Thermodynamics Study Of Phase Equilibrium In Electrolyte Solution

Electrolyte solution is a familiar system in fields like: chemical industry. environmental chemistry biologic chemist hydrometallurgy, the thermodynamics study of it is the base theory of many techniques process, which have very important significance.In this article, we summarized and discussed the electrolyte solution activity coefficient and its mensuration by experiment, water-salt equilibrium calculation methods of simple ternary systems, relevancy of solid activity coefficient and phase equilibrium calculation methods of complex ternary water-salt system which have solid solution.First ,the author set up the experimental equipments to mensurate the average activity coefficient of electrolyte mixture solution and checkout it, second, regressed the ion interaction parameters of every system, by mensurating the ions average activity coefficients that belong to different solutions in NaCl-KCl-H2O system at 35 and KBr-NaBr-H2O system at 25, finally, compared the results that worked out from Pitzer equation with that worked out from dispersion lattice theory formula.To forecast the phase equilibrium of simple water-salt system, this article put forward a new method and give the program of it. Using the theory that every solute has equal chemical potential while it is in equilibrium, give the initial value, then calculat the activity coefficients of each solute, thus we can estimate the equilibrium by comparing the chemical potential. Applied to NaCl-KCl-H2O NaCl-NH4Cl-H2O NaNO3-KNO3-H2O system in 25癈 , this method give satisfied results which verify the feasibility of itself.To study the phase equilibrium of complex ternary water-salt system containing solid solution, the author established the experimental equipments to mensurate the phase equilibrium data, by using XRD, verified that there is solid solution in MgCl2-MgBr2-H2O system when it is in equilibrium, and obtain the equilibrium data of MgCl2-MgBr2-H2O system and (NH4)2SO4-K2SO4-H2O system at 25; Integrated with humid residue method, draw the phase diagram of these systems.Few literature can we find about phase equilibrium forecast in complex ternary water-salt system containing solid solution, there are two ways that this article solve the problem : one of them is: give a method which can calculate the solid solutions' activity coefficients, then we can cancalculate the phase diagram by using the theory that every solute have equal chemical potential while it is in equilibrium; another is that using the equilibrium relationship betweenliquid composing and solid composing to finish the phase diagram by simple iterative calculation. Satisfied results are obtained while these methods are used in the study of NH4C1-KC1-H2O (NH4)2SO4-K2SO4-H2O MgCl2-MgBr2-H2O and K2SO4-K2CrO4-H2O systems at 25.