川东北深层富锂钾溴卤水体系常温到高温相平衡研究及溶解度预测

Underground brine in the Sichuan Basin is widely distributed and rich in useful components such as K+, Br–, I–, B3+, Li+, Sr2+, and Rb+ whose contents exceed industrial requirements for separate mining and have comprehensive development and utilization prospects. The local climate experiences heavy rain and low sunshine, and the high relative humidity of the air makes it impossible to carry out preliminary concentration and separation with salt-field technology like the salt-lake in arid and semi-arid areas. The primary separation of salt in brine can only be accomplished by adding external energy in forced evaporation. To examine the mineralization process of underground brine-salt minerals and guide the exploitation of brine resources, the studies of the phase equilibria and thermodynamic properties of the corresponding systems are necessary. Based on the composition characteristics of the deep underground brine in Northeast Sichuan and the local geological and meteorological conditions, the phase equilibria and relevant thermodynamic properties of the two systems LiCl–NaCl–KCl–H2O and LiBr–NaBr–KBr–H2O and their sub-systems will be studied from 298.15 K to 423.15 K. This will allow phase diagrams of the above systems at various temperatures to be constructed. The isopiestic method and electromotive force methods will be used to determine the osmotic coefficients and activity coefficients of the ternary systems. Based on solubility data, the Pizter electrolyte solution theory model will be used to fit unreported parameters, and the equilibrium solubilities of ternary and quaternary systems will be calculated. An error analysis was performed by comparing the calculated results with the experimental results. The results of this study are not only a useful supplement to current thermodynamic data, but also reveal the dissolution law and geochemical equilibrium process of brine minerals. Additionally, the data provides basic data necessary to rationally develop underground brine resources in Northeast Sichuan.

四川盆地地下卤水分布广泛，品质优良，综合开发利用前景广阔。由于当地空气相对湿度较大，不能利用盐田工艺，只能采用外加能源强制蒸发以达到盐类初步分离目的。为揭示地下卤水-盐类矿物的成矿过程，指导卤水资源的开发，有必要开展相关体系相平衡及热力学性质的研究。本项目将针对川东北深部地下卤水富锂、钾、溴的组成特点，针对LiCl–NaCl–KCl–H2O和LiBr–NaBr–KBr–H2O体系及其子体系，开展从常温298.15 K到高温423.15 K条件下的相平衡和热力学性质研究。绘制出上述体系在各温度条件下的相图，采用等压法以及电动势法测定其渗透系数和活度系数，结合溶解度数据，运用Pizter模型拟合未见报道的参数，对各体系进行相平衡溶解度预测，并与实验结果相比较，进行分析。其研究结果将是对热力学数据有力的补充，可揭示卤水矿物的溶解规律和地球化学平衡过程，为川东北地下卤水资源的合理开发提供基础数据。

卤水是天然存在的水和盐类共同存在的复杂体系，在其开发过程中，各种无机盐的分离提纯常常依靠相平衡与相图作指导。川东北地下卤水品质优异，但由于地形复杂、山势逶迤，且为多雨少阳光的湿润地区，盐田工艺并不适用，需采用强制升温蒸发的方式对其地下卤水资源进行分离提取。因此，本课题针对川东北深部地下卤水的化学组成特点和综合开发利用的需要，系统的开展了相关卤水体系从常温到高温的相平衡及热力学性质研究。.采用等温溶解平衡法分别完成了298.15 K~423.15 K温度范围内五个三元体系LiCl–NaCl–H2O、LiCl–KCl–H2O、NaBr–KBr–H2O、LiBr–NaBr–H2O和LiBr–KBr–H2O，两个四元体系LiCl–NaCl–KCl–H2O和LiBr–NaBr–KBr–H2O，以及298.15 K条件下LiBr–NaBr–KBr–MgBr2–CaBr2–H2O和LiBr–NaBr–KBr–Li2SO4–Na2SO4–K2SO4–H2O体系中相关子体系的稳定相平衡实验研究，根据实验结果绘制出相应的相图，并将同体系不同温度条件下的相图加以比较，分析卤水中各种盐类矿物在多温条件下的溶解、迁移、转化及析盐结晶规律。.采用等圧法测定了三元体系NaBr–KBr–H2O在348.15 K条件下的等压平衡浓度和水活度，获得渗透系数和饱和蒸气压随离子强度的变化规律，结合溶解度数据，进一步回归出相关Pitzer参数与温度的关联方程。采用电动势法分别进行了288.15 K~318.15 K温度范围内三元体系LiBr–NaBr–H2O以及288.15 K~323.15 K温度范围内三元体系LiCl–NaCl–H2O的平均活度系数研究。对计算得到的热力学参数在不同离子强度分数下与总离子强度之间的关系图进行绘制并进行了分析讨论。.通过将实验测定的溶解度数据、渗透系数、活度系数以及结合文献数据的综合处理，拟合出相应温度条件下未见文献报道的参数，并对相关体系进行溶解度预测，绘制出各体系实验与预测相图的对比图，将预测结果与实验结果进行比较，验证参数的可靠性。.成果以论文形式发表，在该领域主流期刊发表SCI论文9篇。本课题的研究成果可用于指导该卤水的开发利用，并且为阐明地下卤水的形成和演化，揭示其成矿规律及矿物的地球化学行为提供了科学依据。