Studies On The Mean Activity Coefficients Of Some Ternary Subystems In Copper And Lead Electrolyte Solutions At 298K

Electrolyte solution system exists widely in nature and industrial production,and it is an important object for many chemical design and wastewater treatment research.The thermodynamic properties of electrolyte solutions are widely used in marine chemistry,salt lake brine extraction,environmental protection,biochemistry and other fields.The study of the thermodynamic properties such as the activity coefficient can provide information on the interaction between ions and ions,ions and solvent in the electrolyte solution,and on the other hand,it can reflect the degree of deviation between the electrolyte solution and the ideal solution.Therefore,it is of great theoretical and practical significance to study the thermodynamic properties of electrolyte solution,such as activity coefficient,permeability coefficient and water activity.Especially in the treatment of heavy metal-containing sewage,studies on the thermodynamic properties of heavy metal-containing electrolyte solutions are relatively less.Therefore,in this paper,the thermodynamic properties of some ternary subsystems containing heavy metals such as copper and lead are studied by the electromotive force method.The main research contents are as follows:The electromotive force method was used to determine the electromotive force values of NaCl-H₂O,KCl-H₂O and NaNO₃-H₂O single electrolyte solutions at 298 K.The experimental standard electromotive force E⁰ and electrode response slope k of each experiment were obtained by linear regression.The relationship diagrams between the mean activity coefficient of single salt and the electromotive force value were drawn,respectively.The experimental results indicate that the ion selective electrode used in the experiment has an ideal Nernst response,and the measured experimental data is accurate and reliable.The electromotive force method was used to determine the electromotive force values of four mixed electrolyte solutions NaCl-CuCl₂-H₂O,KCl-CuCl₂-H₂O,NaNO₃-Cu?NO₃?₂-H₂O and NaNO₃-Pb?NO₃?₂-H₂O at 298 K.According to the measured electromotive force value,and the experimental standard electromotive force and electrode response slope obtained in the single electrolyte solution,the mean activity coefficients of NaCl,KCl and NaNO₃ in each mixed electrolyte solution system were calculated.The relationship diagrams between the mean activity coefficients of NaCl,KCl,and NaNO₃ and the ionic strength fraction were drawn,respectively.The experimental results show that the mean activity coefficients of NaCl and KCl decrease with the increase of ionic strength fraction,and the decreasing trend is obvious.The mean activity coefficient of NaNO₃ in NaNO₃-Cu?NO₃?₂-H₂O system changes little with the increase of ionic strength fraction,while in the NaNO₃-Pb?NO₃?₂-H₂O system,the mean activity coefficient of NaNO₃ increases first and then decreases with the increase of ionic strength fraction.According to the Pitzer equation in the mixed electrolyte solution and the obtained the mean activity coefficients of NaCl,KCl,and NaNO₃,the Pitzer mixed ion parameters of the four mixed electrolyte solutions were fitted(,and,,,_K,Cu and,,,,and,,,,and,,)by linear regression and Matlab program.The obtained mixed ion interaction parameters were substituted into the Pitzer equation and the mean activity coefficients of CuCl₂,Cu?NO₃?₂ and Pb?NO₃?₂ in each mixed electrolyte solution system were obtained,respectively.The relationship diagrams between the mean activity coefficients of CuCl₂,Cu?NO₃?₂ and Pb?NO₃?₂ and the total ionic strength I were also drawn,respectively.The experimental results show that the mean activity coefficients of CuCl₂,Cu?NO₃?₂ and Pb?NO₃?₂ decrease with the increase of total ionic strength I.Finally,the values of permeability coefficient?,water activity a_w,excess Gibbs free energy G^E were calculated using the Pitzer equation.The relationship diagrams between the water activity a_w,the excess Gibbs free energy G^E and the total ionic strength I of each mixed electrolyte solution system were drawn.It can be seen that the water activity a_w and the excess Gibbs free energy G^E of the four groups of mixed electrolyte solutions decrease with the increase of total ionic strength I.