(449cf) H2TiO3 Composite Nanofibers for Lithium Recovery from Seawater and Aqueous Resource

Lithium shortage is inevitable given the massive growth in its demand for use in transportation industry and various technologies. Thus, recovery of lithium from seawater and brine through ion exchange has become an attractive option to potentially alleviate the impending crisis on lithium shortage. Adsorption is considered as one of the simplest and most promising methods to mine lithium from aqueous resources. Manganese-based lithium ion sieves (LIS) have been the most popular and well-studied lithium adsorbents.

Recently, titanium-based inorganic materials (i.e. Li₂TiO₃)have demonstrated a strong potential as LIS for the selective capture of lithium ions. As a precursor, Li₂TiO₃ is transformed as the final LIS material (H₂TiO₃) via acid delithiation. H₂TiO₃ (HTO) has high theoretical capacity (126.47 mg/g) and a chemically stable structure as indicated by its low titanium dissolution upon acid pickling. However, HTO application in actual systems is limited due to the difficulty in its handling. The HTO powders must be incorporated in a suitable solid support for its efficient utilization. Herein, electrospun nanofibers (NFs) with unique dimensional properties were employed to serve as three-dimensional frameworks for HTO.

Different polymeric materials such as polyacrylonitrile (PAN), polysulfone (PSf), polyvinyl chloride (PVC), and polyvinylidene fluoride (PVDF) were screened to identify the most suitable matrix for the HTO powder. NFs with varied HTO loading were prepared by electrospinning method. The composite nanofibers were characterized by SEM-EDS, UTM mechanical test, TGA and then applied for selective lithium ion (Li⁺) adsorption. Selection of the most suitable composite was conducted through a surface response methodology (RSM) using central composite design (CCD) of experiments.

From the developed optimization models and experimental results, it was determined that PAN composite NFs with 100 wt% HTO loading exhibited the highest adsorption capacity (31.4 mg g^-1) and superior mechanical property. It retained up to 93.6% of the adsorption capacity of the pure HTO powder (33.6 mg g^-1). The captured Li⁺ were easily recovered by mild acid treatment (0.25M HCl) of the spent PAN-HTO NF, which was also regenerated for reuse. Cycled experiments showed the reusability (at least 5 times) and stability of the composite NF, which also effectively recovered Li⁺ from an actual source (seawater). Overall, the results of the study showed the feasibility of using PAN-HTO NF for continuous and efficient recovery of lithium ions from aqueous resources.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2009-0093816) and Ministry of Science, ICT and future Planning (2015R1A2A1A15055407).