Process intensification of phenol recovery via carrier-conducted membrane electrodialysis with improved transport and...

The recovery of phenolic compounds from industrial wastewater as value-added chemicals is essential for sustainable economic development and ecological environment safety. Conventional solvent extraction requires stepwise stripping, and electrodialysis is seldom applied to organic pollutants because commercial ion-exchange membranes are primarily designed for inorganic ions. Here, an electrodialysis-integrated carrier-conducted membrane (CCMED) incorporating trioctylmethyl ammonium chloride as the carrier was developed for phenol recovery. The CCMED system exhibited a substantial enhancement in transport performance, with the phenol permeability coefficient increasing from 1.74 μm·s⁻¹ without an electric field to 17.26 μm·s⁻¹ at a current density of 20 mA·cm^-2. Phenolate anion transport, predominant at an alkaline condition (pH > 9), was strongly affected by solution pH and competing salt ions. Under optimum conditions, the extraction and stripping efficiencies reached 87.93 % and 80.63 %, respectively, and the phenol permeability coefficient was two times higher than that of a commercial anion exchange membrane (Astom-AGU). Furthermore, pH adjustment suggested a potential route for selective separation of phenol and other phenolic compounds by maintaining phenol in molecular form while converting nitrophenol to an ionic state. This study demonstrated the potential of CCMED as a process-intensified strategy for efficient phenol recovery and selective separation of phenolic compounds.