Study On The Dissolution Law Of Na₃PO₄ In NaOH-Na₂WO₄ Solution System

With the easy smelting of blac K tungsten concentrate resources continue to be depleted,the theory and technology of tungsten extraction are constantly improved.However,such mainstream processes as al Kaline thermal ball milling,sodium hydroxide autoclave,sodium phosphate decomposition and sodium phosphate roasting methods all have problems with excessive phosphorus concentration.In the ion exchange process,in order to eliminate the effect of competitive adsorption of tungsten and phosphorus,need to control tungsten-phosphorus ratio greater than 1500.Therefore,a dephosphorization process is required.In this paper,to solve the problems of high cost,long process and introduction of new impurities in the current industrial phosphorus removal,by exploring the dissolution law of Na₃PO₄ in NaOH-Na₂WO₄ solution system,proposes the separation of tungsten and phosphorus using the principle of common ion effect.And it mainly includes:?1?The dissolution rules of Na₃PO₄ in NaOH solution and Na₂WO₄ solution were studied respectively.When the temperature is 275.15-353.15 K,within a certain al Kali concentration and sodium tungstate solution concentration range,determination of solubility of sodium phosphate dodecahydrate by dissolution equilibrium method,and establish the optimal model of phosphorus concentration in solution with temperature.The results showed that the solubility of sodium phosphate dodecahydrate gradually decreased with the increase of al Kali concentration and sodium tungstate solution concentration and increased exponentially with the increase of temperature.The SEIS ideal solubility equation has the highest fitting degree to the change of saturated phosphorus concentration in sodium hydroxide solution,and the regression curve R² is as high as 0.997.The average relative error of the verification experiment is only 0.514%.The empirical polynomial equation has the highest fitting degree to the change rule of saturated phosphorus concentration in sodium tungstate solution.The regression curve R² is 0.98,and the average error of the verification experiment is only 2.49%.?2?The dissolution law of Na₃PO₄ in NaOH-Na₂WO₄ solution system was studied.When the temperature was 283.15-323.15 K,in a certain concentration of NaOH-Na₂WO₄ solution,the solubility equilibrium method was used to determine the solubility of sodium phosphate dodecahydrate in the mixed solution.And establish the optimal model of saturated phosphorus concentration with temperature change.The results show that the solubility of sodium phosphate dodecahydrate gradually decreases with the increase of the Na⁺content in the mother liquor,and increases with the temperature.Above 0.99,the average relative error between the experimental value and the theoretical value is only 6%.?3?By simulating the composition of real water leaching solution for industrial phosphorus removal,the separation of tungsten and phosphorus by the principle of common ion effect is feasible and the phosphorus removal effect is better.Experimental data shows that in the Na₃PO₄-Na₂WO₄-NaOH system,the tungsten-phosphorus separation can be efficiently achieved by controlling the dissolution temperature below 313.15 K and the al Kali concentration in the mixed solution above 80 g/L.And the water immersion liquid after the ion exchange process can still be reused,realizing the sustainable use of resources.