A potential-driven FeMnOx/CNTs film electrode for efficient extraction of WO42- via electrochemical coordination and inner-sphere complexation

Abstract

A film electrode materials of iron-manganese oxide composite carbon nanotubes (FeMnOx/CNTs) with dual adsorption sites was obtained by a co-precipitation method, which exhibited excellent selectivity of WO42- in an electrochemically switched ion exchange (ESIX) system. The main components of FeMnOx are MnOx and Fe(OH)3. In FeMnOx/CNTs composite film, Fe(OH)3 with abundant hydroxyl functional groups on its surface improved the ion storage capacity, while MnOx served as the main selective separation material to selectively adsorb the WO42-. A scalable ESIX pilot system was also designed to examine the effect of different operating conditions on system performance. The W(Ⅵ) adsorption capacity was as high as 187.76 mg/g and the separation factor of W/Mo was 21.03. Combining experimental characterization and results, it was confirmed that the highly efficient selective extraction of WO42- in neutral solution should be derived from the dual-site (i.e., electrochemical coordination sites on MnOx and electrochemically induced inner-sphere complexation sites on Fe(OH)3) adsorption. Hence, it is believed that such a novel electroactive FeMnOx/CNTs film electrode with dual adsorption sites could be a promising candidate for industrialized tungsten-molybdenum separation by ESIX technology.