éa 1 International Conference - PowerPoint Presentation

1. éa1International Conference on:Pollution Control & Sustainable Environment April 25-26, 2016 Dubai, UAEWater treatment containing organic compounds by coupling adsorption and electrochemical degradation at BDD anode: Sawdust adsorption performance for the treatment of dilute phenol solutionsInes Bouaziz KARIME, Morched HAMZA, Ahmed SELLAMI, Ridha Abdelhedi, André SAVALL, Karine GROENEN SerranO

2. 1Introduction-Context 2Materials and setups Experimental methods 4 Results and Discussion 5ConclusionContents32

3. TreatmentIntroduction-ContextMaterials andsetups Experimental methodsConclusion Results and Discussion3

4. Introduction-ContextMaterials andSetups Experimental methodsConclusion Results and Discussion4Phenolic compoundsOrigin :pharmaceutical, pesticides, oil, textiles, painting, dyes, plastic, detergent industries …Dangers: Highly toxic, highly oxygen demanding, Carcinogenic, mutagenic, and can cause a severe health hazard to human beings.

5. Biological methodsWaste water treatment processesIntroduction-ContexteDispositifExpérimental Démarche de l’étudeConclusion et perspectivesRésultats et discussionsPhenolic compounds are generally Non-biodegradable5Chemical methodsPhysical methodscost, secondary waste …Electrochemical methodsMain reagent : the electron - Complete oxidation (Mineralization) : possibleTransformation of organic pollutants into biodegradable products: possible

6. Introduction-ContexteDispositifExpérimental Démarche de l’étudeConclusion et perspectivesRésultats et discussions6Electrochemical methods Degradation of organic compounds(R) Anode materialChoice of the anode material: high oxygen overpotential overvoltage for different anode materials1 A m-2 in sulfuric acidAnode materialPt PbO2 SnO2 BDDOverpotential (V)0,270,500,671,27Competing Reactions: 

7. Introduction-ContexteDispositifExpérimental Démarche de l’étudeConclusion et perspectivesRésultats et discussions7Electrochemical methodsLow current efficiency for the treatment of dilute solutionsMass transfer limitations Not economically viableCoupling of electrochemical processes with a pre-concentration step is needed How?Adsorption- electochemical oxidation couplingObjective of the work

8. Materials and Setups Experimental methodsConclusion Results and DiscussionIntroduction8AdsorbentsCommercial activated carbonOrigin: woodParticles size: 0.4 mmSpecific area: 980 m2/gPHPZC= 8,9Red wood sawdustOrigin : Coniferous trees(by-product of furniture industry)Specific area: 0.4 m2/gParticles size: 0.5-1.12 mm

9. Materials and Setups Experimental methodsConclusion Results and DiscussionIntroduction9Model compound Phenol

10. 10 Démarche De l’étudeConclusion et perspectivesRésultats et discussionsDispositif ExpérimentalIntroduction-ContexteExperimental setupsBatch adsorption Column adsorption Electrochemical degradationConditions:Anode: boron doped diamond (BDD)Cathode: cylindrical mesh of platinumElectrolyte: Na2SO4

11. Conclusion Materials and SetupsIntroduction11 Experimental methodsResults and DiscussionAnalytical techniquesHigh Performance Liquid Chromatography (HPLC) Phenol and its oxidation intermediatesCharacterization of adsorbentsCyclic voltammetry Electrochemical behavior of the activated carbon paste Automated gas sorption system BET surface

12. Introduction Experimental methodsConclusion 12Materials andSetupsResults and DiscussionGeneral approach Kinetics study adsorption isothermsSaturation of adsorbents Study of the pollutants desorption without polarization Study of the pollutants desorption under polarization

13. Introduction Experimental methodsConclusion 13Materials andSetupsResults and DiscussionDesorption studiesQuantify the long term desorption without polarization.Simple desorptionLoaded adsorbentDosage of desorbed pollutantStirring In the case of sawdust : Solution used : Na2SO4(neutral pH)In the case of activated carbon: Solution used : Na2SO4+ NaOH (pH=13)!Multiple desorptionThe process was repeated 4 timesDesorption equilibrium StirringVolume of the solution for each step = 1/4 of the simple desorption volume

14. Introduction Experimental methodsConclusion 14Materials andSetupsResults and DiscussionElectrochemical degradation of phenolDesorption of the pollutantElectrochemical degradationElectrolysis conditions: Anode: BDD Cathode: cylindrical mesh of platinumElectrolyte: Na2SO4 (0,1M) of desired pH Desorption equilibrium

15. initial (C0) and final (Cf) concentrations of MBV :volume of solution M: weight of adsorbent Activated carbon Internal transport of phenol in the pores of activated carbon reduces the pollutant scavenging rate on the activated carbon adsorption sites. The rate of adsorption is much slower for the activated carbonIntroductionConclusion Experimental methodsAdsorption kinetics of phenol onto activated carbon and sawdust15Materials andSetupsResults and DiscussionActivated carbon0.10.20.30.40.5SawdustActivated carbon: equilibrium time=3 daysSawdust: equilibrium time=20 minPseudo-second order modelSawdustThe phenol adsorption follows a pseudo-second order kinetic for both adsorbents

16. IntroductionConclusion Experimental methodsAdsorption isotherms of phenol at 30°C16Materials andSetupsResults and DiscussionEquilibrium data are well represented by the Langmuir isotherm equation. Linearization of Langmuir equation Ce : equilibrium concentration of the adsorbate (mg/L) qe :adsorption capacity (mg g-1),qm : maximum adsorption capacity (mg g-1) KL : Langmuir isotherm constant (L mg-1).

17. IntroductionConclusion Experimental methodsAdsorption isotherms of phenol at 30°C17Materials andSetupsResults and DiscussionAdsorbentLangmuir constantsqm/S(mg/m2)qm (mg/g)KL (L/mg)Sawdust18,20,00345,5Activated carbon333,30,020,3qm of the activated carbon is the highestActivated carbon has the highest specific surface The sawdust is capable to adsorb a higher phenol weight per surface unit S= 980 m2/gS= 0.4 m2/g

18. IntroductionConclusion Experimental methods18Materials andSetupsResults and DiscussionPhenol desorptionActivated carbonDesorption kinetics of phenolSawdustpH of the solution: 13pH of the solution: neutral The desorption kinetics of the phenol is very fast.15 min5 minIn the case of sawdust: maximum desorption rate=38%Value relatively high : phenol is still in its undissociated formHypothesis: an important part of phenol retained on sawdust is rather weakly adsorbed In the case of activated carbon: maximum desorption rate =50%Activated carbonv----------Solution of pH 13pH˃pHPZCpH˃pKa +1The phenol retained by the activated carbon comes in two states: strongly adsorbed (chemisorption)and weakly adsorbed (physisorption)

19. IntroductionConclusion Experimental methodsMaterials andSetupsResults and DiscussionPhenol desorptionMultiple desorptionPhenol desorption during multiple desorption stepsThe % of the desorbed phenol does not exceed 60%A part of the phenol adsorption is rather chemical and irreversibleRe-adsorption of phenol on activated carbon obtained after multiple desorption E (%) = Adsorptive capacity of the activated carbon after multiple desorption Initial adsorption capacity of the fresh activated carbon * 100Regeneration efficiency : E = 73%E obtained (73%) is higher than expected (60%)Changes in the properties of activated carbon after contact with NaOH during the desorption stepsFragmentation of the activated carbon particles by stirring

20. IntroductionConclusion Experimental methodsMaterials andSetupsResults and DiscussionElectrochemical degradation of phenolOxydation of phenol on BDD anode at i=0.215 A/cm2The total disappearance of the phenol is achieved in the presence of adsorbentsElectrolysis time=0:Desorbed phenol in the solutionElectrolysis time =0:Desorbed phenol in the solutionThe rate of disappearance of phenol alone ˃ that in the presence of the adsorbentA part of the initially adsorbed phenol was desorbed during electrolysis. `The experiments of degradation of phenol was carried out in two steps: Simple desorption then Electrolyses with the presence of the adsorbent under galvanostatic conditions.

21. IntroductionConclusion Experimental methodsMaterials andSetupsResults and DiscussionElectrochemical degradation of phenolModeling of phenol degradation in the presence of sawdust k= 0.0252 m.min-1kdes= 0.0516 min-1

22. 22Adsorption/electrochemical regeneration cyclesElectrolysis conditions: i=0.215 A/cm2 electrolysis time=5 hoursPhenol/activated carbon coupleRegeneration efficiency= 59,5 %The remaining chemisorbed phenol is not affected by the electrochemical regenerationA possible electro-polymerization of the phenol at the boundary of the activated carbon grainsPhenol/sawdust coupleRegeneration efficiency˃ 100 % after four cyclesSawdust is more easily regenerated because of its surface properties unlike activated carbon Electrochemical treatment seems to activate sawdust by changing its physicochemical properties IntroductionMaterials andSetupsResults and Discussion Experimental methodsConclusion Regeneration efficiency ( Re)(1) Initial adsorption + (2) Electrochemical degradation + (3) Re-adsorptionAdsorption/Regeneration CyclesRepetition: (2) Electrochemical degradation + (3) Re-adsorption

23. IntroductionConclusion Experimental methodsMaterials andSetupsResults and DiscussionElectrochemical behavior study of activated carbon by cyclic voltammetryOxidation of phenol solution on a virgin activated carbon pasteE (mV/ESM) I (µA)CV of phenol in Na2SO4 (0.5M) 1st scan2nd scanThe oxidation pic of phenol disappears completely from the second cycle Electro-polymerization of phenol on the surface of activated carbon

24. IntroductionConclusion Experimental methodsMaterials andSetupsResults and DiscussionElectrochemical behavior study of activated carbon by cyclic voltammetryElectrolyte oxidation on an activated carbon (obtained after multiple desorption) paste electrode1st scanCV of electrolyte Na2SO4 (0,5M) I (µA)E (mV/ESM)The deactivation of the activated carbon could be associated to the electropolymerization of the phenol strongly retained by the activated carbon The oxidation pic of adsorbed phenol disappears completely during the following cyclesHypothesis confirmed: the electropolymerization of the strongly adsorbed phenol can explain the deterioration in performance of activated carbon by the obstruction of its pores during the electrolysis. The Search of other nonconductive adsorbentsSawdust

25. IntroductionConclusion 25 Experimental methodsMaterials andSetupsResults and DiscussionConclusionAdsorption study: Both adsorbents (activated carbon and sawdust) follow a Langmuir adsorption isotherm. The maximum adsorption capacity of the activated carbon is 18 times greater than the one obtained with sawdust.Desorption study: An important part of phenol retained on the activated carbon is rather irreversible. An important part of phenol retained on the sawdust is rather weakly adsorbed.

26. IntroductionConclusion 26 Experimental methodsMaterials andSetupsResults and DiscussionConclusionElectrochemical regeneration study: The regeneration efficiency of the activated carbon is only 59% after 1 cycle of adsorption and regeneration: The regeneration efficiency of sawdust is more than 100% at the end of the fourth adsorption-regeneration cycle: Low reversibility of the adsorption. Electropolymerization of the phenol on the surface of the activated carbon during anodic electrolysis Sawdust is easily regenerated because of its surface properties. Electrochemical treatment seems to activate sawdust by changing its physiochemical properties.

27. IntroductionConclusion 27Materials andSetups Experimental methodsResults and DiscussionPerspectivesUnderstanding the mechanism of sawdust activation. The application of this method on other types of organic pollutants.Studying the competition of several organic compounds which may be present in a real effluent on their abilities to be adsorbed, desorbed and oxidized.Development of a reactor (adsorption+regeneration):

28. PublicationsI. Bouaziz, C. Chiron, R. Abdelhedi, A. Savall, K. Groenen Serrano, Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration, Environ. Sci. Pollut. Res., 2014, 21, 8565-8572.I. Bouaziz, M. Hamza, R. Abdelhedi, A. Savall, K. Groenen Serrano, Treatment of diluted solutions of methylene blue by adsorption coupled with electrochemical regeneration: a comparative study of three adsorbents, ECS Trans., 2014, 59(1), 495-502.

29. Thank you 29