Method for improving arsenic removal from gold leaching tail liquid of pyrite desulfurization thiosulfate

Abstract

The application discloses a method for improving arsenic removal in a gold leaching tail liquid of hematite from thiosulfate, and belongs to the technical field of environmental engineering. 2+ The concentration of Cu is 35-40 mmol / L, the pH of the gold leaching tail liquid is adjusted to 10-11, and the concentration of thiosulfate in the gold leaching tail liquid is less than or equal to 0.1 mol / L; and (2) hematite powder is added into the gold leaching tail liquid after the adjustment in the step (1), and stirring is conducted to remove arsenic. The application effectively strengthens the adsorption and arsenic removal effect of hematite in the gold leaching tail liquid by regulating and controlling the content of copper ions and thiosulfate ions in the gold leaching tail liquid in combination with pH regulation, and lays an excellent foundation for realizing simple, low-cost and high-efficiency adsorption and arsenic removal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental engineering and relates to a method for improving the removal of arsenic in a thiosulfate leaching gold tail liquid by hematite. BACKGROUND

[0002] Arsenic and its compounds can enter the organism through the respiratory tract, digestive tract and skin, etc., causing poisoning of the organism, and therefore, arsenic belongs to toxic substances, and the discharge of arsenic can cause serious pollution to the environment, thereby endangering human health. In the thiosulfate gold leaching process, arsenic (As) will enter the solution with gold leaching. Since arsenic enters the solution, the solution has toxicity, and therefore, the solution needs to be dearsenicated.

[0003] The conventional dearsenication methods include adsorption, chemical precipitation, ion exchange, etc., wherein the chemical precipitation and ion exchange have problems of relatively complex operation and high cost, and relatively, the adsorption process is simple and has low cost, but on the one hand, the dearsenication effect of the adsorption method is relatively poor, and on the other hand, the components in the gold leaching tail liquid are complex, which greatly interferes with the dearsenication process and further weakens the dearsenication effect of the adsorption method in the gold leaching tail liquid, and therefore, the adsorption method cannot fully play the dearsenication effect in the gold leaching tail liquid, resulting in the failure to achieve simple, low-cost and efficient dearsenication.

[0004] Hematite (α-Fe2O3) is a natural iron oxide, which has the characteristics of large specific surface area and rich surface active sites, and has excellent adsorption capacity for arsenate (AsO4 3- ) and arsenite (AsO3 3- ), and mainly adsorbs arsenic to the surface of hematite particles in the form of Fe-O-AsO3 and (Fe-O)2-AsO2 complexes. However, compared with other methods, the adsorption and removal effect of hematite on arsenic in the gold leaching tail liquid is still limited, and in addition to the interference of complex components on the adsorption and dearsenication process, the dearsenication effect of hematite in the gold leaching tail liquid is still greatly limited.

[0005] Therefore, it is necessary to provide a method for improving the removal of arsenic in a thiosulfate leaching gold tail liquid by hematite, effectively improve the dearsenication effect of hematite in the thiosulfate leaching gold tail liquid, make the adsorption method more fully play the advantages, and achieve simple, low-cost and efficient dearsenication. SUMMARY

[0006] In order to overcome the problems in the background art, the application adjusts the content of Cu 2+ in the gold leaching tail liquid, and adjusts the content of Cu 2+Specifically reacts with arsenate to generate a basic copper arsenate precipitate (Cu3(AsO4)(OH)3), and through the coordination adsorption synergy of the aforementioned precipitate and the hydroxyl group on the surface of hematite, the arsenic removal effect in the gold leaching tail liquid is significantly improved; meanwhile, by regulating the pH of the gold leaching tail liquid, the pH is prevented from being too high, so that the surface of hematite is negatively charged, the electrostatic attraction and surface complexation are weakened, and the adsorption effect is reduced; and then by regulating the content of thiosulfate in the gold leaching tail liquid, the thiosulfate is prevented from being decomposed to generate sulfate, so that the sulfate reacts with Fe(II) to generate basic ferrous sulfate attached to the surface of hematite, the gap on the surface of hematite is reduced, the chemical reaction adsorption site is reduced, and the adsorption effect is weakened.

[0007] In order to achieve the above purpose, the present application is realized through the following technical solutions:

[0008] The method comprises the following steps:

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

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

[0011] Preferably, in the step (1), CuCl2 is added to the gold leaching tail liquid to increase the concentration of Cu 2+ , and Na2S is added to reduce the concentration of Cu 2+ .

[0012] Preferably, in the step (1), the gold leaching tail liquid is one of Cu(II)-NH3-S2O3 2- or Cu(II)-EDA-S2O3 2- ; ammonia water is added to the Cu(II)-NH3-S2O3 2- gold leaching tail liquid to increase the pH of the gold leaching tail liquid, and HCl is added to reduce the pH of the gold leaching tail liquid; ethylenediamine is added to the Cu(II)-EDA-S2O3 2- gold leaching tail liquid to increase the pH of the gold leaching tail liquid, and HCl is added to reduce the pH of the gold leaching tail liquid.

[0013] Preferably, in the step (1), BaCl2 is added to the gold leaching tail liquid to reduce the concentration of thiosulfate in the gold leaching tail liquid.

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

[0015] Preferably, the hematite powder has a specific surface area of 70-100 m 2 / g and an average particle size of 75 μm.

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

[0017] S1: FeCl3·6H2O is added to ethanol, water is added, and sodium acetate is added under stirring until the solid is completely dissolved to obtain a solution;

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

[0019] S3: the reaction product obtained in step S3 is subjected to centrifugation to obtain a precipitate, and the precipitate is alternately washed with anhydrous ethanol and water;

[0020] S4: the precipitate after washing in step S3 is subjected to freeze-drying and calcination in sequence to obtain a hematite powder.

[0021] Preferably, in step S1, the solid-liquid ratio of the amount of FeCl3·6H2O added to ethanol is FeCl3·6H2O:ethanol=0.41 g:15 mL, the volume ratio of the amount of water added to the volume 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;

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

[0023] In step S4, the calcination temperature is 400℃, and the calcination time is 2 h.

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

[0025] Preferably, the hematite powder has a (001) crystal plane exposed.

[0026] The beneficial effects of the present application are:

[0027] 1. The present application adjusts the content of Cu 2+ , thiosulfate (S2O3 2- ) in gold leaching tail liquid, and adjusts the pH value of the gold leaching tail liquid at the same time, thereby enhancing the adsorption effect of hematite on arsenic in thiosulfate gold leaching tail liquid, and improving the arsenic removal effect.

[0028] 2. In the process of calcining gold ore minerals, a large amount of iron-based oxides in the minerals will be converted into hematite, which is waste for the gold leaching process, and the application uses hematite to remove arsenic in the gold leaching tail liquid, realizes the resource utilization of waste, reduces the potential impact of hematite waste on the environment, is conducive to reducing the cost of arsenic removal, and meets the concept of waste treatment and green recycling economy.

[0029] 3. In the gold leaching process, Cu 2+ As a catalyst, the leaching of gold is promoted by forming Cu(NH3)4 2+ Or Cu(EDA)2 2+ Complex, thereby, the Cu 2+ Content in the gold leaching process can be regulated to a certain extent, which is convenient for subsequent regulation of Cu 2+ Content in the gold leaching tail liquid, and the arsenic removal process and the gold leaching process can be closely combined to realize good process flow.

[0030] 4. The application can realize rapid removal of arsenic within 6h, effectively shortening the arsenic removal period and improving the arsenic removal efficiency.

[0031] 5. The raw materials of the application are easy to obtain, and the cost is easy to control. After adsorption of arsenic, the arsenic is enriched on the hematite, and the hematite and the solution have a large density difference. Only by means of simple solid-liquid separation method, the separation of arsenic and solution can be realized. The application has good application prospect and is suitable for industrialized popularization and application. BRIEF DESCRIPTION OF DRAWINGS

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

[0033] Figure 2 The XRD spectrum of the hematite after adsorption of arsenic in Example 2 is shown in the figure.

[0034] Figure 3 The XPS spectrum of the hematite after adsorption of arsenic in Comparative Example 2 and Comparative Example 6 is shown in the figure, 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 application will be described in further detail below with reference to the drawings and specific embodiments, but the scope of protection of the application is not limited to the described content.

[0036] In the examples and comparative examples of the present application, the chemical reagents not specifically mentioned were used in experiments in the form of commercially available analytical grade.

[0037] In the examples and comparative examples of the present application, experiments were carried out by preparing gold leaching tail liquid simulation liquid, and hematite was used to remove arsenic in the gold leaching tail liquid simulation liquid.

[0038] Example 1

[0039] In this example, arsenic was removed according to the following steps:

[0040] (1) Cu(II)-NH3-S203 2- leaching tail liquid simulation liquid, in the simulation liquid, Cu 2+ concentration was 40 mmol / L, pH was 11, S203 2- concentration was 0.1 mol / L.

[0041] (2) Hematite powder was added to the above prepared simulation liquid in a liquid-solid ratio of 60 mL:1 g.

[0042] (3) The simulation liquid was stirred to remove arsenic at 25-30°C.

[0043] After 6 hours of arsenic removal in this example, the arsenic removal rate was tested, and the result was that the arsenic removal rate in this example was 100%.

[0044] Example 2

[0045] In this example, arsenic was removed according to the following steps:

[0046] (1) Cu(II)-NH3-S203 2- leaching tail liquid simulation liquid, in the simulation liquid, Cu 2+ concentration was 35 mmol / L, pH was 10, S203 2- concentration was 0.05 mol / L.

[0047] (2) Hematite powder was added to the above prepared simulation liquid in a liquid-solid ratio of 60 mL:1 g.

[0048] (3) The simulation liquid was stirred to remove arsenic at 25-30°C.

[0049] In this example, the arsenic removal rate was close to that of Example 1.

[0050] Example 3

[0051] In this example, arsenic was removed according to the following steps:

[0052] (1) Cu(II)-NH3-S203was prepared 2- The concentration of Cu was 38 mmol / L, the pH was 10.5, and the concentration of S203was 0.08 mol / L. 2+ The concentration of Cu was 38 mmol / L, the pH was 10.5, and the concentration of S203was 0.08 mol / L. 2- The concentration of Cu was 38 mmol / L, the pH was 10.5, and the concentration of S203was 0.08 mol / L.

[0053] (2) Hematite powder was added to the prepared simulated solution at a liquid-solid ratio of 360 mL: 1 g.

[0054] (3) The simulated solution was stirred to remove arsenic at 25-30°C.

[0055] In this example, the arsenic removal rate was close to that of Example 1.

[0056] Comparative Example 1

[0057] This comparative example used the same method as Example 1 to remove arsenic from the simulated solution, except that in this comparative example, no Cu 2+ was added to the simulated solution. 2+ The concentration of Cu was 38 mmol / L, the pH was 10.5, and the concentration of S203was 0.08 mol / L.

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

[0059] Comparative Example 2

[0060] This comparative example used the same method as Example 1 to remove arsenic from the simulated solution, except that in this comparative example, the concentration of Cu 2+ in the simulated solution was 5 mmol / L.

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

[0062] Comparative Example 3

[0063] This comparative example used the same method as Comparative Example 2 to remove arsenic from the simulated solution, except that in this comparative example, the pH was 13.

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

[0065] Comparative Example 4

[0066] This comparative example used the same method as Comparative Example 2 to remove arsenic from the simulated solution, except that in this comparative example, the concentration of S203 2- in the simulated solution was 0.15 mol / L.

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

[0068] Comparative Example 5

[0069] The present comparative example removes arsenic from the simulated solution using the same method as Comparative Example 1, except that in the present comparative example, Cu(II)-EDA-S203 2- The simulated solution of the gold leaching tail liquid.

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

[0071] Comparative Example 6

[0072] The present comparative example removes arsenic from the simulated solution using the same method as Comparative Example 2, except that in the present comparative example, Cu(II)-EDA-S203 2- The simulated solution of the gold leaching tail liquid.

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

[0074] Comparative Example 7

[0075] The present comparative example removes arsenic from the simulated solution using the same method as Comparative Example 3, except that in the present comparative example, Cu(II)-EDA-S203 2- The simulated solution of the gold leaching tail liquid.

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

[0077] Comparative Example 8

[0078] The present comparative example removes arsenic from the simulated solution using the same method as Comparative Example 4, except that in the present comparative example, Cu(II)-EDA-S203 2- The simulated solution of the gold leaching tail liquid.

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

[0080] For ease of comparison, the arsenic removal rates in the examples and comparative examples are listed in Table 1 as follows:

[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] As can be seen from Table 1, the arsenic removal rate of Example 1 is significantly improved compared to Comparative Example 1, indicating that the Cu 2+ The concentration control is within the scope of the present application, which can effectively improve the arsenic removal effect of hematite on the thiosulfate leaching tail liquid of gold. 2+ In the arsenic removal system, Cu3(As04)(OH)3precipitate is formed by reacting with arsenate, and the coordination adsorption synergistic effect is formed by the precipitate and the hydroxyl group on the surface of hematite, which significantly improves the arsenic removal effect in the gold leaching tail liquid.

[0084] As can be seen from Table 1, with the increase of Cu 2+ concentration, the arsenic removal rate is improved, but when the Cu 2+ concentration reaches 40 mmol / L, the arsenic removal rate has reached 100%, and further increase of Cu 2+ concentration will only cause waste, so the gold leaching tail liquid is controlled within the concentration range of the present application, which has the best arsenic removal effect.

[0085] As can be seen from Table 1, 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 influence on the arsenic removal rate. In Comparative Example 3, due to the too high pH value, the hematite surface is negatively charged, which weakens the electrostatic attraction and surface complexation, resulting in a decrease in the adsorption rate and thus a decrease in the arsenic removal rate. When the pH is too low, a large amount of H + will compete with arsenate ions for the adsorption sites on the hematite surface. Because H + is numerous and has a small ionic radius and fast movement speed, it can quickly occupy part of the adsorption sites on the hematite surface, so that the available adsorption sites for arsenate ions are reduced, which is not conducive to the adsorption of arsenic.

[0086] As can be seen from Table 1, the arsenic removal rate of Comparative Example 2 is significantly improved compared with Comparative Example 4, which proves that the thiosulfate ion in the gold leaching tail liquid needs to be controlled within 0.1 mol / L to ensure that the hematite has a good adsorption and arsenic removal effect on the gold leaching tail liquid. Since S2O3 2- is unstable, it is easily oxidized and reduced to generate SO4 2- , and SO4 2- reacts with Fe(II) to generate basic ferrous sulfate, which precipitates on the hematite surface, reduces the adsorption sites of the hematite, and thus weakens the adsorption and arsenic removal effect of the hematite.

[0087] As can be seen from Table 1, the arsenic adsorption and removal rates of Comparative Examples 5-8 are similar to those of Comparative Examples 1-4, which proves that the method of the present application is also applicable to Cu(II)-EDA-S2O3 2- gold leaching tail liquid.

[0088] As can be seen from Figure 1 , before adsorbing arsenic, the hematite surface shows many ravines and pores (as shown in (a)), and after the hematite adsorbs arsenic, the surface becomes smoother and the number of ravines is reduced (as shown in (b) and (c)), which proves that the hematite can adsorb and remove arsenic. Figure 1 Figure 1

[0089] As can be seen from 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 pattern of hematite after adsorption correspond to hematite (alpha-Fe2O3) of iron oxide (JCPDS card No.). The peak intensity at 24.8 and 26.6 degrees is obviously enhanced, and the characteristic peaks corresponding to the PDF card 00-042-1357 of Cu3(AsO4)(OH)3 appear, and the characteristic peaks corresponding to the PDF card 00-039-0379 of Fe2(SO4)2(OH)2·3H2O appear at 12.4, 17.8 and 21.7. It is proved that the basic copper arsenate precipitate is formed in the adsorption process, and the adsorption effect of removing arsenic in the gold leaching tail liquid is significantly improved by the coordination adsorption synergistic effect of the basic copper arsenate precipitate and the hydroxyl group on the surface of hematite.

[0090] By Figure 3 It can be seen that in the gold leaching tail liquid, the 3d spectrum of As shows an As 3d 5 / 2 peak at about 46eV, which corresponds to As 5+ (as arsenate form), indicating that arsenic is mainly adsorbed on the surface of hematite in the +5 valence state, which shows that the present application mainly removes arsenic by adsorption.

[0091] In summary, the present application effectively enhances the adsorption and removal effect of arsenic on hematite in the gold leaching tail liquid by adjusting the content of copper ions, thiosulfate and pH value in the gold leaching tail liquid, and realizes simple, low-cost and efficient adsorption and removal of arsenic.

[0092] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application and are not limiting, although the present application 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 application.

Claims

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

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

3. The method according to claim 1, characterized in that: In step (1), the gold leaching tail solution is Cu(II)-NH3-S2O3. 2- Gold leaching tailings or Cu(II)-EDA-S2O3 2- One of the gold leaching tailings; to the Cu(II)-NH3-S2O3 2- Ammonia was added to the gold leaching tail solution to raise its pH, and HCl was added to lower its pH; Cu(II)-EDA-S2O3 was added to... 2- Ethylenediamine was added to the gold leaching tail solution to increase its pH, while HCl was added to decrease its pH.

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

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

6. The method according to claim 1, characterized in that: The specific surface area of ​​the hematite powder is 70~100m². 2 / g, the average particle size of hematite powder is 75μm.

7. The method according to claim 1, characterized in that: The hematite powder was prepared by the following method: S1: Add FeCl3·6H2O to ethanol, then add water, and add sodium acetate under stirring until the solid is completely dissolved to obtain a solution; S2: The solution obtained in step S1 is subjected to a hydrothermal reaction to obtain the reaction product; S3: Centrifuge the reaction product obtained in step S2 to obtain a precipitate, and wash the precipitate alternately with anhydrous ethanol and water; S4: The precipitate washed in step S3 is freeze-dried and calcined sequentially to obtain hematite powder.

8. The method according to claim 7, characterized in that: In step S1, the solid-liquid ratio of FeCl3·6H2O to ethanol is FeCl3·6H2O:ethanol = 0.41g:15mL, the volume ratio of water to ethanol is water:ethanol = 0.7:10, and the mass ratio of sodium acetate to FeCl3·6H2O is sodium acetate:FeCl3·6H2O = 1.2:0.

41. In step S2, the hydrothermal reaction temperature is 180℃ and the hydrothermal reaction time is 12h. In step S4, the calcination temperature is 400℃ and the calcination time is 2h.

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

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