Synthesis of a carbon nanotube-modified NH2-MIL-53(Fe) adsorbent and efficient adsorption and separation of gallium ions

Abstract

As strategic emerging industries represented by clean energy technologies develop rapidly, gallium (Ga), one of the critical elements due to its use in these technologies and limited supply, has attracted worldwide attention. The discovery of appropriate materials to adsorb Ga is crucial for improving the utilization of Ga resources. With the goal to recover Ga ions more efficiently and selectively, carbon nanotubes (CNTs) and amino-functionalized MIL-53 series metal–organic skeletons were hydrothermally synthesized into CNT/NH₂-MIL-53(Fe) composite adsorbents. The composite's morphology, structure, chemistry and other physicochemical features were characterized, and the adsorption conditions including pH, initial Ga concentration, along with adsorbent dosage were optimized. The outcomes suggest that 2-CNT/NH₂-MIL-53(Fe) performs better than the unmodified material in adsorption, and the theoretical maximum adsorption amount of Ga is 1483.8 mg g⁻¹. The adsorption exhibited a single layer chemisorption with an endothermic spontaneous reaction. The adsorption mechanism for Ga onto 2-CNT/NH₂-MIL-53(Fe) was mainly via ion exchange and chelation, accompanied by hydrogen bond interaction. The outstanding adsorption capacity and reproducibility using CNT/NH₂-MIL-53(Fe) composites provide a novel method for adsorbing Ga from aqueous solutions.