Post on 26-Feb-2022
Precious metal recovery from nanowaste for sustainable nanotechnology:
Current challenges and life cycle considerations
pvikes@vt.edu smcginn@vt.edu param@vt.edu
Dr. Peter Vikesland Dr. Sean McGinnis Paramjeet Pati
SUN-SNO-GUIDENANO
Conference 2015
‘Synthetic’ Chemicals
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
sodium borohydride
hydrazine
Green Chemicals
grape pomace cypress leaves
coriander leaves
soybean
cinnamon
borohydridecitra
te
hydrazine
soybean seed
sugarbeet pulp
Cum
ula
tive E
nerg
y D
em
and (
MJ)
0.0
0.2
0.4
0.6
0.8
1.0 Error bars represent 95% confidence interval
Uncertainty results from gold salt model and energy use
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
borohydrid
ecitra
te
grape pomace
hydrazine
cypress le
af extra
ct
C. camphora
vitamin B
cinnamon
ginseng
soybean seed
mushroom
C.album extract
D-glucose
sugarbeet pulp
soybean seed extra
ct
coriander
Cum
ula
tive
En
erg
y D
em
and (
MJ)
0
1
2
3
4
5
6
Strong reducing agents (100% yield assumed)
Reported yields
100% yield (assumed)
75% yield (assumed)
50% yield (assumed)
“Life Cycle Assessment of “Green” Nanoparticle Synthesis Methods”, Environmental Engineering Science (2014). Paramjeet Pati, Sean McGinnis and Peter J. Vikesland.
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
From a life cycle perspective, gold NP synthesis using bio-based (“green”) reducing agents can have substantial environmental impacts.
Gold Chlorine
Gold Salt
Citric Acid
Sodium Carbonate
Sodium Citrate
Deionized Water
TapWater
CleaningSolvent
HCl HNO3
Electrical Energy
HeatingStirring
1 mg Gold NPs
If gold is the key driver of life cycle impacts, can we reduce impacts
by recovering/recycling gold?
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
The embodied energy of gold drives most of the life cycle impacts of gold nanoparticle synthesis.
(Red ‘flow’ lines show the energy associated with each input. Thicker lines imply higher energy inputs.)
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Recovering gold from nanowaste…
AuBr4-
K(OH2)6+
AuBr4-Hydrogen
bonding
htt
p:/
/un
am.b
ilken
t.ed
u.t
r
… using α-cyclodextrin
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
“Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin”. Nature Communications, Liu et al. (2013)
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Gold nanowaste
Precipitation Dissolution in HBr/HNO3
Selective recovery ofgold using
α-cyclodextrin Filtration
Sonication(Resuspension)
Schematic of gold recycling experiments
HAuCl4 solution Gold nanoparticles
HCl/HNO3
Reduction
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Precipitation of goldusing Na2S2O5
Powder XRD
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
0
0,5
1
1,5
2
250 300 350 400 450 500 550 600
Ab
sorb
ance
Wavelength (nm)
Stock_HAuCl4 Recycled_HAuCl4
HAuCl4 solution
UV-vis
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
2.392.06
1.461.25, 1.19
2.362.04
1.441.23, 1.18
Calculated d-spacing (Å)
d-spacing for gold (Å)
Diffraction
Gold nanoparticles
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Can we recover gold from nanowaste? Yes, we can. (But should we?)
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
1 mg AuNP
DI water
Citrate
Gold
HCl
Aqua regia
HNO3
Stirring HeatingCleaning
waterCooling
water
HAuCl4
Other chemicals
ElectricityWater
Synthesis
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Gold nanowaste
Precipitation Dissolution in HBr/HNO3
Selective recovery ofgold using
α-cyclodextrin Filtration
Sonication(Resuspension)
HAuCl4 solution Gold nanoparticles
HCl/HNO3
Reduction
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Precipitation of goldusing Na2S2O5
Dissolution in HBr/HNO3
HNO3
HBr
Gold-CD complex
α-CD
Precipitate & resuspendthe complex
Recover gold
precipitate
NaHSO5
Precipitate
NaCl
To waste treatment
1 mg AuNP
Recycle
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
HCl
HAuCl4 fromrecovered
gold
HNO3
Electricity
Heating
Synthesis RecyclingBackground | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Synthesis Recycling
Actual LCA model for 90% recycle scenario
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
10% recycle
50% recycle
90% recycle
Dispose all gold as waste
Note: 10% recycle means: 10% of the gold nanowaste is recovered and reused for gold nanoparticle synthesis.
The rest 90% gold is not recovered, and goes into waste disposal.
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
10% recycle
50% recycle
90% recycle
Dispose all gold as waste
Error bars represent 95% confidence intervals
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Hmm.. overlapping error
bars… means the difference
isn’t statistically significant,
right? Makes no difference
whether we recycle or not…
WRONG! You have
correlateduncertainties!
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Product A Product B
Aluminium 1 kg 0.8 kg
Cast iron 1 kg 0.8 kg
Polystyrene 1 kg 0.8 kg
Q: Which of the two has a lower environmental impact?a) Product Ab) Product Bc) It dependsd) Is this a trick question?
Comparing 1 kg of product A vs. 1 kg of Product B:
(Product B uses 20% less inputs compared to Product A. There are no extra, hidden inputs in products A and B)
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Correlated uncertainties in LCA: An example
Q: Which of the two has a lower environmental impact?a) Product Ab) Product Bc) It dependsd) Is this a trick question?
The key here: correlated uncertainties.All three inputs (aluminium, cast iron and polystyrene) have uncertainties that
are common to both Product A and Product B.
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Metal depletion
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Freshwater ecotoxicity
Metal depletion
Climate change
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Fossil depletion
Ozone depletion
Natural land transformationUrban land occupation
Agricultural land occupationIonizing radiation
Marine ecotoxicityFreshwater ecotoxicityTerrestrial ecotoxicity
Metal depletionWater depletion
Climate change
Terrestrial acidification
Particulate matter formationPhotochemical oxidant formation
Human toxicityMarine eutrophication
Freshwater eutrophication
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
10% recycle
50% recycle
90% recycle
Dispose all gold as waste
Metal depletion
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Metal depletion
Fossil depletion
Ozone depletion
Natural land transformationUrban land occupation
Agricultural land occupationIonizing radiation
Marine ecotoxicityFreshwater ecotoxicity
Terrestrial ecotoxicity
Metal depletionWater depletion
Climate change
Terrestrial acidification
Particulate matter formationPhotochemical oxidant formation
Human toxicityMarine eutrophicationFreshwater eutrophication
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Fossil depletion
Ozone depletion
Natural land transformationUrban land occupation
Agricultural land occupationIonizing radiation
Marine ecotoxicityFreshwater ecotoxicity
Terrestrial ecotoxicity
Metal depletionWater depletion
Climate change
Terrestrial acidification
Particulate matter formationPhotochemical oxidant formation
Human toxicityMarine eutrophication
Freshwater eutrophication
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Fossil depletion
Ozone depletion
Natural land transformationUrban land occupation
Agricultural land occupationIonizing radiation
Marine ecotoxicityFreshwater ecotoxicity
Terrestrial ecotoxicity
Metal depletionWater depletion
Climate change
Terrestrial acidification
Particulate matter formationPhotochemical oxidant formation
Human toxicityMarine eutrophication
Freshwater eutrophication
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Synthesis Recycling
90% recycle scenario
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
High impacts in climate change and fossil fuel depletion are driven by mainly the boiling step in the recovery process.
Fossil depletion
Ozone depletion
Natural land transformationUrban land occupation
Agricultural land occupationIonizing radiation
Marine ecotoxicityFreshwater ecotoxicity
Terrestrial ecotoxicity
Metal depletionWater depletion
Climate change
Terrestrial acidification
Particulate matter formationPhotochemical oxidant formation
Human toxicityMarine eutrophication
Freshwater eutrophication
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Conclusion:
Gold recovery from nanowaste is feasible
Even at low yields, recovery beats regular gold nanowaste disposal
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Challenges:
Reducing the energy footprint of the recovery step.
Refining the models to account for different waste disposal and recovery scenarios (e.g., recovery but no reuse).
Acknowledgments
Virginia Tech Centre for Sustainable Nanotechnology (VTSuN)
Institute for Critical Technology and Applied Science (ICTAS)
Dr. Sean McGinnisDirector, Green Engineering
Program, Virginia Tech
Leejoo WiUndergraduate researcher
(Vikesland group)
Email: pvikes@vt.edu
Spam slides
Here be dragons…
Synthesis Recycling
90% recycle
1
2: Gold from recycling
1: Gold obtained from mining
2
Gold
HAuCl4
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Synthesis Recycling
1
2: Gold from recycling
1: Gold obtained from mining
2
50% recycle
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Synthesis Recycling
1
2: Gold from recycling
1: Gold obtained from mining
2
10% recycle
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Gold nanowaste
Precipitation Dissolution in HBr/HNO3
Selective recovery ofgold using
α-cyclodextrin Filtration
Sonication(Resuspension)
HAuCl4 solution Gold nanoparticles
HCl/HNO3
Reduction
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Precipitation of goldusing Na2S2O5
Gold-cyclodextrincomplex
Gold nanoparticles
Sodium borohydride
1 2 3 4 5 6 7 8 9 10
keV
0.0
0.5
1.0
1.5
2.0
2.5
3.0
cps/eV
Au Au Au Au Br Br K K
O
EDS spectra showed the signature peaks for
Au, Br, K, O
No AuNPs
AuNPs
(a) SEM images of a crystalline sample prepared by spin-coating an aqueous suspension of α·Br onto a silicon substrate, and then air-drying the suspension. (b) TEM images of α·Br prepared by drop-casting an aqueous suspension of α·Br onto a specimen grid covered with a thin carbon support film and air-dried. (c) Cryo-TEM image (left) and SAED pattern (right) of the nanostructures of α·Br. As the selected area includes several crystals with different orientations and the crystals are so small that the diffraction intensities are relatively weak, we can assign the diffraction rings composed of diffraction dots but not the specific angles between different diffraction dots from the same crystal. The scale bars in a and b are 25 (left), 5 (right), 10 (left), 5 μm (right) and in c are 1 μm(left) and 1 nm−1(right), respectively.
“Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin”. Nature Communications, Liu et al. (2013)
“Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin”. Nature Communications, Liu et al. (2013)
“Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin”. Nature Communications, Liu et al. (2013)