A half-wave rectified alternating current …...Uranium extraction from sea water using HW-ACE...

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SUPPLEMENTARY INFORMATIONARTICLE NUMBER: 17007 | DOI: 10.1038/NENERGY.2017.7

NATURE ENERGY | www.nature.com/natureenergy 1

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Supplementary Information

A Half-Wave Rectified Alternating Current Electrochemical Method for Uranium Extraction from Sea Water

Chong Liu1, Po-Chun Hsu1, Jin Xie1, Jie Zhao1, Tong Wu1, Haotian Wang†2, Wei Liu1, Jinsong Zhang1, Steven Chu3,4, Yi Cui*1,5.

1. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA

2. Department of Applied Physics, Stanford University, Stanford, California 94305, USA 3. Department of Physics, Stanford University, Stanford, California 94305, USA 4. Department of Molecular and Cellular Physiology, Stanford University, Stanford,

California 94305, USA 5. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator

Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA †Present Address: Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts 02142, USA

*Correspondence should be addressed to Y.C. ([email protected]).

A half-wave rectified alternating currentelectrochemical method for uranium extractionfrom seawater

http://dx.doi.org/10.1038/nenergy.2017.7

http://www.nature.com/natureenergy



SUPPLEMENTARY INFORMATIONDOI: 10.1038/NENERGY.2017.7

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Supplementary Figure 1. Additional hydrothermal reaction to substitute the nitrile functional groups on PAN polymer with amidoxime functional groups.






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Supplementary Figure 2. Photos showing water splitting on C-Ami electrode at different frequency. a, 50 Hz; b, 100 Hz and c, 400 Hz. At all cases the HW-ACE voltage was from -5 V to 0 V and the solution is unspiked real sea water.






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Supplementary Figure 3. HW-ACE extraction performance under different alternating voltages. In all HW-ACE cases, the frequencies were 400 Hz.






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Supplementary Figure 4. Confirmation of the HW-ACE extraction on C-Ami electrode surface rather than the counter electrode (C rod) surface by measuring the uranium extraction by HW-ACE method using different electrode configuration.






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Supplementary Figure 5. HW-ACE uranium extraction performance in simulated sea water. Uranium extraction from sea water using HW-ACE method comparing to physicochemical method with initial uranium concentration of a, ~100 ppb, b, ~1.0 ppm, c, ~10 ppm, d, ~300 ppm, e, ~600 ppm and f, ~1000 ppm. Simulated sea water was made using deionized water as solvent1.






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Supplementary Figure 6. Photo showing new C-Ami electrode (right) and electrode after HW-ACE extraction using 1000 ppm uranium sea water solution (left). No damage was observed. Scale bar, 1 cm.






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Supplementary Figure 7. Comparison of physicochemical and HW-ACE extraction performance at low initial concentration (~1 ppm) by continuously feeding spiked real sea water uranium solution. HW-ACE extraction did not show extraction performance decay while physicochemical extraction did.






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Supplementary Figure 8. Kinetics fitting of both physicochemical and HW-ACE extraction. The rate constants for physicochemical adsorption case are 4.4 × 10-3 s-1 (1st order) and 5.0 × 10-6 M-1s-1 (2nd order). The rate constants for HW-ACE case are 1.5 × 10-2 s-1 (1st order) and 2.0 × 10-5 M-1s-1 (2nd order).






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Supplementary Figure 9. XPS characterization of the uranium extracted by both physicochemical (left) and HW-ACE (right) methods.






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Supplementary Figure 10. SEM images of C-Ami electrode after long term U extraction using flow systems. a,b, SEM images showing the morphologies of two different locations on the C-Ami electrode at different magnification after long term HW-ACE U extraction. c, SEM image showing the morphology of C-Ami electrode after long term physicochemical adsorption.






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Supplementary Figure 11. Kinetics evaluation using real sea water without additional uranium between HW-ACE and physicochemical adsorption method.






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Supplementary Figure 12. Extraction efficiencies of U, V, Fe and Cu in a mixture solution with real sea water as background. All ions are of ~1 ppm at start.






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Supplementary Figure 13. Extraction efficiency of U and other competing ions (Na, Ca, V, Fe and Cu) compared between HW-ACE and physicochemical adsorption methods using spiked real sea water with 1 ppm of U, V, Fe and Cu after 24 hours.






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Supplementary Figure 14. Uranium desorption percentage comparison between different extract methods, different desorption conditions and elution solutions. (A: physicochemical adsorption, 0.1M Na2CO3 elution; B: physicochemical adsorption, 0.1M HCl elution; C: HW-ACE extraction, 0.1M Na2CO3 elution; D: HW-ACE extraction, 0.1M Na2CO3 elution with reversed bias. E: HW-ACE extraction, 0.1M HCl elution; F: HW-ACE extraction, 0.1M HCl elution with reversed bias.)






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Supplementary Figure 15. Recovery percentage of U, V, Fe and Cu compared between HW-ACE and physicochemical adsorption. For physicochemical adsorption the elution solution was 0.1M HCl. For HW-ACE the elution condition was using 0.1 M HCl with a reverse bias. Extraction was performed using ~1 ppm U, V, Fe and Cu spiked real sea water for 24 hours.






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Supplementary Figure 16. Extraction efficiencies of U using HW-ACE method for three cycles. ~1ppm U spiked sea water was used for all three tests.






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Supplementary Discussion

Cost Analysis

The power consumption and electricity cost during operation was summarized in the following table. The price of electricity used was 4 ¢ /kWh (Washington State, USA).

Voltage/V Power (W) Daily Cost ($) 5 0.0068 6.56×10-6 4 0.0042 4.10×10-6 3 0.0026 2.50×10-6 2 0.0014 1.41×10-6

In the real sea water tests, the voltage used was 5 V. Based on the flow system result. Using a flow rate of 6 mL/min (0.1 cm/s), the extracted mass for 4 L was 1. 62 µg. The daily extracted U mass would be ~3.5 µg. This corresponds to U price of ~$1.9/g. The target price of U extraction from sea water is $0.2-0.3/g. This is not an unreachable price, considering that more optimization work can be done to decrease the cost of HW-ACE method. Further optimization can be done to increase the uptake of U by increasing the electrode surface area, designing better operation system, decreasing the operation voltage and also increase the coulombic efficiency (suppress the unwanted by-products). If from optimization, the applied voltage can be reduced to <2V, then the energy consumption would decrease 5 times and the price will be $0.4/g which is very close to the target price. The material cost from additional activated carbon is equivalent to only 7.6% of the electricity cost which does not play a vital role in the final cost.

The benefit of using HW-ACE method which could reduce the cost is that the extraction capacity is much larger than physicochemical adsorption. Therefore, the need for recycle is reduced which could save some cost from regeneration.

In summary, the HW-ACE showed advantages in extracting U from sea water like high capacity, faster kinetics and so on. Further effort is needed to keep optimizing the system to reduce the power consumption, increase the coulombic efficiency and increase the extraction kinetics in order to make its cost competitive.






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Supplementary References:

1. Yue, Y.F. et al. Seawater uranium sorbents: preparation from a mesoporous copolymer initiator by atom-tansfer radical polymerization. Angew. Chem. Int. Ed. 52, 13458-13462 (2013).



A half-wave rectified alternating current …...Uranium extraction from sea water using HW-ACE...

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