High-Efficiency Recovery of Acetic Acid from Water Using Electroactive Gas-Stripping Membranes

Abstract

Recovery of carbon-based resources from waste is a critical need for achieving carbon neutrality and reducing fossil carbon extraction. We demonstrate a new approach for extracting volatile fatty acids (VFAs) using a multifunctional direct heated and pH swing membrane contactor. The membrane is a multilayer laminate composed of a carbon fiber (CF) bound to a hydrophobic membrane and sealed with a layer of polydimethylsiloxane (PDMS); this CF is used as a resistive heater to provide a thermal driving force for PDMS that, while a highly hydrophobic material, is known for its ability to rapidly pass gases, including water vapor. The transport mechanism for gas transport involves the diffusion of molecules through the free volume of the polymer matrix. CF coated with polyaniline (PANI) is used as an anode to induce an acidic pH swing at the interface between the membrane and water, which can protonate the VFA molecule. The innovative multilayer membrane used in this study has successfully demonstrated a highly efficient recovery of VFAs by simultaneously combining pH swing and joule heating. This novel technique has revealed a new concept in the field of VFA recovery, offering promising prospects for further advancements in this area. The energy consumption was 3.37 kWh/kg for acetic acid (AA), and an excellent separation factor of AA/water of 51.55 ± 2.11 was obtained with high AA fluxes of 51.00 ± 0.82 g.m–2hr–1. The interfacial electrochemical reactions enable the extraction of VFAs without the need for bulk temperature and pH modification.

Maximizing Biochemical and Energy Recovery from Wastewater Using Vapor-Gap Membranes

“…The locally increased pH protonated VFAs, and allowed their transfer across the VGM. 146 A challenge outside the separation process stems from the biological production of VFAs, as the mixed culture fermentation results in a wide spectrum of end products. In particular, carbohydrate fermentation leads to various products including VFAs and larger fatty acids, alcohols, carbon dioxide, and hydrogen.…”

“…The conductive layer of the membrane serves as an anode, producing protons in the vicinity of the VGM. The locally increased pH protonated VFAs, and allowed their transfer across the VGM . A challenge outside the separation process stems from the biological production of VFAs, as the mixed culture fermentation results in a wide spectrum of end products.…”