Molecular Tuning of Redox‐Copolymers for Selective Electrochemical Remediation

Abstract

Molecular design of redox-materials provides a promising technique for tuning physicochemical properties which are critical for selective separations and environmental remediation. Here, the structural tuning of redox-copolymers, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TMA) and 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine (TMPMA), denoted as P(TMA x-co-TMPMA 1−x), is investigated for the selective separation of anion contaminants ranging from perfluorinated substances to halogenated aromatic compounds. The amine functional groups provide high affinity toward anionic functionalities, while the redox-active nitroxyl radical groups promote electrochemically-controlled capture and release. Controlling the ratio of amines to nitroxyl radicals provides a pathway for tuning the redox-activity, hydrophobicity, and binding affinity of the copolymer, to synergistically enhance adsorption and regeneration. P(TMA x-co-TMPMA 1−x) removes a model perfluorinated compound (perfluorooctanoic acid (PFOA)) with a high uptake capacity (>1000 mg g −1) and separation factors (500 vs chloride), and demonstrates exceptional removal efficiencies in diverse perand polyfluoroalkyl substances (PFAS) and halogenated aromatic compounds, in various water matrices. Integration with a boron-doped diamond electrode allows for tandem separation and destruction of pollutants within the same electrochemical cell, enabling the energy integration of the separation step with the catalytic degradation step. The study demonstrates for the first time the tuning of redox-copolymers for selective remediation of organic anions, and integration with an advanced electrochemical oxidation process for energy-efficient water purification.

Electrochemical approaches for selective recovery of critical elements in hydrometallurgical processes of complex feedstocks

“…Combined efforts for engineering of heterogeneous electrode interfaces, electrolytes, fluid dynamic behavior, and operational parameters are needed. For example, judicious selection of cell architecture and electrochemical design has enabled tandem separations on both working and counter electrodes ( Su et al., 2017 ), as well integrated reactive separations ( Kim et al., 2020a , 2020b ; Su et al., 2018 ), with energy consumption being minimized through overpotential control. We believe that synergistic design of molecular interfaces and electrochemical engineering can pave the way to a promising future for process intensification.…”

Reversible adsorption and desorption of PFAS on inexpensive graphite adsorbents via alternating electric field

“…When an external electric eld is applied across the electrodes submerged in water, the ionized contaminants are attracted and adsorb to an electrode surface with an opposite charge. 44,45,56,57 Thus, PFAS dissolved in water can adsorb to an anode upon application of an electric eld. For example, Li et al 44 demonstrated that PFOA adsorbed to a multiwalled carbon nanotube electrode upon application of voltage (V ¼ 0.6 V) resulting in a 150-fold increase in adsorption capacity compared to that without an electric eld.…”

Electrically Controlled Anion Exchange Based on a Polypyrrole/Carbon Cloth Composite for the Removal of Perfluorooctanoic Acid

“…Various PFAS removal methods have been reported. − Among them, adsorption is a mature and feasible process for both in situ and ex situ removal of PFAS from contaminated water. The most widely used adsorbent, activated carbon (AC), has proven to be a useful adsorbent for PFAS, but its low regeneration efficiency and safety concerns about the disposal of used AC could be troublesome. , Therefore, extensive research is needed to develop adsorbent materials with high adsorption capacity and excellent regeneration ability.…”