Adsorption of Li(I) Ions through New High-Performance Electrospun PAN/Kaolin Nanofibers: A Combined Experimental and Theoretical Calculation

Lithium (Li), as a strategic energy source in the 21st century, has a wide range of application prospects. As the demand for lithium resources grows, refining lithium resources becomes increasingly important. A novel method was proposed to directly prepare polyacrylonitrile–LiCl·2Al­(OH)3·nH2O (PAN–Li/Al-LDH) composites from kaolin with simple operation and low cost, showing effective adsorption performance for the removal of Li­(I) from brine in a salt lake. Moreover, several techniques have been applied for characterization, including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and the Brunauer–Emmett–Teller method. Batch adsorption experiments were conducted to investigate the adsorption behaviors of PAN–Li/Al-LDHs for Li­(I) in salt-lake brines, indicating that the adsorption equilibrium could reach within 2 h, and the adsorption kinetics for Li­(I) conforms to the pseudo-second-order model. The adsorption isotherms are consistent with those obtained by the Langmuir model, with a maximum adsorption capacity of 5.2 mg/g. The competitive experimental results indicated that PAN–Li/Al-LDHs exhibited specific selectivity for Li­(I) in the mixed solutions of Mg­(II), Na­(I), K­(I), and Ca­(II) with the selectivity coefficients of 9.57, 19.38, 43.40, and 33.05, respectively. Moreover, the PAN–Li/Al-LDHs could be reused 60 times with basically unchanged adsorption capacity, showing excellent stability and regeneration ability. Therefore, PAN–Li/Al-LDHs would have promising industrial application potential for the adsorption and recovery of Li­(I) from salt-lake brines

DataSheet1_Adsorption performance and mechanism of Li+ from brines using lithium/aluminum layered double hydroxides-SiO2 bauxite composite adsorbents.docx

A combined method of solid-phase alkali activation and surface precipitation was used to prepare the lithium/aluminum layered double hydroxides-SiO2 loaded bauxite (LDH-Si-BX) and applied to adsorb Li+ in brines. In the study, various characterization techniques such as SEM, XRD, BET, Zeta potential, and x-ray photoelectron spectroscopy (XPS) were applied to characterize and analyze the adsorbents. The adsorption-desorption performance of LDH-Si-BX for Li+ in brines was systematically investigated, including adsorption temperature, adsorption time, Li+ concentration, and regeneration properties. The results indicated that the adsorption kinetics were better fitted by the pseudo-second-order model, whereas the Langmuir model could match the adsorption isotherm data and the maximum Li+ capacity of 1.70 mg/g at 298K. In addition, in the presence of coexisting ions (Na+, K+, Ca2+, and Mg2+), LDH-Si-BX showed good selective adsorption of Li+, and the pH studies demonstrated that the adsorbents had better Li+ adsorption capacity in neutral environments. In the adsorption process of real brines, LDH-Si-BX had a relatively stable adsorption capacity, and after 10 cycles of adsorption and regeneration, the adsorption capacity decreased by 16.8%. It could be seen that the LDH-Si-BX adsorbents prepared in this report have the potential for Li+ adsorption in brines.</p

DataSheet1_Recovery of Lithium Ions From Salt Lakes Using Nanofibers Containing Zeolite Carriers.PDF

Lithium is a key strategic metal in the 21st century and an important raw material in the new energy sector. With rapid growth of the market demand for lithium, the high-efficient extraction of lithium resources is of important economic significance. Taking zeolite as the carrier and using chemical grafting and electrospinning technologies, a kind of nanofiber containing crown ether (CE) was synthesized to adsorb Li(I) from the salt lake brine. This realizes the selective adsorption of Li(I) while retaining specific vacancies of epoxy groups in CE. The adsorption mechanism of nanofibers containing zeolite carriers and CE for Li(I) was revealed by the use of Fourier transform infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The results show that after dsp3 hybridization of the outer orbit (2s) of Li(I), outer electrons on the nanofibers containing zeolite carriers and CE mainly migrate to the orbit for coordination with Li(I) thereat, thus realizing the capture of Li(I). The novel adsorbing material can reach adsorption equilibrium within 2.5 h and the adsorption kinetics for Li(I) conforms to the pseudo-second-order model and a maximum adsorption capacity of 8.6 mg/g. It can be found that the correlation coefficient fitted by Langmuir adsorption isotherm model is closer to 1, and the calculated maximum adsorption capacity is closer to the adsorption capacity obtained experimentally, therefore, it can be concluded that the adsorption process is more consistent with the Langmuir adsorption isotherm model, and the adsorption process can be regarded as monolayer adsorption. The adsorption capacity remains at 7.8 mg/g after 5 adsorption–desorption cycles, showing favorable stability and a strong ability to be regenerated. The research provides insights into the adsorption and recovery of Li(I) from the salt lake brine.</p

DataSheet1_Polyacrylonitrile/Crown Ether Composite Nanofibres With High Efficiency for Adsorbing Li(I): Experiments and Theoretical Calculations.docx

Lithium, as the lightest alkali metal, is widely used in military and new energy applications. With the rapid growth in demand for lithium resources, it has become necessary to improve the effectiveness of extraction thereof. By using chemical grafting and electrospinning techniques, nanofibres containing crown ether were developed for adsorbing Li(I) from the brine in salt lakes, so as to selectively adsorb Li(I) on the premise of retaining specific vacancies of epoxy groups in crown ether. In lithium-containing solution, the adsorbing materials can reach adsorption equilibrium within three hours, and the maximum adsorption capacity is 4.8 mg g−1. The adsorption mechanisms of the adsorbing materials for Li(I) were revealed by combining Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) with density functional theory (DFT) calculation. The results indicated that in crown ether, O in epoxy groups was coordinated with Li(I) to form Li–O and four O atoms in the epoxy groups were used as electron donors. After coordination, two O atoms protruded from the plane and formed a tetrahedral structure with Li(I), realising the specific capture of Li(I). By desorbing fibres that adsorbed Li(I) with 0.5-M HCl, the adsorption capacity only decreased by 10.4% after five cycles, proving ability to regenerate such materials. The nanofibres containing crown ether synthesised by chemical grafting and electrospinning have the potential to be used in extracting lithium resources from the brine in salt lakes.</p