Synthesis and Characterization of Mesoporous Carbon Hybrids for Environmental Applications

Transcription

1 Synthesis and Characterization of Mesoporous Carbon Hybrids for Environmental Applications M.A.Karakassides Department of Materials Science & Engineering University of Ioannina, Greece Olomouc March 2011

2 Environmental Remediation Why mesoporous carbon? Why hybrids? activated carbon mesoporous carbon High surface area (up to 1700 m 2 g -1 ) Uniform pore size Large pore volumes High Periodicity R. Ryoo, S. Hoon and S. Jun, J. Phys. Chem. B, 103 (1999) 7743 hybrids Various properties possible depending on precursors and processing Nanomaterial properties Magnetic properties Catalytic properties hybrids ( mesoporous carbon + magnetic nanoparticles )

3 OUTLINE Introduction to mesoporous carbons Synthesis of hybrids, type-a (/magnetic nanoparticles) Synthesis of hybrids type-b (/ZVi nanoparticles) Study of synthesis stages and characterization of hybrids Example of use of hybrids (sorption of hexavalent chromium) Conclusions

4 Pore geometry Pore dimensions Introduction to mesoporous carbons classification M41S zeolite microporous d<2 nm mesoporous d=2-50 nm foams macroporous d>50 nm MATERIALS 1D 3D CNTs 2D SBA-15 Graphite sheets LDH

5 CMK: Mesoporous carbon materials with ordered crystalline structure SBA-15 Mesoporous Carbon/silicon Mesoporous carbon MCM-48 R. Ryoo, S. Hoon and S. Jun, J. Phys. Chem. B, 103 (1999) 7743

6 P. Selvam, S. K. Bhatia and C. S. Sonwane, Ind. Eng. Chem. Res., 40 (2001) 3237

7 SBA-15 Synthesis of C 2 H 5 C 2 H 5 O O Si O C 2 H 5 O C 2 H 5 TEOS 38 o C 95 o C 500 o C 22 hours 24 hours 6 hours SBA-15 Template P123/HCl/H 2 O SBA o C 160 o C 877 o C/N 2 6 hours 6 hours 6 hours Sugar/H 2 O/H 2 SO 4 1,25 / 5 / 0,14κ.β. Sugar /H 2 O/H 2 SO 4 0,8 / 5 / 0,07κ.β.

8 Hybrids based on type-a with nanoparticles Fe x O y -----@Fe x O y type-b with nanoparticles Fe @ZVI

9 Preparation of carbon hybrids ( /Fe x O y ) H 2 O OCH 2 (CH)O OCH 2 (CH 3 )O OH 2 + HO Fe OCH 2 (CH 3 )O Fe OCH 2 (CH 2 )O Fe OH NO 3 - H 2 O OCH 2 (CH 3 )O OCH 2 (CH 3 )O OH 2 HOOC HOOC HOOC COOH COOH COOH Fe(NO 3 ) 3 9H 2 O 1:4 Vapor CH 3 COOH pyrolysis 400 ο C/Ar Fe x O y -O -O@Fe -O@ac -O@m4 vapor CH 3 COOH pyrolysis 400 ο C/Ar Fe x @mx

10 (110) (200) Intensity (100) (110) (200) (100) Characterization of SBA-15 SBA d 100 = 9.0 nm P6mm pore 10 1,5 2,0 2,5 3,0 3,5 4,0 d 100 = 10.5 nm θ( ο ) SBA-15 a o =2d 100 / 3 a o = 12.1 nm a o = 10.4 nm

11 Absorbance Characterization x O y Hybrids FT-IR Spectroscopy -O@m COO Fe-O 567 O-C=O H 2 O OCH 2 (CH)O OCH 2 (CH 3 )O OH 2 HO Fe OCH 2 (CH 3 )O Fe OCH 2 (CH 2 )O Fe OH H 2 O OCH 2 (CH 3 )O OCH 2 (CH 3 )O OH 2 -O@m4 + NO 3 - NO 3 -COO - Fe COOH, -COO O@ac C=C C-H 661 -O@Fe -O Wavenumbers (cm -1 )

12 Characterization x O y Hybrids Raman spectra I D /I G = FWHF~110cm @m1

13 Intensity Intensity (110) (200) (110) (200) (100) (100) Characterization x O y Hybrids X-ray Diffraction -O -O@m θ( θ( ο )

14 Intensity Characterization x O y Hybrids X-ray Diffraction (XRD) Fe 3 O 4 (311) Scherrer: D 0,9* Cu B*cos Β (400) Average size Fe x O y 20nm 13nm γ-fe 2 O θ (degrees)

15 endo %TG Characterization x O y Hybrids Thermal Analysis 100 DTA exo iron oxide content (Fe 2 O 3 ) of hybrids 27.3 wt% 40 -O@m O@m wt% Temperature( o C) ,6% Temperature( o C)

16 Vads (cm 3 /g) V liq (cm 3 /g) dv/dr Characterization x O y Hybrids SURFACE AREA MEASUREMENTS Isotherms V-t plots r~1.7nm r(nm) -O O O@m p/p t/nm

17 Characterization x O y Hybrids Mössbauer Μössbauer parameters resulting from least square fits of the spectra γ-fe 2 O 3

18 Characterization x O y Hybrids Magnetic T (K) M max+ (7 T) (emu/g) H C (Oe) M R , K

19 Characterization x O y Hybrids Transmission Electron Microscopy (ΤΕΜ) -O@m4

20 Characterization x O y Hybrids Transmission Electron a o =9 nm d=3 nm

21 Synthesis of /Fe 0 Hybrids FeCl 3 6H 2 O NaBH 4

22 Intensity Characterization of /Fe 0 44,9 35,5 o <2,7nm ~2,7nm Scherrer: D 0,9* Cu B *cos Β ZVI Fe θ( ο ) ~11,2nm

23 Vads (cm 3 /g) Vads (cm 3 /g) Characterization of /Fe 0 Hybrids S BET (m 2 /g) S BET (m 2 /g) V pore (cm 3 /g) 0,65 0, V pore (cm 3 /g) 0,54 0, p/p p/p 0

24 Absorbance Absorbance Environmental remediation ( aqueous solution Cr 6+ ) Cr ,5-diphenylcarbohydrazide 1,00 542nm 0,90 0,75 1 mg/l 0,75 A=0,85186*C-0, ,50 0,8 mg/l 0,6 mg/l 0,60 0,45 0,25 0,4 mg/l 0,2 mg/l 0, Wavelength (nm) 0,30 0,15 0,00 0,0 0,2 0,4 0,6 0,8 1,0 1,2 Συγκέντρωση Cr(VI) mg/l

25 Absorbance Absorbance Absorbance Absorbance Environmental remediation ( aqueous solution Cr 6+ - Hybrid Cr 6+ =6ppm 0,6 0,5 0,4 0, h 0,5h 1h 2h 6h 9h , h 0.5h 1h 2h 3h 6h 9h 24h Cr 6+ =6ppm =180ppm 0,2 0,1 ph=5,5 0, Wavelength (nm) 0,6 0,5 0,4 0,3 0, h 0,5h 1h 2h 3h 6h 9h 24h Wavelength (nm) 0h h 1h 2h 3h 6h 9h 24h 0,2 0,1 0,0375 ph=3 0, Wavelength (nm) ph= Wavelength (nm)

26 r (mg*l -1 *h -1 ) Evaluation of hybrids 1,0 (ph=5,5) [Cr 6+ ] t / [Cr 6+ ] 0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 (ph=5,5) (ph=3) (ph=3) 0, time (hours) ,4 ph=3 1/[Cr(VI)] - Hybrid [ Cr( VI )] time (hours) t second order 1 k2t [ Cr( VI )] Second order equation K 2 (L mg -1 h -1 ) R 2 t 1/2 (h) 0,066 0,989 0,417 0,986 0, , [Cr(VI)] (mg*l-1 ) r k 2 2 ([ Cr( VI )] t )

27 r (mg*l -1 *h -1 ) Evaluation of hybrids 1,0 0,8 x O y - Hybrid 5 [Cr 6+ ] t / [Cr 6+ ] 0 0,6 0,4 0,2 0, time (hours) (ph=5,5) ph=3 1/[Cr(VI)] t [ Cr( VI )] t 1 k2t [ Cr( VI )] time (hours) second order , [Cr(VI)] (mg*l-1 ) r k Second order reaction k 2 (L mg -1 h -1 ) R 2 t 1/2 0,434 0,983 0,4 0,082 0,989 2,1 2 2 ([ Cr( VI )] t )

28 Conclusions Hybrids for environmental applications were prepared: a) via interaction of acetic acid vapors with iron cations dispersed on the surface of a mesoporous carbon. (@Fe x O y ) b) using a carbon as a matrix for wet impregnation of FeCl 3, followed by reduction of iron species by means of NaBH 4 and drying of the sample in vacuum. (@Fe 0 ) The XRD, FT-IR, TEM, DTA/TG and surface area measurements revealed the well defined carbon mesoporous structure and the successfully preparation of hybrids. Magnetic experiments suggested the ultrafine character of the iron oxide nanoparticles which exhibit a superparamagnetic behaviour. Mössbauer measurements showed: a) γ-fe 2 O 3 as the major magnetic iron oxide phase x O y hybrids b) the well known iron core-shell structure for the ZVI nanoparticles 0 c) almost zero recoil-free nanoparticles at temperatures above 77K in 0 x O y hybrids showed very rapid uptake kinetics in the removal of aqueous Cr 6+ ions and total remediation of aqueous solution of Cr 6+ at conditions- ph: 3, concentration: 6ppm, treatment time: 24hours. Both type of hybrids showed significant improvement of sorption and/or reduction capability of Cr 6+ ions/g of specific sorbent in comparison with pristine or unsupported ZVI nanoparticles.

29 Acknowledgements Dr. M.Baikousi Dr. D.Dimos Mrs. E.Petala, M.Sc. Department of Materials Science &Engineering University of Ioannina Greece Assist. Prof. A.Bourlinos Assist. Prof. A.Douvalis Professor T.Bakas Department of Physics University of Ioannina Greece Professor R.Zboril Dr. Jiří Tuček Dr.Klára Šafářová Dr. Jan Filip

30 Thank you