Electrochemically Mediated Sustainable Separations in Water

Tan, Kai‐Jher; Hatton, T. Alan

doi:10.1002/9781119740117.ch1

Cited by 3 publications

(4 citation statements)

References 375 publications

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“…Electrochemical water treatment technologies possess several advantages over established methods in that they can be fabricated in a compact and modular fashion for incorporation with other units and devices, automated for remote monitoring and control, adjusted easily to accommodate input stream variations, and operated without manual chemical addition. However, to ensure their adoption for water purification moving forward, important issues such as energy consumption, electrode stability, and toxic by-product formation must be addressed. , Electrochemically mediated separation processes that leverage redox-active materials for selective species removal have been identified as a prospective solution to meet this need due to their propensities for reversible operation, designed analyte targeting, and lower energetic requirements …”

Section: Introductionmentioning

confidence: 99%

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments

Tan,

Morikawa,

Hemmatifar

et al. 2023

ACS Appl. Mater. Interfaces

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Adaptable redox-active materials hold great potential for electrochemically mediated separation processes via targeted molecular recognition and reduced energy requirements. This work presents molecularly tunable vinylferrocene metallopolymers (P-(VFc-co-X)) with modifiable operating potentials, charge storage capacities, capacity retentions, and analyte affinities in various electrolyte environments based on the hydrophobicity of X. The styrene (St) co-monomer impedes hydrophobic anions from ferrocene access, providing P(VFc-co-St) with specific response capabilities for and greatly improved cyclabilities in hydrophilic anions. This adjustable electrochemical stability enables preferential chromium and rhenium oxyanion separation from both hydrophobic and hydrophilic electrolytes that significantly surpasses capacitive removal by an order of magnitude, with a robust perrhenate uptake capacity of 329 mg/g VFc competitive with established metal−organic framework physisorbents and 17-fold selectivity over 20-fold excess nitrate. Pairing P(VFc-co-X) with other solution-specific electroactive macromolecules such as the pH-dependent poly(hydroquinone) (PHQ) and the cesium-selective nickel hexacyanoferrate (NiHCF) generates dual-functionalized electrosorption cells. P(VFc-co-X)//PHQ offers optimizable energetics based on X and pH for a substantial 4.6-fold reduction from 0.21 to 0.04 kWh/mol rhenium in acidic versus near-neutral media, and P(VFc-co-St)//NiHCF facilitates simultaneous extraction of rhenium, chromium, and cesium ions. Proof-of-concept reversible perrhenate separation in flow further highlights such frameworks as promising approaches for next-generation water purification technologies.

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Section: Introductionmentioning

confidence: 99%

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments

Tan,

Morikawa,

Hemmatifar

et al. 2023

ACS Appl. Mater. Interfaces

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“…Redox-active compounds are employed ubiquitously in a wide range of electrochemically mediated applications such as energy storage, , sensing, catalysis, and, more recently, separations. , The electroactive properties of such molecules can be activated homogeneously as a liquid or via dissolution in aqueous or organic solvents, for subsequent leverage of their resulting flowability in multiple areas such as flow batteries, chemical conversion, and electrochemical carbon dioxide removal. , Alternatively, materials developed from redox-active species can also be configured for use on heterogeneous electrodes in the form of chemically synthesized polymers, electropolymerized films, self-assembled monolayers, crystalline structures, , and organic–inorganic hybrids. , In addition to practical considerations like ease of preparation, the operational performance, tunability, and stability of such redox-active surfaces in differing solutions are key points of interest.…”

Section: Introductionmentioning

confidence: 99%

Electroactive Behavior of Adjustable Vinylferrocene Copolymers in Electrolyte Media

Tan,

Morikawa,

Hatton

2024

J. Phys. Chem. B

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The redox-active properties of a series of ferrocene-containing vinyl polymers were investigated in aqueous and organic media. Each metallopolymer contained vinylferrocene (VFc) and a non-redox-active species (X), and was combined with carbon nanotubes (CNT) to generate P(VFc n -co-X1–n )–CNT composites for heterogeneous electrochemical analysis. Tunable pseudocapacitances spanning ca. 0.03–280 F/g VFc in aqueous solution were achieved by varying the copolymer composition, with P(VFc0.11-co-HEMA0.89) producing standardized values at ca. 160–180 F/g VFc even for differently hydrated anions. Additionally, the polymer-bound ferrocene/ferrocenium redox potential was seen to depend prominently on its electrolyte anion’s Gibbs free energy of hydration. Although the hydrophilic chloride anion negatively influenced the electrochemical stability of the VFc units when in their PVFc homopolymer, copolymerizing them with 2-hydroxyethyl methacrylate (HEMA) and introducing perchlorate anions ameliorated their overall capacity retention by 64% and 38%, respectively. Lastly, the electrodes’ responses in aprotic and protic solvents were examined for correlations with numerous solvent polarity metrics and solubility measures, with a notable observation being the stability and pseudocapacitive increase of the styrene (St)-containing P(VFc0.27-co-St0.73)–CNT from 5 to ca. 190 F/g VFc when in methanol instead of water. This study can help provide insight regarding material design considerations for redox moiety implementation in electrochemical applications.

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“…Redox-active species find great application in a plethora of areas, with the most notable being energy storage, sensing, catalysis, and more recently, the burgeoning field of electrochemically mediated separation techniques. , The unique nature of these compounds allows their oxidation states to be altered chemically or through the more utile approach of an electrochemical stimulus. Molecular recognition is a key requirement for many redox-based processes .…”

Section: Introductionmentioning

confidence: 99%

“…Redox-active macromolecules have previously been developed and investigated as potential materials for electrochemically mediated analyte targeting. , Specificity can be imparted through molecular imprinting techniques but can also be an innate property. For example, coordination polymers such as transition metal hexacyanoferrates and metal–organic frameworks have been shown to be able to electrochemically detect metal ions, conducting polymers have been utilized for gas sensing, and polymeric quinones have exhibited pH- and carbon dioxide-dependent electroactive responses .…”

Section: Introductionmentioning

confidence: 99%

Redox Polyelectrolytes with pH-Sensitive Electroactive Functionality in Aqueous Media

et al. 2023

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A framework of ferrocene-containing polymers bearing adjustable pH-and redox-active properties in aqueous electrolyte environments was developed. The electroactive metallopolymers were designed to possess enhanced hydrophilicity compared to the vinylferrocene (VFc) homopolymer, poly-(vinylferrocene) (PVFc), by virtue of the comonomer incorporated into the macromolecule, and could also be prepared as conductive nanoporous carbon nanotube (CNT) composites that offered a variety of different redox potentials spanning a ca. 300 mV range. The presence of charged non-redox-active moieties such as methacrylate (MA) in the polymeric structure endowed it with acid dissociation properties that interacted synergistically with the redox activity of the ferrocene moieties to impart pH-dependent electrochemical behavior to the overall polymer, which was subsequently studied and compared to several Nernstian relationships in both homogeneous and heterogeneous configurations. This zwitterionic characteristic was leveraged for the enhanced electrochemical separation of several transition metal oxyanions using a P(VFc 0.63 -co-MA 0.37 )-CNT polyelectrolyte electrode, which yielded an almost twofold preference for chromium as hydrogen chromate versus its chromate form, and also exemplified the electrochemically mediated and innately reversible nature of the separation process through the capture and release of vanadium oxyanions. These investigations into pH-sensitive redox-active materials provide insight for future developments in stimuliresponsive molecular recognition, with extendibility to areas such as electrochemical sensing and selective separation for water purification.

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Electrochemically Mediated Sustainable Separations in Water

Cited by 3 publications

References 375 publications

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments

Hydrophobicity Tuned Polymeric Redox Materials with Solution-Specific Electroactive Properties for Selective Electrochemical Metal Ion Recovery in Aqueous Environments

Electroactive Behavior of Adjustable Vinylferrocene Copolymers in Electrolyte Media

Redox Polyelectrolytes with pH-Sensitive Electroactive Functionality in Aqueous Media

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