Refined magnesium sodium sulfate prepared by roasting serpentine tailings mixed with auxiliary agent and preparation method of refined magnesium sodium sulfate

Abstract

The invention provides refined magnesium sodium sulfate prepared by roasting serpentine tailings mixed with an auxiliary agent and a preparation method, and the preparation method comprises the following steps: proportioning serpentine tailings powder and a reaction auxiliary agent, and then putting the mixture into a high-temperature roasting furnace for roasting treatment to obtain a roasted product; the roasted product is placed in a reactor containing a leaching solution to be subjected to leaching treatment, and turbid liquid containing magnesium sodium sulfate is obtained; filtering the turbid liquid to obtain a refined magnesium sulfate sodium solution; and carrying out evaporative crystallization on the refined magnesium sodium sulfate solution to obtain refined magnesium sodium sulfate. The purity of the refined magnesium sulfate sodium ranges from 98.889% to 99.995%. According to the preparation method, the magnesium ion leaching rate reaches 70.0%-90.0%, the iron ion leaching rate is controlled to be 0.1%-1.5%, the purpose of treating waste with waste is achieved, the problems of land occupation and pollution caused by open-air accumulation of the two kinds of waste residues are solved from the source, the solid waste stockpiling environmental risk is reduced, and the concept of circular economy and green development is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste valuable component extraction and new material preparation, in particular to refined magnesium sodium sulfate prepared by serpentine tailings mixed additives roasting and a preparation method thereof. BACKGROUND

[0002] China is rich in chrysotile mineral resources and serpentinite mineral resources. However, a large amount of serpentine tailings will be produced in the process of mining and processing of asbestos and serpentinite mineral resources. According to statistics, about 10 tons of tailings will be produced for every ton of asbestos produced, including stripped serpentine waste rock, tailings produced in the process of asbestos beneficiation, and solid waste produced in the process of serpentine mining and beneficiation. For a long time, these tailings are mostly treated by open-air stacking, which not only causes serious waste of valuable mineral resources such as magnesium and silicon, but also occupies a large amount of land resources. More attention should be paid to the fact that the fine fibers contained in the asbestos tailings are easily diffused into the atmosphere under the action of wind, and can cause lung diseases and other health problems after being inhaled by the human body. In addition, the heavy metal elements contained in the tailings will also penetrate into the soil and groundwater under the long-term differentiation effect, causing persistent pollution to the surrounding ecological environment.

[0003] In the field of industrial production, sodium sulfate slag is a typical solid waste discharged by chemical, metallurgical and other industries, which is mainly derived from the process of sulfuric acid production and non-ferrous metal smelting. This kind of waste slag has a huge output, and because it contains soluble salts such as sodium sulfate and ammonium sulfate and a small amount of heavy metal components, if it is directly stacked or landfilled, it will cause soil salinization, groundwater pollution and other secondary environmental problems, which is extremely difficult to handle, and has been a difficult problem for enterprises and environmental protection departments. At present, the disposal of sodium sulfate slag is mainly simple stacking, and there is a lack of economic and efficient resource utilization approach, which not only wastes the sulfur resources in it, but also increases the pressure of solid waste treatment.

[0004] In the prior art, the process for extracting magnesium from serpentine tailings mainly includes acid leaching method, alkali melting method and the like. The acid leaching method usually needs to use a large amount of strong acid, which not only has high cost, but also produces a large amount of acid wastewater, which is difficult to handle subsequently; the alkali melting method has problems such as high energy consumption and serious equipment corrosion, and the extraction rate of magnesium is often not ideal. At the same time, most of these processes do not consider the synergistic treatment with other solid wastes, and cannot realize the concept of "waste treatment with waste" in circular economy. In addition, in the process of extracting magnesium, a large amount of impurity ions such as iron and aluminum will be leached out, which leads to complex refining process of magnesium products and makes it difficult to guarantee the purity, further limiting the high-value utilization of serpentine tailings.

[0005] Therefore, developing a method for extracting magnesium by synergistically treating serpentine tailings and sodium sulfate residue, which is simple, low-cost, environmentally friendly and efficient, can not only solve the accumulation problem of the two types of solid waste and realize the recycling of resources, but also provide strong support for the sustainable development of related industries, which has important economic and environmental significance. SUMMARY

[0006] The present application aims to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the purposes of the present application is to provide a method for preparing refined magnesium sodium sulfate by roasting serpentine tailings mixed with an auxiliary agent; the second purpose of the present application is to provide a method for preparing refined magnesium sodium sulfate by roasting serpentine tailings mixed with an auxiliary agent.

[0007] To achieve the above-mentioned purposes, the present application provides a method for preparing refined magnesium sodium sulfate by roasting serpentine tailings mixed with an auxiliary agent, the preparation method comprising: 1) After mixing serpentine tailings powder with reaction auxiliary agent, the mixture is placed in a high-temperature roasting furnace for roasting treatment to obtain a roasting product; 2) The roasting product is placed in a reactor containing leaching liquid for leaching treatment to obtain a suspension containing magnesium sodium sulfate; 3) The suspension is filtered to obtain a refined magnesium sodium sulfate solution; 4) The refined magnesium sodium sulfate solution is evaporated and crystallized to obtain refined magnesium sodium sulfate.

[0008] Alternatively, the serpentine tailings powder is obtained by crushing and grinding asbestos tailings, serpentine stripping waste rock and serpentine beneficiation tailings, the particle size of the serpentine tailings powder is-50 mesh~+200 mesh; the chemical composition of the serpentine tailings powder includes, by mass percentage: SiO2 is 37.0%~42.0%, MgO is 36.0%~42.0%, Al2O3 is 0.8%~1.2%, TFe2O3 is 3.0%~8.0%, CaO is 0.4%~0.7%, and the loss on ignition is 12.0%~13.5%; the mineral types of the serpentine tailings powder include serpentine, and a small amount of one or more of talc, quartz, magnetite, brucite and chlorite.

[0009] Alternatively, the reaction auxiliary agent includes a mixture of sodium sulfate residue and sulfuric acid, the proportion of sulfuric acid is 20%~50%, the phase composition of the sodium sulfate residue includes sodium sulfate and ammonium sulfate, and a small amount of one or more of quartz, limestone minerals.

[0010] Optionally, the ratio in step 1) is 1.0-2.0 in terms of the molar ratio of sulfate in the reaction aid to magnesium ion in the serpentine tailings powder; the temperature of the roasting treatment is 550-750℃, and the time is 60-120 min; the roasting product contains one or more of sodium magnesium sulfate (chemical formula Na6Mg(SO4)4), hematite, amorphous silicon dioxide, and unreacted serpentine.

[0011] Optionally, the leaching solution in step 2) is a sulfuric acid solution with a pH of 2.5-5.5, and the liquid-solid ratio of the leaching solution to the roasting product is 5-10 mL / g; the temperature of the leaching reaction is 30-60℃, and the time is 30-90 min; the sodium magnesium sulfate-containing suspension has sodium magnesium sulfate solution as the liquid and one or more of hematite, amorphous silicon dioxide, and unreacted serpentine as the suspended substance; and the reactor is a reaction kettle with stirring and heating devices.

[0012] Optionally, the filtration in step 3) includes filtration and washing using a filter press with a washing device, and the filter residue obtained after filtration contains one or more of hematite, amorphous silicon dioxide, talc, quartz, and unreacted serpentine.

[0013] Optionally, the refined sodium magnesium sulfate solution in step 3) has a magnesium ion concentration of 15.12-45.36 g / L, an iron ion concentration of 0.0021-0.17 g / L, a magnesium ion leaching rate of 70.0%-90.0%, and an iron ion leaching rate of 0.1%-1.5%.

[0014] Optionally, the evaporation crystallization in step 4) is performed using one of a multi-effect evaporation crystallization system, a natural circulation type evaporation crystallization system, a forced circulation type evaporation crystallization system, and a vacuum type evaporation crystallization system.

[0015] Another aspect of the present application provides a refined sodium magnesium sulfate prepared by roasting a serpentine tailings mixed aid, which can be obtained by the preparation method mentioned above; the purity of the refined sodium magnesium sulfate is 98.889%-99.995%.

[0016] Optionally, the application of the refined sodium magnesium sulfate solution and the refined sodium magnesium sulfate includes use as raw materials for preparing a series of magnesium-containing compound products such as magnesium sulfate and basic magnesium carbonate.

[0017] Compared with the prior art, the present application has the following beneficial effects: (1) The application effectively reduces the activation temperature of sodium sulfate by adding sulfuric acid in the reaction aid, creates more favorable thermodynamic conditions for the reaction of sodium sulfate and magnesium components in serpentine tailings, significantly promotes the generation of target products such as magnesium sodium sulfate in the calcination process, and improves the reaction efficiency.

[0018] (2) The application realizes that the magnesium ion leaching rate is 70.0%~90.0%, the iron ion leaching rate is controlled in 0.1%~1.5%, the leaching of impurity ions is inhibited, and the waste residue generated in the subsequent impurity removal process is reduced.

[0019] (3) The purity of the refined magnesium sodium sulfate can reach 98.889%~99.995%, and can be used as a raw material for preparing magnesium sulfate, basic magnesium carbonate and other series of magnesium compound products, realizing the high-value utilization of serpentine tailings.

[0020] (4) The application mixes serpentine tailings and sodium sulfate slag under strong acid conditions and sulfuric acid roasting, so that the magnesium resources in the serpentine tailings are efficiently extracted, and the components such as sulfate in the sodium sulfate slag are fully utilized as reaction aids, achieving the purpose of "waste treatment with waste". From the source, the problems of land occupation, air pollution and soil and groundwater pollution caused by open-air stacking of serpentine tailings and sodium sulfate slag are avoided, the environmental risk of solid waste storage is significantly reduced, and the concept of circular economy and green development is met. BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and other objects and / or characteristics of the present application will become more apparent by describing in detail the present application with reference to the attached drawings, wherein: Figure 1 A process flow diagram of the preparation method of the application is shown.

[0022] Figure 2 The XRD pattern of the calcined product and its water leaching residue after mixing and calcining serpentine tailings, sodium sulfate and sulfuric acid in Example 1 of the application is shown. DETAILED DESCRIPTION

[0023] In the following, the refined magnesium sodium sulfate prepared by mixing and calcining serpentine tailings with an aid agent and the preparation method thereof will be described in detail with reference to exemplary embodiments.

[0024] The preparation principle of the application is: (1) Sodium sulfate needs a high temperature of 884℃ or higher under conventional conditions to decompose, and the addition of sulfuric acid can significantly reduce its decomposition temperature.

[0025] (2) The serpentine tailings are first decomposed at high temperature in the calcination process, the MgO component after decomposition reacts with sodium sulfate slag and sulfuric acid to generate soluble magnesium sodium sulfate, and then the magnesium ions are extracted into the solution by leaching.

[0026] Mg3Si2O5(OH)4+ 3H2SO4+ 9Na2SO4= 3Na6Mg(SO4)4+ 2SiO2+ 5H2O.

[0027] Example 1 The example embodiment provides a method for preparing refined magnesium sodium sulfate by roasting serpentine tailings mixed with an auxiliary agent, Figure 1 The process flow diagram of the preparation method is shown in the figure, which comprises the following steps: Figure 1 As shown in the figure, the preparation method can comprise: S1, the serpentine tailings powder is mixed with the reaction auxiliary agent, and then placed in a high-temperature roasting furnace for roasting treatment to obtain a roasting product.

[0028] In this embodiment, the serpentine tailings powder is obtained by crushing and grinding asbestos tailings, serpentine stripping waste rock and serpentine beneficiation tailings, and the particle size of the serpentine tailings powder is-50 mesh to +200 mesh; the chemical composition of the serpentine tailings powder includes, by mass percentage, SiO2 37.0% to 42.0%, MgO 36.0% to 42.0%, Al2O3 0.8% to 1.2%, TFe2O3 3.0% to 8.0%, CaO 0.4% to 0.7%, and loss on ignition 12.0% to 13.5%; the mineral types of the serpentine tailings powder include serpentine, and a small amount of one or more of talc, quartz, magnetite, brucite and chlorite.

[0029] In this embodiment, the reaction auxiliary agent includes a mixture of sodium sulfate residue and sulfuric acid, and the sulfuric acid accounts for 20% to 50%, such as 21%, 30%, 36% and 49%, etc. Too little sulfuric acid will cause incomplete decomposition of sodium sulfate, and too much sulfuric acid will cause the product to be converted into magnesium sulfate, and too little consumption of sodium sulfate residue will not achieve the effect of "waste treatment with waste".

[0030] In this embodiment, the ratio is 1.0 to 2.0 in terms of the molar ratio of sulfate in the reaction auxiliary agent to magnesium ions in the serpentine tailings powder, such as 1.1, 1.5 and 1.9, etc. Too little auxiliary agent will cause incomplete reaction of serpentine, and low extraction efficiency of magnesium ions; too much auxiliary agent will increase the leaching rate of iron ions and cause resource waste.

[0031] In this embodiment, the roasting temperature is 550°C to 750°C, such as 551°C, 600°C, 670°C and 749°C, etc. Too low roasting temperature will cause incomplete reaction of serpentine and auxiliary agent, and low extraction efficiency of magnesium ions; too high roasting temperature will cause energy waste.

[0032] In this embodiment, the calcination time is 60~120min, such as 61min, 90min, 100min and 119min. If the calcination time is too short, the reaction between the additive and serpentine will be incomplete, reducing the extraction rate of magnesium ions; if the calcination time is too long, the energy consumption will increase, which is not economical.

[0033] In this embodiment, the roasting product contains one or more of the following: sodium magnesium sulfate (chemical formula Na6Mg(SO4)4), hematite, amorphous silica, and unreacted serpentine.

[0034] S2. The roasted product is placed in a reactor containing leaching solution for leaching treatment to obtain a suspension containing sodium magnesium sulfate.

[0035] In this embodiment, the leaching solution is a sulfuric acid solution with a pH of 2.5 to 5.5, such as 2.55, 3.4, 4.2 and 5.4. If the leaching pH is too low, the leaching rate of impurity ions such as iron ions will be too high; if the leaching pH is too high, the leaching rate of magnesium ions will be too low.

[0036] In this embodiment, the liquid-to-solid ratio of the leaching solution to the calcined product is 5~10mL / g, such as 5.5mL / g, 7mL / g, 8.5mL / g and 9.8mL / g. Too small a liquid-to-solid ratio will result in a low magnesium ion leaching rate, while too large a liquid-to-solid ratio will result in resource waste.

[0037] In this embodiment, the leaching reaction temperature is 30℃~60℃, such as 31℃, 45℃, 50℃ and 59℃. Too low a temperature will result in an incomplete reaction and a low magnesium ion leaching rate.

[0038] In this embodiment, the leaching reaction time is 30~90min, such as 31min, 60min, 75min and 89min. Too short a reaction time will result in incomplete reaction, while too long a reaction time will increase time cost.

[0039] In this embodiment, the liquid in the suspension containing sodium magnesium sulfate is a sodium magnesium sulfate solution, and the suspended matter is one or more of hematite, amorphous silica, and unreacted serpentine; the reactor is a reaction vessel equipped with a stirring and heating device.

[0040] S3. Filter the suspension to obtain a refined sodium magnesium sulfate solution.

[0041] In this embodiment, the filtration includes filtration and rinsing using a filter press with a rinsing device. The filter residue obtained after filtration contains one or more of the following: hematite, amorphous silica, talc, quartz, and unreacted serpentine.

[0042] In this embodiment, the magnesium ion concentration in the refined sodium magnesium sulfate solution is 15.12~45.36 g / L, the iron ion concentration is 0.0021~0.17 g / L, the magnesium ion leaching rate is 70.0%~90.0%, and the iron ion leaching rate is 0.1%~1.5%.

[0043] S4. Evaporate and crystallize the refined magnesium sodium sulfate solution to obtain refined magnesium sodium sulfate.

[0044] In this embodiment, the evaporation crystallization is carried out using one of the following systems: multi-effect evaporation crystallization system, natural circulation evaporation crystallization system, forced circulation evaporation crystallization system, and vacuum evaporation crystallization system.

[0045] Exemplary Example 2 This exemplary embodiment provides a method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives. The refined sodium magnesium sulfate can be prepared by the preparation method mentioned above. The purity of the refined sodium magnesium sulfate is 98.889%~99.995%.

[0046] In this embodiment, the refined magnesium sodium sulfate solution and the refined magnesium sodium sulfate are used as raw materials for preparing a series of magnesium-containing compound products such as magnesium sulfate and basic magnesium carbonate.

[0047] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific examples.

[0048] Example 1 The Aksai asbestos tailings selected in this example mainly contains serpentine, with small amounts of talc, magnetite, and quartz. The main chemical composition is shown in Table 1. Table 1. Main chemical components of asbestos tailings

[0049] The preparation method in this example is as follows: S1: The reaction aid and asbestos tailings powder are mixed at a molar ratio of sulfate ions in the aid to magnesium ions in the asbestos tailings of 1.0, and then placed in a high-temperature furnace and calcined at 750℃ for 60 minutes to obtain the calcined product. The calcined product mainly contains sodium magnesium sulfate, hematite, and amorphous silica. The reaction aid is a mixture of 20% sulfuric acid and 80% sodium sulfate slag.

[0050] Figure 2 The XRD patterns of the roasted product and its water-leached residue described in this example are shown. As can be seen from the figure, the roasted product mainly contains sodium magnesium sulfate and unreacted serpentine. After water leaching, the sodium magnesium sulfate is completely dissolved, and the water-leached residue mainly contains unreacted serpentine and hematite.

[0051] S2: The calcined product in S1 is placed in a reaction vessel containing a dilute sulfuric acid solution with a pH of 2.5 and equipped with a stirring and heating device for leaching. The liquid-to-solid ratio of the leaching reaction is 5 mL / g, the temperature is 30°C, and the time is 30 min. After leaching, a suspension containing sodium magnesium sulfate is obtained.

[0052] S3: The magnesium sulfate sodium suspension in S2 is filtered to obtain filter residue and refined magnesium sulfate sodium solution; the filter residue mainly contains hematite and amorphous silica. The magnesium ion concentration in the refined magnesium sulfate sodium solution is 15.12 g / L, and the iron ion concentration is 0.17 g / L; the magnesium ion leaching rate is 70.0%, and the iron ion leaching rate is 1.5%.

[0053] S4: The refined sodium magnesium sulfate solution in S3 is subjected to multi-effect evaporation and crystallization to obtain refined sodium magnesium sulfate with a purity of 98.889%.

[0054] Example 2 The minerals contained in the serpentine stripping waste rock from Mangya, Qinghai, selected in this example experiment are mainly serpentine, with small amounts of talc, magnetite, and quartz. The main chemical components are shown in Table 2. Table 2. Main chemical components of serpentine stripping waste rock

[0055] The preparation method in this example is as follows: S1: The reaction aid and powder are mixed according to a molar ratio of sulfate ions in the aid to magnesium ions in the serpentine stripping waste rock of 2.0, and then placed in a high-temperature furnace and calcined at 550℃ for 120 min to obtain the calcined product. The calcined product mainly contains sodium magnesium sulfate, hematite, and amorphous silica. The reaction aid is a mixture of 50% sulfuric acid and 50% sodium sulfate slag.

[0056] S2: The calcined product in S1 is placed in a reaction vessel containing a dilute sulfuric acid solution with a pH of 5.5 and equipped with a stirring and heating device for leaching. The liquid-to-solid ratio of the leaching reaction is 10 mL / g, the temperature is 60℃, and the time is 90 min. After leaching, a suspension containing sodium magnesium sulfate is obtained.

[0057] S3: The magnesium sulfate sodium suspension in S2 is filtered to obtain filter residue and refined magnesium sulfate sodium solution; the filter residue mainly contains hematite and amorphous silica. The magnesium ion concentration in the refined magnesium sulfate sodium solution is 45.36 g / L, and the iron ion concentration is 0.0021 g / L; the magnesium ion leaching rate is 90.0%, and the iron ion leaching rate is 0.1%.

[0058] S4: The refined sodium magnesium sulfate solution in S3 is subjected to natural circulation evaporation and crystallization to obtain refined sodium magnesium sulfate with a purity of 99.995%.

[0059] Example 3 The Aksai asbestos tailings selected in this example experiment mainly contains serpentine, with small amounts of talc, magnetite, and quartz. The main chemical composition is shown in Table 3. Table 3 Main chemical components of asbestos tailings

[0060] The preparation method in this example is as follows: S1: The reaction aid and asbestos tailings powder are mixed at a molar ratio of sulfate ions in the aid to magnesium ions in the asbestos tailings of 2.0, and then placed in a high-temperature furnace and calcined at 600℃ for 90 minutes to obtain the calcined product. The calcined product mainly contains sodium magnesium sulfate, hematite, amorphous silica, and serpentine. The reaction aid is a mixture of 30% sulfuric acid and 70% sodium sulfate slag.

[0061] S2: The calcined product in S1 is placed in a reaction vessel containing a dilute sulfuric acid solution with a pH of 4.5 and equipped with a stirring and heating device for leaching. The liquid-to-solid ratio of the leaching reaction is 8 mL / g, the temperature is 45℃, and the time is 60 min. After leaching, a suspension containing sodium magnesium sulfate is obtained.

[0062] S3: The magnesium sulfate sodium suspension in S2 is filtered to obtain filter residue and refined magnesium sulfate sodium solution; the filter residue mainly contains hematite and amorphous silica. The magnesium ion concentration in the refined magnesium sulfate sodium solution is 35.17 g / L, and the iron ion concentration is 0.051 g / L; the magnesium ion leaching rate is 83.4%, and the iron ion leaching rate is 1.1%.

[0063] S4: The refined sodium magnesium sulfate solution in S3 is subjected to forced circulation evaporation and crystallization to obtain refined sodium magnesium sulfate with a purity of 99.855%.

[0064] Example 4 The serpentine tailings from the Da'an serpentine beneficiation project in this example experiment mainly contains serpentine, with small amounts of talc, magnetite, chlorite, brucite, and quartz. The main chemical composition is shown in Table 4. Table 4. Main chemical components of serpentine beneficiation tailings

[0065] The preparation method in this example is as follows: S1: The reaction aid and serpentine beneficiation tailings powder are mixed at a molar ratio of sulfate in the aid to magnesium ions in the serpentine beneficiation tailings of 1.5, and then placed in a high-temperature furnace and roasted at 600℃ for 80 minutes to obtain the roasted product. The roasted product mainly contains sodium magnesium sulfate, hematite, and amorphous silica. The reaction aid is a mixture of 40% sulfuric acid and 60% sodium sulfate slag.

[0066] S2: The calcined product in S1 is placed in a reaction vessel containing a dilute sulfuric acid solution with a pH of 4.5 and equipped with a stirring and heating device for leaching. The liquid-to-solid ratio of the leaching reaction is 7 mL / g, the temperature is 60℃, and the time is 40 min. After leaching, a suspension containing sodium magnesium sulfate is obtained.

[0067] S3: The magnesium sulfate sodium suspension in S2 is filtered to obtain filter residue and refined magnesium sulfate sodium solution; the filter residue mainly contains hematite and amorphous silica. The magnesium ion concentration in the refined magnesium sulfate sodium solution is 40.17 g / L, and the iron ion concentration is 0.0078 g / L; the magnesium ion leaching rate is 76.54%, and the iron ion leaching rate is 0.75%.

[0068] S4: The refined sodium magnesium sulfate solution in S3 is subjected to vacuum evaporation and crystallization to obtain refined sodium magnesium sulfate with a purity of 99.981%.

[0069] Example 5 The main minerals contained in the serpentine stripping waste rock from Mangya, Qinghai Province, selected in this example experiment are serpentine, with small amounts of talc, magnetite, and brucite. The main chemical composition is shown in Table 5. Table 5. Main chemical components of serpentine stripping waste rock

[0070] The preparation method in this example is as follows: S1: The reaction aid and serpentine stripping waste rock powder are mixed at a molar ratio of sulfate in the aid to magnesium ions in the serpentine stripping waste rock of 1.0, and then placed in a high-temperature furnace and calcined at 700℃ for 120 min to obtain the calcined product. The calcined product mainly contains sodium magnesium sulfate, hematite, and amorphous silica. The reaction aid is a mixture of 35% sulfuric acid and 65% sodium sulfate slag.

[0071] S2: The calcined product in S1 is placed in a reaction vessel containing a dilute sulfuric acid solution with a pH of 5.0 and equipped with a stirring and heating device for leaching. The liquid-to-solid ratio of the leaching reaction is 9 mL / g, the temperature is 30°C, and the time is 60 min. After leaching, a suspension containing sodium magnesium sulfate is obtained.

[0072] S3: The magnesium sulfate sodium suspension in S2 is filtered to obtain filter residue and refined magnesium sulfate sodium solution; the filter residue mainly contains hematite and amorphous silica. The magnesium ion concentration in the refined magnesium sulfate sodium solution is 23.85 g / L, and the iron ion concentration is 0.0095 g / L; the magnesium ion leaching rate is 88.0%, and the iron ion leaching rate is 1.0%.

[0073] S4: The refined sodium magnesium sulfate solution in S3 is subjected to multi-effect evaporation and crystallization to obtain refined sodium magnesium sulfate with a purity of 99.960%.

[0074] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing refined sodium magnesium sulfate by calcining serpentine tailings mixed with additives, characterized in that, The method includes: 1) After mixing serpentine tailings powder with reaction aids, place it in a high-temperature roasting furnace for roasting treatment to obtain roasted products; 2) The roasted product is placed in a reactor containing a leaching solution for leaching treatment to obtain a suspension containing sodium magnesium sulfate; 3) Filter the suspension to obtain a purified sodium magnesium sulfate solution; 4) Evaporate and crystallize the refined magnesium sodium sulfate solution to obtain refined magnesium sodium sulfate.

2. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The serpentine tailings powder is obtained by crushing and grinding asbestos tailings, serpentine stripping waste rock, and serpentine beneficiation tailings. The particle size of the serpentine tailings powder is -50 mesh to +200 mesh. The chemical composition of the serpentine tailings powder, by mass percentage, includes: SiO2 37.0% to 42.0%, MgO 36.0% to 42.0%, Al2O3 0.8% to 1.2%, TFe2O3 3.0% to 8.0%, CaO 0.4% to 0.7%, and loss on ignition 12.0% to 13.5%. The mineral types of the serpentine tailings powder include serpentine, and a small amount of one or more of talc, quartz, magnetite, brucite, and chlorite.

3. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The reaction aid includes a mixture of sodium sulfate residue and sulfuric acid, wherein the sulfuric acid accounts for 20% to 50%, and the phase composition of the sodium sulfate residue is sodium sulfate and ammonium sulfate, as well as one or more of quartz and limestone minerals.

4. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The ratio mentioned in step 1) is 1.0~2.0 based on the molar ratio of sulfate ions in the reaction aid to magnesium ions in the serpentine tailings powder; the roasting temperature is 550℃~750℃ and the time is 60~120min; the roasting product contains one or more of sodium magnesium sulfate, hematite, amorphous silica and unreacted serpentine.

5. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The leaching solution in step 2) is a sulfuric acid solution with a pH of 2.5 to 5.5, and the liquid-to-solid ratio of the leaching solution to the roasted product is 5 to 10 mL / g; the leaching reaction temperature is 30℃ to 60℃, and the time is 30 to 90 min; the liquid in the suspension containing sodium magnesium sulfate is a sodium magnesium sulfate solution, and the suspended matter is one or more of hematite, amorphous silica, and unreacted serpentine; the reactor is a reaction vessel equipped with a stirring and heating device.

6. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The filtration described in step 3) includes filtration and rinsing using a filter press with a rinsing device. The filter residue obtained after filtration contains one or more of the following: hematite, amorphous silica, talc, quartz, and unreacted serpentine.

7. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, In step 3), the concentration of magnesium ions in the refined sodium magnesium sulfate solution is 15.12~45.36 g / L, the concentration of iron ions is 0.0021~0.17 g / L, the leaching rate of magnesium ions is 70.0%~90.0%, and the leaching rate of iron ions is 0.1%~1.5%.

8. The method for preparing refined sodium magnesium sulfate by roasting serpentine tailings mixed with additives according to claim 1, characterized in that, The evaporation crystallization described in step 4) is carried out using one of the following systems: multi-effect evaporation crystallization system, natural circulation evaporation crystallization system, forced circulation evaporation crystallization system, and vacuum evaporation crystallization system.

9. A refined sodium magnesium sulfate prepared by roasting serpentine tailings mixed with additives, characterized in that, The refined sodium magnesium sulfate is prepared by the preparation method according to any one of claims 1-8; the purity of the refined sodium magnesium sulfate is 98.889%~99.995%.

10. The application of refined sodium magnesium sulfate prepared by roasting the serpentine tailings mixture according to claim 9, characterized in that, The refined magnesium sodium sulfate solution and the refined magnesium sodium sulfate are used as raw materials for the preparation of magnesium sulfate and a series of magnesium-containing compound products, including basic magnesium carbonate.

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