A process for the separation and recovery of arsenic and iron from a biological leach liquor containing both

Abstract

This invention relates to a method for separating and recovering arsenic and iron from arsenic- and iron-containing bioleaches. The specific steps are as follows: An adsorbent is added to the arsenic- and iron-containing bioleach, mixed thoroughly, and reacted. After adsorption is complete, the solid and liquid phases are separated to obtain an arsenic-iron solution free of bacterial residues. A reducing agent is added to the obtained arsenic-iron solution. After detection, all arsenic and iron are converted to trivalent and divalent valences, respectively, and the reaction is complete, yielding a solution containing low-valent arsenic and low-valent iron. An extractant is added to the reduced arsenic-iron solution to obtain an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate is returned to the bioleaching process, and the organic phase is back-extracted to obtain an arsenic-containing back-extract. The back-extracted organic phase is reused to extract arsenic. Sodium hydroxide is added to the arsenic-containing back-extract, mixed thoroughly, and then benzyl chloride is added. After stirring and reacting, the mixture is allowed to stand for layering and the acidity is adjusted for crystallization. The crystals are washed and dried to obtain benzylarsine product. This invention solves the shortcomings of existing neutralization processes, such as large slag volume, difficulty in product purification, complex processes, and low arsenic and iron recovery rates. It fully utilizes the arsenic and iron resources in the bioleaching solution and has the advantages of high recovery rate, high product added value, no secondary pollution generated in the process, and low investment.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, and more specifically, it relates to a method for separating and recovering arsenic and iron from arsenic- and iron-containing bioleaching solutions. Background Technology

[0002] Arsenic-containing refractory gold ores have complex compositions and require pre-oxidation treatment before cyanide extraction. Currently, the main pre-oxidation methods for refractory gold ores include roasting, pressure oxidation, and biological oxidation. Biological oxidation utilizes microorganisms that can oxidize sulfide minerals to break down the mineral's crystal lattice, releasing the gold trapped within the ore particles through the oxidation and decomposition of the sulfide minerals. It has significant advantages such as low investment, low production costs, simple processes, and convenient operation, and is used by mines both domestically and internationally, including the Olympia Mine in Macedonia, Greece; the Hatu Gold Mine in Xinjiang; the Hetai Gold Mine in Gaoyao City, Guangdong; the Yangjingou Gold Mine in Hunchun City, Jilin; and the Pangjiahe Gold Mine in Feng County, Shaanxi. However, the bioleaching process for arsenic-containing gold ores generates large amounts of highly acidic, high-iron, and high-sulfur arsenic-containing wastewater, which is highly toxic and difficult to dispose of economically and environmentally, seriously hindering the normal development of enterprises.

[0003] The commonly used processes for treating arsenic and iron-containing bioleaching solutions are neutralization methods, such as the lime method, lime-iron salt method, lime-aluminum salt method, arsenic-iron co-precipitation method, and sodium sulfide precipitation method, which form arsenic, iron, and sulfur into precipitated slag products. These products cannot be used directly and become hazardous waste due to their arsenic content, posing a significant threat to enterprises and the local ecosystem. Although some have reduced the amount of neutralization slag by using magnesium salts and sodium salts, these methods still suffer from drawbacks such as high economic costs, high wastewater hardness, difficulty in separation and purification, and low slag utilization. Therefore, the safe disposal and resource utilization of arsenic and iron-containing bioleaching solutions remain a major technical challenge for gold mining enterprises. Summary of the Invention

[0004] This invention provides a method for separating and recovering arsenic and iron from arsenic and iron-containing bioleaching solutions. It overcomes the technical shortcomings of existing neutralization methods and changes the existing technology, which mainly targets the separation of high-valence arsenic and high-valence iron. By reducing the valence of arsenic and iron before separation and recovery, the method improves the separation efficiency of arsenic and iron, maximizes the utilization of arsenic and iron ions, and ultimately achieves full resource utilization.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for separating and recovering arsenic and iron from arsenic- and iron-containing bioleaching solutions, characterized in that the method includes the following steps:

[0006] S1: Adsorption and impurity removal: Add adsorbent to the arsenic and iron-containing bioleaching solution, mix evenly and react. After adsorption is complete, separate the solid and liquid to obtain the arsenic and iron solution L1 with bacterial residue removed.

[0007] S2: Reduction of arsenic and iron: A reducing agent is added to the arsenic and iron solution L1. After detection, the arsenic and iron are completely converted to trivalent and divalent, respectively, and the reaction is completed, resulting in a solution L2 containing low-valent arsenic and low-valent iron.

[0008] S3: Arsenic extraction: Add extractant to arsenic-iron solution L2 to obtain arsenic-containing organic phase and iron-containing raffinate. The iron-containing raffinate is used for return to bioleaching. The organic phase is back-extracted to obtain arsenic-containing back-extract L3. The back-extracted organic phase is reused for arsenic extraction.

[0009] S4: Arsenic product preparation: Add sodium hydroxide to the back-extraction solution L3, mix well, add benzyl chloride, stir the reaction, let stand to separate the layers and adjust the acidity to crystallize, wash and dry the crystals to obtain benzylarsine product.

[0010] The adsorbent mentioned in step S1 is one of lignin, chitosan, polyacrylamide, starch, and cellulose.

[0011] The adsorption reaction conditions described in step S1 are: adsorbent concentration 1-10 mg / L, pH value 0.1-2.0, temperature 25-60℃, and reaction time 10-90 min.

[0012] The reducing agent mentioned in step S2 is one or more of the following: sulfur dioxide gas, sodium sulfite, sodium dithionite, sodium metabisulfite, sodium thiosulfate, thiourea, sodium borohydride, sodium hypophosphite, and ascorbic acid.

[0013] The reduction reaction conditions described in step S2 are: temperature 35–85°C, stirring intensity 200–600 r / min, gaseous reducing agent flow rate 10–200 mL / min, and other reducing agent concentrations 5–500 g / L.

[0014] The extractant in step S3 is one or more of the following: tributyl phosphate, trialkylmethylamine chloride, chloroform, carbon tetrachloride, octane, thiol, diethyl ether, dipentyl ester, xylene, triisooctylamine, methyl isobutyl ketone, trioctylmethylammonium chloride, 2-ethyl-2-thiocarbamate, and sodium diisooctyl dithiophosphate.

[0015] The extraction conditions described in step S3 are: extractant mass concentration of 5-60%, extraction time of 5-30 min, oil-water ratio of 0.5-5, and acid concentration of 0.1-10 mol / L.

[0016] The stripping agent mentioned in step S3 is one of water, sodium hydroxide, and sodium carbonate. The concentration of sodium hydroxide and sodium carbonate is 1-3 mol / L.

[0017] The total mass concentration of sodium hydroxide in step S4 is 5-10 mol / L, and the mass ratio of benzyl chloride to arsenic is (1-5):1.

[0018] The stirring reaction conditions described in step S4 are: temperature 25–85°C, rotation speed 100–500 r / min, reaction time 0.5–5 h, and the acidity of the crystals after standing and stratification is pH 1–4.

[0019] Compared with traditional neutralization methods for treating bioleaches containing arsenic and iron, the present invention has the following advantages:

[0020] 1. This invention does not generate a large amount of arsenic-containing hazardous waste neutralization residue, but directly transforms arsenic into high-value-added products, turning waste into treasure and achieving economic and environmental benefits.

[0021] 2. This invention makes full use of arsenic and iron resources, directly converting iron into metal ions required for bioleaching in a low valence state, further reducing the amount of slag formed by iron, making the process environmentally friendly and less prone to secondary pollution.

[0022] 3. This invention uses an extraction method to separate low-valent iron and arsenic, which solves the traditional problem of separating high-valent arsenic and high-valent iron, and achieves high separation efficiency of arsenic and iron.

[0023] 4. The arsenic product obtained by this invention has high purity and can be used directly in production without further deep purification. The process is simple and practical, with low production costs, low investment, and easy to promote and apply.

[0024] The method of this invention realizes the comprehensive utilization of arsenic and iron-containing bioleaching solutions, which can bring economic, social and environmental benefits to biometallurgical enterprises and has good application prospects. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the product of the present invention, the accompanying drawings are briefly described below. The drawings, together with the following detailed description, are used to explain the present invention, but do not constitute a limitation thereof.

[0026] Figure 1 A schematic diagram of the process flow of this invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments. However, the scope of protection of the present invention is not limited thereto.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] In the embodiments of this invention, the arsenic and iron-containing bioleaching solutions used contain arsenic and iron at concentrations of 10.12 g / L and 25.07 g / L, respectively. However, this should not be construed as limiting the invention to the aforementioned concentrations and element types. Arsenic and iron are expressed as arsenate and Fe, respectively. 3+ It exists in the form of [a substance], and the pH value of the biological oxidation solution is 1.2.

[0030] Example 1

[0031] 1 mg / L lignin was added to the arsenic and iron bioleach solution to adjust the pH to 0.1. The temperature was controlled at 25℃, and the mixture was thoroughly mixed before adsorption for 10 min. After adsorption, the solid and liquid phases were separated to obtain an arsenic-iron solution free of bacterial residue. Sulfur dioxide gas was then introduced into this arsenic-iron solution at a flow rate of 10 mL / min, while maintaining the temperature at 35℃ and the stirring intensity at 200 r / min. The reaction was completed when all arsenic and iron were converted to trivalent and divalent valences, respectively, yielding a solution containing low-valent arsenic and low-valent iron. Tributyl phosphate was added to the reduced arsenic-iron solution as an extractant, with an extractant concentration of 60%, an oil-to-water ratio of 0.5, an acid concentration of 0.1 mol / L, and an extraction time of 5 min. This yielded an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate was reused for bioleaching, and the arsenic-containing organic phase was back-extracted with water to obtain an arsenic-containing back-extract and organic phase. The back-extracted organic phase was then reused for arsenic extraction. Sodium hydroxide was added to the arsenic-containing back-extraction solution to make the total mass concentration of sodium hydroxide 5 mol / L. After mixing evenly, benzyl chloride with a mass ratio of 1:1 to arsenic was added. The mixture was stirred for 0.5 h at a controlled temperature of 25℃ and a stirring speed of 100 r / min. After standing and separating into layers, the acidity was adjusted to 1 for crystallization. The crystals were washed and dried to obtain benzylarsine product 1.

[0032] Example 2

[0033] 10 mg / L polyacrylamide was added to the arsenic and iron bioleach solution to adjust the pH to 2.0. The temperature was controlled at 60℃, and the mixture was thoroughly mixed before adsorption for 90 min. After adsorption, the solid and liquid phases were separated to obtain an arsenic-iron solution free of bacterial residues. Sulfur dioxide gas was then introduced into this arsenic-iron solution at a flow rate of 200 mL / min, while maintaining a temperature of 85℃ and a stirring intensity of 600 r / min. The reaction was completed when all arsenic and iron were converted to trivalent and divalent valences, respectively, yielding a solution containing low-valent arsenic and low-valent iron. A mixture of trialkylmethylamine chloride and chloroform (volume ratio 1:1) was added to the reduced arsenic-iron solution as an extractant. The extractant concentration was controlled at 5%, the oil-to-water ratio at 5%, the acid concentration at 10 mol / L, and the extraction time at 30 min. This yielded an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate was reused for bioleaching, while the arsenic-containing organic phase was back-extracted with 1 mol / L sodium hydroxide to obtain an arsenic-containing back-extract and organic phase. The back-extracted organic phase was then reused for arsenic extraction. Sodium hydroxide was added to the arsenic-containing back-extraction solution to make the total mass concentration of sodium hydroxide 10 mol / L. After mixing evenly, benzyl chloride with a mass ratio of 5:1 to arsenic was added. The mixture was stirred for 5 hours under controlled conditions of 85℃ and 500 r / min. After standing and separating into layers, the acidity was adjusted to 4 to crystallize. The crystals were washed and dried to obtain benzylarsine product 2.

[0034] Example 3

[0035] 5.3 mg / L chitosan was added to the arsenic and iron bioleach solution to adjust the pH to 1.7. The temperature was controlled at 46℃, and the mixture was thoroughly mixed before adsorption reaction for 73 min. After adsorption, the solid and liquid phases were separated to obtain an arsenic-iron solution free of bacterial residues. 5 g / L sodium sulfite was added to this arsenic-iron solution, and the temperature was controlled at 41℃ with a stirring intensity of 252 r / min. The reaction was completed when arsenic and iron were completely converted to trivalent and divalent valences, respectively, yielding a solution containing low-valent arsenic and low-valent iron. A mixture of carbon tetrachloride, octane, and thiol (volume ratio 1:0.1:3) was added to the reduced arsenic-iron solution as an extractant. The extractant concentration was controlled at 48%, the oil-to-water ratio at 4.5, the acid concentration at 5 mol / L, and the extraction time at 24 min. This yielded an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate was reused for bioleaching, and the arsenic-containing organic phase was back-extracted with 3 mol / L sodium hydroxide to obtain an arsenic-containing back-extract and organic phase. The back-extracted organic phase was then reused for arsenic extraction. Sodium hydroxide was added to the arsenic-containing back-extraction solution to make the total mass concentration of sodium hydroxide 8.9 mol / L. After mixing evenly, benzyl chloride with a mass ratio of 4.6:1 to arsenic was added. The mixture was stirred for 3.7 h at a controlled temperature of 82℃ and a stirring speed of 458 r / min. After standing and separating into layers, the acidity was adjusted to 2.6 to crystallize. The crystals were washed and dried to obtain benzylarsine product 3.

[0036] Example 4

[0037] Add 3.8 mg / L starch to the arsenic and iron bioleaching solution, adjust the pH to 0.5, control the temperature at 32℃, mix thoroughly, and allow the adsorption reaction to proceed for 15 min. After adsorption is complete, separate the solid and liquid phases to obtain an arsenic and iron solution free of bacterial residue. Add a mixture of 500 g / L sodium dithionite, sodium metabisulfite, and sodium thiosulfate (mass ratio 1:1:1) to this arsenic and iron solution, control the temperature at 41℃, and stir at 252 r / min until all arsenic and iron are converted to trivalent and divalent valences, respectively. The reaction is then complete, yielding a solution containing low-valent arsenic and low-valent iron. A mixture of methyl isobutyl ketone, trioctylmethylammonium chloride, and 2-ethyl-2-thiocarbamate (volume ratio 1:1.1:1.3) was added to the reduced arsenic-iron solution as an extractant. The extractant concentration was controlled at 24%, the oil-to-water ratio at 1.2, the acid concentration at 1.5 mol / L, and the extraction time at 18 min. This yielded an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate was reused for bioleaching. The arsenic-containing organic phase was back-extracted with 1 mol / L sodium carbonate to obtain an arsenic-containing back-extract and organic phase. The back-extracted organic phase was reused for arsenic extraction. Sodium hydroxide was added to the arsenic-containing back-extract to achieve a total sodium hydroxide concentration of 5.2 mol / L. After thorough mixing, benzyl chloride (at a mass ratio of 1.8:1 to arsenic) was added. The mixture was stirred at 37℃ and 255 r / min for 1.3 h, followed by standing and layering. The acidity was adjusted to 1.9 for crystallization. The crystals were washed and dried to obtain benzylarsine product 4.

[0038] Example 5

[0039] 9.3 mg / L cellulose was added to a bioleach solution containing arsenic and iron, the pH was adjusted to 1.8, and the temperature was controlled at 57℃. After thorough mixing, the adsorption reaction was carried out for 80 min. After adsorption was complete, the solid and liquid phases were separated to obtain an arsenic and iron solution free of bacterial residues. A mixture of 467 g / L thiourea and sodium borohydride (mass ratio 1:0.5) was added to this arsenic and iron solution, the temperature was controlled at 69℃, and the stirring intensity was 516 r / min. The reaction was completed when arsenic and iron were completely converted to trivalent and divalent valences, respectively, yielding a solution containing low-valent arsenic and low-valent iron. A mixture of dipentyl acetate, xylene, and triisooctylamine (volume ratio 1:0.5:1.4) was added to the reduced arsenic-iron solution as an extractant. The extractant concentration was controlled at 58%, the oil-to-water ratio at 4.5, the acid concentration at 9.6 mol / L, and the extraction time at 22 min. This yielded an arsenic-containing organic phase and an iron-containing raffinate. The iron-containing raffinate was reused for bioleaching. The arsenic-containing organic phase was back-extracted with 3 mol / L sodium carbonate to obtain an arsenic-containing back-extract and organic phase. The back-extracted organic phase was reused for arsenic extraction. Sodium hydroxide was added to the arsenic-containing back-extract to achieve a total sodium hydroxide concentration of 9.6 mol / L. After thorough mixing, benzyl chloride (4.2:1 mass ratio to arsenic) was added. The mixture was stirred at 77℃ and 482 r / min for 3.9 h, followed by standing and layering. The acidity was adjusted to 3.3 for crystallization. The crystals were washed and dried to obtain benzylarsine product 5.

[0040] Analysis revealed that the arsenic recovery rates in Examples 1-5 were 95.5%, 93.8%, 97.2%, 96.3%, and 95.9%, respectively; the iron recovery rates were 98.4%, 98.8%, 99.3%, 99.1%, and 98.5%, respectively; and the purities of benzylarsonic acid products 1-5 were 92.9%, 92.6%, 93.8%, 94.3%, 92.7%, and 93.2%, respectively. Therefore, this invention successfully achieves the comprehensive utilization of arsenic and iron, producing benzylarsonic acid products with high added value without forming neutralization slag, demonstrating significant economic, social, and environmental benefits.

[0041] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art can make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention's technical solution shall still fall within the protection scope of the present invention's technical solution.

Claims

1. A process for the separation and recovery of arsenic and iron from a biological leachate containing arsenic and iron, characterised in that: The method includes the following steps: S1: Adsorption and impurity removal: Add adsorbent to the arsenic and iron-containing bioleaching solution, mix evenly and react. After adsorption is completed, separate the solid and liquid to obtain arsenic and iron solution L1 with bacterial residue removed. S2: Reduced arsenic and iron: Add a reducing agent to the arsenic and iron solution L1. After detection, the reaction is complete when arsenic and iron are completely converted to trivalent and divalent, respectively, and a solution L2 containing low-valent arsenic and low-valent iron is obtained. S3: Arsenic extraction: Add extractant to arsenic-iron solution L2 to obtain arsenic-containing organic phase and iron-containing raffinate. The iron-containing raffinate is used for return to bioleaching. The organic phase is back-extracted to obtain arsenic-containing back-extract L3. The back-extracted organic phase is reused for arsenic extraction. S4: Arsenic product preparation: Add sodium hydroxide to the back-extraction solution L3, mix well, add benzyl chloride, stir the reaction, let stand to separate the layers and adjust the acidity to crystallize, wash and dry the crystals to obtain benzylarsine product.

2. A process for the separation and recovery of arsenic and iron from a bioleaching solution containing arsenic and iron as claimed in claim 1, wherein: The adsorbent mentioned in step S1 is one of lignin, chitosan, polyacrylamide, starch, and cellulose.

3. A process for the separation and recovery of arsenic and iron from a bioleaching solution containing arsenic and iron as claimed in claim 1, wherein: The adsorption reaction conditions described in step S1 are: adsorbent concentration 1-10 mg / L, pH value 0.1-2.0, temperature 25-60℃, and reaction time 10-90 min.

4. A process for the separation and recovery of arsenic and iron from a bioleaching solution containing arsenic and iron as claimed in claim 1, wherein: The reducing agent mentioned in step S2 is one or more of the following: sulfur dioxide gas, sodium sulfite, sodium dithionite, sodium metabisulfite, sodium thiosulfate, thiourea, sodium borohydride, sodium hypophosphite, and ascorbic acid.

5. A process for separation and recovery of arsenic and iron from a bioleaching solution containing arsenic and iron as claimed in claim 1, wherein: The reduction reaction conditions described in step S2 are: temperature 35–85°C, stirring intensity 200–600 r / min, gaseous reducing agent flow rate 10–200 mL / min, and other reducing agent concentrations 5–500 g / L.

6. The method for separating and recovering arsenic and iron from an arsenic- and iron-containing bioleach as described in claim 1, characterized in that: The extractant in step S3 is one or more of the following: tributyl phosphate, trialkylmethylamine chloride, chloroform, carbon tetrachloride, octane, thiol, diethyl ether, dipentyl ester, xylene, triisooctylamine, methyl isobutyl ketone, trioctylmethylammonium chloride, 2-ethyl-2-thiocarbamate, and sodium diisooctyl dithiophosphate.

7. A process for separation and recovery of arsenic and iron from a bioleach solution containing arsenic and iron as claimed in claim 1, wherein: The extraction conditions described in step S3 are: extractant mass concentration of 5-60%, extraction time of 5-30 min, oil-water ratio of 0.5-5, and acid concentration of 0.1-10 mol / L.

8. A process for separation and recovery of arsenic and iron from a bioleach solution containing arsenic and iron as claimed in claim 1, wherein: The stripping agent in step S3 is one of water, sodium hydroxide, and sodium carbonate; the concentration of sodium hydroxide and sodium carbonate is 1-3 mol / L.

9. A process for separation and recovery of arsenic and iron from a bioleaching solution containing arsenic and iron as claimed in claim 1, wherein: The total mass concentration of sodium hydroxide in step S4 is 5-10 mol / L, and the mass ratio of benzyl chloride to arsenic is (1-5):

1.

10. The method for separating and recovering arsenic and iron from an arsenic- and iron-containing bioleach as described in claim 1, characterized in that: The stirring reaction conditions described in step S4 are: temperature 25–85°C, rotation speed 100–500 r / min, reaction time 0.5–5 h, and the acidity of the crystals after standing and stratification is pH 1–4.

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