4. Conclusions

The study, we can conclude that FPX66 resin is an effective adsorbent for phenol removal from aqueous solutions.

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 isotherms with good correlation coefficient R2 . The adsorption kinetics followed the 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 with the increase in the initial concentration of phenol.

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

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

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

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

temperature, respectively.

Sorption in 2020s

Figure 6.

96

than other polyphenols by the FPX66 resin.

sites could be blocked by the polyphenol molecules.

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

From the fixed bed investigations, as the flow rate increased, the breakthrough curve became steeper. The breakpoint time was obtained earlier at a high flow rate and effluent phenol concentration ratio increased more rapidly. For lower bed height, the effluent phenol concentration ratio increased more rapidly than for higher bed height. For larger initial phenol concentration, steeper breakthrough curves were obtained and breakpoint time was achieved sooner. The column experimental data were fitted well to the Thomas and Yoon-Nelson models. Coming to the end, we can draw a conclusion that, the use of resin column could be completely regenerated by a 50% (v/v) ethanol aqueous solution.

BV bed volumes (mL)

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

<sup>C</sup>\* normalized concentration ()

Co initial concentration (mg/L) Ct effluent concentration (mg/L) D desorption ratio of the resin (%) kTh Thomas rate constant (L/min/mg) kYN Yoon-Nelson rate constant (1/min) m initial mass of resin in batch mode (g)

(mg) Q volumetric flow rate (mL/min)

t, ttotal time and total flow time (min)

Vd volume of desorption solution (L)

X amount of adsorbent in the column (g)

ρ<sup>a</sup> density of the adsorbent material (g/L)

the fixed bed (cm)

R gas constant (J/mol/K)

Veff effluent volume (mL)

ε void fraction in the bed ()

T temperature (K) V volume of solution (L)

99

Cad (Cad = Co Ct) adsorbed phenol concentration (mg/L)

C constant that gives an idea about the thickness of the boundary layer (mg/g)

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

mtotal total amount of phenol in the feeding sent to the column

qo(cal) adsorption capacity calculated using three models (mg/g) qt, qe amounts of adsorbed at time t and at equilibrium (mg/g)

R2 determination coefficient associated with data fitting ()

Z bed height column or upward vertical axial distance inside

τ time required for 50% of adsorbate breakthrough (min)

q0(Th) maximum Thomas adsorption capacity (mg/g)

Cd concentration in the desorption solution (mg/L) Ce equilibrium concentration of phenol (mg/L) Cmax highest initial concentration in solution (mg/L)
