Determinate The Average Activity Coefficients Of Na⁺,K⁺,Cd²⁺//Cl^-,NO₃^--H₂O Ternary Sub-systems By Ion Selective Electrodes

Rich underground brine resources contain a large number of Na, K and other alkali metal, heavy metals go into the environment groundwater due to improper treatment of industrial wastewater, and forming the electrolyte solution with Na, K and other alkali metal elements. In industrial waste water is often involved in the rapid determination of the ion content and the average activity coefficient in the calculation of electrolyte solution. In this paper, the properties of sodium, chlorine,potassium and nitrate ion selective electrodes were studied and applied. On this basis,the electromotive force in single salt solutions and mixed salt solutions were further measured to calculate the average activity coefficients of 1-1 type electrolyte.The Pitzer parameters of the solution were obtained by linear regression method, then used the Pitzer parameters to calculate the other thermodynamic parameters such as:permeability coefficient, water activity and excess Gibbs free energy, and providing basic data for the latter part of the industrial wastewater treatment?the required material extraction?remove the ingredients whose caused environmental pollution.Then according to the research systems, First, the optimum pH measurement range? selectivity? response time? stability? reproducibility and other properties of the sodium ion selective electrode, the potassium ion selective electrode, the chloride ion selective electrode, the nitrate ion selective electrode involved in the solution were studied. Next, the content of Na+?K+?Cl-?NO3- in the river were measured and the recovery rate were analyzed.According to the best parameters of four kinds of ion selective electrodes, the four groups of electrodes were applied to measure the NaCl?KCl?NaNO3?KNO3 single salt solutions at total ionic strength of 0.0010-1mol·kg-1,respectively,and found that the experimental results had a good linear response relationship, met the demand of experiment. And then measured the four mixed solutions NaCl-CdCl2-H2O?KCl-CdCl2-H2O?NaNO3-Cd(NO3)2-H2O?KNO3-Cd(NO3)2-H2O with total ionic strength of 0.01-1 mol·kg-1,respectively. And the mean activity coefficients of each component of the four mixed systems were calculated by using the obtained electromotive force values. Then, the Pitzer mixed ion interaction parameters were obtained by linear regression of Matlab program, then used the Pitzer parameters to calculate the other thermodynamic parameters such as permeability coefficient ?,water activity ?w and excess Gibbs free energy GE.Finally, the uncertainty of the average activity coefficients ?±+NaCl??±KCl??±NaNO3??±KNO3?were evaluated in the above four mixed salt solutions.