Solid-liquid Phase Equilibria Of The Quinary Salt-Water System Containing Lithium,Sodium,Potassium,Chloride,and Metaborate Ions

Salt lakes are scattered all over China,and the salt lakes are rich in various elements such as lithium,potassium,magnesium,boron,rubidium,cesium,strontium,uranium,bromine,iodine and so on.There are four salt lake areas in China,among which the qinghai-Tibet Plateau salt lake has the most economic value,the Qinghai-Tibet Plateau special salt lake is rich in lithium,potassium,boron in the salt lake valley’s most widely distributed,the largest number and proportion is as high as 93%,The salt lake area is represented by Dongxitai Jiner Salt Lake and Qarhan Salt Lake in Qaidam Basin,which is a comprehensive liquid mineral deposit with important development and utilization value.The daytime temperature in summer is about 288.15K in Qaidam Basin.In this paper,the stable phase equilibria of the interactive quinary system（K⁺,Na⁺,Li⁺//BO₂^-,Cl^--H₂O）at this temperature are studied,and the phase equilibria of the sub-systems of the quinary system at different temperatures are also explored.These studies can guide the rational development of relevant salt lake resources at the theoretical level.At 288.15 K,the ternary system（NaBO₂+KBO₂+H₂O）shows hydrate type I with no solid solution and double salt.It contains one zero variable point E（equilibrium solid phases are NaBO₂·4H₂O and KBO₂·1.33H₂O）,two univariate solubility curves and two single salt crystallization regions.The equilibrium liquid phase composition of the point E is 100w（NaBO₂）=6.84,100w（KBO₂）=35.80.The quaternary system（LiBO₂+NaBO₂+KBO₂+H₂O）has no ion interaction and belongs to a simple quaternary system.Two zero variable points（F₁and F₂）appear in the phase diagram at 288.15 K.The equilibrium solid phases of F₁are LiBO₂·2H₂O+LiBO₂·8H₂O+NaBO₂·4H₂O,respectively.The equilibrium solid phases of F₂are LiBO₂·2H₂O+NaBO₂·4H₂O+KBO₂·1.33H₂O,The phase diagram consists of 5 univariate solubility curves,and each point on the line represents the co-saturation of two different salts.In the phase diagram,the four single salt crystal regions are LiBO₂·2H₂O,KBO₂·1.33H₂O,LiBO₂·8H₂O and NaBO₂·4H₂O,respectively.The equilibrium liquid solubility data of the co-saturation point F₁are as follows:100w（LiBO₂）=3.62、100w（NaBO₂）=10.21、100w（KBO₂）=30.48.The equilibrium liquid solubility data of the saturation point F₂are as follows:100w（LiBO₂）=3.44、100w（NaBO₂）=10.23、100w（KBO₂）=32.29.The results show that LiBO₂·8H₂O is easily converted to LiBO₂·2H₂O in the presence of KBO₂·1.33H₂O.The quaternary system（LiBO₂+NaBO₂+KBO₂+H₂O）belongs to the simple quaternary system at 298.15 K.The phase diagram contains two zero variable points F₁and F₂.The equilibrium solid phases of F₁are LiBO₂·2H₂O+LiBO₂·8H₂O+NaBO₂·4H₂O,respectively.The equilibrium solid phases F₂rae LiBO₂·2H₂O+NaBO₂·4H₂O+KBO₂·1.33H₂O,respectively.The phase diagram includes five univariate solubility curves,and each point on the line represents the co-saturation of two different salts.The crystalline phase regions are LiBO₂·2H₂O,KBO₂·1.33H₂O,LiBO₂·8H₂O and NaBO₂·4H₂O,respectively.The equilibrium liquid phase solubility data of the co-saturation point F₁are as follows:100w（LiBO₂）=4.45,100w（NaBO₂）=13.61,100w（KBO₂）=27.14.The equilibrium liquid solubility data of the saturation point F₂are as follows:100w（LiBO₂）=3.62,100w（NaBO₂）=13.09,and 100w（KBO₂）=33.32.The results show that LiBO₂·8H₂O is easily converted to LiBO₂·2H₂O in the presence of KBO₂·1.33H₂O.The quaternary system（LiBO₂+NaBO₂+KBO₂+H₂O）belongs to the simple quaternary system at 323.15 K.The phase diagram contains two zero variable points F₁and F₂.The equilibrium solid phases of F₁are LiBO₂·2H₂O+NaBO₂·2H₂O+NaBO₂·4H₂O,respectively.The equilibrium solid phases of F₂are LiBO₂·2H₂O+NaBO₂·2H₂O+KBO₂·1.33H₂O,respectively.The phase diagram includes five univariate solubility curves,and each point on the line represents the co-saturation of two different salts.The four single salt crystal regions of the phase diagram,Are the crystalline phase regions of LiBO₂·2H₂O,NaBO₂·2H₂O,NaBO₂·4H₂O and KBO₂·1.33H₂O,respectively.The equilibrium liquid phase solubility data of the co-saturation point F₁are as follows:100w（LiBO₂）=6.07,100w（NaBO₂）=26.10,100w（KBO₂）=9.38.The equilibrium liquid solubility data of the saturation point F₂are as follows:100w（LiBO₂）=5.84,100w（NaBO₂）=17.26,and100w（KBO₂）=29.92.The results show that LiBO₂·8H₂O is easily converted to LiBO₂·2H₂O in the presence of KBO₂·1.33H₂O.The quinary system（Li⁺,Na⁺,K⁺//Cl^-,BO₂^--H₂O）has the interaction between ions,which belongs to the quinary system.The phase diagram contains three saturation points at288.15K.The satiation points are F₁:Na Cl+Li Cl·H₂O+LiBO₂·2H₂O+KCl;F₂:Na Cl+LiBO₂·8H₂O+LiBO₂·2H₂O+KCl;F₃:Na Cl+LiBO₂·8H₂O+LiBO₂·2H₂O+NaBO₂·Na Cl·2H₂O.The points on the seven saturation solubility curves of the phase diagram represent three different salts,and there are five crystallization divisions in total:LiBO₂·2H₂O,LiBO₂·8H₂O,KCl,Li Cl·H₂O and NaBO₂·Na Cl·2H₂O,the J（H₂O）values and physicochemical properties（refraction rate,density）at complex points show regular changes with the increase of J（Li⁺）.