Redox-Active Interfaces for Electrochemical Reactive Separations and Process Intensification

Abstract

The modular nature of an electrochemical system makes it a promising platform for process intensification, enabling to combine reactions and separations. Redox-functionalized materials can play a major role in integrating electrochemical reactions and separations, especially for water purification and environmental applications.1, 2 In this approach, molecular engineering of redox-active materials provides a way of tuning physicochemical properties which are critical for selective separations, regeneration, and conversion. In our work, we discuss the development of redox-active electrodes and systems for electrochemical reactive separations of heavy metal and organic micropollutants. First, the tandem selective capture and conversion of As(III) to As(V) is achieved using an asymmetric design of two redox‐active polymers, poly(vinyl)ferrocene (PVF) and poly‐TEMPO‐methacrylate (PTMA).3 During capture, PVF selectively removes As(III) with exceptional uptake (>100 mg As/g adsorbent), and during release, synergistic electrocatalytic oxidation of As(III) to As(V) with >90% efficiency can be achieved by PTMA, a radical‐based redox polymer. The system demonstrates >90% removal efficiencies with real wastewater and concentrations of arsenic as low as 10 ppb. By integrating electron‐transfer through the judicious design of asymmetric redox‐materials, an order‐of‐magnitude energy efficiency increase can be achieved compared to non‐faradaic, carbon‐based materials. Second, the molecular tuning of redox-copolymers is leveraged for controlling synergistic electrostatic and hydrophobic interactions, enabling selective capture and reversible release of organic micropollutants of emerging concern including per- and polyfluoroalkyl substances (PFAS).4 Various PFASs are separated in different water matrices, with the high separation factor of > 500. The integrated capture and degradation of PFAS is enabled based on judicious design of electrode materials and electrochemical parameters. Our findings are expected to provide an energy-efficient and sustainable platform for integrating reactions and separations electrochemically, for the process intensification in water purification and environmental remediation.