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Manganese dioxide ion‐sieves are known to be highly efficient lithium adsorbents, owing to their high adsorption capacity and selectivity. However, their manganese dissolution rate during acid desorption is high. Therefore, electrically switched ion exchange (ESIX) was proposed to recover Li+ from brine. Cyclic voltammetry results indicated that ESIX could be applied to capture lithium from the Li+‐containing solutions. Besides, the electrochemical behaviour of Li+ in LiMn2O4/λ‐MnO2 structures was studied, wherein Na+, K+, Ca2+, and Mg2+ naturally coexisted with Li+ in the brine. No redox peaks were observed between 0.3–1.2 V in the MCl solution (MCl = NaCl, KCl, CaCl2, and MgCl2), and the positions of the redox peaks in the LiCl solution were similar to those in the LiCl and MCl mixed solution, indicating that Na+, K+, Ca2+, and Mg2+ barely interacted with the λ‐MnO2 electrode under the experimental conditions. Based on the experimental results, the Li+ adsorption capacity was determined to be ∼2 mmol · g−1, and the selectivity coefficients of Li+ for Na+, K+, Ca2+, and Mg2+ were 38.78, 35.63, 29.04, and 120.08, respectively. Furthermore, by using ESIX, the Li+ adsorption capacity of the λ‐MnO2 electrode was 82.8 % of its initial value after 50 adsorption‐desorption cycles. Thus, we concluded that ESIX involving an λ‐MnO2 electrode can be used to separate Li+ from brine with excellent selectivity coefficients. [ABSTRACT FROM AUTHOR]

The cubic phase LiMnO precursors are prepared by high-temperature calcinations (1003 K) of LiOH⋅HO and MnO mixture with Li/Mn molar ratio = 0.55. The LiMnO precursors are synthesized via low-temperature solid-phase reaction (673 K) of LiNO and MnO mixture with Li/Mn molar ratio = 1.0. The ion-sieves counterparts (named SMO-H and SMO-L, respectively) are obtained by the acid treatment of Li-Mn-O precursors. The structure, chemical stability, morphology, ion-exchange property and mechanism of Li-Mn-O precursors and MnO ion-sieve were systematically examined via X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), Infrared Spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and lithium ion selective adsorption measurements. The result shows the more compact Mn-O lattice makes the LiMnO spinel more stable after the Li is extracted. The results of IR and XPS show adsorption process of SMO-H exists ion-exchange between the Li and protons, and redox reaction, but only exists ion-exchange between the Li and protons in SMO-L. Agglomeration is well-improved by low calcination temperature and the morphology of the LiMnO precursor and final MnO ion-sieve are effectively controlled within low-dimensional structure. The maximum pH titration capacity of SMO-L for Li is 6.76 mmol⋅g, but only 3.47 mmol⋅g for SMO-H. The ion-sieve obtained from LiMnO precursor is promising in the lithium extraction from brine or seawater. [ABSTRACT FROM AUTHOR]

Spinel-type ternary LiMn2O4 oxide precursor was synthesized by direct hydrothermal synthesis of Mn(NO3)2, LiOH, and H2O2 at 383 K for 8 h, a better technique for controlling the nanocrystalline structure with well-defined pore size distribution and high surface area than the traditional solid state reaction method. The final low-dimensional MnO2 nanorod ion-sieve with a lithium ion selective adsorption property was further prepared by an acid treatment process to completely extract lithium ions from the Li–Mn–O lattice. The effects of hydrothermal reaction conditions on the nanostructure, chemical stability, and ion-exchange property of the LiMn2O4 precursor and MnO2 ion-sieve were systematically examined via powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), and lithium ion selective adsorption measurements. The results show that this new kind of low-dimensional MnO2 nanorod can be used for lithium extraction from aqueous environments, including brine, seawater, and waste water. [ABSTRACT FROM AUTHOR]

In this study, a process for preparing battery-grade lithium carbonate with lithium-rich solution obtained from the low lithium leaching solution of fly ash by adsorption method was proposed. A carbonization-decomposition process was carried out to remove impurities such as iron and aluminum. First, primary Li2CO3 was treated by CO2 to get the more soluble bicarbonates. The decomposition of LiHCO3 produced insoluble Li2CO3 at 90 °C And Li2CO3 was smashed by air stream pulverization. The final precipitation yielded a high purity (99.6%) and homogeneous Li2CO3. Some factors affecting production efficiency were investigated. The results showed that a liquid-solid ratio of 25:1, a carbonization temperature of 25 °C, an air velocity of 2 L/min, and a stirring speed of 400 rpm; a decomposition temperature of 90 °C and a stirring speed of 400 rpm, a molar ratio of EDTA to Ca 2:1; an air pressure of 0.3 MPa and hot water washing precipitate (L/S mass ratio 2:1) promoted ions removal. [ABSTRACT FROM AUTHOR]

In this work, a physical–chemical activation desilication process was proposed to extract silica from high alumina fly ash (HAFA). The effects of fly ash size, hydrochloric acid concentration, acid activation time, and reaction temperature on the desilication efficiency were investigated comprehensively. The phase and morphology of the original fly ash and desilicated fly ash were analyzed by X-ray diffraction (XRD) and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS). Compared with the traditional desilication process, the physical–chemical activation desilication efficiency is further increased from 38.4% to 53.2% under the optimal conditions. Additionally, the kinetic rules and equations were confirmed by the experimental data fitting with shrinking core model of liquid–solid multiphase reaction. Kinetic studies show that the enhanced desilication process is divided into two processes, and both steps of the two-step reaction is controlled by chemical reaction, and the earlier stage activation energy is 52.05 kJ/mol and the later stage activation energy is 58.45 kJ/mol. The results of mechanism analysis show that physical activation breaks the link between the crystalline phase and the amorphous phase, and then a small amount of alkali-soluble alumina in the amorphous phase is removed by acid activation, thereby suppressing the generation of side reactions of the zeolite phase. [ABSTRACT FROM AUTHOR]