Redox-Active Magnetic Composites for Anionic Contaminant Removal from Water

Abstract

Global water security is jeopardized by the presence of anthropogenic contaminants, which can persist resiliently in the environment and adversely affect human health. Surface adsorption of polluting species is an effective technique for water purification. In this work, redox-active magnetic compounds were designed for the targeted removal of inorganic and organic anions in water via polymeric redox-active vinylferrocene (VFc) and pyrrole (Py) moieties. An Fe3O4@SiO2@PPy@P­(VFc-co-HEMA) composite was prepared in a four-step process, with the outermost layer possessing heightened hydrophilicity as a result of the optimized incorporation of 2-hydroxyethylmethacrylate (HEMA) monomers into the backbone of the ferrocene macromolecule. The synthesized materials are able to separate carcinogenic hexavalent chromium oxyanions and other charged micropollutants, and exhibit a 2-fold or greater enhancement in adsorption uptake once the redox-active ferrocene groups are oxidized to ferrocenium cations, with capacities of 23, 49, 66, and 95 mg/g VFc for maleic acid, 2-(6-methoxy-2-naphthyl)­propionic acid (Naproxen), (2,4-dichlorophenoxy)­acetic acid (2,4-D), and (2-dodecylbenzene)­sulfonic acid (DBS), respectively, and a > 99% extractability of chromium in the 1 ppm range. The application of redox-active components to a magnetic particulate scaffold improves maneuverability and phase contact, giving rise to new potential aqueous separation process frameworks for water or product purification.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

“…While redox homopolymers are efficient for applications that demand ion selectivity, redox copolymers extend these capabilities by combining orthogonal properties. For example, redox copolymers have enhanced electrochemical regeneration, chemical binding of rare-earth elements, and control of hydrophobicity, affinity, and electrostatics within redox adsorbents for PFAS molecules and other micropollutants. ,, Nanostructured combination of two distinct redox polymers has also enabled the reversible electrochemical binding and control of neutral molecules through redox-tunable hydrophobicity . Similar concepts of hybrid materials may be generalized to redox crystals and various multicomponent separations, in which reversibility or selectivity could be enhanced through hybridization to achieve properties beyond the base chemical structure.…”

“…In these hybrid processes, a conductive membrane serves as a flow-through anode, which filters the wastewater and drives oxidation of the organic contaminants and pharmaceutical residues . Moreover, integration of redox processes and magnetic nanoparticles enables selective separation of various organic and inorganic micropollutants . We envision that emerging electrosorption and electrokinetic systems coupled with advanced oxidation processes can provide efficient process intensification for wastewater treatment.…”

“…1270 Moreover, integration of redox processes and magnetic nanoparticles enables selective separation of various organic and inorganic micropollutants. 1252 We envision that emerging electrosorption and electrokinetic systems coupled with advanced oxidation processes can provide efficient process intensification for wastewater treatment.…”

Redox Polyelectrolytes with pH-Sensitive Electroactive Functionality in Aqueous Media

“…The synthesis procedures were developed from previously reported methodologies for the free-radical polymerization of vinylferrocene-containing polymers. 33,36,37 Briefly, PVFc, P(VFc 1−m -co-HEMA m ), and P-(VFc 1−m -co-MA m ) were generally synthesized in anhydrous 1,4dioxane at 70 °C with a total monomer concentration of ca. 10 M and ca.…”

“…Ferrocene has previously been reported to exhibit selective affinities for vanadium and chromium oxyanions over competing electrolyte species, 24,27 and can remove such anions via the redox-mediated formation of surface-attached ferrocenium-anion complexes (Figure 6a). 24,25,27,33 As such, these strongly binding oxyanions were selected as the analytes in this study with the intention of allowing any effects of the non-redox-active anionic moiety on the electrosorption capacity of the overall ferrocene polymer to be more clearly observed. Pentavalent vanadium in the form of metavanandate oxyanions was subjected to electrosorption by PVFc-CNT and P(VFc 0.63 -co-MA 0.37 )-CNT at the as-made solution pH of 1 mM NaVO 3 (pH ca.…”