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Efficient lithium extraction from salt lakes is essential for a sustainable resource supply. This study tackles the challenge of separating Li+from Mg2+in complex brines by innovatively integrating two-dimensional (2D) graphene oxide (GO) with bimetallic metal–organic frameworks (MOFs). Zn2+and Co2+ions are confined within GO interlayers through an in situ synthesis, forming a 2D Zn-Co MOFs/GO membrane (Zn-Co-GOM). This design exploits the unique advantages of bimetallic MOFs, including enhanced structural stability and superior ion separation capabilities due to the synergistic effects of Zn and Co. The Zn-Co-GOM demonstrates an impressive separation factor of 191 for Li+over Mg2+, significantly surpassing traditional membranes. This exceptional selectivity is achieved through a combination of size exclusion effects and ion transport energy barriers. Our approach not only enhances the practical application of membrane technology for lithium extraction from salt lakes but also provides valuable insights into the underlying separation mechanisms.

The solid–liquid phase equilibria of brine systems containing boric acid are the theoretical basis for the development of boric acid from brine resources. The phase equilibria of the systems NaCl–CaCl2–H3BO3–H2O and CaCl2–H3BO3–H2O at 323.15 K were investigated by the isothermal solution method. The phase diagram for the ternary system is composed of one co-saturation point, two univariant solubility curves, and two singe-salt crystallization fields of CaCl2·2H2O and H3BO3. The dry-salt phase diagram for the quaternary system consists of one invariant point, three univariant solubility curves, and three single-salt crystallization fields for NaCl, CaCl2·2H2O, and H3BO3. In the phase diagrams of the quaternary system at 298.15 and 323.15 K, the areas of sodium chloride and calcium chloride salt regions are enlarged, whereas the area of the H3BO3region is diminished significantly with the increase of temperature. Using the Pitzer model, the lacking Pitzer parameters for H3BO3were obtained by fitting the solubilities in the CaCl2–H3BO3–H2O system. The calculated solubilities with the Pitzer model were in accord with the experimental data.

A magnesium hydroxide coprecipitation method for the determination of trace elements in high-salt samples from salt lake brines by inductively coupled plasma optical emission spectrometry (ICP-OES) was developed. Some effects on the coprecipitation and analysis, such as the pH value and Na and Mg amounts in primary brines, have been thoroughly investigated and optimized. After adjusting the pH to 8.70, associated with sodium hydroxide, the complicated matrix was removed from high salt brines, and thus trace amounts of Al, Co, Cu, Fe, Mn, Ni, V, and Zn were simultaneously coprecipitated and precisely determined. Recoveries of all the determined trace elements in the samples of both synthesized and real salt lake brines were more than 90%. The detection limit in the range of 0.62–14.4 μg L−1was obtained and the precision was less than 3% relative standard deviation. The optimized method has been successfully applied for the determination of trace elements in the intercrystal brine mined from Dachaidan salt lake located in the Qaidam Basin, China.