Ferrous sulfate magnesium, and a preparation method and application thereof

Abstract

The present application relates to wastewater comprehensive utilization technical field, specifically relates to a ferrous sulfate magnesium and its preparation method and application, the present application can remove the residue and solid particles in wastewater by sequentially carrying out primary filtration to gold mine pre-acidification wastewater, the present application carries out nanofiltration to the wastewater after primary filtration, due to the special screening effect, donnan effect and electrostatic repulsion effect of nanofiltration membrane, the wastewater is purified well, first reduction treatment under acid, then concentration, the problem that stable ferrous sulfate magnesium cannot be formed due to the existence of trivalent iron in nanofiltration concentrated solution is solved, the method for preparing ferrous sulfate magnesium by using gold mine pre-oxidation acidic wastewater provided by the present application overcomes the defects that sulfate and various heavy metal resources cannot be recycled and utilized in the process of treating gold mine pre-oxidation acidic wastewater, high-purity, stable, mass-produced ferrous sulfate magnesium product is obtained, and the product has good application prospect in gypsum, fertilizer and drug for preventing and treating yellow leaf disease.

Description

Technical Field

[0001] This invention relates to the field of wastewater comprehensive utilization technology, specifically to a magnesium ferrous sulfate, its preparation method, and its application. Background Technology

[0002] Pre-oxidized acidic mine wastewater (AMD) is a serious and persistent environmental pollution problem. AMD is generated in areas that have been mined and contain pyrite material in tailings or spoil heaps. The pyrite in the tailings reacts chemically with oxygen and water, promoting the formation of AMD, facilitated by sulfate bacteria. Therefore, AMD is a hazardous industrial byproduct, highly acidic and rich in sulfates. The recycling of this secondary waste can reduce environmental risks and improve the economic profitability of the mining industry. As mine waste accumulates, AMD continues to form, and its pollution of surface water, along with other mine wastewater, both within and around coal mines has a severe environmental impact.

[0003] Currently, the common method for treating pre-oxidized acidic mine wastewater is lime neutralization. Lime neutralization for treating AMD has advantages such as requiring fewer types of reagents, high precipitation efficiency, stable and compliant wastewater discharge, and convenient operation. However, it is costly, requires large quantities of reagents, is prone to secondary pollution, and cannot recover metal ions and sulfates from AMD, leading to resource waste. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide ferrous magnesium sulfate, its preparation method, and its applications. The method provided by this invention solves the problem of wasted sulfuric acid, iron, and magnesium resources in acidic wastewater from gold mine pre-oxidation processes, and produces a high-purity ferrous magnesium sulfate product.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing ferrous magnesium sulfate from acidic wastewater pre-oxidized from gold mines, comprising the following steps:

[0007] The gold mine pre-acidification wastewater was subjected to primary filtration and nanofiltration in sequence to obtain nanofiltration concentrate and nanofiltration dilute solution, respectively.

[0008] The pH of the nanofiltration concentrate was adjusted to acidic using concentrated sulfuric acid, then mixed with iron powder, and after reduction treatment, solid-liquid separation was performed to obtain crystallization mother liquor.

[0009] The mother liquor for crystallization is concentrated and then subjected to thermal solid-liquid separation to obtain thermally concentrated crystallization liquid and slag, respectively.

[0010] The hot concentrated crystallization solution is cooled and crystallized to obtain ferrous magnesium sulfate product.

[0011] Preferably, the filtration accuracy of the initial filtration is 1-2 nm.

[0012] Preferably, the nanofiltration conditions include: using a Wharton nanofiltration membrane, a temperature of 21–25°C, and a transmembrane pressure of 20–35 Bar.

[0013] Preferably, the mass ratio of the nanofiltration concentrate to iron powder is 1:0.01 to 0.05.

[0014] Preferably, the acidic pH value is 0.8 to 1.2;

[0015] The reduction treatment is performed at a temperature of 30–40°C for a time of 30–50 minutes.

[0016] Preferably, the volume of the thermally concentrated crystallizing liquid is 1 / 6 to 2 / 3 of the volume of the crystallizing mother liquor.

[0017] Preferably, the temperature of the thermally concentrated crystallizing solution is ≥65℃;

[0018] The final temperature for cooling and crystallization is 20–35°C, the stirring speed is 100–500 r / min, and the total time is 4–8 h.

[0019] Preferably, after cooling and crystallization, the process further includes aging the obtained cooled crystallization liquid to cultivate crystals.

[0020] The aging and crystal growth process takes place at a temperature of 20–35°C for 4–6 days.

[0021] The present invention provides a ferrous magnesium sulfate product prepared by the method described above, wherein the molar ratio of iron to magnesium is 1.0 to 1.5:1.

[0022] This invention provides the application of the ferrous magnesium sulfate product described in the above technical solution in fertilizers and in the preparation of drugs for preventing and treating yellow leaf disease.

[0023] This invention removes residues and solid particles from gold mine pre-acidification wastewater through initial filtration. Following this initial filtration, the wastewater undergoes nanofiltration. Due to the unique sieving effect (steric hindrance), Donnan effect (charge effect), and electrostatic repulsion of the nanofiltration membrane, it exhibits excellent removal performance for multivalent ions and small organic molecules, and good separation performance for monovalent and multivalent ions, thus effectively purifying the wastewater. This invention employs a method of reducing the nanofiltration concentrate under acidic conditions followed by concentration, solving the problem that the presence of trivalent iron in the nanofiltration concentrate prevents the formation of stable ferrous magnesium sulfate. The method provided by this invention for preparing ferrous magnesium sulfate from gold mine pre-oxidation acidic wastewater overcomes the defect of unrecoverable sulfate and various heavy metal resources during the treatment of gold mine pre-oxidation acidic wastewater, yielding a high-purity, stable, and mass-producible ferrous magnesium sulfate product. This invention utilizes sulfuric acid, iron, and magnesium in acidic wastewater from gold mine pre-oxidation to produce an economically valuable ferrous magnesium sulfate product containing iron, magnesium, and sulfur. Magnesium sulfate acts as a stabilizer for ferrous iron, maintaining its long-term stability. Simultaneously, magnesium enhances fertilizer efficiency and promotes crop growth. The iron in ferrous magnesium sulfate promotes chlorophyll formation, and magnesium is the central atom of chlorophyll, which contains approximately 4% magnesium. Sulfur is a component of amino acids, proteins, and protoplasm. Therefore, the combined use of iron, magnesium, and sulfur in the ferrous magnesium sulfate product can prevent yellow leaf disease, especially effective for fruit trees, mulberry trees, and lawns. As shown in the test results of the examples, the purity of the ferrous magnesium sulfate product prepared by this invention is ≥97.36%.

[0024] Furthermore, the aging process of this invention makes the crystallization liquid easier to separate into solid and liquid phases, which is beneficial for obtaining high-purity ferrous magnesium sulfate products. Attached Figure Description

[0025] Figure 1 A flowchart for preparing ferrous magnesium sulfate from acidic wastewater pre-oxidized in gold mines. Detailed Implementation

[0026] This invention provides a method for preparing ferrous magnesium sulfate from acidic wastewater pre-oxidized from gold mines, comprising the following steps:

[0027] The gold mine pre-acidification wastewater was subjected to primary filtration and nanofiltration in sequence to obtain nanofiltration concentrate and nanofiltration dilute solution, respectively.

[0028] The pH of the nanofiltration concentrate was adjusted to acidic using concentrated sulfuric acid, then mixed with iron powder, and after reduction treatment, solid-liquid separation was performed to obtain crystallization mother liquor.

[0029] The mother liquor for crystallization is concentrated and then subjected to thermal solid-liquid separation to obtain thermally concentrated crystallization liquid and slag, respectively.

[0030] The hot concentrated crystallization solution is cooled and crystallized to obtain ferrous magnesium sulfate product.

[0031] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0032] This invention involves subjecting gold mine pre-acidification wastewater to primary filtration and nanofiltration sequentially to obtain concentrated nanofiltration solution and diluted nanofiltration solution, respectively.

[0033] This invention does not specifically limit the gold mine pre-acidification wastewater; pre-oxidized acidic wastewater obtained from gold mines using a pressurized pre-oxidation method, which is well known to those skilled in the art, can be used. In a specific embodiment of this invention, the composition of the gold mine pre-acidification wastewater includes: 1.2 wt% MgSO4, 2.12 wt% FeSO4, and 2.78 wt% Fe2(SO4)3.

[0034] In this invention, the filtration accuracy of the initial filtration is preferably 1-2 nm, more preferably 1-1.5 nm. In this invention, the initial filtration is preferably performed using filter paper, preferably quantitative filter paper. This invention does not have a specific limitation on the size of the filter paper; it can be determined according to actual needs, such as a diameter of 18 cm. In this invention, the purpose of the initial filtration is to remove residues and solid particles from the gold mine pre-acidification wastewater.

[0035] In this invention, the nanofiltration conditions include: the nanofiltration membrane used preferably includes a Wharton nanofiltration membrane; the temperature is preferably 21–25°C, more preferably 22–24°C, and even more preferably 23°C; the transmembrane pressure (TMP) is preferably 20–35 Bar, more preferably 22–32 Bar, and even more preferably 25–30 Bar. In this invention, the nanofiltration is preferably performed by placing the filtrate obtained from the initial filtration in a nanofiltration device, adjusting the pressure valve to 20–35 Bar and the temperature to 21–25°C, and after the pressure and temperature stabilize, then performing nanofiltration.

[0036] In this invention, the nanofiltration dilute solution is preferably used as a gold ore flotation modifier.

[0037] After obtaining the nanofiltration concentrate, the present invention uses concentrated sulfuric acid to adjust the pH value of the nanofiltration concentrate to acidic, then mixes it with iron powder, performs reduction treatment, and then separates the solid and liquid to obtain the crystallization mother liquor.

[0038] In this invention, the pH value of the acid is preferably 0.8 to 1.2, more preferably 0.9 to 1.1, and even more preferably 1.

[0039] In this invention, the mass ratio of the nanofiltration concentrate to the iron powder is preferably 1:0.01 to 0.05, more preferably 1:0.01 to 0.03, and even more preferably 1:0.01 to 0.02.

[0040] In this invention, the temperature of the reduction treatment is preferably 30-40°C, more preferably 35°C, and the time is preferably 30-50 min, more preferably 40 min.

[0041] The present invention does not have any particular limitation on the solid-liquid separation, and any solid-liquid separation method known to those skilled in the art can be used, such as filtration, vacuum filtration or centrifugation.

[0042] After obtaining the crystallization mother liquor, the present invention concentrates the crystallization mother liquor and then performs thermal solid-liquid separation to obtain thermally concentrated crystallization liquid and slag respectively.

[0043] In this invention, the volume of the thermally concentrated crystallizing liquid is 1 / 6 to 2 / 3 of the volume of the mother crystallizing liquid, more preferably 1 / 5 to 1 / 2, and even more preferably 1 / 4 to 1 / 3.

[0044] In this invention, the temperature of the thermally concentrated crystallizing liquid (i.e., the temperature of thermal solid-liquid separation) is preferably ≥65°C, more preferably 65-70°C.

[0045] The present invention does not have any particular limitation on the thermo-solid-liquid separation, and any thermo-solid-liquid separation method known to those skilled in the art can be used, such as thermal filtration, thermal vacuum filtration or thermal centrifugation.

[0046] In this invention, the slag is preferably used to prepare gypsum.

[0047] After obtaining the thermally concentrated crystallizing liquid, the present invention cools and crystallizes the thermally concentrated crystallizing liquid to obtain ferrous magnesium sulfate product.

[0048] In this invention, the initial temperature of the cooling crystallization is the temperature of the thermally concentrated crystallizing liquid, and the final temperature is preferably 20-35°C, more preferably 30-35°C. The cooling rate from the initial temperature to the final temperature is preferably 0.1-1°C / min, more preferably 0.5-0.7°C / min. The cooling crystallization is carried out under stirring conditions, and the stirring speed is preferably 100-500 r / min, more preferably 200-400 r / min, and even more preferably 240-300 r / min. The total cooling crystallization time is preferably 4-8 hours, more preferably 5-6 hours.

[0049] After the cooling crystallization is completed, the present invention preferably further includes aging the obtained cooling crystallization solution for crystal growth. In the present invention, the aging temperature is preferably 20-35°C, more preferably 30-35°C, and the time is preferably 4-6 days, more preferably 5 days.

[0050] After completing the cooling crystallization or aging crystal growth process, the present invention preferably further includes solid-liquid separation of the obtained crystallization liquid and drying of the obtained solid product to obtain ferrous magnesium sulfate. The present invention does not have specific limitations on the solid-liquid separation; any solid-liquid separation method well known to those skilled in the art can be used, such as filtration, vacuum filtration, or centrifugation. In the present invention, the drying temperature is preferably 30–40°C, more preferably 35°C, and the drying time is preferably 3–5 hours, more preferably 4 hours.

[0051] The present invention provides a ferrous magnesium sulfate product prepared by the method described above, wherein the molar ratio of iron to magnesium is 1.0 to 1.5:1, preferably 1.1 to 1.4:1, and more preferably 1.2 to 1.3:1.

[0052] This invention provides the application of the ferrous magnesium sulfate product described in the above-mentioned technical solution in gypsum, fertilizers, and the preparation of drugs for preventing and treating yellow leaf disease. In this invention, the yellow leaf disease preferably includes one or more types of yellow leaf disease in fruit trees, mulberry trees, and lawns. This invention utilizes sulfuric acid, iron, and magnesium elements in the pre-oxidation acidic wastewater of gold mines to produce an economically valuable ferrous magnesium sulfate product containing iron, magnesium, and sulfur. Magnesium sulfate is used as a stabilizer for ferrous iron to maintain its long-term stability; simultaneously, magnesium can be used to improve fertilizer efficiency and promote crop growth. The iron in ferrous magnesium sulfate promotes chlorophyll formation, and magnesium is the central atom of chlorophyll, with approximately 4% magnesium in the chlorophyll molecule. Sulfur is a component of amino acids, proteins, and protoplasm. Therefore, the combined use of iron, magnesium, and sulfur in the ferrous magnesium sulfate product can prevent and treat yellow leaf disease, especially effective for fruit trees, mulberry trees, and lawns.

[0053] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a magnesium ferrous sulfate, its preparation method, and its application, should not be construed as limiting the scope of protection of the present invention.

[0054] In the following examples, the composition of the gold mine pre-acidification wastewater includes: MgSO4 1.2wt%, FeSO4 2.12wt%, and Fe2(SO4)3 2.78wt%.

[0055] Example 1

[0056] use Figure 1 The flowchart described above describes the preparation of ferrous magnesium sulfate from acidic wastewater pre-oxidized from gold mines. The specific steps are as follows:

[0057] The gold mine pre-acidification wastewater was initially filtered using quantitative filter paper with a filtration accuracy of 1 nm, and then nanofiltration was performed using a Wharton nanofiltration membrane at 21–25 °C and 25 Bar to obtain concentrated nanofiltration solution and dilute nanofiltration solution, respectively; the concentration factor of the nanofiltration was 5 times; the dilute nanofiltration solution was used as a flotation modifier for gold ore.

[0058] Add concentrated sulfuric acid to 200g of nanofiltration concentrate to adjust the pH to 1, add 2g of iron powder, and reduce the solution at 35℃ with stirring for 40min. Then filter to obtain the crystallization mother liquor.

[0059] The mother liquor was concentrated under vacuum at 0.7 MPa and 65°C to half its volume using a vacuum pump, and then filtered while hot to obtain a thermally concentrated crystallizing solution.

[0060] The hot concentrated crystallization liquid was cooled to 30°C at 300 r / min and then kept at that temperature for crystallization for a total time of 7 h. After that, it was aged for 5 days to grow crystals. The solid and liquid were separated, and the resulting solid product was dried at 35°C for 4 h to obtain ferrous magnesium sulfate product (purity of 97.36%, Fe content of 13.18%, and Mg content of 4.32%).

[0061] Example 2

[0062] Ferrous magnesium sulfate was prepared from acidic wastewater pre-oxidized from gold mines according to the method in Example 1. The only differences from Example 1 were: 100g of nanofiltration concentrate, 1g of iron powder added, crystallization temperature of 35℃, stirring rate of 240r / min, total crystallization time of 6h, and the purity of the ferrous magnesium sulfate product was 98.26%, with Fe content of 12.51wt% and Mg content of 4.85wt%.

[0063] Example 3

[0064] Ferrous magnesium sulfate was prepared from acidic wastewater pre-oxidized from gold mines according to the method in Example 1. The only differences from Example 1 were: 400g of nanofiltration concentrate, 4g of iron powder added, crystallization temperature of 40℃, stirring rate of 360r / min, total crystallization time of 8h, and the purity of the ferrous magnesium sulfate product was 97.51%, with Fe content of 13.09% and Mg content of 4.57%.

[0065] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing ferrous magnesium sulfate from acidic wastewater from gold mine pre-oxidation, comprising the following steps: The acidic wastewater from the gold mine pre-oxidation process was subjected to primary filtration and nanofiltration in sequence to obtain concentrated nanofiltration solution and dilute nanofiltration solution, respectively. The pH of the nanofiltration concentrate was adjusted to acidic using concentrated sulfuric acid, then mixed with iron powder, and after reduction treatment, solid-liquid separation was performed to obtain crystallization mother liquor. The mother liquor for crystallization is concentrated and then subjected to thermal solid-liquid separation to obtain thermally concentrated crystallization liquid and slag, respectively. The hot concentrated crystallization solution is cooled and crystallized to obtain ferrous magnesium sulfate product; the purity of the ferrous magnesium sulfate product is ≥97.36%.

2. The method according to claim 1, characterized in that, The conditions for nanofiltration include: the nanofiltration membrane used is a Wharton nanofiltration membrane, the temperature is 21~25℃, and the transmembrane pressure is 20~35 Bar.

3. The method according to claim 1, characterized in that, The mass ratio of the nanofiltration concentrate to iron powder is 1:0.01~0.

05.

4. The method according to claim 1 or 3, characterized in that, The acidity has a pH value of 0.8 to 1.2; The reduction treatment is performed at a temperature of 30-40°C for a time of 30-50 minutes.

5. The method according to claim 1, characterized in that, The volume of the thermally concentrated crystallization liquid is 1 / 6 to 2 / 3 of the volume of the mother liquor.

6. The method according to claim 1, characterized in that, The temperature of the thermally concentrated crystallizing solution is ≥65℃; The final temperature for cooling and crystallization is 20~35℃, the stirring speed is 100~500r / min, and the total time is 4~8h.

7. The method according to claim 1 or 6, characterized in that, After cooling and crystallization, the process also includes aging and cultivating the resulting cooled crystallization liquid. The aging and crystal growth process takes place at a temperature of 20-35°C for 4-6 days.

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