Treatment method of baotite transformation magnesium sulfate wastewater

Abstract

The invention discloses a treatment method of baotite transformed magnesium sulfate wastewater. The treatment method comprises the following steps: (1) adding an ammonia water solution into baotite transformed magnesium sulfate wastewater at 20-60 DEG C to obtain a first reaction product; performing solid-liquid separation on the first reaction product to obtain magnesium hydroxide and filtrate; the molar ratio of SO4 < 2-> contained in the baotite transformation magnesium sulfate wastewater to ammonia water contained in the ammonia water solution is 1: (1.2-3.5); and (2) reacting the filtrate with calcium chloride to obtain an ammonium chloride solution. According to the treatment method, magnesium in the wastewater can be fully recycled, and high-purity magnesium hydroxide and ammonium chloride are obtained.

Description

Technical Field

[0001] The invention relates to a method for treating magnesium sulfate wastewater from Baotou mine transformation. Background Art

[0002] The main components of the rare earth concentrate in Bayan Obo, Baotou are bastnaesite and monazite. The concentrated sulfuric acid enhanced roasting process is usually used to combine the rare earth elements and sulfuric acid to form a roasted ore containing rare earth sulfate. The roasted ore is subjected to water leaching, filtration, neutralization, filtration and other processes to obtain a rare earth sulfate water extract. The rare earth sulfate water extract is made of magnesium oxide saponified P 507 The whole process is transformed to obtain a mixed rare earth chloride solution and transformed magnesium sulfate wastewater. The cost of evaporation and crystallization of transformed magnesium sulfate wastewater is high, which is mainly due to the Cl in the transformed magnesium sulfate wastewater. - The content is high, and a large amount of magnesium chloride mother liquor is produced during the evaporation and crystallization process. However, the solubility of magnesium chloride does not change significantly with temperature, and a large amount of energy is required to evaporate the water in it. - High content increases the difficulty and cost of separating chloride salts and magnesium sulfate.

[0003] CN105884065A discloses a method for treating magnesium sulfate wastewater from Baotou mine transformation, which includes adding magnesium sulfate wastewater from transformation into a reactor and heating it to 40-50°C, adding a CaCl2 solution into the reactor, and performing an aging reaction to obtain calcium sulfate crystals and a mixed solution containing CaCl2 and MgCl2; and adding quicklime into the mixed solution to obtain calcium magnesium slag and a calcium chloride solution. This method cannot separate and utilize the magnesium element. Summary of the invention

[0004] The object of the present invention is to provide a method for treating magnesium sulfate wastewater from Baotou mine transformation, which can fully recover magnesium in the wastewater to obtain high-purity magnesium hydroxide. The method can also obtain high-purity ammonium chloride.

[0005] The present invention provides a method for treating magnesium sulfate wastewater from Baotou mine transformation, comprising the following steps:

[0006] (1) adding an ammonia solution to the magnesium sulfate wastewater from the Baotou mine transformation at 20 to 60° C. to obtain a first reaction product; separating the first reaction product into a solid and a liquid to obtain magnesium hydroxide and a filtrate; and removing SO4 contained in the magnesium sulfate wastewater from the Baotou mine transformation. 2- The molar ratio of the aqueous ammonia to the aqueous ammonia solution is 1:(1.2-3.5);

[0007] (2) reacting the first filtrate with calcium chloride to obtain an ammonium chloride solution.

[0008] Preferably, the ammonia solution is added to the Baotou mine transformation magnesium sulfate wastewater at 30-50° C. The ammonia solution can be added to the Baotou mine transformation magnesium sulfate wastewater in a dropwise manner.

[0009] SO4 contained in magnesium sulfate wastewater from Baotou mine transformation 2- The molar ratio of the ammonia water contained in the ammonia solution is 1:(1.2-3.5); preferably 1:(1.4-3). In some embodiments, the SO4 contained in the Baotou mine transformation magnesium sulfate wastewater 2- The molar ratio of the aqueous ammonia to the aqueous ammonia solution is 1:(1.6-2).

[0010] The molar ratio of Mg contained in the magnesium sulfate wastewater from Baotou mine transformation and the ammonia contained in the ammonia solution is (0.3-1.6):1; preferably (0.5-1.2):1. In certain embodiments, the molar ratio of Mg contained in the magnesium sulfate wastewater from Baotou mine transformation and the ammonia contained in the ammonia solution is (0.7-0.95):1.

[0011] According to the treatment method of the present invention, preferably, the concentration of the aqueous ammonia solution is 1 to 10 mol / L.

[0012] The concentration of the aqueous ammonia solution may be 1 to 10 mol / L, preferably 3 to 8 mol / L. In certain embodiments, the concentration of the aqueous ammonia solution is 5 to 7 mol / L.

[0013] According to the treatment method of the present invention, preferably, the concentration of Mg in the magnesium sulfate wastewater from Baotou mine transformation is 0.8-3 mol / L, SO4 2- The concentration of Cl is 0.5~1.8mol / L, - The concentration is 0.4~1.7mol / L.

[0014] In the magnesium sulfate wastewater from Baotou mine transformation, the concentration of Mg can be 0.8 to 3 mol / L, preferably 1 to 2.5 mol / L. In some embodiments, the concentration of Mg is 1.5 to 2 mol / L.

[0015] In the magnesium sulfate wastewater from Baotou Mine Transformation, SO4 2- The concentration of SO4 can be 0.5 to 1.8 mol / L; preferably 0.7 to 1.5 mol / L. 2- The concentration is 0.9~1.1mol / L.

[0016] In the magnesium sulfate wastewater from Baotou mine transformation, Cl - The concentration of Cl may be 0.4 to 1.7 mol / L; preferably 0.6 to 1.4 mol / L. - The concentration is 0.9~1.1mol / L.

[0017] The magnesium sulfate wastewater from Baotou mine transformation can be the evaporated magnesium sulfate wastewater from Baotou mine transformation formed by evaporation and enrichment treatment.

[0018] According to the treatment method of the present invention, preferably, the volume ratio of the ammonia solution to the Baotou mine transformation magnesium sulfate wastewater is (150-400):500.

[0019] More preferably, the volume ratio of the ammonia solution to the Baotou mine-transformed magnesium sulfate wastewater is (200-300): 500. In certain embodiments, the volume ratio of the ammonia solution to the Baotou mine-transformed magnesium sulfate wastewater is (220-260): 500.

[0020] According to the treatment method of the present invention, preferably, in step (1), after the addition of the aqueous ammonia solution is completed, the reaction system is allowed to react for 0.5 to 5 hours.

[0021] More preferably, after the addition of the aqueous ammonia solution is completed, the reaction system is allowed to react for 1.5 to 3 hours.

[0022] Specifically, the process further comprises the following steps: filtering the first reaction product, collecting a solid product and a filtrate. The filtrate comprises unreacted ammonia water, ammonium chloride and ammonium sulfate. The solid product is washed, filtered and dried to obtain magnesium hydroxide. The solid product can be washed with water.

[0023] According to the treatment method of the present invention, preferably, calcium chloride and SO4 contained in Baotou mine transformation magnesium sulfate wastewater 2- The molar ratio is (0.3~1):1.

[0024] More preferably, calcium chloride and SO4 contained in Baotou mine transformation magnesium sulfate wastewater 2- The molar ratio of calcium chloride to magnesium sulfate wastewater is (0.5-0.9): 1. In some embodiments, the calcium chloride and SO4 contained in the magnesium sulfate wastewater from Baotou mine transformation 2- The molar ratio is (0.6~0.8):1.

[0025] According to the treatment method of the present invention, preferably, the reaction time of the filtrate and calcium chloride is 1 to 5 hours. More preferably, the reaction time of the filtrate and calcium chloride is 2 to 4 hours.

[0026] Specifically, the method further comprises the following steps: filtering the second reaction product obtained by reacting CaCl2 with the first filtrate to obtain an ammonium chloride solution. The filtered precipitate is calcium sulfate.

[0027] The treatment method according to the present invention preferably further comprises the following step: concentrating the ammonium chloride solution to obtain ammonium chloride.

[0028] According to the treatment method of the present invention, preferably, the ammonium chloride solution is concentrated by a triple-effect ammonia evaporation process to obtain ammonium chloride.

[0029] The temperature of the first-effect heating chamber can be 100-150°C, preferably 110-130°C; the solution temperature can be 90-120°C, preferably 100-110°C.

[0030] The temperature of the second-effect heating chamber can be 90-120°C, preferably 100-110°C; the solution temperature can be 70-100°C, preferably 80-90°C.

[0031] The temperature of the triple-effect heating chamber can be 75-95°C, preferably 80-85°C; the solution temperature can be 60-80°C, preferably 65-75°C.

[0032] According to the treatment method of the present invention, preferably, the purity of magnesium hydroxide is ≥80wt%, and the purity of ammonium chloride is ≥95wt%.

[0033] More preferably, the purity of the magnesium hydroxide is ≥84 wt %. More preferably, the purity of the ammonium chloride is ≥98 wt %.

[0034] The treatment method of the present invention can fully recover magnesium in the magnesium sulfate wastewater of Baotou mine transformation to obtain high-purity magnesium hydroxide. The obtained magnesium hydroxide can be recycled as a raw material for the roasting ore neutralization process. The treatment method can also obtain high-purity ammonium chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the XRD pattern of the magnesium hydroxide obtained in Example 1. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0037] Here is the test method:

[0038] The purity of magnesium hydroxide was tested by the following method: EDTA titration method.

[0039] The purity of ammonium chloride was tested by the following method: colorimetric method.

[0040] Examples 1 to 3

[0041] (1) Evaporating and enriching the magnesium sulfate wastewater from Baotou mine transformation to obtain evaporated magnesium sulfate wastewater from Baotou mine transformation. Add 500 mL of evaporated magnesium sulfate wastewater from Baotou mine transformation to the reactor. After heating the evaporated magnesium sulfate wastewater from Baotou mine transformation to 40°C, add an ammonia solution to the reactor; after the addition of the ammonia solution is completed, age the reaction for 2 hours to obtain a first reaction product. Filter the first reaction product, and collect the solid product and the filtrate respectively. Wash the solid product with water, filter and dry it to obtain magnesium hydroxide.

[0042] (2) Add CaCl2 to the filtrate; after the addition of CaCl2 is complete, react for 3 hours to obtain a second reaction product. Filter the second reaction product to obtain an ammonium chloride solution.

[0043] The ammonium chloride solution is concentrated by a three-effect ammonia evaporation process to obtain ammonium chloride. The temperature of the first-effect heating chamber is 120°C and the solution temperature is 106°C; the temperature of the second-effect heating chamber is 103°C and the solution temperature is 89°C; the temperature of the third-effect heating chamber is 84°C and the solution temperature is 70°C.

[0044] The specific process parameters, as well as the purity of magnesium hydroxide and ammonium chloride are shown in Table 1.

[0045] Table 1

[0046]

[0047] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for treating magnesium sulfate wastewater from Baotou mine transformation, characterized in that: The steps include: (1) adding an ammonia solution to the magnesium sulfate wastewater from Baotou mine transformation at 20-60° C. to obtain a first reaction product; separating the first reaction product into a solid and a liquid to obtain magnesium hydroxide and a filtrate; and removing SO4 contained in the magnesium sulfate wastewater from Baotou mine transformation. 2- The molar ratio of the aqueous ammonia to the aqueous ammonia solution is 1:(1.2-3.5); (2) The filtrate is reacted with calcium chloride to obtain an ammonium chloride solution.

2. The processing method according to claim 1, characterized in that: The concentration of the ammonia solution is 1 to 10 mol / L.

3. The processing method according to claim 1, characterized in that: The concentration of Mg in the magnesium sulfate wastewater from the Baotou mine is 0.8-3 mol / L, SO4 2- The concentration of Cl is 0.5~1.8mol / L, - The concentration is 0.4~1.7mol / L.

4. The processing method according to claim 1, characterized in that: The volume ratio of ammonia solution to Baotou mine transformation magnesium sulfate wastewater is (150-400):

500.

5. The processing method according to claim 1, characterized in that: In step (1), after the addition of the aqueous ammonia solution is completed, the reaction system is allowed to react for 0.5 to 5 hours.

6. The processing method according to claim 1, characterized in that: SO4 contained in wastewater from calcium chloride and magnesium sulfate transformed from Baotou mine 2- The molar ratio is (0.3~1):

1.

7. The processing method according to claim 1, characterized in that: The reaction time of the filtrate and calcium chloride is 1 to 5 hours.

8. The processing method according to any one of claims 1 to 7, characterized in that: The following steps are also included: The ammonium chloride solution was concentrated to obtain ammonium chloride.

9. The processing method according to claim 8, characterized in that: The ammonium chloride solution is concentrated by a triple-effect ammonia distillation process to obtain ammonium chloride.

10. The processing method according to claim 8, characterized in that: The purity of magnesium hydroxide is ≥80wt%, and the purity of ammonium chloride is ≥95wt%.

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