Precious metal recovery from nanowaste for sustainable - - PowerPoint PPT Presentation
Precious metal recovery from nanowaste for sustainable nanotechnology: Current challenges and life cycle considerations Dr. Peter Vikesland Dr. Sean McGinnis Paramjeet Pati pvikes@vt.edu smcginn@vt.edu
pvikes@vt.edu smcginn@vt.edu param@vt.edu
SUN-SNO-GUIDENANO Conference 2015
‘Synthetic’ Chemicals Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Green Chemicals
grape pomace cypress leaves coriander leaves
s
b e a n
cinnamon
borohydride citrate hydrazine soybean seed sugarbeet pulp Cumulative Energy Demand (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
borohydride citrate grape pomace hydrazine cypress leaf extract
vitamin B cinnamon ginseng soybean seed mushroom C.album extract D-glucose sugarbeet pulp soybean seed extract coriander
Cumulative Energy Demand (MJ)
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 Tap Water Cleaning Solvent HCl HNO3 Electrical Energy Heating Stirring 1 mg Gold NPs
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
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
AuBr4
+
AuBr4
bonding
http://unam.bilkent.edu.tr
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 of gold 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 gold using Na2S2O5
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
0,5 1 1,5 2 250 300 350 400 450 500 550 600
Absorbance Wavelength (nm) Stock_HAuCl4 Recycled_HAuCl4 HAuCl4 solution
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
2.39 2.06 1.46 1.25, 1.19 2.36 2.04 1.44 1.23, 1.18 Calculated d-spacing (Å) d-spacing for gold (Å)
Gold nanoparticles Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
1 mg AuNP
DI water Citrate Gold HCl Aqua regia HNO3 Stirring Heating Cleaning water Cooling water
HAuCl4 Other chemicals Electricity Water
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Gold nanowaste Precipitation Dissolution in HBr/HNO3 Selective recovery of gold using α-cyclodextrin Filtration Sonication (Resuspension) HAuCl4 solution Gold nanoparticles HCl/HNO3 Reduction Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions Precipitation of gold using Na2S2O5
Dissolution in HBr/HNO3
HNO3 HBr
Gold-CD complex
α-CD
Precipitate & resuspend the complex Recover gold precipitate
NaHSO5
Precipitate
NaCl
To waste treatment 1 mg AuNP
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
HCl
HAuCl4 from recovered gold
HNO3 Electricity Heating
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
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…
You have
correlated
uncertainties!
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 A b) Product B c) It depends d) 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 A b) Product B c) It depends d) 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 transformation Urban land occupation Agricultural land occupation Ionizing radiation Marine ecotoxicity Freshwater ecotoxicity Terrestrial ecotoxicity Metal depletion Water depletion Climate change Terrestrial acidification Particulate matter formation Photochemical oxidant formation Human toxicity Marine eutrophication Freshwater eutrophication Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
10% recycle 50% recycle 90% recycle Dispose all gold as waste
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 transformation Urban land occupation Agricultural land occupation Ionizing radiation Marine ecotoxicity Freshwater ecotoxicity Terrestrial ecotoxicity Metal depletion Water depletion Climate change Terrestrial acidification Particulate matter formation Photochemical oxidant formation Human toxicity Marine eutrophication Freshwater eutrophication Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Fossil depletion Ozone depletion Natural land transformation Urban land occupation Agricultural land occupation Ionizing radiation Marine ecotoxicity Freshwater ecotoxicity Terrestrial ecotoxicity Metal depletion Water depletion Climate change Terrestrial acidification Particulate matter formation Photochemical oxidant formation Human toxicity Marine eutrophication Freshwater eutrophication Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Fossil depletion Ozone depletion Natural land transformation Urban land occupation Agricultural land occupation Ionizing radiation Marine ecotoxicity Freshwater ecotoxicity Terrestrial ecotoxicity Metal depletion Water depletion Climate change Terrestrial acidification Particulate matter formation Photochemical oxidant formation Human toxicity Marine eutrophication Freshwater eutrophication Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
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 transformation Urban land occupation Agricultural land occupation Ionizing radiation Marine ecotoxicity Freshwater ecotoxicity Terrestrial ecotoxicity Metal depletion Water depletion Climate change Terrestrial acidification Particulate matter formation Photochemical oxidant formation Human toxicity Marine 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).
Virginia Tech Centre for Sustainable Nanotechnology (VTSuN) Institute for Critical Technology and Applied Science (ICTAS)
Director, Green Engineering Program, Virginia Tech Leejoo Wi Undergraduate researcher (Vikesland group)
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions
Gold nanowaste Precipitation Dissolution in HBr/HNO3 Selective recovery of gold using α-cyclodextrin Filtration Sonication (Resuspension) HAuCl4 solution Gold nanoparticles HCl/HNO3 Reduction Background | Research Gap | Method | Life Cycle Assessment | Results | Conclusions Precipitation of gold using Na2S2O5
Gold-cyclodextrin complex Gold nanoparticles Sodium borohydride
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
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
(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)