Wet Phosphoric Acid Ion Exchange Method In Addition To Magnesium

When phosphate rock is reacted with phosphoric acid and sulfuric acid to produce phosphoric acid, known as the wet process, the impurity of magnesium that is in the rock is dissolved in the acid. The magnesium in wet process phosphoric acid will increase the acid viscosity and the mass transfer resistance, also reduce the rate of decomposition of phosphate rock when wet process phosphoric acid is produced, and increase energy consumption of the wet process. In addition, the magnesium ions also affect the performance of products which are attained by processing the wet process phosphoric acid, not only reduce the content of water-soluble P₂O₅ in fertilizer, but also the physical properties of fertilizer products worsen, such as rising caking which is not conductive for transportation, storage and use of the fertilizer; it lead to forming sludge in concentrated wet process phosphoric acid, resulting in scaling equipment and plugging the pipeline. Therefore, the purification of wet process phosphoric acid to remove magnesium ions that has been concerned and researched by people is significant in practice.In this paper, ion exchange method is selected to purify the magnesium of wet process phosphoric acid. The 001×7 resin made in China that belongs to poly-styrene aryl sulfonic strongly acidic cationic ion-exchange resin is chosen to remove magnesium from the wet process phosphoric acid.The result of purification by static ion exchange research to remove the magnesium impurity from wet process phosphoric acid show that: the exchange process at room temperature, the reaction time is 10min, dealing with 150ml raw material phosphoric acid need 60g resin. The purification rate of magnesium can reach to 55.75 percent when purify wet process phosphoric acid to remove magnesium with the said technology. Within the scope of the study, the exchange process between the hydrogen ions on the resin and the magnesium ions in the wet process phosphoric acid is particle diffusion limited. Saturated ammonium sulfate solution is chose to regenerate the spent resin because of its better regeneration effect. The operating condition of resin regeneration is that for 60. 0g used resin, the amount of regenerant solution of saturated ammonium sulfate is 100ml, reaction temperature is 70℃, with moderate mixing speed, reaction time need 20min, and the regeneration process is film diffusion limited.The purification result of dynamic ion exchange experiment to purify the magnesium of wet process phosphoric acid show that within the framework of the research, the optimum technical condition is that room temperature operation, operating flow rate is 0. 849cm/min, the ratio of resin bed high with diameter is 8, contact time for 28. 3min. In the said operating condition, the average capacity of ion exchange column is 10. 59g/L; the utilization rate of resin is 50.13 percent. The magnesium of purified phosphoric acid is less than 0. 56g/L. Operating with the said technology condition, the high of exchange zone is 238.5mm and the moving rate of exchange zone is 0. 448cm/min.Mg²⁺outflow curve function model for the mathematical expression obtainedby dynamic ion exchange research is lg.ln[1/(1-(c/c₀))] = 1.76341g(t-26.940)-2.567(Correlation coefficient R=0. 99002) .The spent resin is regenerated utilizing a saturated solution of ammonium sulfate, then contacting the resin with weight 10 percent sulfuric to change the resin from ammonium ion to hydrogen ion form.