Study On The Thermodynamics Of Ion Exchange In Tungsten Smelting

Ion exchange has an important application in tungsten smelting process,but the related thermodynamics research is not systematic.In other fields,Langmiur and Freundlich's two classic models of solid-gas adsorption have been used extensively to study ion exchange processes.However,there are essential differences between ion exchange and the adsorption of solids on gases.For the gas adsorption process,the active site of the adsorbent may adsorb gas or may exist in the form of vacancies.In the process of ion exchange,the charged functional groups of the resin must attract different types of charged ions and cannot exist in the form of vacancies.Therefore,whether the classical adsorption model can be applied to the study of ion exchange equilibrium deserves further discussion.In this paper,tungsten metallurgy ion exchange process is the object of research and theoretical verification.Based on the basic principle of ion exchange reaction,it aims to find a thermodynamic research method suitable for ion exchange equilibrium.The calculation includes the static ion exchange process and the dynamics in the exchange column.Thermodynamic parameters of the ion exchange process.The main work and conclusions of this paper are as follows:?1?Equilibrium data with ion exchange at different temperatures were obtained through ion exchange equilibrium experiments,WO₄^2-and Cl^-equilibrium data of common anions and ion exchanges in tungsten solutions at 25°C were obtained.According to the basic relationship of ion exchange,the mathematical relationship between the amount of resin added and the desorbed or adsorbed ions was deduced.This mathematical relationship was used to process the above experimental data,and the equilibrium constant of the ion exchange reaction was obtained by direct fitting.For WO₄^2-and Cl^-ion exchange,?H and?S 9.574 and 0.074 kJ/mol,respectively,this indicates that the process is an endothermic reaction.The equilibrium constants of common anions and Cl^-ion exchanges in tungsten smelting increase in the order of F-?WO₄^2-?MoO₄^2-?PO₄^3-?AsO₄^3-?MoS₂O₂^2-and MoS₄^2-.?2?Based on full argumentation and experiments,the rationality of classical Langmuir model and Freundlich model for ion exchange equilibrium was carefully evaluated.By comparing the ability of each method to process experimental data,it can be seen that in the exchange reaction of chlorinated quaternary ammonium resins with various valence anions and in the exchange reaction of sodium-type strong acidic cation resins with K⁺and Ca²⁺,a new algorithm based on ion exchange equilibrium is known.The degree of fit to the experimental data is good,and the resulting constant term has a clear physical meaning and exhibits a certain degree of superiority.?3?Using ion chromatography to study the dynamic exchange behavior of common anions of tungsten smelting system under different elution conditions.Based on the column retention time data of ions at different column temperatures,the isothermal thermodynamic parameters of each ion exchanged on the column under NaOH and Na₂CO₃ elution conditions were calculated.The results show that the dynamic exchange of ions under Na₂CO₃ rinsing conditions is significantly less than that obtained from NaOH leaching conditions,indicating that the thermal effect of ion exchange in the system is small.The size of each ion in these two elution systems is exactly the same as the order of retention of these ions under the elution conditions.Thus,for the multi-ion coexistence system,it is effective to use ion chromatography to study the thermodynamics of the dynamic exchange process.