Magnesium germanium oxide hydrate nanowires with outstanding surface stability for selective cationic dye removal

Physical adsorption is one of the most promising methods for organic dye removal in wastewater. However, existing adsorbent materials lack a combination of selectivity, efficiency, stable performance over a wide pH range, and reusability after repeated regeneration. In this work, we presented a novel adsorbent, magnesium germanium oxide hydrate (MGOH) nanowires. Utilizing electrochemical and acid-base titration methods, we found that MGOH possesses a unique crystal structure that is rich in hydroxyl (-OH) groups. These -OH groups keep the surface of MGOH negatively charged over a wide pH range from 0 to 10.6, which hasn’t been achieved by any adsorbent to date. Using rhodamine B (RhB) as a model cationic dye, we demonstrated that a 97.4 % removal efficiency can be achieved within 15 min in contact with MGOH at room temperature. The adsorption selectivity of MGOH toward cationic dyes was further demonstrated by effective removal of target dyes in dye mixtures. In addition, MGOH can be easily regenerated through solvent washing and thermal annealing for multiple cycles without losing its adsorption capability.