A method of controlling the crystal form of ferrous sulphide for solution purification

Abstract

The application discloses a method for controlling ferrous sulfide crystal form for solution purification, which comprises the following steps: mixing elemental iron powder and elemental sulfur, sintering under the condition of argon gas through a microwave tube furnace to obtain monoclinic ferrous sulfide; taking an acidic solution containing arsenic which needs to be purified, adding the monoclinic ferrous sulfide, stirring under the condition of room temperature and ultrasonic, filtering under the condition of normal pressure after the reaction is completed to obtain filter residue and dearsenification purified filtrate. The application artificially synthesizes monoclinic ferrous sulfide by a microwave tube furnace to serve as a sulfur ion supplier, which guarantees the supply of sulfur ions under the premise of not introducing sodium ions; the monoclinic ferrous sulfide slowly releases S 2‑ under the acidic condition, greatly weakens the competitive reaction of H + , does not produce violent reaction and slowly releases hydrogen sulfide gas; meanwhile, the use of monoclinic ferrous sulfide can greatly shorten the arsenic removal time, iron ions can be used for subsequent solution purification and do not bring burden to the recycling of the purified solution.

Description

Technical Field

[0001] This invention relates to the field of industrial solution treatment technology, and in particular to a method for solution purification by regulating the crystal form of ferrous sulfide. Background Technology

[0002] Arsenic is often found in association with metallic minerals in nature, so arsenic-containing wastewater is inevitably generated during production processes in chemical and metallurgical industries. Specifically, the flue gas produced during sulfuric acid production generates highly arsenic-containing acidic wastewater during the washing and acidification process. Secondly, arsenic is also leached into the acidic leachate during the acidic leaching processes in chemical and hydrometallurgical processes. Acidic arsenic-containing solutions are characterized by complex composition, high acidity, and high hazard. Arsenic, in particular, requires special treatment due to its high carcinogenicity and harmfulness.

[0003] In the existing technology, there are many methods for removing arsenic from arsenic-containing solutions, such as lime-ferric salt method, sulfide precipitation method, ion exchange method, adsorption method, and membrane separation method. Lime precipitation method and sulfide precipitation method are widely used in the purification of arsenic-containing solutions due to their simple operation and readily available raw materials.

[0004] The lime precipitation method generates a large amount of gypsum slag during arsenic removal, which requires treatment. Ca3(AsO4)2, a gypsum slag, is an unstable compound that can easily cause secondary pollution if not stored properly, limiting its further development. The sulfide precipitation method typically adds a sulfiding agent, such as Na2S or NaHS, to an acidic arsenic-containing solution. The sulfiding agent dissolves rapidly in the solution, generating hydrogen sulfide gas, which acts as a sulfur ion donor. Arsenic in the solution reacts with sulfur ions to form sulfide precipitates, thus removing arsenic from the solution. While the sulfide precipitation method is effective in arsenic removal, the sulfiding agent continuously introduces sodium ions into the system during use. The accumulation of these difficult-to-treat sodium ions puts significant pressure on the entire smelting system and subsequent concentration and crystallization of related products, and also burdens the recycling of the purified solution. Furthermore, the generation and overflow of H2S gas during arsenic removal, along with low utilization rates, contribute to the high cost and large consumption of sulfiding agents in the sulfide precipitation process. Therefore, finding a sulfiding agent with a slow-release effect that does not introduce difficult-to-treat metal cations into the solution is crucial.

[0005] In recent years, many novel sulfiding agents have been developed and utilized, among which iron sulfides have been widely used in the purification of solutions containing arsenic and heavy metals. Chinese invention patent application publication number CN202210175100.2 discloses a porous FeS material, its preparation method, and its application in the purification of arsenic / or heavy metal-containing wastewater. This method uses iron powder and pyrite, prepared through a one-step calcination process, to produce FeS with a large specific surface area, numerous reactive sites, and high reactivity for adsorbing arsenic and heavy metals, achieving wastewater purification. While achieving groundwater purification, it avoids the release of hydrogen sulfide gas, reducing environmental pollution. However, this porous material requires a neutral or weakly alkaline environment and a solution temperature of 80℃ to maintain its activity. In actual industrial production, heating the solution is not economically viable, and at high temperatures, sulfite ions and dissolved sulfur dioxide in acidic wastewater will be released, posing environmental risks and increasing treatment costs and energy consumption. Chinese invention patent application publication number CN202211263146.6 discloses a process for the clean and efficient removal and comprehensive utilization of arsenic from waste acid. By adding a certain amount of FeS, the arsenic in the waste acid precipitates as arsenic sulfide. Although no hydrogen sulfide gas is produced in the process, strict control of the reaction temperature is required, which will increase energy consumption and environmental pressure. Furthermore, this method produces ferric arsenite, which reacts with acid to produce arsenic trioxide, posing a safety hazard. Summary of the Invention

[0006] To address the problems of existing technologies, this invention proposes a method for solution purification by controlling the crystal form of ferrous sulfide. The reagent is added at room temperature, eliminating the need for pH adjustment, and ultrasonic technology is introduced to promote the reaction and shorten the reaction time. Arsenic in the solution precipitates as arsenic sulfide, resulting in high hydrogen sulfide utilization. This method solves the technical problems of conventional sulfidation reagents, such as the easy leakage of H2S gas and the accumulation of sodium ions in the system due to vigorous reactions.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for deeply purifying a solution by controlling the crystal form of ferrous sulfide includes the following steps: (1) Synthesis of monoclinic ferrous sulfide: Elemental iron powder and elemental sulfur are mixed and sintered in a microwave tube furnace under inert gas protection to obtain monoclinic ferrous sulfide; (2) Arsenic removal: Take an acidic arsenic-containing solution that needs to be purified, add the monoclinic ferrous sulfide described in step (1), and stir for 25 to 30 minutes at room temperature and under ultrasonic conditions; Solid-liquid separation: After the reaction in step (2) is completed, the mixture is filtered under normal pressure to obtain filter residue and arsenic removal filtrate.

[0008] Conventional sulfiding agents react rapidly, posing a high risk of hydrogen sulfide gas escape and creating a poor operating environment. Sodium ions, a difficult-to-handle metal cation, are introduced into the system, making the reuse of the purified solution challenging. Traditional tube furnaces heat up slowly, resulting in a long preparation time for monoclinic ferrous sulfide. This invention uses a microwave tube furnace to artificially synthesize monoclinic ferrous sulfide as a sulfur ion donor, ensuring a sulfur ion supply without introducing sodium ions. The monoclinic ferrous sulfide slowly releases sulfur under acidic conditions. 2- Greatly reduced H + The competitive reaction prevents violent reactions and allows for the slow release of hydrogen sulfide gas. At the same time, compared with traditional sulfiding agents such as sodium sulfide and sodium hydrosulfide, the use of monoclinic ferrous sulfide can greatly shorten the arsenic removal time. The iron ions can be used for further purification of the solution without burdening the recycling of the purified solution.

[0009] This invention utilizes a microwave tube furnace to artificially synthesize monoclinic crystalline ferrous sulfide as a sulfur ion donor, ensuring a sufficient supply of sulfur ions without introducing cations that would increase the burden on the solution purification system. Common FeS typically has a hexagonal structure. While hexagonal ferrous sulfide is structurally stable, its solubility is insufficient for practical solution purification requirements. Increasing solubility through heating would lead to increased energy consumption and solution evaporation, hindering energy conservation, emission reduction, and green development. This invention controls the crystal form of FeS and prepares monoclinic crystalline ferrous sulfide via microwave sintering. In this crystalline state, the coordination between Fe and S is flexible, and the intermolecular bonds are more easily broken compared to hexagonal ferrous sulfide. However, the reaction remains mild under acidic conditions with a slow-release effect, avoiding the violent reaction that instantaneously generates large amounts of inefficiently utilized hydrogen sulfide gas, thus meeting the basic requirements of enterprises for solution purification. Iron ions have mature removal processes in existing solution purification procedures; the introduction of iron ions does not incur additional costs for solution purification, nor does it burden the recycling of the purified solution.

[0010] By adding a predetermined amount of monoclinic ferrous sulfide to an acidic arsenic-containing solution, and simultaneously stirring with ultrasonic enhancement, only 25-30 minutes of stirring are required. Finally, solid-liquid separation is performed, and after filtration, arsenic-removed filtrate and precipitated impurities are obtained. The ultrasonic-enhanced arsenic removal method in acidic industrial solutions provided by this invention can improve arsenic removal efficiency and achieve deep arsenic removal. No sodium ions are introduced during the arsenic removal process, greatly alleviating the pressure on subsequent resource utilization and recycling of waste acid, while reducing treatment costs and saving energy. For the sulfide-lime-iron salt method of arsenic removal used in industry, this arsenic removal method shows good prospects in reducing slag volume, reducing iron salt usage, and utilizing lime slag.

[0011] Preferably, the molar ratio of elemental iron powder and elemental sulfur in step (1) is 1:1.4 to 1.6; the inert gas is argon. Preferably, the sintering in step (1) is performed at 400-450°C for 30-150 min.

[0012] Preferably, the molar ratio of arsenic to monoclinic ferrous sulfide in the acidic arsenic-containing solution in step (2) is 1:1.4 to 1.6.

[0013] Preferably, the ultrasonic conditions in step (2) are: frequency 15-25 kHz, power 10-120 W / L.

[0014] The beneficial effects of this invention are as follows: 1. This invention utilizes artificially synthesized monoclinic ferrous sulfide as a sulfur ion donor, ensuring the supply of sulfur ions without introducing sodium ions; the monoclinic ferrous sulfide slowly releases sulfur under acidic conditions. 2- Greatly reduced H + The competitive reaction allows for the slow release of hydrogen sulfide gas, improving gas utilization, reducing the risk of gas spillage, and improving the operating environment. It solves the problems of gas spillage and sodium ion accumulation caused by the vigorous reaction of conventional sodium-containing sulfide reagents. The introduction of ultrasonic technology enhances mass transfer between ions in the solution system, making the system more homogeneous and stable. Simultaneously, ultrasonic technology accelerates the forward reaction, shortens reaction time, avoids incomplete reactions due to uneven contact between the solution and reagent, and the ultrasonic cavitation effect raises the solution temperature, promoting the dissolution of ferrous sulfide and improving arsenic removal efficiency. In the preparation of monoclinic crystalline ferrous sulfide, a microwave tube furnace, which heats up faster and provides more uniform material heating, can shorten the material preparation time to a certain extent. Compared to the resistance heating method of traditional tube furnaces, microwave heating allows the material to heat from within, reducing material loss and improving the purity of the synthesized crystals.

[0015] 2. This invention can be carried out under the original acidity of the solution, without the need to add lime to adjust the pH value. Only arsenic slag is produced in this stage, without the generation of large amounts of arsenic-containing lime slag. Fe in monoclinic ferrous sulfide 2+ The introduction of this substance can play a role in the iron salt stage, further reducing the amount of ferrous sulfate used in the iron salt addition stage. While reducing the cost of arsenic removal, it does not cause pollution to the solution. The lime slag produced in the subsequent deep arsenic removal stage has the characteristic of uniform arsenic distribution, making it easier to be used in cement production and creating certain economic value.

[0016] 3. The hydrogen sulfide gas generated during the arsenic removal process of this invention has a higher utilization rate, a more stable arsenic removal effect, and the raw materials are inexpensive and readily available, which can greatly reduce the cost of arsenic removal agents. Attached Figure Description

[0017] Figure 1 This is a microscopic morphology diagram of monoclinic ferrous sulfide according to the present invention.

[0018] Figure 2 This is a comparison of the morphology of the arsenic removal products under conventional conditions and the surface morphology of the arsenic removal products under ultrasonic conditions. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Example 1

[0021] This embodiment provides a method for controlling the crystal form of ferrous sulfide for solution purification, including the following steps: (1) Elemental iron and elemental sulfur were mixed in a molar ratio of 1:1.5 and sintered in a microwave tube furnace at 400℃ for 150 min under argon gas protection to obtain monoclinic crystalline ferrous sulfide; the prepared monoclinic crystalline ferrous sulfide is as follows: Figure 1 As shown.

[0022] (2) Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and mix it according to the As:S ratio. 2- A monoclinic ferrous sulfide solution was added at a ratio of 1:1.5. The mixture was reacted for 30 min at an initial temperature of 25℃, an ultrasonic frequency of 20 kHz, a power of 100 W / L, and a stirring rate of 300 r / min, followed by filtration. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 15.3 mg / L; the arsenic removal rate in the waste acid solution was 99.1%.

[0023] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide evaporation showed that after the addition of monoclinic ferrous sulfide, the concentration of evaporating hydrogen sulfide was approximately 6.3 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes.

[0024] Comparative Example 1: This comparative example is a comparative example of Example 1. Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and adjust the concentration according to the As:S ratio. 2- Sodium sulfide was added at a ratio of 1:1.5, and the mixture was reacted at an initial temperature of 25℃ and a stirring rate of 300 r / min for 180 min, followed by filtration. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 759.9 mg / L; the arsenic removal rate in the waste acid solution was 55.3%.

[0025] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (mass fraction) Monitoring the emission of hydrogen sulfide showed that the concentration of hydrogen sulfide emitted immediately exceeded the maximum range after the addition of sodium sulfide, and then decreased after 2 minutes. After 6 minutes, no hydrogen sulfide gas was detected.

[0026] Experimental results show that, compared to sodium sulfide, a commonly used sulfiding agent for treating acidic industrial solutions, monoclinic ferrous sulfide slowly releases sulfur under acidic conditions. 2- weakened H + The competing reaction allows for the slow release of hydrogen sulfide gas. This slow-release behavior improves the operating environment by allowing hydrogen sulfide gas to be released gradually.

[0027] Comparative Example 2: This comparative example is a comparative example of Example 1. Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and adjust the concentration according to the As:S ratio. 2- Sodium sulfide was added at a ratio of 1:1.5, and the mixture was reacted for 180 min at an initial temperature of 25℃, an ultrasonic frequency of 20 kHz, an ultrasonic power of 100 W / L, and a stirring rate of 300 r / min. The mixture was then filtered. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). After 30 min of reaction, the arsenic concentration was 920 mg / L, indicating an arsenic removal rate of 45.8% in the acidic waste solution. After 180 min of reaction, the arsenic concentration was 530.4 mg / L, indicating an arsenic removal rate of 68.8% in the acidic waste solution.

[0028] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (mass fraction) Monitoring the emission of hydrogen sulfide showed that the concentration of hydrogen sulfide emitted immediately exceeded the maximum range after the addition of sodium sulfide, and then decreased after 2 minutes. After 6 minutes, no hydrogen sulfide gas was detected.

[0029] Experimental results show that monoclinic ferrous sulfide has a significant advantage over sodium sulfide in arsenic removal, achieving better arsenic removal in a shorter time and significantly shortening the reaction time.

[0030] Comparative Example 3 This comparative example is a comparative example of Example 1. Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and adjust the concentration according to the As:S ratio. 2- A cubic ferrous sulfide mixture was added at a ratio of 1:1.5, and the mixture was reacted at an initial temperature of 25°C and a stirring rate of 300 r / min for 180 min, followed by filtration. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 932.6 mg / L; the arsenic removal rate in the waste acid solution was 45.2%.

[0031] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide escaping showed that after the addition of cubic ferrous sulfide, the hydrogen sulfide escaping concentration was approximately 5.8 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes.

[0032] Experimental results show that both monoclinic and hexagonal ferrous sulfide have a slow-release effect, but the hydrogen sulfide gas leakage indicates that the intervention of ultrasound can promote the dissolution of ferrous sulfide. After the intervention of ultrasound, there are obvious differences in the hydrogen sulfide leakage between monoclinic and hexagonal ferrous sulfide.

[0033] Comparative Example 4: This comparative example is a comparative example of Example 1. Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and adjust the concentration according to the As:S ratio. 2- A cubic ferrous sulfide mixture was added at a ratio of 1:1.5 and reacted for 180 min at an initial temperature of 25℃, an ultrasonic frequency of 20 kHz, an ultrasonic power of 100 W / L, and a stirring rate of 300 r / min. The mixture was then filtered. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 527 mg / L; the arsenic removal rate in the waste acid solution was 69.0%.

[0034] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide escaping showed that after the addition of cubic ferrous sulfide, the hydrogen sulfide escaping concentration was approximately 5.8 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes.

[0035] Experimental results show that monoclinic ferrous sulfide has a significantly better arsenic removal effect than hexagonal ferrous sulfide, and monoclinic ferrous sulfide has a clear advantage in shortening reaction time and improving arsenic removal efficiency.

[0036] Comparative Example 5: This comparative example is a comparative example of Example 1. Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and adjust the concentration according to the As:S ratio. 2- The monoclinic ferrous sulfide prepared in Example 1 was added at a ratio of 1:1.5. After reacting for 180 min at an initial temperature of 25°C and a stirring rate of 300 r / min, the mixture was filtered. The arsenic content of the filtrate was determined by inductively coupled plasma atomic emission spectrometry, and the result was 470.9 mg / L; the arsenic removal rate in the waste acid solution was 72.3%.

[0037] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide evaporation showed that after the addition of monoclinic ferrous sulfide, the concentration of evaporating hydrogen sulfide was approximately 6.3 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes.

[0038] The morphology of the arsenic removal products in this comparative example under normal conditions is shown in the figure below. Figure 2 As shown in (a), the surface morphology of the arsenic removal product under ultrasonic conditions is as follows. Figure 2 As shown in (b). Experimental results show that under ultrasonic conditions, the monoclinic ferrous sulfide exhibits a flake-like fragmented microstructure, while under conventional conditions, the reactants exhibit a large-particle block structure. The flake-like structure has a larger specific surface area. Under ultrasonic conditions, monoclinic ferrous sulfide is more soluble and exhibits stronger arsenic removal performance in solution. Under both conventional and ultrasonic conditions, arsenic removal products accumulate around the incompletely reacted reactants. Compared to the arsenic removal products adhering to the reactant surface under conventional conditions, the reactant surface is smoother under ultrasonic conditions. This indicates that the ultrasonic cavitation effect continuously erodes the reactant surface, peeling away the arsenic removal products and re-exposing the reactants for further reaction. This is a key reason for the higher arsenic removal efficiency under ultrasonic conditions. Example 2

[0039] This embodiment provides a method for controlling the crystal form of ferrous sulfide for solution purification, including the following steps: (1) Mix elemental iron and elemental sulfur in a molar ratio of 1:1.4 and sinter them in a microwave tube furnace at 450°C for 150 min under vacuum and argon gas protection to obtain monoclinic ferrous sulfide. (2) Take 1000 ml of an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and mix it according to the As:S ratio.2- A monoclinic ferrous sulfide solution was added at a ratio of 1:1.4. The mixture was reacted for 25 min at an initial temperature of 25℃, an ultrasonic frequency of 17 kHz, a power of 90 W / L, and a stirring rate of 300 r / min, followed by filtration. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 183.6 mg / L; the arsenic removal rate in the waste acid solution was 89.2%.

[0040] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide evaporation showed that after the addition of monoclinic ferrous sulfide, the concentration of evaporating hydrogen sulfide was approximately 5.8 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes. Example 3

[0041] This embodiment provides a method for controlling the crystal form of ferrous sulfide for solution purification, including the following steps: (1) Mix elemental iron and elemental sulfur in a molar ratio of 1:1.6 and sinter them in a tube furnace at 420°C for 180 min under vacuum and argon gas protection to obtain monoclinic ferrous sulfide. (2) Take an arsenic-containing solution with an acidity of 120 g / L and an arsenic content of 1.7 g / L, and mix it with an arsenic solution at an As:S ratio of 1000 ml. 2- A monoclinic ferrous sulfide solution was added at a ratio of 1:1.6. The mixture was reacted for 28 minutes at an initial temperature of 25℃, an ultrasonic frequency of 25 kHz, a power of 110 W / L, and a stirring rate of 300 r / min, followed by filtration. The arsenic content of the filtrate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the result was 178.5 mg / L; the arsenic removal rate in the waste acid solution was 89.5%.

[0042] A handheld hydrogen sulfide detector (maximum value: 1×10⁻⁶) was used during the experiment. -4 (Mass fraction) Monitoring of hydrogen sulfide evaporation showed that the concentration of evaporating hydrogen sulfide after the addition of monoclinic ferrous sulfide was approximately 6 × 10⁻⁶. -5 The emission then rapidly decreased, and no hydrogen sulfide gas was detected after 4 minutes.

[0043] The specific embodiments of the invention have been described in detail above, but these are merely examples, and the invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of this invention. Therefore, all equivalent transformations, modifications, and improvements made without departing from the spirit and principles of this invention should be included within the scope of this invention.

Claims

1. A method for controlling the crystal form of ferrous sulfide for solution purification, characterized in that, Includes the following steps: (1) Synthesis of monoclinic ferrous sulfide: Elemental iron powder and elemental sulfur are mixed and sintered in a microwave tube furnace under inert gas protection to obtain monoclinic ferrous sulfide; (2) Arsenic removal: Take an acidic arsenic-containing solution that needs to be purified, add the monoclinic ferrous sulfide described in step (1), and stir for 25 to 30 minutes at room temperature and under ultrasonic conditions; (3) Solid-liquid separation: After the reaction in step (2) is completed, vacuum filtration is performed to obtain filter residue and arsenic-removed purified filtrate; The molar ratio of elemental iron powder and elemental sulfur in step (1) is 1:1.4 to 1.6; the inert gas is argon. The sintering described in step (1) is sintering at 400-450℃ for 30-150 min; The molar ratio of arsenic to monoclinic ferrous sulfide in the acidic arsenic-containing solution in step (2) is 1:1.4 to 1.

6.

2. The method for controlling the crystal form of ferrous sulfide for solution purification according to claim 1, characterized in that, The ultrasonic conditions described in step (2) are: frequency 15-25 kHz, power 10-120 W / L.

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