Method for improving arsenic in hematite thiosulfate gold leaching tail liquid

Abstract

The invention discloses a method for improving arsenic in hematite thiosulfate gold leaching tail liquid, and belongs to the technical field of environmental engineering technologies. The method comprises the steps that (1) the concentration of Cu < 2 + > in the thiosulfate gold leaching tail liquid is adjusted to 35-40 mmol / L, the pH of the gold leaching tail liquid is adjusted to 10-11, and the concentration of thiosulfate radicals in the gold leaching tail liquid is adjusted to be smaller than or equal to 0.1 mol / L; and (2) adding hematite powder into the adjusted gold leaching tail liquid in the step (1), and stirring to remove arsenic. According to the method, the content of copper ions and thiosulfate ions in the gold leaching tail liquid is regulated and controlled, pH regulation and control are combined, the arsenic adsorption and removal effect of hematite in the gold leaching tail liquid is effectively enhanced, and an excellent foundation is laid for achieving simple, convenient, low-cost and efficient arsenic adsorption and removal.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering and relates to a method for improving the removal of arsenic in thiosulfate gold leaching tailings from hematite. Background Art

[0002] Arsenic and its compounds can enter the body through the respiratory tract, digestive tract and skin, causing poisoning. Therefore, arsenic is a toxic substance. The discharge of arsenic will cause serious pollution to the environment, thus endangering human health. In the process of thiosulfate gold extraction from arsenic-containing gold mines, arsenic (As) will enter the solution along with the gold leaching. As arsenic enters the solution, the solution becomes toxic, so it is necessary to remove arsenic from the solution.

[0003] Conventional arsenic removal methods include adsorption, chemical precipitation, ion exchange, etc. Among them, chemical precipitation and ion exchange have the problems of complex operation and high cost. Relatively speaking, the adsorption process is simple and the cost is low. However, on the one hand, the arsenic removal effect of the adsorption method itself is relatively poor. On the other hand, the components in the gold leaching tail liquid are relatively large and complex, which greatly interferes with the arsenic removal process and further weakens the arsenic removal effect of the adsorption method in the gold leaching tail liquid. Therefore, in the gold leaching tail liquid, the adsorption method cannot fully exert the arsenic removal effect, resulting in the inability to achieve simple, low-cost and efficient arsenic removal.

[0004] Hematite (α-Fe 2 O 3 ) is a natural iron oxide with large specific surface area and abundant surface active sites. 4 3- ) and arsenite (AsO 3 3- ) has excellent adsorption capacity, mainly Fe-O-AsO 3 、(Fe-O) 2 -AsO 2 Arsenic is adsorbed onto the surface of hematite particles in the form of a complex. However, compared with other methods, the effect of hematite on the adsorption and removal of arsenic in gold leaching tailings is still limited. In addition, the interference of complex components on the adsorption and removal of arsenic in the gold leaching tailings still greatly limits the effect of hematite on the removal of arsenic in gold leaching tailings.

[0005] Therefore, it is necessary to provide a method for improving the removal of arsenic in thiosulfate gold leaching tailings from hematite, effectively improving the effect of removing arsenic in thiosulfate gold leaching tailings from hematite, making the adsorption method more fully exert its advantages, and achieving simple, low-cost and efficient arsenic removal. Summary of the invention

[0006] In order to overcome the problems in the background technology, the present invention adjusts the Cu in the gold leaching tail solution. 2+ Content, through Cu2+ It reacts specifically with arsenate to form basic copper arsenate precipitate (Cu 3 (AsO 4 )(OH) 3 ), and through the aforementioned precipitation and the hydroxyl group on the surface of hematite, a coordinated adsorption synergistic effect is formed, which significantly improves the arsenic removal effect in the gold leaching tail liquid; at the same time, by adjusting the pH of the gold leaching tail liquid to avoid the pH being too high, the surface of the hematite is made negatively charged, the electrostatic attraction and surface complexation are weakened, and the adsorption effect is reduced; and then by adjusting the thiosulfate content in the gold leaching tail liquid, the decomposition of thiosulfate to form sulfate is avoided, resulting in the sulfate reacting with Fe(II) to form basic ferrous sulfate attached to the surface of the hematite, resulting in a decrease in the voids on the surface of the hematite, a decrease in the chemical reaction adsorption sites, and a weakening of the adsorption effect.

[0007] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0008] The method comprises the following steps:

[0009] (1) Adjusting the Cu content in the thiosulfate gold leaching tail solution 2+ The concentration is 35-40mmol / L, the pH of the gold leaching tail solution is adjusted to 10-11, and the concentration of thiosulfate in the gold leaching tail solution is adjusted to ≤0.1mol / L;

[0010] (2) adding hematite powder to the gold leaching tailings after adjustment in step (1) and stirring to remove arsenic.

[0011] Preferably, in step (1), CuCl is added to the gold leaching tail solution. 2 To increase the Cu content in the gold leaching tail solution 2+ concentration, adding Na 2 S can reduce the Cu content in the gold leaching tail solution. 2+ concentration.

[0012] Preferably, in step (1), the gold leaching tail solution is Cu(II)-NH 3 -S 2 O 3 2- Gold immersion tail solution or Cu(II)-EDA-S 2 O 3 2- One of the gold leaching tail solutions; to the Cu(II)-NH 3 -S 2 O 3 2- Adding ammonia to the gold leaching tail solution increases the pH of the gold leaching tail solution, and adding HCl to reduce the pH of the gold leaching tail solution; 2 O 3 2-Ethylene diamine is added to the gold leaching tail solution to increase the pH of the gold leaching tail solution, and HCl is added to reduce the pH of the gold leaching tail solution.

[0013] Preferably, in step (1), BaCl is added to the gold leaching tail solution. 2 Reduce the concentration of thiosulfate in the gold leaching tail solution.

[0014] Preferably, in the step (2), the liquid-to-solid ratio of the mass of the added hematite powder to the gold leaching tail liquid is gold leaching tail liquid: hematite = 60-360 mL: 1 g.

[0015] Preferably, the specific surface area of ​​the hematite powder is 70 to 100 m 2 / g, and the average particle size of hematite powder is 75μm.

[0016] Preferably, the hematite powder is prepared by the following method:

[0017] S1: FeCl 3 6H 2 O is added to ethanol, and water is added, and sodium acetate is added under stirring until the solid is completely dissolved to obtain a solution;

[0018] S2: subjecting the solution obtained in step S1 to a hydrothermal reaction to obtain a reaction product;

[0019] S3: centrifuging the reaction product obtained in step S3 to obtain a precipitate, and washing the precipitate alternately with anhydrous ethanol and water;

[0020] S4: freeze-drying and calcining the precipitate washed in step S3 to obtain hematite powder.

[0021] Preferably, in step S1, FeCl 3 6H 2 The solid-liquid ratio of FeCl 3 6H 2 O: ethanol = 0.41g: 15mL, the volume ratio of water added to ethanol is water: ethanol = 0.7: 10, the amount of sodium acetate added is the same as FeCl 3 6H 2 The mass ratio of O is sodium acetate:FeCl 3 6H 2 O=1.2:0.41;

[0022] In step S2, the hydrothermal reaction temperature is 180° C. and the hydrothermal reaction time is 12 h;

[0023] In step S4, the calcination temperature is 400° C. and the calcination time is 2 hours.

[0024] Preferably, in step (2), the arsenic removal temperature is 25-30°C.

[0025] Preferably, the (001) crystal plane of the hematite powder is exposed.

[0026] Beneficial effects of the present invention:

[0027] 1. The present invention regulates the Cu in the gold leaching tail solution 2+ , thiosulfate (S 2 O 3 2- ) content, and at the same time adjust the pH value of the gold leaching tailings to enhance the adsorption of arsenic by hematite in the thiosulfate gold leaching tailings, thereby improving the arsenic removal effect.

[0028] 2. During the calcination of gold ore, a large amount of iron-based oxides in the mineral will be converted into hematite. Hematite is a waste for the gold leaching process. The present invention utilizes hematite to remove arsenic in the gold leaching tailings, thereby realizing the resource utilization of waste and reducing the potential impact of hematite waste on the environment. It is beneficial to reduce the cost of arsenic removal and complies with the concept of waste treatment and circular green economy.

[0029] 3. During the gold immersion process, Cu can be added 2+ As a catalyst, Cu(NH 3 ) 4 2+ or Cu(EDA) 2 2+ The complex promotes the leaching of gold, thus, the Cu 2+ The content can be regulated to a certain extent, which is convenient for the subsequent adjustment of Cu 2+ The content can be regulated, and the arsenic removal process and the gold leaching process can be closely combined to achieve a smooth process.

[0030] 4. The present invention can achieve rapid removal of arsenic within 6 hours, effectively shortening the arsenic removal cycle and improving the arsenic removal efficiency.

[0031] 5. The raw materials of the present invention are easy to obtain and the cost is easy to control. After adsorption, arsenic is enriched on hematite. There is a large density difference between hematite and the solution. Arsenic can be separated from the solution by simple solid-liquid separation means. The process has a good effect of removing arsenic from gold leaching tail liquid, has excellent application prospects, and is suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1The figures are SEM images of hematite in Example 1 and Example 2 of the present invention, wherein (a) is a SEM image of hematite before adsorption, (b) is a SEM image of hematite after arsenic adsorption in Example 1, and (c) is a SEM image of hematite after arsenic adsorption in Example 2;

[0033] Figure 2 This is the XRD pattern of hematite after arsenic adsorption in Example 2;

[0034] Figure 3 These are the XPS spectra of the hematite in Comparative Example 2 and Comparative Example 6 after arsenic adsorption, wherein a is the XPS total spectrum of Comparative Example 2, b is the Fe 2p fine spectrum of Comparative Example 2, c is the Cu 2p fine spectrum of Comparative Example 2, d is the As 3d fine spectrum of Comparative Example 2, e is the XPS total spectrum of Comparative Example 6, f is the Fe 2p fine spectrum of Comparative Example 6, g is the Cu 2p fine spectrum of Comparative Example 6, and h is the As 3d fine spectrum of Comparative Example 6. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the described contents.

[0036] In the examples and comparative examples of the present invention, chemical reagents not otherwise specified were all commercially available analytically pure reagents for the experiments.

[0037] In the embodiments of the present invention and the comparative examples, experiments were conducted by preparing a simulated gold leaching tail liquid, and hematite was used to remove arsenic in the simulated gold leaching tail liquid.

[0038] Example 1

[0039] This embodiment removes arsenic according to the following steps:

[0040] (1) Preparation of Cu(II)-NH 3 -S 2 O 3 2- Gold immersion tail liquid simulation liquid, in the simulation liquid, Cu 2+ The concentration is 40mmol / L, pH is 11, S 2 O 3 2- The concentration is 0.1mol / L.

[0041] (2) Add hematite powder into the simulated liquid prepared above at a liquid-to-solid ratio of 60 mL:1 g.

[0042] (3) Stir the simulated liquid at 25-30°C to remove arsenic.

[0043] After removing arsenic for 6 hours in this embodiment, the arsenic removal rate was tested, and the result showed that in this embodiment, the arsenic removal rate was 100%.

[0044] Example 2

[0045] This embodiment removes arsenic according to the following steps:

[0046] (1) Preparation of Cu(II)-EDA-S 2 O 3 2- Gold immersion tail liquid simulation liquid, in the simulation liquid, Cu 2+ The concentration is 35mmol / L, pH is 10, S 2 O 3 2- The concentration is 0.05mol / L.

[0047] (2) Add hematite powder into the simulated liquid prepared above at a liquid-to-solid ratio of 300 mL:1 g.

[0048] (3) Stir the simulated liquid at 25-30°C to remove arsenic.

[0049] In this embodiment, the arsenic removal rate is close to that in embodiment 1.

[0050] Example 3

[0051] This embodiment removes arsenic according to the following steps:

[0052] (1) Preparation of Cu(II)-NH 3 -S 2 O 3 2- Gold immersion tail liquid simulation liquid, in the simulation liquid, Cu 2+ The concentration is 38mmol / L, pH is 10.5, S 2 O 3 2- The concentration is 0.08mol / L.

[0053] (2) Add hematite powder into the simulated liquid prepared above at a liquid-to-solid ratio of 360 mL:1 g.

[0054] (3) Stir the simulated liquid at 25-30°C to remove arsenic.

[0055] In this embodiment, the arsenic removal rate is close to that in embodiment 1.

[0056] Comparative Example 1

[0057] This comparative example uses the same method as Example 1 to remove arsenic from the simulated liquid, except that: in this comparative example, Cu is not added to the simulated liquid. 2+ , Cu2+ The concentration is 0.

[0058] The arsenic removal rate in this comparative example is 42%.

[0059] Comparative Example 2

[0060] This comparative example uses the same method as Example 1 to remove arsenic from the simulated liquid, except that: in this comparative example, the simulated liquid, Cu 2+ The concentration is 5mmol / L.

[0061] The arsenic removal rate in this comparative example is 76%.

[0062] Comparative Example 3

[0063] This comparative example uses the same method as comparative example 2 to remove arsenic in the simulated liquid, except that in this comparative example, pH=13.

[0064] The arsenic removal rate in this comparative example is 46%.

[0065] Comparative Example 4

[0066] This comparative example uses the same method as comparative example 2 to remove arsenic from the simulated liquid, except that: in this comparative example, the simulated liquid, S 2 O 3 2- The concentration is 0.15mol / L.

[0067] The arsenic removal rate in this comparative example is 54%.

[0068] Comparative Example 5

[0069] This comparative example uses the same method as comparative example 1 to remove arsenic from the simulated liquid, except that: in this comparative example, the Cu(II)-EDA-S 2 O 3 2- Gold immersion tail liquid simulation liquid.

[0070] The arsenic removal rate in this comparative example is 39%.

[0071] Comparative Example 6

[0072] This comparative example uses the same method as comparative example 2 to remove arsenic from the simulated liquid, except that: in this comparative example, the Cu(II)-EDA-S 2 O 3 2- Gold immersion tail liquid simulation liquid.

[0073] The arsenic removal rate in this comparative example is 62%.

[0074] Comparative Example 7

[0075] This comparative example adopts the same method as that of comparative example 3 to remove arsenic in the simulated liquid, except that: in this comparative example, the Cu(II)-EDA-S 2 O 3 2- Gold immersion tail liquid simulation liquid.

[0076] The arsenic removal rate in this comparative example is 40%.

[0077] Comparative Example 8

[0078] This comparative example uses the same method as comparative example 4 to remove arsenic from the simulated liquid, except that: in this comparative example, the Cu(II)-EDA-S 2 O 3 2- Gold immersion tail liquid simulation liquid.

[0079] The arsenic removal rate in this comparative example is 57%.

[0080] For the convenience of comparison, the arsenic removal rates in the embodiments and comparative examples are statistically shown in Table 1, as shown below:

[0081] Table 1

[0082] Arsenic removal rate (%) Example 1 100 Comparative Example 1 42 Comparative Example 2 76 Comparative Example 3 46 Comparative Example 4 54 Comparative Example 5 39 Comparative Example 6 62 Comparative Example 7 40 Comparative Example 8 57

[0083] It can be seen from Table 1 that the arsenic removal rate of Example 1 is significantly improved compared with that of Comparative Example 1, which indicates that the Cu 2+ The concentration control within the scope of the present invention can effectively improve the removal effect of hematite on arsenic in thiosulfate gold leaching tailings, Cu 2+ In the arsenic removal system, it reacts with arsenate to form Cu 3 (AsO 4 )(OH) 3 The precipitate forms a coordinated adsorption synergistic effect with the hydroxyl groups on the surface of hematite, which significantly improves the removal effect of arsenic in the gold leaching tail liquid.

[0084] It can be seen from Table 1 that compared with Comparative Example 2, Example 1 has a 2+ As the concentration increases, the arsenic removal rate is improved, but when Cu 2+ When the concentration reaches 40mmol / L, the arsenic removal rate has reached 100%. 2+ It will only cause waste. Therefore, the gold leaching tail liquid is regulated within the concentration range of the present invention to achieve the best arsenic removal effect.

[0085] It can be seen from Table 1 that the arsenic removal rate of Comparative Example 2 is significantly improved compared with Comparative Example 3, which proves that the pH value has a significant effect on the arsenic removal rate. In Comparative Example 3, due to the high pH value, the surface of hematite is negatively charged, which weakens the electrostatic attraction and surface complexation, resulting in a decrease in the adsorption rate, thereby reducing the arsenic removal rate. When the pH is too low, a large amount of H + It will compete with arsenate ions for adsorption sites on the surface of hematite. + Due to their large number, small ionic radius and fast movement speed, they can quickly occupy some adsorption sites on the surface of hematite, reducing the available adsorption sites for arsenate ions, which is not conducive to the adsorption of arsenic.

[0086] It can be seen from Table 1 that compared with Comparative Example 4, the arsenic removal rate of Comparative Example 2 is significantly improved, which proves that the thiosulfate ion in the gold leaching tail liquid needs to be controlled within 0.1 mol / L to ensure that hematite has a good adsorption and arsenic removal effect on the gold leaching tail liquid. 2 O 3 2- Unstable, it is easily oxidized and reduced to generate SO 4 2- , SO 4 2- It reacts with Fe(II) to form basic ferrous sulfate, which precipitates on the surface of hematite, reducing the adsorption sites of hematite and weakening the arsenic removal effect of hematite.

[0087] It can be seen from Table 1 that the adsorption removal rate of arsenic in Comparative Examples 5-8 is similar to that in Comparative Examples 1-4, which proves that the method of the present invention has a good effect on the adsorption of arsenic in Cu(II)-EDA-S 2 O 3 2- The same applies to gold immersion tail liquid.

[0088] pass Figure 1 It can be seen that before arsenic adsorption, the surface of hematite showed many grooves and pores (such as Figure 1 (a)), while after hematite adsorbs arsenic, the surface becomes smoother and the number of grooves decreases (as shown in Figure 1 (b) and (c) show that hematite can remove arsenic by adsorption.

[0089] pass Figure 2 It can be seen that the diffraction peaks of iron oxide at 24.0 (012), 33.0 (10.4), 35.5 (110), 40.8 (113), 49.4 (024), 54.0 (116), 62.3 (214) and 63.9 (300) on the XRD spectrum of hematite after adsorption correspond to the hematite (α-Fe2O3) phase (JCPDS card number) of iron oxide. The peak intensities of 24.8 and 26.6 degrees are significantly enhanced, and the peaks consistent with Cu 3(AsO 4 )(OH) 3 The PDF card is the characteristic peak of 00-042-1357, and 12.4, 17.8, and 21.7 appear consistent with Fe 2 (SO4) 2 (OH) 2 ·3H 2 The PDF card of O is the characteristic peak of 00-039-0379. It proves that basic copper arsenate precipitate is formed in the adsorption process. The present invention forms a coordination adsorption synergy with the hydroxyl group on the surface of hematite through the basic copper arsenate precipitate, which significantly improves the adsorption and arsenic removal effect in the gold leaching tail liquid.

[0090] pass Figure 3 It can be seen that in the gold immersion tail solution, the 3d spectrum of As shows an As 3d 5 / 2 peak at around 46 eV, corresponding to As 5+ (Arsenate form), indicating that arsenic is mainly adsorbed on the surface of hematite in the +5 valence state, indicating that the present invention mainly removes arsenic by adsorption.

[0091] In summary, the present invention effectively enhances the adsorption and removal effect of hematite on arsenic in the gold leaching tail solution by regulating the copper ion, thiosulfate content and pH value in the gold leaching tail solution, thereby achieving simple, low-cost and efficient adsorption and removal of arsenic.

[0092] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for improving the removal of arsenic from thiosulfate gold leaching tailings from hematite, characterized in that: The method comprises the following steps: (1) Adjusting the Cu content in the thiosulfate gold leaching tail solution 2+ The concentration is 35-40mmol / L, the pH of the gold leaching tail solution is adjusted to 10-11, and the concentration of thiosulfate in the gold leaching tail solution is adjusted to ≤0.1mol / L; (2) adding hematite powder to the gold leaching tailings after adjustment in step (1) and stirring to remove arsenic.

2. The method according to claim 1, characterized in that: In the step (1), CuCl2 is added to the gold leaching tail solution to increase the Cu 2+ concentration, adding Na2S to reduce the Cu 2+ concentration.

3. The method according to claim 1, characterized in that: In the step (1), the gold leaching tail solution is Cu(II)-NH3-S2O3 2- Gold immersion tail liquid or Cu(II)-EDA-S2O3 2- One of the gold leaching tail liquids; to the Cu(II)-NH3-S2O3 2- Adding ammonia to the gold leaching tail solution increases the pH of the gold leaching tail solution, and adding HCl to reduce the pH of the gold leaching tail solution; 2- Ethylene diamine is added to the gold leaching tail solution to increase the pH of the gold leaching tail solution, and HCl is added to reduce the pH of the gold leaching tail solution.

4. The method according to claim 1, characterized in that: In the step (1), BaCl2 is added to the gold leaching tail solution to reduce the concentration of thiosulfate in the gold leaching tail solution.

5. The method according to claim 1, characterized in that: In the step (2), the liquid-to-solid ratio of the mass of the added hematite powder to the gold leaching tail liquid is gold leaching tail liquid: hematite = 60-360 mL: 1 g.

6. The method according to claim 1, characterized in that: The specific surface area of ​​the hematite powder is 70 to 100 m 2 / g, and the average particle size of hematite powder is 75μm.

7. The method according to claim 1, characterized in that: The hematite powder is prepared by the following method: S1: FeCl3·6H2O is added to ethanol, and water is added, and sodium acetate is added under stirring until the solid is completely dissolved to obtain a solution; S2: subjecting the solution obtained in step S1 to a hydrothermal reaction to obtain a reaction product; S3: centrifuging the reaction product obtained in step S3 to obtain a precipitate, and washing the precipitate alternately with anhydrous ethanol and water; S4: freeze-drying and calcining the precipitate washed in step S3 to obtain hematite powder.

8. The method according to claim 7, characterized in that: In the step S1, the solid-liquid ratio of the amount of FeCl3·6H2O added to ethanol is FeCl3·6H2O:ethanol=0.41g:15mL, the volume ratio of the added water to the volume ratio of ethanol is water:ethanol=0.7:10, and the mass ratio of the amount of sodium acetate added to FeCl3·6H2O is sodium acetate:FeCl3·6H2O=1.2:0.41; In step S2, the hydrothermal reaction temperature is 180° C. and the hydrothermal reaction time is 12 h; In step S4, the calcination temperature is 400° C. and the calcination time is 2 hours.

9. The method according to claim 1, characterized in that: In the step (2), the arsenic removal temperature is 25-30°C.

10. The method according to claim 1, characterized in that: The (001) crystal plane of the hematite powder is exposed.

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