Studies On Activity Coefficient Of Partially Containing Srontium Ternary Subsystems In Na⁺,K⁺,Sr²⁺//Cl^--H₂O At Multi-temperature

Electrolyte solution existing widely in natural world,is an important research object in geochemistry,marine science and electrochemistry.In the industrial field,many production processes involve electrolyte solutions,such as salting out and salt-dissolving effects in seawater desalination,extraction and rectification operations;absorption and removal of acidic gas in natural gas and fuel gas,gas treatment in environmental engineering,waste water treatment,chemical waste treatment;membrane separation of biologically active substances,as well as energy,metallurgical and other processes require the knowledge of phase equilibrium in electrolyte solutions.Furthermore,the activity coefficient is one of the thermodynamics equilibrium properties of electrolyte solutions.Moreover,there are abundant underground brine resources in the western Sichuan Basin.The development of underground brine resources can make up for the shortage of strontium resources,and there are few reports on the thermodynamic properties of strontium-containing systems at multi-temperature.The study of the thermodynamic properties of strontium-containing systems at multi-temperature is also of great significance for the comprehensive utilization of brine.In this article,the strontium-containing systems in the underground brine in the Sichuan Basin are used as the research object,and the activity coefficients of its thermodynamic parameters are also studied by the cell potential method.The mean activity coefficients of Na Cl in the Na Cl-Sr Cl₂-H₂O ternary system and the mean activity coefficients of KCl in the KCl-Sr Cl₂-H₂O ternary system at multi-temperature were determined by using ion meter and ion selective electrode.By means of the experiment method listed above,the cell potential of single salts of Na Cl and KCl in solutions were measured at 278.15 K,288.15 K and 318.15 K,respectively.According to the known data and related single salt parameters,the mean activity coefficients of single salt are calculated by the Pitzer equation.And using the mean activity coefficients of single salt,the diagrams between the mean activity natural logarithm of single salt 2lna_0±and the cell potential of single salt E_awere plotted.According to the Nernst equation principle,the response slope of the single-salt electrodeκand the electrode constant E⁰are further calculated.It can be used with subsequent determination of cell potential in mixed solutions.The cell potential of mixed solutions Na Cl-Sr Cl₂-H₂O and KCl-Sr Cl₂-H₂O were measured at temperatures of 278.15 K,288.15 K and 318.15 K,respectively.According to the calculated cell potential,the mean activity coefficients of the mixed salts in each system were calculated by Nernst equation.The relationship diagrams between the mean activity coefficients of mixed salt are drawn at temperatures of278.15 K,288.15 K and 318.15 K,respectively.For the Na Cl-Sr Cl₂-H₂O system under three temperature conditions,the change trend of the mean activity coefficients of Na Cl is different,however it has some certain regularity.When the ionic strength fraction y_bis constant and the ionic strength I is less than a certain value,the mean activity coefficients of Na Cl decreased with the increasing of ionic strength I.When the ionic strength I is greater than this value,the mean activity coefficients of Na Cl increased with the increase of ionic strength I.For the KCl-Sr Cl₂-H₂O system at three temperature conditions,the change trend of the mean activity coefficients of KCl is basically the same.when ionic strength fraction y_bis constant,the mean activity coefficients of KCl decrease constantly with the increase of ionic strength.When ionic strength I is constant,the mean activity coefficients of KCl increase constantly with the increase of ionic strength fraction y_b.Then using the calculated mean activity coefficients,the weight molar concentration of each component,and combined with the single-salt Pitzer parameters reported in the literature,the mixed interaction parametersθandψof different temperature systems in Pitzer equations were fitted by using the Matlab with multiple and linear regression method.In order to verify the accuracy and reliability of the fitted parameters,the relevant thermodynamic parameters(the mean activity coefficients of Sr Cl₂γ_{±Sr Cl2},Water activity a_w,osmotic coefficientsΦand excess Gibbs free energy G^E)were further calculated.The relationship diagrams between the above thermodynamic parameters and ionic strength I with ionic strength fraction y_bare drawn,respectively.Finally,the research results are also analyzed and discussed.