Applicability of disulfide-polymer particles surface embedded on alginate beads for cadmium removal from airport derived stormwater

D. Ko, H. Kim, H. Lee, C. T. Yavuz, H. R. Andersen, Y. Hwang*
J. Environ. Chem. Eng., 6, 4124–4129 (2018).
DOI: 10.1016/j.jece.2018.06.007

Stormwater runoff derived from airports causes severe cadmium contamination in excess of the maximum limit level and is difficult to treat due to the irregular contamination levels from scattered rainfall. To overcome this and remove cadmium from runoff, a new reactive filtration column is introduced. Sulfur functionalized polymer particles were successfully embedded onto the surface of alginate bead (DiS-algi) and simulated a real stormwater treatment filtration column. The DiS-algi shows 22.3 mg/g of batch and 877 μg/g of continuous flow sorption capacity. Also, the results for the new sorption material show that within 6 mins half of the cadmium was removed with 31 L/mg of Langmuir sorption affinity, outperforming an activated carbon filter. From a breakthrough test the reactive column shows complete uptake of cadmium from a contaminated flow, lasting two hours until reaching the breakthrough point. Furthermore, regeneration tests of the column verified its reusability. DiS-algi appears to be a viable new cadmium sorption material for airport derived stormwater runoff filtration systems.

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Disulfide polymer grafted porous carbon composites for heavy metal removal from stormwater runoff

D. Ko*, P. D. Mines, M. H. Jakobsen, C. T. Yavuz, H. C. B. Hansen, H. R. Andersen
Chem. Eng. J., 348, 685–692 (2018).
DOI: 10.1016/j.cej.2018.04.192

The emerging concern of heavy metal pollution derived from stormwater runoff has triggered a demand for effective heavy metal sorbents. To be an effective sorbent, high affinity along with rapid sorption kinetics for environmental relevant concentrations of heavy metals is important. Herein, we have introduced a new composite suitable for trace metal concentration removal, which consists of cheap and common granular activated carbon covered with polymers containing soft bases, thiols, through acyl chlorination (DiS-AC). Material characterization demonstrated that the polymer was successfully grafted and grown onto the surface of the carbon substrate. The distribution coefficient for Cd2+ bonding was 89·103 L/kg at a solution concentration of 0.35 mg/L, which is notably higher than sorption affinities for Cd2+ seen in conventional sorbents. The sorption isotherm is well described by the Freundlich isotherm and within an hour, half of the initial trace (0.2 mg/L) concentration of Cd2+ was removed by the DiS-AC at a sorbent loading of 2 g/L. Therefore, the novel material DiS-AC promises to be an ideal candidate for filters treating stormwater runoff.

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Selective removal of heavy metal ions by disulfide linked polymer networks

D. Ko, J. S. Lee, H. A. Patel, M. H. Jakobsen, Y. Hwang, C. T. Yavuz, H. C. B. Hansen, H. R. Andersen*
J. Hazard. Mater., 332, 140–148, (2017).
DOI: 10.1016/j.jhazmat.2017.03.007.

Heavy metal contaminated surface water is one of the oldest pollution problems, which is critical to ecosystems and human health. We devised disulfide linked polymer networks and employed as a sorbent for removing heavy metal ions from contaminated water. Although the polymer network material has a moderate surface area, it demonstrated cadmium removal efficiency equivalent to highly porous activated carbon while it showed 16 times faster sorption kinetics compared to activated carbon, owing to the high affinity of cadmium towards disulfide and thiol functionality in the polymer network. The metal sorption mechanism on polymer network was studied by sorption kinetics, effect of pH, and metal complexation. We observed that the metal ions–copper, cadmium, and zinc showed high binding affinity in polymer network, even in the presence of competing cations like calcium in water.

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A Half Millimeter Thick Coplanar Flexible Battery with Wireless Recharging Capability

J. S. Kim, D. Ko, D. J. Yoo, D. S. Jung, C. T. Yavuz, N. I. Kim, I. S. Choi, J. Y. Song*, J. W. Choi*
Nano Lett., 15 (4), 2350–2357, (2015). DOI: 10.1021/nl5045814.
Most read paper in March 2015.

Most of the existing flexible lithium ion batteries (LIBs) adopt the conventional cofacial cell configuration where anode, separator, and cathode are sequentially stacked and so have difficulty in the integration with emerging thin LIB applications, such as smart cards and medical patches. In order to overcome this shortcoming, herein, we report a coplanar cell structure in which anodes and cathodes are interdigitatedly positioned on the same plane. The coplanar electrode design brings advantages of enhanced bending tolerance and capability of increasing the cell voltage by in series-connection of multiple single-cells in addition to its suitability for the thickness reduction. On the basis of these structural benefits, we develop a coplanar flexible LIB that delivers 7.4 V with an entire cell thickness below 0.5 mm while preserving stable electrochemical performance throughout 5000 (un)bending cycles (bending radius = 5 mm). Also, even the pouch case serves as barriers between anodes and cathodes to prevent Li dendrite growth and short-circuit formation while saving the thickness. Furthermore, for convenient practical use wireless charging via inductive electromagnetic energy transfer and solar cell integration is demonstrated.

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Synthesis of a nanoporous 1,2,4-oxadiazole network with high CO2 capture capacity

D. Ko, H. A. Patel, C. T. Yavuz*
Chem. Commun., 51, 2915-2917 (2015). [DOI]

Developing an adsorbent to mitigate carbon dioxide without large energy penalty is highly desired. Here, we present a silylation synthetic route to form a processable and otherwise impossible porous 1,2,4-oxadiazole network, which achieves 2 mmol/g of CO2 capacity owing to nitrogen-rich structure. This network shows high CO2/N2-selectivity, thermal stability up to 450 oC, and low-heat of adsorption (26.4 kJ/mol), facilitating easy regeneration.

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Nanoporous Benzoxazole Networks by Silylated Monomers, Their Exceptional Thermal Stability, and Carbon Dioxide Capture Capacity

H. A. Patel, D. Ko, C. T. Yavuz*
Chem. Mater., 26 (23), 6729–6733 (2014). [DOI]

The pursuit of synthetic routes for design and preparation of nanoporous polymeric networks with inherent permanent microporosity and functionality through bottom-up methodologies remains a driving force in developing CO₂-philic materials. We report nanoporous, processable, benzoxazole-linked covalent organic polymers (Box-COPs) that show exceptional thermal stability up to 576 °C. Box-COPs can be formed into films thanks to the silylation that is used to guide polymeric network formation. Surface areas of up to 606 m2 g–1 and narrow pore sizes of 4.36 Å were observed with a CO₂ uptake capacity of 139.6 mg g–1 at 273 K and 1 bar. Box-COPs were stable in boiling water for a week without deteriorating CO₂ capture capacity.

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