Dye removal by clays as nano-sorbent

Zehra DURMUS
Paper Review
April 6th, 2008
Course: ENVE 540, Advanced Experimental Te...
1

Presentation Content



Adsorption




( !!! not absorption )

sorbents and pollutants

Clay structure


structural...
2
a

dsorption

ads. is a process that occurs when a gas or liquid solute
accumulates on the surface of a solid or a liqui...
3

(Ad) Sorbents

 carboneous materials

(activated carbon, graphite etc.)

 silica gels
 clays / zeolites
 natural or...
4

Clay Structure



Mineralogy / Chemistry / Physics

 Alumino-silicate
 Various geometry


1D

layered

(smectites)
...
5

2:1 structured clays

(montmorillonite)

tetrahedral silicate sheet

octahedral alumina sheet

tetrahedral silicate she...
6

Clay stacks by electron microscopy
S.Y. Lee and S.J. Kim, Applied Clay Sci., 22 (2002) 55–63.

Zehra Durmus, April 06, ...
7

Clays as a cheap adsorbent



(in aqueous or organic media)

natural clays

 it is also possible to synthesize clay s...
8

Chemical modification of clay

Surface characteristics (hydrophilicity/organophilicity) of the clay
layers can be modif...
9

Pollutants

(in aqueous or organic media)

 toxic organics (halogenated compounds, phenol, toluene etc.)
 heavy metal...
10

Papers
P-1

impact factor (2006): 2.497

A brief review on adsorption properties of raw and modified clays and develop...
11

Papers
P-2

impact factor (2006): 2.180

A comprehensive review that cited 227 papers on the subject.
It concludes tha...
12
Compared maximum adsorption capacities (in mg/g) for Basic Blue-9 on several
low-cost sorbents and commercial activated...
13

E. Bulut, M. Özacar, I.A. Sengil, Microporous and Mesoporous Materials (in press) 2008.

key point

Very cheap
(almost...
14

Papers
P-3

impact factor (2006): 2.233

Zehra Durmus, April 06, 2008
15

Goal: investigation of adsorption kinetics and mechanism of
Acid Blue-193 onto Na-bentonite and organo-bentonite
Exp: ...
16

clay (bentonite) / organo-clay (DTMA-bentonite)
DTMA : dodecyltrimethyl ammonium bromide
long-chain quaternary ammoniu...
17
UV Analysis of dye solutions

Batch mixing of dye
solution with an adsorbent

(solid-liquid interaction)
Separation of ...
18

Effect of pH

Zehra Durmus, April 06, 2008
19

Effect of contact time

Na-bentonite

DTMA-bentonite

Zehra Durmus, April 06, 2008
20

Adsorption kinetics

(Langmuir model)

Ce : equilibrium dye concentration in solution (mg/l)
qe : equilibrium dye conc...
21

Adsorption kinetics

(Freundlich model)

Ce : equilibrium dye concentration in solution (mg/l)
qe : equilibrium dye co...
22
Langmuir plots for the adsorption of AB193 at various temperatures

not given in the paper

Zehra Durmus, April 06, 200...
23
Freundlich plots for the adsorption of AB193 at various temperatures

Na-bentonite

DTMA-bentonite

Zehra Durmus, April...
24

kinetic constants

Zehra Durmus, April 06, 2008
25

Activation energy of sorption (Ea)
Ea represents the minimum energy that reactants must have
for the reaction to proce...
26

Activation energy of sorption (Ea)

Zehra Durmus, April 06, 2008
27

Conclusions of the paper

The surface of natural clay is not a more effective adsorbent for
the removal of a hydrophob...
Thanks
Zehra Durmus
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Paper review on dye removing

  1. 1. Dye removal by clays as nano-sorbent Zehra DURMUS Paper Review April 6th, 2008 Course: ENVE 540, Advanced Experimental Techniques in Environmental Pollution Instructor: Dr. Omer ALAGHA Assist. Professor in Environmental Engineering Fatih University Institute of Science & Engineering Chemistry Program
  2. 2. 1 Presentation Content  Adsorption   ( !!! not absorption ) sorbents and pollutants Clay structure  structural, physical and chemical features  modifications  Dye removing  a paper on the subject  spectroscopic analysis  adsorption kinetics Zehra Durmus, April 06, 2008
  3. 3. 2 a dsorption ads. is a process that occurs when a gas or liquid solute accumulates on the surface of a solid or a liquid. !!! not to be confused with absorption that is a process in which atoms, molecules, or ions enter some bulk phase of gas, liquid or solid material. In abs., the molecules are taken up by the volume, not by surface. adsorbent / adsorbate / interaction weak interactions (<40 kJ/mol) Ξ physical adsorption (physisorption) strong interactions (>40 kJ/mol) Ξ chemical adsorption (chemisorption) Zehra Durmus, April 06, 2008
  4. 4. 3 (Ad) Sorbents  carboneous materials (activated carbon, graphite etc.)  silica gels  clays / zeolites  natural organic materials (e.g. rice husk, natural fibers, pine needles etc.)  functionalized polymers  biological materials (viruses, algae) Zehra Durmus, April 06, 2008
  5. 5. 4 Clay Structure  Mineralogy / Chemistry / Physics  Alumino-silicate  Various geometry  1D layered (smectites)  2D tubular (halloysite)  3D pore / cage (zeolites)  Very high surface area (~ 750 m2/g)  Highly hydrophilic  Very cheap as a natural material Zehra Durmus, April 06, 2008
  6. 6. 5 2:1 structured clays (montmorillonite) tetrahedral silicate sheet octahedral alumina sheet tetrahedral silicate sheet Zehra Durmus, April 06, 2008
  7. 7. 6 Clay stacks by electron microscopy S.Y. Lee and S.J. Kim, Applied Clay Sci., 22 (2002) 55–63. Zehra Durmus, April 06, 2008
  8. 8. 7 Clays as a cheap adsorbent  (in aqueous or organic media) natural clays  it is also possible to synthesize clay structure by molecular tailoring (synthetic clays, not interested in here)  adsorption properties is highly depended on structure, surface character and particle size Zehra Durmus, April 06, 2008
  9. 9. 8 Chemical modification of clay Surface characteristics (hydrophilicity/organophilicity) of the clay layers can be modified physically or chemical grafting of  ionic groups  acids (activated clay)  monomers / polymers / copolymers Applied Clay Science, 31 (2006) 262-271. Zehra Durmus, April 06, 2008
  10. 10. 9 Pollutants (in aqueous or organic media)  toxic organics (halogenated compounds, phenol, toluene etc.)  heavy metals (Pb, Cd, Hg etc.)  dyes (cationic, anionic, non-ionic, reactive etc.)  radioactive materials (uranium, radium, cesium etc.)  humic substances  agricultural chemicals  biological contaminants Zehra Durmus, April 06, 2008
  11. 11. 10 Papers P-1 impact factor (2006): 2.497 A brief review on adsorption properties of raw and modified clays and development perpectives for dye removal from aqueous solutions. Zehra Durmus, April 06, 2008
  12. 12. 11 Papers P-2 impact factor (2006): 2.180 A comprehensive review that cited 227 papers on the subject. It concludes that chitosan might be a promising adsorbent for environmental and purification purposes. Zehra Durmus, April 06, 2008
  13. 13. 12 Compared maximum adsorption capacities (in mg/g) for Basic Blue-9 on several low-cost sorbents and commercial activated carbon (CAC). G. Crini, Bioresource Technology, 97 (2006) 1061–1085 Zehra Durmus, April 06, 2008
  14. 14. 13 E. Bulut, M. Özacar, I.A. Sengil, Microporous and Mesoporous Materials (in press) 2008. key point Very cheap (almost free) but low capacity Zehra Durmus, April 06, 2008
  15. 15. 14 Papers P-3 impact factor (2006): 2.233 Zehra Durmus, April 06, 2008
  16. 16. 15 Goal: investigation of adsorption kinetics and mechanism of Acid Blue-193 onto Na-bentonite and organo-bentonite Exp: Synthetic textile dye AB193 (Isolan Dark Blue 2-SGL) Parameters 1- clay structure 2- effect of pH 3- effect of contact time 4- Activation Energy (Ea) of sorption UV-Spectrophotometric Analysis with 50 ml aqueous solution of 250 ppm dye solution (λmax = 609 nm) (SHIMADZU UV-01) Zehra Durmus, April 06, 2008
  17. 17. 16 clay (bentonite) / organo-clay (DTMA-bentonite) DTMA : dodecyltrimethyl ammonium bromide long-chain quaternary ammonium salt (cationic surfactant) simple ion exchange Applied Clay Science, 28 (2005) 43– 54 Zehra Durmus, April 06, 2008
  18. 18. 17 UV Analysis of dye solutions Batch mixing of dye solution with an adsorbent (solid-liquid interaction) Separation of two phases if needed (filtration or centrifuge) UV Analysis of supernatant to monitor changing in dye concentration Y. Iida, T. Kozuka, T. Tuziuti, K. Yasui, Ultrasonics 42 (2004) 635–639. Zehra Durmus, April 06, 2008
  19. 19. 18 Effect of pH Zehra Durmus, April 06, 2008
  20. 20. 19 Effect of contact time Na-bentonite DTMA-bentonite Zehra Durmus, April 06, 2008
  21. 21. 20 Adsorption kinetics (Langmuir model) Ce : equilibrium dye concentration in solution (mg/l) qe : equilibrium dye concentration on adsorbent (mg/g) qmax: monolayer capacity of adsorbent (mg/g) KL : Langmuir adsorption constant (liter/mg) A plot of Ce/qe vs Ce gives a straight line slope: 1/qmax intercept: 1/qmax KL The Langmuir equation is applicable to homogeneous sorption, where the sorption of each sorbate molecule onto the surface has equal sorption activation energy Zehra Durmus, April 06, 2008
  22. 22. 21 Adsorption kinetics (Freundlich model) Ce : equilibrium dye concentration in solution (mg/l) qe : equilibrium dye concentration on adsorbent (mg/g) n, KF : Freundlich constants (l/g) A plot of ln qe vs ln Ce gives a straight line slope: 1/n intercept: KF The Freundlich equation is employed to describe heterogeneous systems and reversible adsorption and is not restricted to the formation of monolayers Zehra Durmus, April 06, 2008
  23. 23. 22 Langmuir plots for the adsorption of AB193 at various temperatures not given in the paper Zehra Durmus, April 06, 2008
  24. 24. 23 Freundlich plots for the adsorption of AB193 at various temperatures Na-bentonite DTMA-bentonite Zehra Durmus, April 06, 2008
  25. 25. 24 kinetic constants Zehra Durmus, April 06, 2008
  26. 26. 25 Activation energy of sorption (Ea) Ea represents the minimum energy that reactants must have for the reaction to proceed k : rate constant A : Arrhenius factor R : universal gas constant (8.314 J/mol K) T : solution temperature (K) Physisorption : Ea = 5–40 kJ/mol Chemisorption : Ea = 40–800 kJ/mol Zehra Durmus, April 06, 2008
  27. 27. 26 Activation energy of sorption (Ea) Zehra Durmus, April 06, 2008
  28. 28. 27 Conclusions of the paper The surface of natural clay is not a more effective adsorbent for the removal of a hydrophobic dye from aqueous solution due to electrically charged and hydrophilic character of the clay surfaces Modification of clay layers with organic cations significantly improves the adsorption capacity of clay for the dye Interestingly, the natural clay showed lower potential barrier (Ea: 12.6 kJ/mol) than the modified clay (Ea: 22.4 kJ/mol) !!! There is no conclusion about this issue in the paper Zehra Durmus, April 06, 2008
  29. 29. Thanks Zehra Durmus

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