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 Starting from the initiation of the reaction, liquid samples were rapidly withdrawn at regular intervals through a porous filter.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.

本对比研究选取了两类不同盐湖的卤水——大柴旦盐湖（硫酸镁亚型）与吉布查卡盐湖（硫酸钠亚型）。初始卤水分别记为DL0与JBL0，其化学组成详见表1。将上述初始卤水置于室温下蒸发，制备得到不同阶段的富硼浓缩卤水，标记为DL5与JBL5。后续实验以该浓缩卤水为对象，开展结晶动力学及基于稀释法的硼提取实验。

采用X射线衍射仪（XRD，PANalytical）对固体样品进行物相分析，测试条件为：Cu Kα1辐射源（λ=0.154 nm），管电压40 kV，管电流30 mA，扫描2θ范围为5°~70°。采用拉曼光谱仪（DXR，赛默飞世尔科技）表征卤水中的硼酸盐形态，该仪器配备532 nm激发激光，光谱采集区间为400~2600 cm⁻¹，曝光时长180 s，光谱分辨率3 cm⁻¹，光栅刻线密度1200 lines/mm。

准确称取一定质量的富硼浓缩卤水（DL5或JBL5），用定量去离子水稀释。将混合体系置于恒温密闭玻璃容器中搅拌，促进固相析出。自反应启动起，定时通过多孔过滤器快速抽取液相样品，测定液相硼浓度以绘制浓度-时间（c-t）曲线。结晶完成后，过滤收集固相产物，依次用去离子水与无水乙醇洗涤，随后于60℃下干燥12小时用于物相鉴定。本实验设置温度为278 K与298 K，质量稀释比（卤水/水）分别为0.5和1.0。

基于尼尔森晶体生长理论（该理论提出晶体生长主要由表面反应过程主导），本研究选用三类模型：多核表面生长模型（MA模型）、单核表面生长模型（MB模型）与线性表面生长模型（MC模型）。借助MATLAB软件，结合数值优化算法与龙格-库塔法（Runge-Kutta method），对不同模型进行求解与分析，以此计算卤水稀释结晶动力学方程，阐明其结晶机理。

参照前期研究，称取一定量的富硼母液（DL5与JBL5），按照质量比（卤水/水）0.5和1.0用水稀释。搅拌混匀后，用铝箔密封稀释溶液，于设定温度下结晶约15天。结晶完成后进行固液分离，滤饼依次用去离子水洗涤3次、无水乙醇洗涤3次，随后干燥。将干燥后的产物通过XRD进行物相鉴定，同时对固、液两相开展化学物相分析以测定硼含量，进而计算结晶产率。