.1.1 Mercury porosimetry

2.6.1 Porosity and microporosity resins

cylindrical pore is given by the following equation:

γ: mercury surface tension and equals to 480 mN.m�<sup>2</sup>

θ: contact angle equal to 141.3 degrees (data Carlo Erba).

2.6.1.2 Measurement of micropores by t-plot method (thickness plot)

breakthrough curve and expressed as [24]:

<sup>C</sup><sup>∗</sup> <sup>¼</sup> Cout Cin

linear form of Adams-Bohart model is expressed as follows:

Cout Cin � Cout

YN <sup>¼</sup> ln Cout

of adsorbent. The AB model was used to describe the initial part of the

where kYN (L/min) the rate constant and τ (min) the time required for 50% of adsorbate breakthrough. The linear form of YN model was expressed as follows:

Adams-Bohart model was based on the assumption that the rate of adsorption was proportional to the concentration of adsorbed species and the residual capacity

¼ exp kABCint � kABN0

Where kAB (l/min.mg) is rate constant of Adams-Bohart model, z (cm) is the bed depth, N0 (mg/L) is maximum ion adsorption capacity per unit volume of the adsorbent column, and U0 (cm/min) is the linear velocity of influent solution. The

ABM <sup>¼</sup> ln C<sup>∗</sup> <sup>¼</sup> kABCint � kABN<sup>0</sup>

Penetration of a liquid in a capillary is related to the shape and dimensions of the capillary, and the surface tension of mercury and the pressure that is exerted on the latter. The relationship between the pressure and the pore radius in the case of a

The measuring instrument used is the automatic mercury porosimetry 2000 Carlo Erba, it gives a distribution based pore volume and the cumulative volume

This method is used to estimate the volume and the surface of the micropores, or

to characterize the material from the point of view of their porosity. The data

Cin � Cout

¼ exp ð Þ kYNt � τkYN (15)

z U0

z U<sup>0</sup>

p:r ¼ 2γ cos θ (19)

. (Data Carlo Erba).

(17)

(18)

¼ kYNt � τkYN (16)

was calculated from the adsorption isotherm, mainly by the BET method depends on the surface, temperature and pressure (STP) and the form of the following linear transform:

$$A = \frac{P\_e}{V\_a(P\_o - P\_e)} = \frac{C - 1}{V\_m C} \frac{P\_e}{P\_o} + \frac{1}{V\_m C} \tag{25}$$

where Vm was the volume of a monolayer,

Va = volume adsorbed at a relative pressure Pe/Po;

Pe = sample equilibrium pressure,

Po = saturation vapor pressure of the gas to the temperature of the experiment, C = relative constant to the enthalpy of adsorption.

The route of A = f (Pe/Po) is a line of a slope (C � 1)/VmC, and intercepts origin at 1/VmC. In practice, this line was checked only in a limited area of relative pressure (0.05 < Pe/Po < 0.2) and in many cases, it is always C > > 1. The BET specific surface area (m<sup>2</sup> /g) was then determined from the following expression:

$$S\_{BET} = \frac{V\_m N A\_m}{M\_v} = V\_m A\_m N.10^{-20} \,\mathrm{(m^2/g)}\tag{26}$$

3. Fixed bed studies

Table 4.

Mediterranea sea column Serial number: NF-21905

3.2 Effect of the flow rate

flow rate [8, 34, 35].

93

3.3 Effect of bed height

3.1 Effect of initial phenol concentration

HPLC parameters for the determination of polyphenols.

DOI: http://dx.doi.org/10.5772/intechopen.90087

The sorption breakthrough curves obtained at inlet phenol concentrations of

Co = 0.03) occurred after 30 hours (3000 mL of effluent) i.e. 200 mg/L phenol inlet concentration. It appeared after 17 hours and 15,5 hours corresponding to 1700 mL and 1550 mL of inlet concentration of phenol 400 and 600 mg/L, respectively.

The effect on flow rate for the adsorption of phenol at flow rates 0.8; 2.0 and 4.0 mL/min at an influent concentration of 600 mg/L and bed height 19.5 cm displayed in Figure 5. It was clearly observed that a rapid uptake was noticed in the initial stages of adsorption and decreases thereafter and finally reaches saturation. The increase in flow rate, the breakthrough curves become steeper and reach the breakpoint quickly. This probe displayed a well-defined of the residence time of the solute in the column, which was not long enough for adsorption equilibrium to be reached at a high flow rate. So at the high flow rate, the phenol solution left the column before equilibrium occurs. Furthermore, a fixed saturation capacity of bed based on the same driving force gave rise to a shorter time for saturation at a higher

The breakthrough curves for the adsorption of phenol on macro-aromatic resin FPX66 at various bed heights by fixing the influent concentration at 600 mg/L and flow rate at 2 mL/min are given in Figure 5. The results indicated that the throughput volume of phenol solution increased with increasing bed height, due to the

A decreasing inlet concentration gave a later breakthrough curve as displayed in Figure 4. The treated volume was greatest at the lowest inlet concentration due to a lower concentration gradient caused a slower transport and the decreasing in diffusion coefficient or decreasing in mass transfer coefficient. The breakpoint time decreased with increasing inlet phenol concentration as the binding sites became more quickly saturated in the system. The breakthrough concentration (Ct/

200, 400 and 600 mg/L at 0.106 L/h flow rate are given in Figure 4.

Parameters Details

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column…

Pressure 150 bars Temperature 20°C Flow rate 1.0 mL/min

Injection volume 20 μL Wavelength 280 nm

Eluant Acetonitrile + acetic acid 0.5%

C18, thickness: 5μm, length 25 cm Diameter: 0.46 mm

where N = is Avogadro constant (6.02x10�23),

Mv = Molecular volume per gram (22,414 cm3 ),

Am = area occupied by each molecule of adsorbate (0.162 nm<sup>2</sup> for N2).

#### 2.6.4 Analysis of phenolic compounds by HPLC

High-pressure liquid chromatography (HPLC) is a technique to identify compounds within a sample by measuring the retention time through a separation column transported by a proper bulk stream. The use of high pressure permits to fasten the separation and obtain the results quicker. The measurement is done by a mass spectrometer at the exit of the separation column and is capable to measure a peak in terms of mAU, strictly connected to the concentration of the compound.

In this work, a C18 column was used. The bulk stream is composed of an aqueous solution of 1% of acetic acid. At the start of each experimental run and afterwards at regular time intervals, samples were withdrawn every 15 min, filtered through a cellulose acetate membrane filter (0.20 mm, Schleicher & Schuell) and analyzed. 25 μL of the sample was injected into the HPLC system. The temperature of the column was 20°C and the flow-rate was 1 mL/min. The mobile phase: 0.5% acetic acid volume ("A") and acetic nitrile ("B"). Elution was performed under conditions:


Polyphenols were detected by a UV detector (280 nm). Beforehand, the retention times of the polyphenolic compounds of interest were measured using single phenol, tyrosol and OH-tyrosol standard solutions ranging from a concentration of 100–600 mg/L. The chromatographic parameters, described in the following in Table 4 [32, 33].

The quantification was based on the size of the chromatogram peaks and achieving a standard range is developed for each of the standards polyphenols. Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column… DOI: http://dx.doi.org/10.5772/intechopen.90087


#### Table 4.

was calculated from the adsorption isotherm, mainly by the BET method depends on the surface, temperature and pressure (STP) and the form of the following linear

> <sup>¼</sup> <sup>C</sup> � <sup>1</sup> VmC

Po = saturation vapor pressure of the gas to the temperature of the experiment,

The route of A = f (Pe/Po) is a line of a slope (C � 1)/VmC, and intercepts origin

at 1/VmC. In practice, this line was checked only in a limited area of relative pressure (0.05 < Pe/Po < 0.2) and in many cases, it is always C > > 1. The BET

Am = area occupied by each molecule of adsorbate (0.162 nm<sup>2</sup> for N2).

High-pressure liquid chromatography (HPLC) is a technique to identify compounds within a sample by measuring the retention time through a separation column transported by a proper bulk stream. The use of high pressure permits to fasten the separation and obtain the results quicker. The measurement is done by a mass spectrometer at the exit of the separation column and is capable to measure a peak in terms of mAU, strictly connected to the concentration of the compound. In this work, a C18 column was used. The bulk stream is composed of an aqueous solution of 1% of acetic acid. At the start of each experimental run and afterwards at regular time intervals, samples were withdrawn every 15 min, filtered through a cellulose acetate membrane filter (0.20 mm, Schleicher & Schuell) and analyzed. 25 μL of the sample was injected into the HPLC system. The temperature of the column was 20°C and the flow-rate was 1 mL/min. The mobile phase: 0.5% acetic acid volume ("A") and acetic nitrile ("B"). Elution was performed under

Polyphenols were detected by a UV detector (280 nm). Beforehand, the retention times of the polyphenolic compounds of interest were measured using single phenol, tyrosol and OH-tyrosol standard solutions ranging from a concentration of 100–600 mg/L. The chromatographic parameters, described in the following in

The quantification was based on the size of the chromatogram peaks and achieving a standard range is developed for each of the standards polyphenols.

Pe Po þ 1

/g) was then determined from the following expression:

<sup>¼</sup> Vm:Am:N:10�<sup>20</sup> <sup>m</sup><sup>2</sup>

),

VmC (25)

=g (26)

<sup>A</sup> <sup>¼</sup> Pe

C = relative constant to the enthalpy of adsorption.

SBET <sup>¼</sup> Vm:N:Am Mv

where N = is Avogadro constant (6.02x10�23), Mv = Molecular volume per gram (22,414 cm3

• At the start of 2 min of the run with 100% of A.

• From 2 to 60 min 40% of A and 60% of B.

2.6.4 Analysis of phenolic compounds by HPLC

where Vm was the volume of a monolayer, Va = volume adsorbed at a relative pressure Pe/Po;

Pe = sample equilibrium pressure,

specific surface area (m<sup>2</sup>

conditions:

Table 4 [32, 33].

92

Vað Þ Po � Pe

transform:

Sorption in 2020s

HPLC parameters for the determination of polyphenols.
