Min Wang

Based on the solubility and supersolubility data of Li₃PO₄ in pure water and sodium carbonate solutions, a new process for preparing battery-grade Li₃PO₄ from salt lake mother liquor via acidification and lithium precipitation was developed.

A novel ternary eutectic salt, NaNO₃-KNO₃-Na₂SO₄ (TMS), was designed and prepared for thermal energy storage (TES) to address the issues of the narrow temperature range and low specific heat of solar salt molten salt. The thermo-physical properties of TMS-2, such as melting point, decomposition temperature, fusion enthalpy, density, viscosity, specific heat capacity and volumetric thermal energy storage capacity (E_TES), were determined. Furthermore, a comparison of the thermo-physical properties between commercial solar salt and TMS-2 was carried out. TMS-2 had a melting point 6.5 °C lower and a decomposition temperature 38.93 °C higher than those of solar salt. The use temperature range of TMS molten salt was 45.43 °C larger than that of solar salt, which had been widened about 13.17%. Within the testing temperature range, the average specific heat capacity of TMS-2 (1.69 J·K⁻¹·g⁻¹) was 9.03% higher than that of solar salt (1.55 J·K⁻¹·g⁻¹). TMS-2 also showed higher density, slightly higher viscosity and higher E_TES. XRD, FTIR and Raman spectra SEM showed that the composition and structure of the synthesized new molten salt were different, which explained the specific heat capacity increasing. Molecular dynamic (MD) simulation was performed to explore the different macroscopic properties of solar salt and TMS at the molecular level. The MD simulation results suggested that cation–cation and cation–anion interactions became weaker as the temperature increased and the randomness of molecular motion increased, which revealed that the interaction between the cation cluster and anion cluster became loose. The stronger interaction between Na-SO₄ cation–anion clusters indicated that TMS-2 molten salt had a higher specific heat capacity than solar salt. The result of the thermal stability analysis indicated that the weight losses of solar salt and TMS-2 at 550 °C were only 27% and 53%, respectively. Both the simulation and experimental study indicated that TMS-2 is a promising candidate fluid for solar power generation systems.

An acid-resistant nanofiltration (NF) membrane with high permeability and rejection is of great significance. A NF membrane was prepared via interfacial polymerization with the assistance of surfactants, where three different common surfactants were used: sodium dodecyl sulfate (SDS), sodium lauryl sulfonate, and sodium dodecyl benzenesulfonate. The addition methods of SDS were optimized, with the results showing that using SDS to activate the substrate surface significantly affects the membrane performance. The surfactant was firstly deposited on a poly(ether)sulfone (PES) support layer prior to the interfacial polymerization of polyethyleneimine (PEI) and cyanuric chloride (CC) to form an active layer. The presence of SDS on the surface of the PES support membrane improves the retention of PEI in the process of the membrane preparation, thus affecting the morphology and cross-linking degree of the membrane, and ultimately affecting its performance. The NF membrane prepared under optimized conditions exhibits a water flux of 144.7 L m⁻² h⁻¹, while its rejection of MgCl₂ was 92.2%, with a decline in the rejection after one-month of acid soaking tests to give a value that is lower by 1.7%. The prepared NF membrane has good water flux and rejection properties, and exhibits long-term acid resistance.

This paper concerns the feasibility of separating Al ³⁺ and Li ⁺ by nanofiltration, and a new method for separating and recovering lithium from lepidolite leaching solution was proposed. Factors like salinity, mass ratio of Al ³⁺ /Li ⁺ , operating pressure, temperature and proportion of SO ₄ ²⁻ were investigated under single‐stage cycle mode. Multiple linear regression was used to further study the mixed effect of pressure and temperature on separation efficiency and membrane flux. The results suggest that the combination of charge effect and steric hindrance effect plays a decisive role in the separation of lithium and aluminum. When the salinity of the feed solution is 45 g/L and the mass ratio of Al/Li is 6, a combination of higher temperature and pressure within the range that the membrane can withstand is beneficial to improve separation efficiency. And a proper amount of SO ₄ ²⁻ is beneficial for the separation of aluminum and lithium. Overall, it is found that nanofiltration has a relatively good separation efficiency of lithium and aluminum and provided a novel vision for future separation from lepidolite leaching solution.