Dataset on Borate Enrichment Patterns and Boron Extraction by Dilution from the Brines of Dachaidan and Jibu Chaka Salt Lakes

Brines from two different types of salt lakes, the Dachaidan Salt Lake (a magnesium sulfate subtype) and the Jibu Chaka Salt Lake (a sodium sulfate subtype), were selected for this comparative study. The chemical compositions of the initial brines, designated DL0 and JBL0, are detailed in Table 1. These initial brines were subjected to evaporation at room temperature to prepare concentrated, boron-rich brines at different stages, labeled DL5 and JBL5. These concentrated brines were subsequently used for crystallization kinetics and dilution-based boron extraction experiments.Phase analysis of solid samples was conducted using an X-ray diffractometer (XRD, PANalytical). The instrument was operated with a Cu Kα1 radiation source (λ = 0.154 nm) at a tube voltage of 40 kV and a tube current of 30 mA. Scans were performed over a 2θ range of 5° to 70°. Borate speciation in the brines was characterized using a Raman spectrometer (DXR, Thermo Fisher Scientific) equipped with a 532 nm excitation laser. Spectra were collected over a range of 400–2600 cm⁻¹, with an exposure time of 180 s, a spectral resolution of 3 cm⁻¹, and a 1200 lines/mm grating.An accurately weighed mass of the boron-rich concentrated brine (DL5 or JBL5) was diluted with a quantitative amount of deionized water. The resulting mixture was placed in a constant-temperature, well-sealed glass vessel and stirred to promote solid precipitation. Starting from the initiation of the reaction, liquid samples were rapidly withdrawn at regular intervals through a porous filter. The boron concentration in the liquid phase was measured to plot concentration-time (c-t) curves. After crystallization was complete, the solid product was collected by filtration, washed sequentially with deionized water and absolute ethanol, and dried at 60°C for 12 hours before phase identification. The experiments were conducted at set temperatures of 278 K and 298 K, with mass dilution ratios (brine/water) of 0.5 and 1.0.Based on Nielsen's crystal growth theory , where crystal growth is primarily controlled by surface reaction processes, three models were considered: the polynuclear surface growth model (MA model), the mononuclear surface growth model (MB model), and the linear surface growth model (MC model). Using MATLAB software, combined with numerical optimization algorithms and the Runge-Kutta method, the different models were solved and analyzed. This approach was used to calculate the kinetic equations for the dilution-crystallization of the brines and to determine the underlying crystallization mechanism.In accordance with preliminary studies, a specific amount of the boron-rich mother liquor (DL5 and JBL5) was weighed and diluted with water at mass ratios (brine/water) of 0.5 and 1.0. After stirring to ensure homogeneity, the diluted solutions were sealed with aluminum foil and allowed to crystallize for approximately 15 days at a set temperature. Following crystallization, solid-liquid separation was performed. The filter cake was washed three times with deionized water and subsequently three times with absolute ethanol, then dried. The dried product underwent phase identification by XRD. Concurrently, chemical phase analysis was conducted on both the solid and liquid phases to determine their boron content, from which the crystallization yield was calculated.