Boussingaultite production process from liquid effluents containing magnesium sulphate
Describes a method of producing a magnesium sulfate and hydrous ammonia double salt or Boussingaultite ((NH 4 ) 2 SO 4 .MgSO 4 .6H 2 O), using as a source of magnesium a liquid effluent rich in magnesium sulfate originally from hydrometallurgical processes for the production of metals such as nickel, copper, rare earths. According to the invention, the process route for the production of Boussingaultite with physical properties suitable for use in fertilizer mixtures involves the steps of precipitating the Boussingaultite double salt, filtration and thermal drying.
1. A method of producing a magnesium sulfate and hydrated ammonium double salt, with the formula MgSO4.(NH4)2SO4.XH20 (Boussingaultite), comprising:
a) providing a synthetic solution of magnesium sulfate or a liquid effluent comprising magnesium sulfate;
b) adding sulfuric acid to the solution of step a) until the pH is in the range from 3.0 to 4.0 to form a reaction medium;
c) adding ammonium hydroxide or ammonia to the reaction medium of step b) until the pH is in the range from 4.0 to 6.0;
d) sequentially repeating steps b) and c) until the consumption of stoichiometric amounts of the reactants for the formation of Boussingaultite solid;
e) crystallizing the Boussinqaultite solid by the evaporation of water from the reaction medium by heating at a temperature of 80±5° C., and filtering.
2. The production method according to claim 1 , wherein the liquid effluent according to step a) originates from hydrometallurgical processes for the production of metals.
3. The production method according to claim 1 , wherein the stoichiometric amounts of reagents used in step d) are according to the stoichiometric balance MgSO4+H2S04+2NH4OH+4H20=(NH4)2S04.MgSO4.6H20.
4. The production method according to claim 1 , further comprising compacting, crushing, and screening.
5. The production method according to claim 1 , wherein the average content of nitrogen, magnesium, and sulfate in the final product is respectively 6-10%, 6-10% and 55-60%.
6. The production method according to claim 1 , wherein the maximum moisture content or free water in the final product is 0.5-1.5%.
7. The production method according to claim 1 , wherein the free acidity value in the final product is 0.1-0.3%.
8. The production method according to claim 1 , wherein the liquid effluent according to step a) originates from hydrometallurgical processes for the production of nickel, copper, or rare earths.
9. The production method according to claim 4 , wherein the solids obtained after the compacting, the crushing, and the screening are in the form of grains with a grain size in the range from 1 to 4 mm.
10. A method of producing a magnesium sulfate and hydrated ammonium double salt, with the formula MgSO4.(NH4)2SO4.XH20 (Boussingaultite) comprising:
adding sulfuric acid to a synthetic solution of magnesium sulfate until the pH is in the range from 3.0 to 4.0 to form a reaction medium;
adding ammonium hydroxide to the reaction medium until the pH is in the range from 4.0 to 6.0;
sequentially repeating the adding of the sulfuric acid to the synthetic solution of magnesium sulfate and the adding of the ammonium hydroxide to the reaction medium until the consumption of stoichiometric amounts of the reactants for the formation of Boussingaultite solid;
crystallizing the Boussingaultite solid by the evaporation of water from the reaction medium by heating at a temperature of 80±5° C.; and
filtering.
11. The production method according to claim 10 , wherein the average content of nitrogen, magnesium and sulfate in the final product is respectively 6-10%, 6-10% and 55-60%.
12. The production method according to claim 10 , wherein the maximum moisture content or free water in the final product is 0.5-1.5%.
13. The production method according to claim 10 , wherein the free acidity value in the final product is 0.1-0.3%.
14. A method of producing a magnesium sulfate and hydrated ammonium double salt, with the formula MgSO4.(NH4)2SO4.XH20 (Boussingaultite) comprising:
adding sulfuric acid to a liquid effluent comprising magnesium sulfate until the pH is in the range from 3.0 to 4.0 to form a reaction medium;
adding ammonium to the reaction medium until the pH is in the range from 4.0 to 6.0;
sequentially repeating the adding of the sulfuric acid to the liquid effluent and the adding of the ammonium to the reaction medium until the consumption of stoichiometric amounts of the reactants for the formation of Boussingaultite solid;
crystallizing the Boussingaultite solid by the evaporation of water from the reaction medium, and filtering; and
compacting, crushing and screening solids obtained from the crystallizing.
15. The production method of claim 14 , wherein the liquid effluent according to the adding of the sulfuric acid to the liquid effluent originates from hydrometallurgical processes for the production of metals.
16. The production method according to claim 14 , wherein the liquid effluent according to the adding of the sulfuric acid to the liquid effluent originates from hydrometallurgical processes for the production of nickel, copper, or rare earths.
17. The production method according to claim 14 , wherein the average content of nitrogen, magnesium, and sulfate in the final product is respectively 6-10%, 6-10% and 55-60%.
18. The production method according to claim 14 , wherein the maximum moisture content or free water in the final product is 0.5-1.5%.
19. The production method according to claim 14 , wherein the free acidity value in the final product is 0.1-0.3%.