Electrically switched cesium ion exchange

Lilga,; Orth, R.J.; Sukamto, J.P.H.; Schwartz, Daniel T.; Haight, S.M.; Genders, J. David

doi:10.2172/495697

Cited by 24 publications

(38 citation statements)

References 3 publications

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“…These composites exhibited superior cation-exchange capacity compared to electrodes with chemically and electrochemically deposited thin MHCF films. 2,5,6,15 The chemical procedure presented here for the incorporation of MHCF into porous SiO 2 -graphite composites offers an important advantage over the process where graphite and MHCF particles are directly encapsulated into a SiO 2 -graphite matrix. Namely, the MHCF compound can efficiently cover the graphite particles, taking full advantage of the large electroactive surface area of the conductive composite.…”

Section: Results and Discusionmentioning

confidence: 99%

“…1,2 This particular property makes MHCFs attractive for the selective removal of radioactive Cs ϩ from high Na ϩ and K ϩ nuclear wastes as well as in the water deionization processes in general. 2 The cation-exchange capability of MHCF compounds arises from an inherent charge imbalance; alkaline cations must intercalate into ͑and deintercalate out of͒ the MHCF matrix in order to maintain electroneutrality. Equation 1 is a simplified representation of this reversible process for a MHCF whose stoichiometry is analogous to soluble prussian blue 3,4 AM II Fe III ͑CN) 6 …”

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confidence: 99%

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High Capacity SiO[sub 2]-Graphite Composite Electrodes with Chemically Incorporated Metal MHCFs for Electrochemically Switched Alkaline Cation Exchange

Reyes-Gómez

Médina

Jeerage

et al. 2004

J. Electrochem. Soc.

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Bulk metal hexacyanoferrate ͑MHCF͒ has been synthesized within the porous microstructure of conductive composite materials using a simple chemical procedure. The composite materials consist of micrometer-size graphite particles encapsulated in a SiO 2 solid matrix using a sol-gel technique. A strong electrochemical signal from the chemically treated composites is associated with electrochemically switched alkaline-cation exchange. The exchange capacity of these composite electrodes exceeds by more than two orders of magnitude that of thin-film MHCF electrodes of comparable dimensions. The effects of some fabrication parameters on the cation-exchange capacity and on the distribution of the hexacyanoferrate within the composite electrodes are presented.Metal hexacyanoferrates ͑MHCFs͒ are inorganic compounds capable of selectively exchanging alkaline cations in aqueous media. 1,2 This particular property makes MHCFs attractive for the selective removal of radioactive Cs ϩ from high Na ϩ and K ϩ nuclear wastes as well as in the water deionization processes in general. 2 The cation-exchange capability of MHCF compounds arises from an inherent charge imbalance; alkaline cations must intercalate into ͑and deintercalate out of͒ the MHCF matrix in order to maintain electroneutrality. Equation 1 is a simplified representation of this reversible process for a MHCF whose stoichiometry is analogous to soluble prussian blue 3,4where M ϭ Ni II , Co II , Zn II , Fe II , or Cu II , A is an intercalated alkaline cation, and A ϩ is an alkaline cation in solution. Note that Eq. 1 assumes completely oxidized and completely reduced iron states. If the iron centers are accessed electrochemically, the life expectancy of MHCF can reach thousands of cation-exchange cycles with minimal capacity losses. 5-9 This process, termed electrochemically switched ion exchange ͑ESIX͒, 2,10,11 controls the cation loading and unloading processes via an applied electrode potential. The separation media used in ESIX processes must first be selective for a target ion; MHCFs are selective for Cs ϩ . Electroactive nickel hexacyanoferrate ͑NiHCF͒, in fact, intercalates ca. 10 4 more Cs ϩ into its matrix than competing alkaline cations present in solution. 4 The separation material must also be able to empty all intercalated alkaline cations as the matrix approaches a fully oxidized state. Recent work using Raman and energy dispersive spectroscopies 12,13 molecular dynamics simulations, 14 and X-ray diffraction ͑XRD͒ and extended X-ray absorption fine structure ͑EXAFS͒ 12 has probed the oxidation state, stoichiometry, cation content, and structure of electroactive NiHCF to address this issue. The third and final characteristic important for an ESIX separation material is high cation-exchange capacity.Thin-film, electroactive NiHCF electrodes can be easily prepared by anodic dissolution of a nickel substrate in a ferricyanide solution 5,11 or by cathodic deposition onto platinum and gold substrates from dilute solutions of ferricyanide and Ni͑II͒. 3,4 Nominal ...

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Section: Results and Discusionmentioning

confidence: 99%

mentioning

confidence: 99%

High Capacity SiO[sub 2]-Graphite Composite Electrodes with Chemically Incorporated Metal MHCFs for Electrochemically Switched Alkaline Cation Exchange

Reyes-Gómez

Médina

Jeerage

et al. 2004

J. Electrochem. Soc.

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“…With the consecutive cycling till the 50th cycle, the oxidation peak shifts negatively and decreases little by little. Since the anion exchange capacity can be estimated by comparing the charge passed, that is, the area under the curve for each potential scan, 24 it is shown that the anion exchange capacity of the copolymer decays with potential scanning.…”

Section: Ion Exchange Between Tsamentioning

confidence: 99%

Electrically controllable perchlorate removal based on poly(aniline‐co‐o‐aminophenol) doped with p‐toluene sulfonate

Dai

Liu

et al. 2015

J of Applied Polymer Sci

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Poly(aniline-co-o-aminophenol) (PANOA) was synthesized via electrochemical copolymerization of o-aminophenol and aniline using p-toluene sulfonate (TSA 2 ) as the counterion. The redox transformation of PANOA is accompanied by the exchange of anions into and out of the copolymer, and the feasibility of perchlorate (ClO 4 2 ) removal via an electrically switched ion exchange process was evaluated in this study. The results of electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared spectroscopy (FTIR) demonstrated the successful release of TSA 2 upon reduction and uptake of ClO 4 2 upon reoxidation of the copolymer. Also, in this work, the possible ion-exchange mechanism of PANOA wasproposed.

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“…This approach appears to suffer from a gradual degradation of the electrodes due to a loss of polypyrolle. Another process involves the use of electrodes coated with films of electroactive ferrocyanide for selective removal Cs+ from solutions of sodium salts [46]. Here too electrode life may be limited by the stability of the electroactive film.…”

Section: Recent Improvements In Ro Technolo~mentioning

confidence: 99%