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

A film electrode materials of iron-manganese oxide composite carbon nanotubes (FeMnO x /CNTs) with dual adsorption sites was obtained by a co-precipitation method, which exhibited excellent selectivity of WO 4 2- in an electrochemically switched ion exchange (ESIX) system. The main components of FeMnO x are MnO x and Fe(OH) 3 . In FeMnO x /CNTs composite film , Fe(OH) 3 with abundant hydroxyl functional groups on its surface improved the ion storage capacity, while MnO x served as the main selective separation material to selectively adsorb the WO 4 2- . 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 WO 4 2- in neutral solution should be derived from the dual-site (i.e., electrochemical coordination sites on MnO x and electrochemically induced inner-sphere complexation sites on Fe(OH) 3 ) adsorption. Hence, it is believed that such a novel electroactive FeMnO x /CNTs film electrode with dual adsorption sites could be a promising candidate for industrialized tungsten-molybdenum separation by ESIX technology.