Preparation of high-purity manganese sulfate from tungsten slag

Currently, tungsten residue from the extraction of scandium strategic materials plurality sulfuric acid as a solvent. In its process, the waste liquid contains a large amount of output manganese sulfate, ferrous sulfate and sulfuric acid. If the waste liquid is directly discharged, it not only seriously pollutes the environment, but also wastes a lot of valuable resources. Manganese sulfate wide use, can be used as paints, inks and coatings driers, organic synthesis catalyst, feed additives, agricultural manganese fertilizer, as well as the preparation of metal manganese, manganese dioxide, manganese salt other materials. With the rapid development of industry, the demand for manganese sulfate must be increasing, and the quality will be increasingly improved.
I. Test part (1) Test material waste liquid: MnSO ₄ 70.56g/L, H ₂ SO ₄ 139.7g/L, FeSO ₄ 138.1 g/L. Pyrolusite: containing Mn32.67%, Fe8.45%, Ca0.28%, Mg0.11% (all mass fraction), 200 mesh. Rhodochrosite: containing Mn 20.18%, Fe2.89%, Ca4.65%. Mgl.82%, Al2.36%, Si 11.63% (both mass fraction), 100 mesh. (II) Test principle Firstly, the ferrous iron in the waste liquid is oxidized to trivalent by using manganese dioxide in pyrolusite; then the sulfuric acid in the waste water of the rhodochrosite is neutralized, and when the pH is greater than 2, the ferric iron the precipitate hydrolysis, acid hydrolysis can also be produced for use in and rhodochrosite; manganese carbonate was then added, the water is released aluminum, iron and further release of water and filtered to obtain a filtrate containing mainly manganese sulphate. The relevant chemical reaction formula is:

Iron is released in the water, the filtrate was added aluminum manganese sulfide, heavy metals cobalt, nickel, copper, zinc, lead and the like is removed. Its chemical reaction formula is:

The newly prepared hydrated manganese dioxide is added to the filtrate after removing the heavy metal, and the silicon is removed by adsorption. Then, manganese fluoride is added to the filtrate after the removal of silicon to remove calcium, magnesium , and rare earth elements (RE). Its chemical reaction formula is:

(3) Test method In a 2000 mL beaker, add the sputum waste liquid, heat to 85 ° C, add pyrolusite in a certain proportion under stirring, and react for 30 min; then, slowly add appropriate amount of rhodochrosite while stirring to maintain the reaction temperature at 85 ° C. The reaction was carried out for 50 min; then, the newly prepared manganese carbonate slurry was added under stirring to adjust the pH to 5.0 to 5.5, hydrolyzed and precipitated to remove iron and aluminum, boiled for 15 min, and filtered. The filter residue was washed with distilled water of 30 to 40 ° C. The filtrate was heated to 90 ° C, and an appropriate amount of manganese sulfide slurry was added under stirring, and boiling was continued for 60 min. The heavy metal formed a sulfide precipitate, allowed to stand, and filtered to remove insoluble matter. In the filtrate after the heavy metal, an appropriate amount of freshly prepared hydrated manganese dioxide was added at room temperature, and the silicon was removed by adsorption, stirring was continued for 30 to 40 minutes, allowed to stand, and insoluble matter was removed by filtration. The filtrate after removing the silicon is heated and boiled, and an appropriate amount of a saturated solution of manganese fluoride is added dropwise with stirring, and stirring is continued for 30 minutes. Calcium, magnesium, and rare earth elements are formed into a fluoride precipitate, which is allowed to stand, and the insoluble matter is removed by filtration. The purified and impurity-removed filtrate is heated and concentrated, and the manganese sulfate crystals are precipitated, and the mixture is filtered while hot, and the crystal is washed with an appropriate amount of a nearly saturated pure manganese sulfate hot solution, and finally dried at 120 ° C for 2 hours to obtain high-purity manganese sulfate.
II. Results and discussion (I) Effect of reaction temperature on manganese leaching rate The dosage of waste liquid, pyrolusite, rhodochrosite and reaction time were kept unchanged, and only the reaction temperature was changed. After completion of the reaction, the pH was adjusted to 5.5 to 6.0 with 3 mol/L ammonia water, boiled, suction filtered and washed. The content of manganese in the filtrate was measured, and the manganese leaching rate was calculated. The effect of the change of reaction temperature on the leaching effect of manganese in manganese ore is shown in Fig. 1. It can be seen from Fig. 1 that the leaching rate of manganese increases with the increase of temperature. When the temperature is higher than 353K, that is, 80 °C, the leaching rate of manganese increases little. The reaction temperature can be selected to be 358 K, i.e., 85 °C.

Figure 1 Effect of reaction temperature on manganese leaching rate

(II) Effect of the amount of rhodochrosite on the leaching rate of manganese Maintain the amount of waste liquid and pyrolusite, reaction time and reaction temperature, and only change the dosage of rhodochrosite. After completion of the reaction, the pH was adjusted to 5.5 to 6.0 with 3 mol/L ammonia water, boiled, suction filtered and washed. The content of manganese in the filtrate was measured, and the manganese leaching rate was calculated. The results are shown in Fig. 2.

Fig. 2 Effect of the dosage of rhodochrosite on the leaching rate of manganese

It can be seen from Fig. 2 that as the amount of rhodochrosite increases, the leaching rate of manganese decreases. Considering the leaching rate of manganese and the utilization rate of sulfuric acid in the waste liquid, it is reasonable to select the amount of rhodochrosite to be 220-230g/L. At this time, the final pH of the neutralization reaction of rhodochrosite is about 3.5. (III) Effect of reaction time of rhodochrosite on manganese leaching rate The reaction time of waste liquid, pyrolusite, rhodochrosite, reaction temperature and pyrolusite remained unchanged, and only the reaction time of rhodochrosite was changed. After completion of the reaction, the pH was adjusted to 5.5 to 6.0 with 3 mol/L ammonia water, boiled, suction filtered and washed. The content of manganese in the filtrate was measured, and the manganese leaching rate was calculated. The effect of the reaction time of rhodochrosite on manganese leaching is shown in Fig. 3.

Fig. 3 Effect of reaction time of rhodochrosite on manganese leaching rate

It can be seen from Fig. 3 that the leaching rate of manganese increases with the increase of the reaction time of rhodochrosite. When the reaction time of rhodochrosite is more than 40 min, the leaching rate of manganese increases little. The reaction time of the rhodochrosite can be selected to be 50 min. (4) Purification of manganese sulfate solution The removal of iron and aluminum by manganese carbonate neutralization hydrolysis method; removal of heavy metals by manganese sulfide method; removal of silicon by hydrated manganese dioxide adsorption method; removal of calcium, magnesium and rare earth elements by manganese fluoride method. The manganese salt is used to remove impurities, and no cationic impurities are introduced; no double salt such as ammonium manganese sulfate is precipitated during crystallization.
2.5 Quality Index of High Purity Manganese Sulfate The filtrate which has been purified and decontaminated is heated and concentrated, and the crystal of manganese sulfate is precipitated, filtered by heat, washed with a nearly saturated pure solution of manganese sulfate, and finally dried to obtain high-purity manganese sulfate. In the crystallization mother liquor, ammonium hydrogencarbonate is added to prepare manganese carbonate; ammonium sulfide is added to prepare manganese sulfide; and hydrated manganese dioxide is prepared by adding hydrogen peroxide and ammonia water. Manganese fluoride is prepared by dissolving manganese carbonate in concentrated hydrofluoric acid.

3. Conclusions The use of ferromanganese in the oxidized waste liquid of ferrous iron; the use of rhodochrosite to neutralize the sulfuric acid in the waste liquid; and the removal of iron and aluminum by manganese carbonate neutralization and hydrolysis; the removal of cobalt, nickel, copper and zinc by manganese sulfide Heavy metals such as lead; hydrated manganese dioxide adsorption method for removing silicon; manganese fluoride method for removing calcium, magnesium and rare earth elements; finally, concentrated crystallization, filtration washing and drying to obtain high-purity manganese sulfate. In this test, in addition to the impurity method, a satisfactory impurity removal effect can be obtained, and the quality index of manganese sulfate is superior to the quality requirement of the national standard first-class product, and the yield of manganese can reach about 90%. The process makes full use of the valuable resources in the waste liquid of the tungsten slag and eliminates the pollution.