RECOVERY,CONCENTRATION AND PURIFICATION OF PHENOLIC COMPOUNDS BY ADSORPTION

1. RECOVERY,CONCENTRATION AND PURIFICATION OF PHENOLICCOMPOUNDS BY ADSORPTION Diego Alonso Martínez Filip Ambroz Javier Marqués de Marino

2. Substances who contains phenol  are very dangerous to the environment at high concentration, so therefore there are very unwanted things in nature. They are not harm in low concentrations like 0,002 mg/L, but higher conc. can cause unpleasant taste in drinking water, they can even adsorbed through the skin.  They are also very useful, we use them in medicine, for example as disinfectants or medical preparations, they have chemopreventive properties too, so they can be useful in treatments of cancer.

3. TECHNOLOGIES Like we heard before, phenols are not environmental friendly so therefore we need some technologies  to sustained water quality. We divide these techn. to three groups. biological, chemical and physically operations. • In physically operations we have: sedimentation, flotation, filtration, flow equalization… • In chemically operations there are: adsorption, disinfection, dechlorination… • In biological operations: trickling filters, pond stabilization, anaerobic digestion, biological nutrient removal… The most widely used treatment is biological because is the most cheapest, here is very  important fact that bacteria is able to accumulate and degrade different pollutants but, these treatment is incapable to remove phenol from process. This is a big problem so therefore we have to use also chemical techniques which remove phenols, but these techniques are very expensive. They are so expensive because we need a lot of electrical energy for them and also we need a lot of chemical reagent.  We have also some alternatives like oxidation processes but this is still very costly. We have also physical techniques, which are widely used but here we also have a problem. In this technique we have membrane processes but this processes don’t have a long lifetime so we have to change them a lot of times and this is costly. Because of all this things adsorption is the most popular method for removal pollutants.

4. ADSORPTION Is also very efficient. Here we use activated carbon for adsorbent, because it has very good adsorption properties for organic pollutants. Activated carbon has high-surface area, pore volume and porosity. But here we again have an economic problem. Activated carbon has high cost for an expensive regeneration system. In adsorption there is also important ionic strength and pH.  At acid pH the uptake of phenolics is enhanced, but alkaline pH  decreases adsorption. In adsorption is very important also the temperature, if we have high temperature then we have irreversible interactions, which favores adsorption.

5. Adsorption is also very important for practical operations, because of the interactions of adsorbate-adsorbent. Here we have Langmuir isotherm, this isotherm is wifely used equation. We use it when we have uniform adsorption energies at the adsorbent surface. When we have nonideal system we use the Freundlich isotherm. This isotherm is also very important, because it gives good interpretation of concentration range.

6. EQUATIONS Freundlich equation: ln(q)= ln(Kf) + 1/nCe Langmuir equation: Ce/Qe=1/Kl +(b/Kl) Ce Dubinin-Radushkevic equation: E= R T e*(1/Ce) These equation is very important, because information was obtained from the adsorbtion experience with p-CP and p-NP.  We use connection between Freundlich and Dubinin-Radushkevic to interpret the result. Another important thing is Lewis acid-base theory, which modified clays including metal cations can be considered as Lewis acids, while phenolic compounds can be regarded as Lewis bases and Bronsted acids.  Her is very tough to predict adsorption capacity, because it depends on the adsorbent property, the solution conditions and the interactions at the solid-liquid interface.  We get majority informations from the experiments of adsorption.

7. Here we have also reversible and irreversible adsorption.  Reversible adsorption we have, when we have physical adsorption, because here are important van der Waals forces, which are very weak so this thing has affect on the adsorption.  If we have chemisorptions and oxidative polymerization of phenolics we have irreversible adsorption. Imoportant method to control adsorption is electrosorption. Here we have electrostatic field, which is applied to the surface of the electrodes and it is immersed in an electrolyte solution.

8. ActivatedCarbon

9. Wastematerialsby-products • Coal • Coal-iron -nitricacid • Mechanims control • Low-costwastematerials

10. Ozonation of activatedcarbons

11. Description: phenoliccompounds • Hightoxicityforhumanbeings and aquaticlife. Biologicaltreatmentnotallowed. • Activatedcarbons (GAC) adsorbphenols. • Ozone treatments: usedtofix SOG.

12. Whatis SOG? • SOG referstoSurfaceOxygenGroupsonthe GAC. • Improvementonthephenoladsorption: - Bonds betweencarbonylgroups and OH groups of phenols. • Ozone produce SOG onthe GAC surface.

13. Experimentation • Twodifferent GAC (F400, AQ40) at twotemperatures (25 and 100 ºC). • Fourexperimentswithozonation, fourwithoutit. • Compounds : phenol (P), chlorophenol (PCP) and nitrophenol (PNP).

14. RESULTS AFTER OZONATION • Enlarging of micropores: gasification. • Microporosityblockage: SOG fixed. • Temperature as animportant factor: - 25ºC: only C=0 SOG. - 100ºC : differentkinds of SOG.

15. Conclusions • Adsorption of P, PNP and PCP dependson: - Chemistry of adsorbates. - Porosity and surface of adsorbent. - Temperature • Ozonationdecreasetheadsorptioncapacity: - Create more bondswithwater. - This blocks theaccessforthephenols.

16. CarbonNanotubes • Materials • Results • diameter • Effects • Aromaticy • -OH • hydrogenbonds

17. Polymericadsorbents

18. Comparison GAC- Polymeric • GAC capacityishigherthanthepolymericone : itshydrophobicsurface produces lowcontactwithaqueoussolutions. • 1990: “HypercrosslinkingTechnique”: - More easilywetted. - Higheradsorption

19. Experiment • Tworesins: - XAD-4: polystyrene-based. - NJ-8: hypercrossed. • Fouradsorbates: - Phenol -P-chlorophenol. - P-cresol -P-nitrophenol.

20. Elaboration of NJ-8 • Foursteps: 1. Synthesis of macroporouspolymer. 2. Chlorometylation. 3. Crosslinking. 4. Filtration and drying.

21. RESULTS • Adsorptioncapacity - Two times higherfor NJ-8 thanfor XAD-4. • Physicaladsorptionin alltheexperiments. - Negativevalues of isostericenthalpies. • NJ8 doesnottrapphenolmolecules - Theamount of desorbantremainsconstant.

22. Natural Materials

23. Clay • Classes • Price • Physicalproperties • Improvements • Clarion vs vlinoptylolite

24. Ciliceous, Zeolite & Biadsorbents • Ciliceous • Physicsproperties • Improvements • Zeolite • Physicsproperties • Improvements • Biadsorbents • Physicsproperties • improvements

25. Peat & biomass • Peat • Limitations • Pre-treatments • Biomass • Affinitywithmicrobialspecies • WorkingSpecificsconditions

26. Wastesmaterials • Agricultural • Sawdust • Bark • Industrial • Flyash • Sludge • Red mud

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28. Bibliography • (4) Maria Luisa Soto, AndresMoure, Herminia Dominguez, Juan Carlos Parajó. «journal of foodengineering.» 5 de febrero de 2011. www.elsevier.com/locate/jfoodeng (último acceso: 5 de 10 de 2011). • (5) Mehmet Akçay, GültenAkçay. «journal of hazardousmaterials.» 21 de agosto de 2004. www.elservier.com/locate/jhazmat (último acceso: 5 de 10 de 2011). • (6) P.M.alvarez, J.F.Garcia-Araya, F.J.Beltran, F.J.Masa, F.Medina. «journal of colloidand interface science.» 16 de diciembre de 2004. www.elsevier.com/locate/jcis(último acceso: 5 de 10 de 2011).