四川盆地地下卤水含锂钾溴碘体系在25℃和50℃时的相平衡和热力学性质研究

A great amount of underground brines in Sichuan Basin contains mineral resources rich in lithium, potassium, bromine, iodine, etc. In order to exploit and utilize these liquid mineral resources, and to understand the dissolution and crystallization behavior of salt minerals in the underground brines, it is necessary to make systematical studies on phase equilibria and thermodynamic properties of related salt solutions at different temperatures. The studies of salt minerals on the thermodynamic properties and phase equilibria are the key and necessary work for salt mineral geochemistry and comprehensive utilization of the brine resources. .In this project, phase equilibria and thermodynamic properties for underground brines of Sichuan basin containing lithium, potassium, bromine and iodine for the six-component system Na-K-Sr-Li-Br-I-H2O at 25℃and 50℃ will be investigated. The solubilities of salts in the ternary, quaternary and quinary subsystems of the six-component system at each temperature will be measured. Also, the corresponding equilibrium solids are determined. The activity coefficients of ions in ternary systems without report of experimental data in the six-component system Na-K-Sr-Li-Br-I-H2O will be determined by measurement of electromotive force. After this work, the experimental data obtained in the work will be used to fit the interaction parameters in the Pitzer electrolyte solution model. The resulting model will be used to calculate the thermodynamic properties of salts and solutions, such as osmotic coefficient of solutions, water activity, the dissolution equilibrium constants of salts，and excess Gibbs free energy. The solid-liquid phase equilibria of related ternary subsystems and some quaternary and quinary subsystems in the six-component system Na-K-Sr-Li-Br-I-H2O at 25℃ and 50℃ will be calculated and predicted using the Pitzer model. The calculated results and experimental results of phase equilibria will be compared and discussed.

我国四川盆地地下卤水储量巨大，含有丰富的锂钾溴碘等稀缺资源。为了开发利用该液态资源，揭示地下卤水－矿物体系中盐类的溶解和结晶规律，有必要开展该卤水体系在不同温度条件下热力学性质和相平衡的研究，该研究也是目前盐矿地球化学和卤水资源综合利用所必需的关键性基础工作。本项目拟开展25℃和50℃时六元体系Na-K-Sr-Li-Br-I-H2O有关子体系相平衡和热力学性质的研究，测定上述六元体系中三元到五元子体系相平衡的溶解度数据，鉴定相应的平衡固相，采用电动势法测定未被报道的三元体系溶液中离子的活度系数，应用完成的实验数据拟合相应温度条件下Pitzer电解质溶液模型有关离子相互作用参数，再用Pitzer模型计算出溶液的渗透系数、水活度、盐类矿物的溶解平衡常数、超额Gibbs自由能等热力学性质，然后对该六元体系的部分三到五元子体系在25℃和50℃时的相平衡进行理论计算和预测，并和实验数据进行对比讨论。

我国四川盆地地下卤水中富含丰富的锂钾溴碘等资源，为了开发利用该液态矿产资源，揭示地下卤水体系中盐类矿物的溶解和结晶规律，本项目开展了25℃和50℃时六元体系Na-K-Sr-Li-Br-I-H2O中有关子体系相平衡和热力学性质的研究，此外，为了建立Pitzer模型有关含锂钾溴碘等离子作用参数和温度的关联方程式，还补充开展了部分含氯溴碘体系多温条件下热力学性质和相平衡的研究。测定了有关三元体系,四元体系和五元体系相平衡的溶解度数据，鉴定了相应的平衡固相，采用电动势法测定了有关三元体系溶液中盐的热力学活度系数，应用完成的实验数据拟合了Pitzer模型有关含氯溴碘体系的混合离子相互作用参数，建立了Pitzer模型离子作用参数和温度的关联方程式，在此基础上应用获得的离子作用参数和Pitzer模型计算出相应溶液体系的渗透系数、水活度、超额Gibbs自由能等重要热力学性质及盐类矿物的溶解平衡常数，应用粒子群优化算法编写了相应的相平衡预测程序，然后对四川盆地地下卤水含锂钾氯溴碘的有关体系在不同温度下的相平衡进行了理论计算和预测，并和相平衡实验数据进行了对比讨论，理论预测结果和实验数据吻合的好，验证了获得的Pitzer模型离子作用参数的可靠性和相平衡预测的适用性。上述相平衡和热力学性质的研究成果，可用于指导四川盆地地下卤水中锂钾氯溴碘资源的综合利用方案，揭示该地下卤水的地球化学平衡行为和成矿规律。.依托本项目，发表了学术论文60篇，其中SCI收录英文学术论文52篇，参加了四次学术会议，提交会议论文14篇，培养了15名硕士研究生和4名博士研究生，超额完成了项目的预期成果。