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• Structure evolution features of LDHs precursors with pH was investigated. • Role of pH on activating the performance of LDHs type adsorbents was concluded. • Precipitative formation mechanism of LDHs adsorbents was firstly proposed. Aluminum-based adsorbents, simply prepared by eluting the lithium-aluminum layered double hydroxide precursors with deionized water, is the only industrialized adsorbents for selectively separating Li+ from saline brines. Taking the roles of lattice and surface Li+ active sites on its performances into consideration, influence of ending pH modulating on prominently improving the adsorbing capacity and stability of aluminum-based adsorbents prepared by precipitation method is initially investigated. As experimentally evidenced that, the maximum desorption amount of Li+ at the eluting stage should be controlled to around 20 mg/g Li+ rather than thoroughly removed to effectively avoid the topotactic solid-phase transformation from adsorbent to α-Al(OH) 3. As-prepared adsorbents not only has high adsorption capacity up to 8.4 mg/g in 400 ppm LiCl solution, but also owns unique self-healing ability, thus promising the excellent cycling stability. It is firstly proposed that the formation of the layer-structured precursor by precipitation method is well in accordance with the three-step formation mechanism and pH modulating mainly contributes to the anions exchange between solution Cl- and interlayer OH–. This study experimentally proves the importance of pH adjusting for preparing high performance lithium adsorbents by precipitation method, which is very significant and important for effectively extracting lithium resources from the complicated multi-component liquid minerals. [ABSTRACT FROM AUTHOR]

Using 3D-rGO, an electrode with a three-dimensional conductive network was successfully constructed, which shortened the transmission path of Li+ and showed excellent kinetic properties (the rate in the first 10 min was 3.58mg·g−1·min−1), and it also has a high adsorption capacity (35.8mg·g−1). [Display omitted] • Significant improvement in the kinetic performance of lithium extraction using the LFP/rGO materials, addressing the low efficiency commonly associated with lithium extraction in salt lakes. • Demonstrated effectiveness of the LFP/rGO materials in real salt lake brine environments, highlighting their potential for practical applications. • The development of a three-dimensional conductive network-incorporated thick electrode provides new insights for the fabrication of high-performance lithium extraction electrodes. Constructing thick electrodes with high Li+ adsorption capacity and excellent kinetic performance effectively addresses the low efficiency of lithium extraction from salt lake brines. However, an increase in the content of active material can hinder the Li+ mass transfer within the electrode, resulting in polarization and reduced kinetic performance, which ultimately affects the extraction efficiency. This study synthesized a three-dimensional(3D) conductive network-incorporated thick electrode (∼20 mg/cm2) composed of the redox graphene oxide-loaded LFP(LFP/rGO) composite through an in situ hydrothermal method. The electrode material showed excellent kinetic performance and a high adsorption capacity for Li+ in salt lake brine. Under a constant voltage of 0.8 V in Li+ solution, the Li+ adsorption capacity reached 36.78 mg·g−1 within 10 min, exhibiting an average coulombic efficiency of over 83.53 %. Furthermore, the LFP/rGO composite thick electrode exhibited a Li+ adsorption capacity of 32.82 mg·g−1, along with an average coulombic efficiency of 74.6 %, even in the West Taijinar old brine solution. Additionally, the electrode material demonstrated remarkable cycling stability, maintaining a capacity of 172.09 mAh·g−1 after 50 cycles at a 0.2C rate in a high-concentration salt lake brine. Our preparation strategy offers novel insights for high-performance lithium extraction electrodes. [ABSTRACT FROM AUTHOR]

The spherical lithium ion-sieve granulations adsorbent materials combining high mechanical stability of polyvinyl chloride (PVC) and good hydrophilicity of polyacrylonitrile (PAN) were prepared, which showed excellent adsorption performance in Salt Lake brine. [Display omitted] • First granulation of adsorbent powder with PVC and PAN as binder. • The spherical adsorbent material combines the high mechanical stability of PVC and the good hydrophilicity of PAN. • The formation and working mechanisms of spherical adsorbent material is studied. • The material maintains excellent adsorption performance during 50 long cycles of adsorption and desorption. In order to effectively solve the problem of adsorbent powder forming and further promote its industrial application, granulated lithium ion-sieve powder with spherical shape by polyvinyl chloride (PVC) with high mechanical stability of and hydrophilicity of polyacrylonitrile (PAN) with good hydrophilicity was initially prepared in our study by a phase transformation method. Based on the various characterization results, spherical particles materials formation mechanisms were summarized below. Langmuir, D-R, pseudo-second-order kinetics and diffusion kinetic indicated that the adsorption process of Li+ was a multi-step controlled monolayer chemisorption process. In addition, after 50 cycles of dynamic column operation, the adsorption capacity remained around 11.90 mg g−1, and the manganese dissolution loss rate was only 0.15%, which is much lower than that as reported. Therefore, the spherical adsorbent could be used for efficiently recovery Li+ from Salt Lake brine as well as its excellent potential for further application. [ABSTRACT FROM AUTHOR]

Li 1.6 Mn 1.6 O 4 (LMO) is deemed as the most promising candidate for Li+ extraction from brine. However, it suffers from structural collapses and capacity fading during lithium adsorption/desorption cycles. To solve this problem, an effortless one-step dry method was adopted to prepared surface-fluorinated Mn-based ion-sieve materials using NH 4 F at low temperatures. XRD, FIB-SEM, HRTEM, XPS, and chemical analyses were used to characterize the crystal structure, morphology, surface information, chemical composition, and adsorption properties of the materials. The surface-fluorinated LMO showed an adsorption capacity of up to 31.86 mg g−1, a low dissolution loss ratio of Mn, and remarkable long cycle stability with a capacity retention rate of 91.29%. The main reason for the improved adsorption capacity was that the surface fluorination eroded the material outside and increased the specific surface area. Furthermore, the bond energy and structural stability of the material were enhanced by the F–Mn bond, which partially replaced the surface O–Mn bond. In addition, DFT simulation was theoretically performed to understand the improvement mechanism of the material properties by fluorination. These results provide insights into the surface fluoridation effect in the optimization of Mn-based adsorbents, and the proposed simple modification strategy has the potential to be applied to large-scale production. The surface-fluorinated Li 1.6 Mn 1.6 O 4 is prepared for the first time by a one-step simple and dry method, and it exhibits higher adsorption capacity, lower Mn loss and excellent cycling stability. [Display omitted] • The surface-fluorinated Li 1.6 Mn 1.6 O 4 is first time prepared by facile and dry method. • The enhanced structure of fluorinated sample can improve cycle stability. • DFT confirms the mechanism of the improvement of material properties. [ABSTRACT FROM AUTHOR]

Solid-phase reactions were used for the synthetization of the spinel Li 1.6 Mn 1.6 O 4 powder and the lithium ion-sieve MnO 2 ·0.5H 2 O was subsequently obtained by the leaching of the lithium. The physical characterization showed that the polycrystalline precursor and the MnO 2 ·0.5H 2 O were nearly pure spinel, as well as that during the process of the adsorption-desorption, the structural stability was high. The Langmuir isotherm and pseudo second-order kinetics model showed consistency with the adsorption behavior, which indicated the presence of homogeneous adsorption sites for the lithium adsorption and that its process was chemisorption. Adsorbents were found to remain being characterized with a relatively high Li+ uptake (26.13 ​mg ​g−1) with low manganese extracted (1.71%) after the circulation experiment was performed up to 5 times, proving a significant repeatability and stability for the lithium ion-sieve. The concentration factors exhibited the highly selective adsorption capacity for absorbent from Qarhan raw brine with high concentrations of Na+, K+, Ca2+, Mg2+. The adsorbents could be efficiently used for Li+ recovery from Salt Lake brine as well as its excellent potential for further application. Due to the sieving effect (steric hindrance effect and hydration free energy effect), the lithium ion-sieve selectively adsorbed Li+ when the ion-sieve was immersed in brine, indicating that the ion-sieve MnO 2 ·0.5H 2 O was expected to recover Li+ from the solutions including Salt Lake brine, seawater, and wastewater. Image 1 • The precursor was prepared by practical two-stage solid-phase sintering technique. • The Li 1.6 Mn 1.6 O 4 exhibited excellent adsorption performance. • The materials showed the highly selective adsorption from Qarhan raw brine. [ABSTRACT FROM AUTHOR]