Method for separating and recovering arsenic and iron from biological leachate containing arsenic and iron

Abstract

The invention relates to a method for separating and recovering arsenic and iron from biological leachate containing arsenic and iron, which comprises the following specific steps: adding an adsorbent into the biological leachate containing arsenic and iron, uniformly mixing, reacting, and separating solid and liquid after adsorption is completed to obtain an arsenic-iron solution without bacterial residues; adding a reducing agent into the obtained arsenic-iron solution, detecting that arsenic and iron are respectively converted into trivalent and bivalent, and completing the reaction to obtain a solution containing low-valent arsenic and low-valent iron; an extracting agent is added into the reduced arsenic-iron solution, an arsenic-containing organic phase and an iron-containing raffinate are obtained, the iron-containing raffinate is used for returning for biological leaching, the organic phase is subjected to reverse extraction, an arsenic-containing reverse extraction solution is obtained, and the organic phase obtained after reverse extraction is used for arsenic extraction again; and adding sodium hydroxide into the arsenic-containing strip liquor, uniformly mixing, adding benzyl chloride, stirring for reaction, standing for layering, adjusting acidity for crystallization, and washing and drying the crystal to obtain the benzyl arsonic acid product. The method overcomes the defects of large slag amount, difficulty in product purification, complex process, low arsenic and iron recovery rate and the like in the existing neutralization process, fully recycles arsenic and iron resources in the bioleaching liquid, and has the advantages of high recovery rate, large product additional value, no secondary pollution in the process, low investment and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular, relates to a method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron. Background Art

[0002] Arsenic-containing refractory gold ores have complex compositions and need to be pre-oxidized before cyanide gold extraction can be performed. At present, the main pre-oxidation methods for refractory gold ores are roasting, pressure oxidation and bio-oxidation. The bio-oxidation process uses microorganisms that can oxidize sulfide minerals to destroy the mineral lattice, release the gold wrapped in the gold ore through the oxidation and decomposition of sulfide minerals, and expose the gold outside the ore particles. It has significant advantages such as low investment, low production cost, simple process and convenient operation. It is used by domestic and foreign mines such as 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 Fengxian County, Shaanxi. However, the bioleaching process of arsenic-containing gold ores will produce a large amount of high-acid, high-iron, high-sulfur arsenic-containing wastewater, which is highly toxic and difficult to be disposed of economically and environmentally, seriously hindering the normal development of enterprises.

[0003] The commonly used process for treating arsenic and iron-containing bioleaching solutions is neutralization, such as lime method, lime-iron salt method, lime-aluminum salt method, arsenic-iron co-precipitation method, sodium sulfide precipitation method, etc., to form precipitated slag products with arsenic, iron and sulfur. These products cannot be used directly, and become hazardous wastes due to arsenic content, posing a huge threat to enterprises and local ecology. Although some people have reduced the amount of neutralization slag by using magnesium salts, sodium salts, etc., there are still defects such as high economic cost, high wastewater hardness, difficult separation and purification, and low slag utilization. Therefore, the safe disposal and resource utilization of arsenic and iron-containing bioleaching solutions are still major technical problems for gold mining companies. Summary of the invention

[0004] The present invention provides a method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron, which changes the technical defects of the existing neutralization method and the existing technology which mainly focuses on the separation of high-valent arsenic and high-valent iron, reduces the arsenic and iron to low valence and then separates and recovers them, thereby improving the separation efficiency of arsenic and iron, and making the best use of arsenic and iron ions, thereby finally realizing full resource utilization.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: a method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron, characterized in that the method comprises the following steps:

[0006] S1: Adsorption and impurity removal: add adsorbent to the biological leaching solution containing arsenic and iron, mix well and react, separate the solid and liquid after adsorption is completed, and obtain the arsenic and iron solution L1 with bacterial residues removed.

[0007] S2: Reduction of arsenic and iron: Add a reducing agent to the arsenic and iron solution L1. After testing, the reaction is completed after all the arsenic and iron are converted into trivalent and divalent respectively, to obtain a solution L2 containing low-valent arsenic and low-valent iron.

[0008] S3: Extracting arsenic: adding an extractant to the arsenic-iron solution L2 to obtain an arsenic-containing organic phase and an iron-containing raffinate, the iron-containing raffinate is used to return to bioleaching, the organic phase is stripped to obtain an arsenic-containing stripping solution L3, and the organic phase after stripping is reused for extracting arsenic.

[0009] S4: Preparation of arsenic product: sodium hydroxide is added to the stripping solution L3, benzyl chloride is added after mixing evenly, the mixture is stirred for reaction, the mixture is allowed to stand for stratification and the acidity is adjusted for crystallization, and the crystals are washed and dried to obtain the benzyl arsenic acid product.

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

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

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

[0013] The reduction reaction conditions in step S2 are as follows: temperature of 35-85° C., stirring intensity of 200-600 r / min, gas reducing agent flow rate of 10-200 mL / min, and other reducing agent concentration of 5-500 g / L.

[0014] The extractant described in step S3 is one or more of tributyl phosphate, trialkylmethylammonium chloride, chloroform, carbon tetrachloride, octane, mercaptan, diethyl ether, diamyl ester, xylene, triisooctylamine, methyl isobutyl ketone, trioctylmethylammonium chloride, 2-ethyl 2-thiocarbamate ammonium, and diisooctyl sodium dithiophosphate.

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

[0016] The stripping agent described 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 in step S4 are a temperature of 25 to 85° C., a rotation speed of 100 to 500 r / min, a reaction time of 0.5 to 5 h, and a crystallization acidity of pH 1 to 4 after standing and stratification.

[0019] Compared with the traditional neutralization method for treating biological leaching solution containing arsenic and iron, the present invention has the following advantages:

[0020] 1. The present invention does not produce a large amount of arsenic-containing hazardous waste neutralization slag, but directly converts arsenic into high value-added products, turning waste into treasure, and achieving economic and environmental benefits.

[0021] 2. The present invention makes full use of the resources of arsenic and iron, directly converts iron in a low-valent state into metal ions required for bioleaching, further reducing the amount of slag formed by iron. The process is environmentally friendly and not prone to secondary pollution.

[0022] 3. The present invention adopts an extraction method to separate low-valent iron and arsenic, which changes the traditional problem of difficult separation of high-valent arsenic and high-valent iron, and the separation efficiency of arsenic and iron is high.

[0023] 4. The arsenic product obtained by the present invention has high purity and can be directly used in production without deep purification. The process is simple and practical, the production cost is low, the investment is small, and it is easy to promote and apply.

[0024] The method of the present invention realizes the comprehensive utilization of biological leaching solution containing arsenic and iron, can bring economic, social and environmental benefits to biometallurgical enterprises, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the product of the present invention, the following is a brief introduction to the drawings of the present invention. The drawings and the following specific embodiments are used to explain the present invention, but do not constitute a limitation of the present invention.

[0026] Figure 1 Schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] The contents of arsenic and iron in the arsenic- and iron-containing bioleaching solution used in the present invention are 10.12 g / L and 25.07 g / L, respectively. However, this should not be construed as limiting the present invention to the above contents and element types. Arsenic and iron are present in the form of arsenate and Fe, respectively. 3+ The pH value of the biological oxidation liquid is 1.2.

[0030] Example 1

[0031] Add 1 mg / L lignin to the arsenic and iron-containing bioleaching solution, adjust the pH value to 0.1, control the temperature to 25°C, mix evenly and then adsorb for 10 minutes. After the adsorption is completed, separate the solid and liquid to obtain an arsenic-iron solution with bacterial residues removed. Pass 10 mL / min of sulfur dioxide gas into the arsenic-iron solution, control the temperature to 35°C, stir at 200 r / min, and react until arsenic and iron are completely converted to trivalent and divalent, respectively, and then the reaction is completed to obtain a solution containing low-valent arsenic and low-valent iron. Add the extractant tributyl phosphate to the reduced arsenic-iron solution, control the extractant mass concentration to 60%, the oil-water ratio to 0.5, the acid concentration to 0.1 mol / L, and the extraction time to 5 minutes to obtain an arsenic-containing organic phase and an iron-containing raffinate, the iron-containing raffinate is used to return to the bioleaching, and the arsenic-containing organic phase is stripped with water to obtain an arsenic-containing stripping solution and an organic phase, and the stripped organic phase is reused to extract arsenic. Sodium hydroxide was added to the arsenic-containing stripping solution to make the total mass concentration of sodium hydroxide 5 mol / L. After mixing evenly, benzyl chloride was added in a mass ratio of 1:1 to arsenic. The temperature was controlled at 25°C and the speed was 100 r / min. The reaction was stirred for 0.5 h and then allowed to stand for stratification. The acidity was adjusted to 1 for crystallization. The crystals were washed and dried to obtain benzyl arsenic acid product 1.

[0032] Example 2

[0033] 10 mg / L polyacrylamide is added to the arsenic and iron-containing bioleaching solution, the pH value is adjusted to 2.0, the temperature is controlled to 60°C, and the mixture is uniformly mixed and then adsorbed for 90 minutes. After the adsorption is completed, the solid and liquid are separated to obtain an arsenic-iron solution with bacterial residues removed. 200 mL / min of sulfur dioxide gas is introduced into the arsenic-iron solution, the temperature is controlled to 85°C, the stirring intensity is 600 r / min, and the reaction is completed after the arsenic and iron are completely converted to trivalent and divalent, respectively, to obtain a solution containing low-valent arsenic and low-valent iron. A mixture of extractant trialkylmethylamine chloride and chloroform (volume ratio 1:1) is added to the reduced arsenic-iron solution, the mass concentration of the extractant is controlled to 5%, the oil-water phase ratio is 5, the acid concentration is 10 mol / L, the extraction time is 30 minutes, and an arsenic-containing organic phase and an iron-containing raffinate are obtained. The iron-containing raffinate is used to return to the bioleaching, and the arsenic-containing organic phase is stripped with 1 mol / L sodium hydroxide to obtain an arsenic-containing stripping solution and an organic phase, and the stripped organic phase is reused for extracting arsenic. Sodium hydroxide was added to the arsenic-containing stripping solution to make the total mass concentration of sodium hydroxide 10 mol / L. After mixing evenly, benzyl chloride was added in a mass ratio of 5:1 to arsenic. The reaction was stirred for 5 hours under the conditions of controlling the temperature to 85°C and the rotation speed to 500 r / min, and then allowed to stand for stratification. The acidity was adjusted to 4 for crystallization. The crystals were washed and dried to obtain benzyl arsenic acid product 2.

[0034] Example 3

[0035] 5.3 mg / L chitosan was added to the arsenic and iron-containing bioleaching solution, the pH value was adjusted to 1.7, the temperature was controlled to 46°C, and the mixture was uniformly mixed and then adsorbed for 73 minutes. After the adsorption was completed, the solid and liquid were separated to obtain an arsenic-iron solution with bacterial residues removed. 5 g / L sodium sulfite was added to the arsenic-iron solution, the temperature was controlled to 41°C, the stirring intensity was 252 r / min, and the reaction was completed after the arsenic and iron were completely converted to trivalent and divalent, respectively, to obtain a solution containing low-valent arsenic and low-valent iron. A mixture of extractants of carbon tetrachloride, octane and mercaptan (volume ratio 1:0.1:3) was added to the reduced arsenic-iron solution, the mass concentration of the extractant was controlled to 48%, the oil-water ratio was 4.5, the acid concentration was 5 mol / L, the extraction time was 24 minutes, and an arsenic-containing organic phase and an iron-containing raffinate were obtained. The iron-containing raffinate was used to return to the bioleaching, and the arsenic-containing organic phase was stripped with 3 mol / L sodium hydroxide to obtain an arsenic-containing stripping solution and an organic phase, and the stripped organic phase was reused for extracting arsenic. Sodium hydroxide was added to the arsenic-containing stripping solution to make the total mass concentration of sodium hydroxide 8.9 mol / L. After mixing evenly, benzyl chloride was added in a mass ratio of 4.6:1 to arsenic. The temperature was controlled at 82°C and the speed was 458 r / min, and the reaction was stirred for 3.7 hours. After that, the reaction was allowed to stand and separate. The acidity was adjusted to 2.6 for crystallization. The crystals were washed and dried to obtain benzyl arsenic acid product 3.

[0036] Example 4

[0037] Add 3.8 mg / L starch to the arsenic and iron-containing bioleaching solution, adjust the pH value to 0.5, control the temperature to 32°C, mix well and adsorb for 15 minutes. After the adsorption is completed, separate the solid and liquid to obtain an arsenic-iron solution with bacterial residues removed. Add 500 g / L of a mixture of sodium dithionite, sodium pyrosulfite and sodium thiosulfate (mass ratio of 1:1:1) to the arsenic-iron solution, control the temperature to 41°C, stir at 252 r / min, and react until arsenic and iron are completely converted to trivalent and divalent, respectively, and the reaction is completed to obtain a solution containing low-valent arsenic and low-valent iron. A mixture of extractants methyl isobutyl ketone, trioctyl methyl ammonium chloride and 2-ethyl 2-thiocarbamate (volume ratio 1:1.1:1.3) was added to the reduced arsenic iron solution, the mass concentration of the extractant was controlled to be 24%, the oil-water phase ratio was 1.2, the acid concentration was 1.5 mol / L, and the extraction time was 18 min, to obtain an arsenic-containing organic phase and an iron-containing raffinate, the iron-containing raffinate was used to return to bioleaching, the arsenic-containing organic phase was stripped with 1 mol / L sodium carbonate to obtain an arsenic-containing stripping solution and an organic phase, and the stripped organic phase was reused to extract arsenic. Sodium hydroxide was added to the arsenic-containing stripping solution to make the total mass concentration of sodium hydroxide 5.2 mol / L, and benzyl chloride was added in a mass ratio of 1.8:1 to arsenic after mixing evenly, and the reaction was stirred for 1.3 hours under the conditions of controlling the temperature at 37°C and the rotation speed at 255 r / min, and then the reaction was allowed to stand for stratification, the acidity was adjusted to 1.9 for crystallization, and the crystals were washed and dried to obtain benzyl arsenic acid product 4.

[0038] Example 5

[0039] Add 9.3 mg / L cellulose to the arsenic and iron-containing bioleaching solution, adjust the pH value to 1.8, control the temperature to 57°C, mix well and adsorb for 80 minutes. After the adsorption is completed, separate the solid and liquid to obtain an arsenic-iron solution with bacterial residues removed. Add 467 g / L of a mixture of thiourea and sodium borohydride (mass ratio of 1:0.5) to the arsenic-iron solution, control the temperature to 69°C, stir at 516 r / min, and react until the arsenic and iron are completely converted to trivalent and divalent, respectively, and the reaction is completed to obtain a solution containing low-valent arsenic and low-valent iron. A mixture of extractants diamyl ester, xylene and triisooctylamine (volume ratio 1:0.5:1.4) was added to the reduced arsenic iron solution, the mass concentration of the extractant was controlled to be 58%, the oil-water phase ratio was 4.5, the acid concentration was 9.6 mol / L, and the extraction time was 22 min, to obtain an arsenic-containing organic phase and an iron-containing raffinate, the iron-containing raffinate was used to return to bioleaching, the arsenic-containing organic phase was stripped with 3 mol / L sodium carbonate to obtain an arsenic-containing stripping solution and an organic phase, and the stripped organic phase was reused to extract arsenic. Sodium hydroxide was added to the arsenic-containing stripping solution to make the total mass concentration of sodium hydroxide 9.6 mol / L, and after mixing evenly, benzyl chloride was added at a mass ratio of 4.2:1 to arsenic, and the reaction was stirred for 3.9 hours under the conditions of controlling the temperature to 77°C and the rotation speed to 482 r / min, and then the reaction was allowed to stand for stratification, the acidity was adjusted to 3.3 for crystallization, and the crystals were washed and dried to obtain the benzyl arsenic acid product 5.

[0040] After analysis and detection, the recovery rates of arsenic in embodiments 1 to 5 are respectively 95.5%, 93.8%, 97.2%, 96.3% and 95.9%, the recovery rates of iron are respectively 98.4%, 98.8%, 99.3%, 99.1% and 98.5%, and the purity of benzyl arsenic acid products 1 to 5 are respectively 92.9%, 92.6%, 93.8%, 94.3%, 92.7% and 93.2%. Therefore, the present invention successfully realizes the comprehensive utilization of arsenic and iron, does not form neutralized slag and outputs benzyl arsenic acid products with high added value, and has significant economic, social and environmental benefits.

[0041] Finally, it should be noted that the above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any person skilled in the art can use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron, characterized in that: The method comprises the following steps: S1: Adsorption and impurity removal: add adsorbent to the biological leaching solution containing arsenic and iron, mix well and react, separate the solid and liquid after adsorption is completed, and obtain the arsenic and iron solution L1 with bacterial residues removed. S2: Reduction of arsenic and iron: Add a reducing agent to the arsenic and iron solution L1. After testing, the reaction is completed after all the arsenic and iron are converted into trivalent and divalent respectively, to obtain a solution L2 containing low-valent arsenic and low-valent iron. S3: Extracting arsenic: adding an extractant to the arsenic-iron solution L2 to obtain an arsenic-containing organic phase and an iron-containing raffinate, the iron-containing raffinate is used to return to bioleaching, the organic phase is stripped to obtain an arsenic-containing stripping solution L3, and the organic phase after stripping is reused for extracting arsenic. S4: Preparation of arsenic product: sodium hydroxide is added to the stripping solution L3, benzyl chloride is added after mixing evenly, the mixture is stirred for reaction, the mixture is allowed to stand for stratification and the acidity is adjusted for crystallization, and the crystals are washed and dried to obtain the benzyl arsenic acid product.

2. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The adsorbent described in step S1 is one of lignin, chitosan, polyacrylamide, starch and cellulose.

3. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The adsorption reaction conditions described in step S1 are as follows: adsorbent concentration 1-10 mg / L, pH value 0.1-2.0, temperature 25-60° C., and reaction time 10-90 min.

4. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The reducing agent described in step S2 is one or more of sulfur dioxide gas, sodium sulfite, sodium dithionite, sodium pyrosulfite, sodium thiosulfate, thiourea, sodium borohydride, sodium hypophosphite, and ascorbic acid.

5. The method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The reduction reaction conditions in step S2 are as follows: temperature of 35-85° C., stirring intensity of 200-600 r / min, gas reducing agent flow rate of 10-200 mL / min, and other reducing agent concentration of 5-500 g / L.

6. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The extractant described in step S3 is one or more of tributyl phosphate, trialkylmethylammonium chloride, chloroform, carbon tetrachloride, octane, mercaptan, diethyl ether, diamyl ester, xylene, triisooctylamine, methyl isobutyl ketone, trioctylmethylammonium chloride, 2-ethyl 2-thiocarbamate ammonium, and diisooctyl sodium dithiophosphate.

7. A method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The extraction conditions described in step S3 are as follows: the mass concentration of the extractant is 5-60%, the extraction time is 5-30 min, the oil-water phase ratio is 0.5-5, and the acid concentration is 0.1-10 mol / L.

8. The method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: The stripping agent described 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 method for separating and recovering arsenic and iron from a biological leaching solution containing arsenic and iron as claimed in claim 1, characterized in that: 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 a biological leaching solution containing arsenic and iron according to claim 1, characterized in that: The stirring reaction conditions in step S4 are a temperature of 25 to 85° C., a rotation speed of 100 to 500 r / min, a reaction time of 0.5 to 5 h, and a crystallization acidity of pH 1 to 4 after standing and stratification.

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