3.4.1 Thomas model

The adsorption data were applied to the Thomas model and the results are presented in Table 5.

Table 5 shows that the Thomas constant (kTh) as the equilibrium capacity q0(Th) increases with the increase of the phenol concentration, the bed height increases with the decrease of the flow rate. A negligible difference was observed between experimental and calculated values of the bed capacity q0(Th) obtained at all inlet phenol concentrations studied although the deviations of experimental data from predicted values were evident at 2.0 and 4.0 mL/min flow rates. Thomas model gives a good correlation with the experimental data at flow rates, bed heights for all

inlet phenol concentrations. Thomas model is suitable for adsorption processes where the external and internal diffusions will not be the limiting step [34, 36].

Parameters Experimental conditions

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

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Thomas parameters at different conditions using linear regression analysis

Yoon-Nelson parameters at different conditions using linear regression analysis

Thomas and Yoon-Nelson kinetic model for phenol onto FPX66 in a fixed bed.

Feed stock C0 (mg/L) 200 400 600 400 400 400 Flow rate Q (mL/min) 2.0 2.0 2.0 4.0 2.0 2.0 Bed height Z (cm) 19.5 19.5 19.5 19.5 9.5 14.5 Mass of sorbent X (g) 41.6 41.6 41.6 41.6 20.8 30.9 Mass sorbate X (mg) 1372.84 1740.50 2204 1603.90 814.23 1336.92 q0 (exp) (mg/g) 31.40 41.84 52.98 48.55 39.15 40.26

kT (mL/min/mg) <sup>10</sup><sup>5</sup> 2.08 2.13 3.21 3.12 2.7 2.43 q0 (Th) (mg/g) 32.48 42.44 51.34 48.35 40.16 43.14 R2 0.984 0.910 0.961 0.915 0.914 0.918 Sd 0.18 0.10 0.27 0.03 0.16 0.48

q0 (YN) (mg/g) 29.64 36.15 41.26 48.30 48.61 37.64 <sup>K</sup> (YN) (L/min) <sup>10</sup><sup>2</sup> 1.12 1.14 1.93 1.25 1.07 0.85 τ (min) 3082 1879 1430 1256 1264 1454 R<sup>2</sup> 0.959 0.918 0.961 0.15 0.914 0.966 Sd 0.29 0.94 1.95 0.04 1.57 0.43

Table 5 showed the rate of constant kYN of Yoon-Nelson increased with increasing phenol concentration. This was due to the fact that the increase in initial phenol from 200 to 600 mg/L. This displayed an increase in the competition between phenol molecules for the adsorption sites, which ultimately results in increased uptake rate. The rate constant increased with increasing the flow rate and decreased with an increase in bed height. At high flow rate, the number of phenol molecules passing through an adsorbent was more which increased the rate. The time required for 50% breakthrough τ decreases with increasing as the phenol

The adsorption capacities calculated based on Thomas and Yoon-Nelson models are in good agreement with the observed value with high R2 values and very low error analysis (0.03 ≤ Sd ≤ 1.95). Both models describe the behaviour of phenol onto FPX66 resin column. The obtained results are in agreement with other authors

In order to determine the adsorption effectiveness in a more complex and realistic scenario, the FPX66 resin in fixed mode was exposed to an OMWW NF concentrated containing all polyphenols from the membrane of nanofiltration plant selected for this work [21, 22, 38]. The influent flow rate was kept at a constant flow

3.4.2 Yoon-Nelson model

Table 5.

[34, 36, 37].

95

concentration, flow rate and bed height.

3.4.3 Adsorption of OMWW NF concentrate by FPX66 resin

Figure 4. Throughput volume and breakthrough for phenol at inlet concentrations.

Figure 5. Effect of bed height (a) and flow rate (b) for the removal of phenol on FPX66 column.


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

#### Table 5.

availability of more sorption sites due to the increase in the total surface for adsorption [34]. The equilibrium capacity decreases with the increase of the bed height. In a fixed bed method the probability of contact between the adsorbate and the adsorbent is less when compared to the batch mode, which results in lesser

The adsorption data were applied to the Thomas model and the results are

Table 5 shows that the Thomas constant (kTh) as the equilibrium capacity q0(Th) increases with the increase of the phenol concentration, the bed height increases with the decrease of the flow rate. A negligible difference was observed between experimental and calculated values of the bed capacity q0(Th) obtained at all inlet phenol concentrations studied although the deviations of experimental data from predicted values were evident at 2.0 and 4.0 mL/min flow rates. Thomas model gives a good correlation with the experimental data at flow rates, bed heights for all

equilibrium sorption capacity in column mode.

3.4 Dynamic adsorption models

3.4.1 Thomas model

Sorption in 2020s

presented in Table 5.

Figure 5.

94

Figure 4.

Effect of bed height (a) and flow rate (b) for the removal of phenol on FPX66 column.

Throughput volume and breakthrough for phenol at inlet concentrations.

Thomas and Yoon-Nelson kinetic model for phenol onto FPX66 in a fixed bed.

inlet phenol concentrations. Thomas model is suitable for adsorption processes where the external and internal diffusions will not be the limiting step [34, 36].

### 3.4.2 Yoon-Nelson model

Table 5 showed the rate of constant kYN of Yoon-Nelson increased with increasing phenol concentration. This was due to the fact that the increase in initial phenol from 200 to 600 mg/L. This displayed an increase in the competition between phenol molecules for the adsorption sites, which ultimately results in increased uptake rate. The rate constant increased with increasing the flow rate and decreased with an increase in bed height. At high flow rate, the number of phenol molecules passing through an adsorbent was more which increased the rate. The time required for 50% breakthrough τ decreases with increasing as the phenol concentration, flow rate and bed height.

The adsorption capacities calculated based on Thomas and Yoon-Nelson models are in good agreement with the observed value with high R2 values and very low error analysis (0.03 ≤ Sd ≤ 1.95). Both models describe the behaviour of phenol onto FPX66 resin column. The obtained results are in agreement with other authors [34, 36, 37].

#### 3.4.3 Adsorption of OMWW NF concentrate by FPX66 resin

In order to determine the adsorption effectiveness in a more complex and realistic scenario, the FPX66 resin in fixed mode was exposed to an OMWW NF concentrated containing all polyphenols from the membrane of nanofiltration plant selected for this work [21, 22, 38]. The influent flow rate was kept at a constant flow rate of 2 mL/min whereas the bed height, the diameter of the column and resin particle size were Z = 3.8 cm, D = 4 cm, 0.600 ≤ d ≤ 0.750 mm) at ambient temperature, respectively.

A considerable reduction in breakthrough time was observed for tyrosol i.e. 12; 11.5 and 6.5 hours respectively in single, binary and multiple component systems. Although the increase of breakthrough time was observed for the phenol during 17; 18 and 22.5 hours respectively proved that the selectivity was observed for phenol than other polyphenols by the FPX66 resin.

This could be attributed to competition between adsorbates for the same sites and adsorbates include benzoic acids and its derivatives (gentisic, vanillic, gallic, syringic acids), cinnamic acids and derivatives such as caffeic, ferulic, sinapic acids, and phenolic alcohols, secoiridoides aglycones (oleuropein, ligstroside), flavonols, flavones and fignans etc. coexisting frequently in OMWW (Figure 6) and more in NF concentrate [18, 39, 40]. The macro-reticular aromatic resin pore adsorption sites could be blocked by the polyphenol molecules.

The overall outlet capacities estimated for the tyrosol and the hydroxytyrosol were only slightly enhanced plausibly indicating a combination of pore blockage and unique interactions with the FPX66 surface. Phenol (pKa = 9.95) has a net neutral charge, so that means binding onto FPX66 is probably to be attributed to several types of molecular interactions, including hydrophobic interaction, hydrogen bonding, ionic attraction and complex formation [41]. Azonova and Hradil [42] found that hydrophobic interaction was the binding mechanism for adsorption by the hypercrosslinked Amberlite XAD-4. In addition, Maity et al. [43] showed that the degrees of adsorption for phenols, alcohols and aromatic amines increased with the strength of the hydrogen bond between the organic chemicals and the resin. Juang and Shiau [44] found that adsorption of phenol and chlorophenol by the macroporous Amberlite XAD resins was affected by the resin's hydrophobicity, the number of active sites and pore size distribution. By comparing the adsorption of five organic chemicals, Weber and Van Vliet [45] concluded that hydrophobic interaction played a key role in the adsorption of macroporous Amberlite XAD resins. In addition, the swelling of resin-like, in this case, increases the volume of the polymer phase and, thus, the absorption capacities of organic chemicals and it is

probably affected by hydrogen bonding of polar organic chemicals and the

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

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

After the dynamic adsorption experiments, a 50% (v/v) EtOH solution at a flow rate of 0.1 L/h was used to purge the resin column. Desorption results are displayed in Figure 7 for different inlet phenol concentrations of 200, 400 and 600 mg/L. About 3.0; 5.0 and 6.0-bed volumes of 50% (v/v) EtOH aqueous solution were used to regenerate the FPX66 resin column, for initial phenol concentrations of 200, 400 and 600 mg/L respectively. The desorption capacities of phenol from FPX66 resin were calculated to be 31.86, 37.06 and 48.00 mg/g at initial phenol concentrations of 200, 400 and 600 mg/L, respectively, which agrees well with the dynamic adsorption capacities of phenol with three inlet columns. This is also in agreement with the

The study, we can conclude that FPX66 resin is an effective adsorbent for

pseudo-second-order model with a maximum capacity of 28.44 mg/g and obeyed the intra-particle diffusion with high R<sup>2</sup> (>0.999). Higher desorption efficiency was obtained after 20 min of shaking time and the percentage of desorption decreased

From batch investigations, the effect of contact time for phenol removal by the FPX66 resin showed rapid adsorption of phenol in the first 30 min. The equilibrium data were fitted by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich iso-

. The adsorption kinetics followed the

macroporous resins, such as Amberlite XAD-8 [43].

Dynamic desorption curves of phenol concentrations on FPX66 resin.

3.5 Dynamic adsorption/desorption

results obtained by Li et al. [46].

phenol removal from aqueous solutions.

therms with good correlation coefficient R2

with the increase in the initial concentration of phenol.

4. Conclusions

97

Figure 7.

Figure 6. Profile of the phenolic compounds identified in nanofiltration fraction of OMWW.

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

Figure 7. Dynamic desorption curves of phenol concentrations on FPX66 resin.

probably affected by hydrogen bonding of polar organic chemicals and the macroporous resins, such as Amberlite XAD-8 [43].

### 3.5 Dynamic adsorption/desorption

After the dynamic adsorption experiments, a 50% (v/v) EtOH solution at a flow rate of 0.1 L/h was used to purge the resin column. Desorption results are displayed in Figure 7 for different inlet phenol concentrations of 200, 400 and 600 mg/L. About 3.0; 5.0 and 6.0-bed volumes of 50% (v/v) EtOH aqueous solution were used to regenerate the FPX66 resin column, for initial phenol concentrations of 200, 400 and 600 mg/L respectively. The desorption capacities of phenol from FPX66 resin were calculated to be 31.86, 37.06 and 48.00 mg/g at initial phenol concentrations of 200, 400 and 600 mg/L, respectively, which agrees well with the dynamic adsorption capacities of phenol with three inlet columns. This is also in agreement with the results obtained by Li et al. [46].
