1) Glass wool and AuNPs of size 10-15nm reduced 4-nitrophenol most effectively, while activated carbon adsorbed but did not reduce it. Zeolites performed poorly due to their porous structure trapping smaller AuNPs. 2) Larger, more uniformly sized AuNPs of 10-15nm had the highest rate constants, indicating better surface coating and accessibility compared to smaller, randomly shaped particles. 3) The best catalyst was glass wool coated with 10nm AuNPs, which maintained a high rate constant over multiple reduction cycles, decreasing gold loading by 34% after recycling.

1. Angelica Jusino, MS ENVS Candidate and Tarek Abdel-Fattah
Christopher Newport University, Newport News, VA 23606
Figure 2. UV-Vis spectra of the 4-NP reduction by the 4 supports (no AuNP coating) after 2 hours.
After 2 hours
• Glass wool reduced after 2 hours
• Activated carbon adsorbed – did not reduce (no 300 peak)
• Neither zeolite adsorbed or reduced
Hypothetical Zeolite Bead Cross-section
Summary: Supports
• Activated Carbon did not reduce 4-NP, but it did absorb it
(400 peak decreased, but 300 did not form)
• Glass wool finished the reduction the fastest for all AuNP
sizes
• Both zeolites performed poorly (texture porosity of bead)
Summary: AuNPs
• C60 and H20 are random in size and shape; H15 and H10 are
more uniform
• The uniform particles prove that higher loading = larger rate
constant (even surface coating & accessibility)
• Random particles had uneven accessibility
• C60 did not work on zeolites because it was stuck in the
“void space” of the bead framework (high loading, low
performance)
•
• GW/H10 was used for recyclability
• Rate became 0 order
• Time increased from 13.3 min to 28.3 min (still lower than all
other variables)
• % gold loading decreased from 1.13% to 0.742% (34% )
•
• Accessibility of the AuNP depends on two factors:
nanoparticle size and characteristic of each support.
• Although smaller sizes = more surface area, the largest
particle in this study proved to be the best catalyst due to
accessibility (surface coating)
• Zeolites have void spaces that trap smaller AuNPs and do not
allow them to come in contact with 4-NP
• Glass wool is fibrous and non-porous so it allows maximum
contact
•
• Dr. Fattah, Thesis Advisor; Dr. Whiting and Dr. Atkinson, Thesis Committee;
Dr. Wei Cao, Thomas Dushatinski, Clay Huff, characterization assistance.
• This material is based upon work supported by the National Science
Foundation under Grant Number (NSF 0841295), GK12 Program.
Supported Gold Nanoparticles as a Heterogeneous
Catalyst for the 4-Nitrophenol Reduction
Gold Nanoparticles (AuNPs) are prepared and grafted onto
economically favorable supports (zeolites 13X & 5A, glass wool,
and activated carbon). The catalytic activity is tested with the
reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP).
• Bulk gold is chemically inert due to its large particle size and
the highly positive Fermi levels
• Nanoparticles can serve as catalysts in electron transfer
processes such as hydrogenation reactions
1. Four sizes of nanoparticles were synthesized
2. 2mg of AuNP was evaporated onto 500mg of support
3. Gold only, support only, and supported gold were all tested
as catalysts
4. Strongest catalyst was tested for recyclability
5. Characterization with TEM & XRF
Figure 1. UV-Vis curve of the 4-NP reduction by the 4 AuNPs (homogeneous) – times in legend
• Peaks: 400 = 4-NP; 300 = 4-AP
• Within 5 minutes, all 4 colloids reduced the 4-NP
• Homogenous pollutes the system – must be supported
OBJECTIVE RESULTS: Support Only
RESULTS: AuNP Only (Homogenous)
METHODS
RESULTS: Supported AuNP (Heterogeneous)
Reduction of 4-NP via GW/H10
heterogeneous catalyst
Acknowledgements
BACKGROUND
0.0
0.5
1.0
1.5
2.0
250 300 350 400 450 500
Absorbance(a.u.)
Wavelength (nm)
t = 0
AC t = 120
GW t = 120
5A t = 120
13X t = 120
TEM images of all AuNPs
Conclusion
0.0
0.5
1.0
1.5
2.0
250 300 350 400 450 500
Absorbance(a.u.)
Wavelength (nm)
Start (0:00) H15 (1:30)
H20 (1:30) H10 (1:45)
C60 (4:33)
Support
Material
Parameter
No
AuNPs
C60
(7.4nm)
H15
(21.7nm)
H20
(25.5nm)
H10
(53.5nm)
No Support
TIME (min) 4.55 1.50 1.50 1.75
RATE
CONSTANT
1.44x106 2.87x106 4.15x106 3.10x106
% GOLD -- -- -- --
Activated
Carbon
TIME (min) Adsorb Adsorb Adsorb Adsorb Adsorb
RATE
CONSTANT
-- -- -- -- --
% GOLD -- -- -- -- --
Glass Wool
TIME (min) 120.00 28.33 31.67 38.33 13.33
RATE
CONSTANT
10.1 218.4 205.3 125.4 231.2
% GOLD 0.000 0.340 0.500 0.510 1.130
Zeolite 13X
TIME (min) No Rxn Not Comp. 90.00 112.50 57.50
RATE
CONSTANT
-- -- 33.5 33.2 99.4
% GOLD 0.000 2.010 0.490 0.843 0.0250
Zeolite 5A
TIME (min) No Rxn Not Comp. 40.00 91.67 40.00
RATE
CONSTANT
-- -- 133.8 58.6 134.1
% GOLD 0.000 2.500 0.650 1.120 0.820
Table 1. Summary results of all catalysts. Time is displayed in minutes and rate constants (all
1st order) are displayed in min-1x10-3. “Adsorb” indicates the 4-NP was adsorbed and not
reduced, “No Rxn” indicates that there was no change in 4-NP UV-Vis peak at 400nm after 2
hours, and “Not Comp.” indicates that the reaction began to reduce, but was incomplete
after 2 hours.
RESULTS: Supported AuNP (Heterogeneous)
Recyclability
Surface (black edge)
Framework (gray circles – pores are Å scale)
Void Space (blue spaces – larger than pores )