A method and apparatus for selectively removing thallium from a thallium-containing solution

Abstract

The application discloses a method and device for selectively removing thallium from a thallium-containing solution. + The method uses ozone as an oxidant, and uses a shearing strengthening method during the reaction, so that Tl + Is converted into Tl2O3 which is difficult to dissolve and has good stability, thereby realizing efficient removal of thallium in the solution. The reaction equipment is composed of a stirring device, a reaction tank, a temperature control device, a shearing machine, a circulating pump and the like. Compared with other methods, the application has the advantages of low production cost, high thallium removal selectivity, small thallium removal residue yield, no introduction of impurity ions and the like, and has good industrial application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the fields of metallurgy, chemical industry, new energy, etc., and particularly relates to a method and device for selectively removing thallium from a thallium-containing solution. BACKGROUND

[0002] Thallium is a toxic and rare metal, which is more toxic to mammals than mercury, cadmium and lead, and is a very dangerous chemical element. In addition, thallium is also a common impurity in non-ferrous metal smelting process; it not only affects the purity of the final product, but also has a certain impact on the production process. Tl(I) has a large solubility in water and can exist stably in a wide pH range, so thallium often enters the human body through drinking water or the food chain, causing serious poisoning events. Therefore, based on human health, environmental protection and production operation requirements, thallium removal from thallium-containing solution is a very critical task.

[0003] At present, the methods for removing thallium from solution mainly include chemical precipitation method, adsorption method, ion exchange method, displacement method and biological preparation method, etc. Among them, the chemical precipitation method has the advantages of high efficiency, simple operation and low cost, and is one of the most widely used thallium removal methods in industrial production.

[0004] According to the different precipitates, the chemical precipitation method can be divided into oxidation precipitation method, sulfidation precipitation method and chlorination precipitation method. The oxidation precipitation method uses the low solubility of Tl(III) in a specific pH range, and removes thallium in the form of (hydro) oxide by adding a strong oxidizing agent to the thallium-containing solution. The sulfidation method converts thallium into thallium sulfide with extremely low solubility by adding soluble sulfide to the thallium-containing solution. The chlorination method uses the principle that thallium chloride has low solubility in saturated sodium chloride solution to remove thallium. Since most sulfides are difficult to dissolve in water, it is difficult to achieve selective precipitation of thallium by sulfidation method, which is generally only suitable for the treatment of thallium-containing wastewater. In addition, sulfidation precipitation slag often has a pungent odor and has the risk of generating hydrogen sulfide, which is not conducive to on-site management or further treatment. The chlorination method needs to be carried out in saturated sodium chloride solution, and the high-salt wastewater generated during the thallium removal process is also a difficult problem in actual production. In addition, the operating pH of the chlorination method is also very narrow. Compared with the above two methods, the application scene of the oxidation precipitation method is relatively wide, and it is possible to achieve selective removal of thallium. However, the oxidizing agent used in this process is mainly expensive potassium permanganate, hydrogen peroxide, etc., and the production cost is high. At the same time, the introduction of potassium permanganate may cause secondary pollution to the valuable metal solution.

[0005] In summary, the existing mainstream thallium removal technology from thallium-containing solution has problems such as high reagent cost, great limitation, serious secondary pollution, etc., which has become a technical bottleneck in the field. Therefore, a new type, efficient and clean thallium removal method needs to be proposed. SUMMARY

[0006] The present application aims to provide a method and device for selectively removing thallium from a thallium-containing solution, and aims to solve the technical problems of poor selectivity, high cost of reagents and difficulty in processing the thallium removal product in the prior art.

[0007] To solve the above problems, the present application proposes to use shear-assisted ozone oxidation to achieve rapid and selective removal of thallium from the solution. Unlike the traditional oxidative hydrolysis method for removing thallium, the thallium removal method described in the present application uses a shear strengthening method, which can achieve high unification of gas and liquid phases in time and space sites. Unlike the traditional oxidative hydrolysis thallium removal product (thallium hydroxide), the product of the thallium removal method described in the present application is thallium trioxide, which has higher stability and can still exist stably in an acidic solution (pH = 0.9-7). Therefore, compared with the traditional oxidative hydrolysis thallium removal method, the application range of the method described in the present application is more extensive.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A method for selectively removing thallium from a thallium-containing solution, comprising the following steps:

[0010] (1) heating the solution to a set temperature;

[0011] (2) immediately after the solution reaches the set temperature, shear treatment is performed on the solution, and ozone is introduced into the solution during the shear treatment to achieve sufficient mixing of gas and liquid; when the predetermined time is reached, the shear and ozone introduction are stopped;

[0012] (3) separating the thallium-containing precipitate from the solution by liquid-solid separation.

[0013] The heating temperature in step (1) is above 0℃, and considering the reaction rate and energy consumption, it is preferably 25-65℃.

[0014] The shear method in step (2) is one or a combination of internal shear and / or external shear.

[0015] The shear rate in step (2) is 1000-10000 r / min, and considering the actual effect and equipment wear problems, it is preferably 2000-6000 r / min.

[0016] The pH during the reaction process in step (2) is not less than 0.9.

[0017] When the thallium-containing solution contains Fe 2+ or Fe 3+ , in this solution system, if the simultaneous removal of thallium and iron is to be achieved, the pH is controlled at 3.5-4.0; if the separate removal of thallium is to be achieved, the pH is controlled at 0.9-2.5.

[0018] The theoretical amount in step (2) is the amount of Tl + oxidized to Tl 3+ The required theoretical amount of ozone.

[0019] Preferably, the ozone concentration is above 1%; the amount of ozone introduced can be adjusted according to the need, the preparation scale and the efficiency, and the amount of ozone introduced is 0.5-10 times, further preferably 3-10 times, the required theoretical amount of ozone. + oxidized to Tl 3+ The required theoretical amount of ozone.

[0020] The flow rate of ozone introduced in step (2) is above 10 mL / min, further above 100 mL / min, and more further 100-100000 mL / min.

[0021] The predetermined time in step (2) is above 5 min, but preferably 10-90 min, considering the oxidation and precipitation rate of thallium.

[0022] In order to better apply the technology to industrial production, the application also designs a device that is beneficial to industrial application. The device is used to realize the above method, and comprises a reaction tank (3), a stirring paddle (5), a stirring motor (1), a shearing machine (8) and a circulating pump (10). The reaction tank (3) is a hollow tank body, and a feeding port (2) is arranged at the top of the tank body. A valve-equipped discharge port (6) is connected to the bottom of the tank body through a pipeline. A heating pipe (4) is arranged on the inner wall of the reaction tank (3). The stirring paddle (5) is arranged in the reaction tank (3) and is driven by the stirring motor (1) arranged outside the reaction tank (3). The shearing machine feeding port (7) of the shearing machine (8) is connected to the bottom of the reaction tank (3) through a pipeline with a valve to be parallel to the discharge port (6). An ozone inlet (9) connected to an external ozone source is also connected to the shearing machine feeding port (7) in parallel. The outlet of the shearing machine (8) is connected to the material circulating outlet (11) at the top of the reaction tank (3) through a pipeline. The circulating pump (10) is arranged on the pipeline before the shearing machine feeding port (7) or on the pipeline after the outlet of the shearing machine (8), so as to compensate for the flow rate and head of the shearing machine.

[0023] Advantages of the application

[0024] The application proposes a method for selectively oxidizing and precipitating thallium by shearing-assisted ozone oxidation. The introduction of shearing can realize the full mixing of gas and liquid phases in the treatment process, and effectively improve the utilization rate of ozone. At the same time, the test results show that in the application, thallium is removed in the form of more stable Tl2O3, which is different from the removal of thallium in the form of hydroxide in most of the previous related reports.

[0025] The present application can achieve selective removal of thallium in a wide pH range (pH > 0.9). Since the present application uses ozone as an oxidant, no other impurity ions are introduced during the reaction process. Therefore, the present application is not only suitable for the treatment of thallium-containing wastewater, but also can achieve effective removal of harmful impurity ions such as thallium from other valuable metal solutions. Taking the common impurity ions iron and chlorine in non-ferrous metal smelting process as an example: in a certain pH range, ozone can oxidize Fe 2+ in the solution to Fe 3+ and remove it by hydrolysis precipitation; in addition, ozone can also oxidize chloride ions in the solution to chlorine gas, thereby achieving the removal of chloride ions in the solution to a certain extent. In addition, the thallium removal product of the present application is also relatively simple, and the amount of thallium removal residue is small, and the treatment difficulty is low. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A device for selectively removing thallium from a thallium-containing solution according to the present application;

[0027] 1 - stirring motor, 2 - feed inlet, 3 - reaction tank, 4 - heating pipe, 5 - stirring paddle, 6 - discharge port, 7 - shear machine feed inlet, 8 - shear machine, 9 - ozone inlet, 10 - circulating pump, 11 - material circulating outlet.

[0028] Figure 2 The XRD pattern of the thallium removal residue in Example 1. DETAILED DESCRIPTION

[0029] The following examples are intended to further illustrate the present application, but not to limit the present application.

[0030] Example 1

[0031] A certain thallium-containing zinc sulfate solution mainly contains Zn 2+ 120 g / L, Cd 2+ 1.1 g / L, Fe 2+ 0.56 g / L, Cu 2+ 0.26 g / L, Tl + 0.41 g / L, and the solution pH is 2.01. 1 L of the solution is added to the reaction tank and heated to 40°C. Then, ozone is introduced into the inlet part of the shear machine and the shear machine is started to react for 30 min. The pH is maintained during the reaction, the ozone production amount is 10 g / h (calculated, the ozone concentration is greater than 1%, and the flow rate is about 77 ml / min), and the shear rate is 4000 r / min. After the reaction, the filter residue and the thallium-removed solution are obtained by filtration.

[0032] The concentration of thallium in the solution after the reaction was reduced to 50.11 μg / L, and the concentrations of other ions remained essentially unchanged. It was calculated that the removal rate of thallium was 99.99%, and the precipitation removal rates of other ions were all less than 1.5%. Figure 2 The XRD pattern of the thallium removal residue in Example 1 proved that it was thallium trioxide.

[0033] Example 2

[0034] The other conditions of Example 2 were the same as those of Example 1, and the only difference was that zinc oxide was used to adjust the pH of the solution to 3.5 in the shearing oxidation removal of thallium in Example 2.

[0035] The concentration of thallium in the solution after the reaction was reduced to 48.22 μg / L, and the concentration of iron was reduced from 0.56 g / L to 5.03 mg / L, and the concentrations of other ions remained essentially unchanged. It was calculated that the removal rate of thallium was 99.99% (thallium was precipitated in the form of thallium trioxide), the precipitation rate of Fe was 99.12%, and the precipitation removal rates of other ions were all less than 5%.

[0036] Example 3

[0037] The composition of a certain alkaline thallium-containing solution was Tl + 0.98 g / L, Zn 2+ 0.0005 g / L, Cd 2+ 0.028 g / L, F - 0.6 g / L, Cl - 2.12 g / L, and the pH of the solution was 9.5. 1 L of the solution was taken into the reaction tank and heated to 30°C. Then, ozone was introduced into the inlet part of the shearing machine, and the shearing machine was started to react for 45 min. The pH was controlled unchanged during the reaction, the ozone generation amount was 10 g / h, and the shearing rate was 5000 r / min. After the reaction, the filter residue and the thallium-removed solution were obtained by filtration.

[0038] The concentration of thallium in the solution after the reaction was reduced to 48.25 μg / L, and the concentration of Cl - was reduced to 1.42 g / L, and the concentrations of other ions remained essentially unchanged. It was calculated that the precipitation rate of thallium was 99.99%, the removal rate of Cl - was 33.95%, and the losses of other ions were all less than 1%.

[0039] Comparative Example 1

[0040] The other conditions of Comparative Example 1 were the same as those of Example 1, and the only difference was that the shearing strengthening device was not started in Comparative Example 1.

[0041] After the reaction, the concentration of thallium in the solution was reduced to 80 mg / L, and the concentrations of other ions remained basically unchanged. The removal rate of thallium was calculated to be 80.12%, and the removal rates of other ions were all less than 1.5%. In addition, thallium hydroxide and thallium trioxide coexisted in the product under this condition.

[0042] Comparative Example 2

[0043] The other conditions of Comparative Example 2 were the same as those of Example 1, except that the pH of the solution during the reaction was controlled at 0.5 ± 0.1.

[0044] After the reaction, the concentration of thallium in the solution was 0.40 g / L, and the concentrations of other ions remained basically unchanged. The removal rate of thallium was calculated to be 2.37%, and the removal rates of other ions were all less than 1.5%.

[0045] Comparative Example 3

[0046] The other conditions of Comparative Example 2 were the same as those of Example 1, except that air was used instead of ozone to participate in the reaction during the reaction.

[0047] After the reaction, the concentration of thallium in the solution was reduced to 0.4 g / L, and the concentrations of other ions remained basically unchanged. The removal rate of thallium was calculated to be 2.39%, and the removal rates of other ions were all less than 1.5%.

[0048] Reference Figure 1The device for selectively removing thallium from a thallium-containing solution provided by the embodiment comprises a reaction tank 3, a stirring paddle 5, a stirring motor 1, a shearing machine 8 and a circulating pump 10. The reaction tank 3 is a hollow tank body, and a feeding port 2 for injecting a solution is arranged on the top of the reaction tank 3. The bottom of the reaction tank 3 is connected to a discharge port 6 with a valve through a pipeline. In order to heat the solution, a heating pipe 4 is arranged on the inner wall of the reaction tank 3. The stirring paddle 5 in the embodiment is arranged in the reaction tank 3 and is driven to stir by the stirring motor 1 arranged outside the reaction tank 3 through a rotating shaft. The stirring paddle in the embodiment is a double-layer stirring paddle, and the number and size of the stirring paddle can be adjusted according to the size of the reaction tank 3 and other specific requirements in actual implementation. The shearing machine feeding port 7 of the shearing machine 8 is connected to the bottom of the reaction tank 3 through a pipeline with a valve, and forms a connection parallel to the discharge port 6, so that when shearing treatment is needed, the valve on the side of the discharge port 6 is closed, and the valve on the side of the shearing machine feeding port 7 is opened, so that the solution circulates between the reaction tank 3 and the shearing machine 8. When discharging is needed, the valve on the side of the shearing machine feeding port 7 is closed, and the valve on the side of the discharge port 6 is opened to discharge. In addition, the ozone inlet 9 connected to an external ozone source is also connected in parallel at the shearing machine feeding port 7, so that ozone is introduced into the solution during shearing treatment. The outlet of the shearing machine 8 is connected to the material circulating outlet 11 at the top of the reaction tank 3 through a pipeline to realize solution circulation. In addition, in order to compensate for the flow and head of the shearing machine and realize solution circulation, a circulating pump is arranged on the pipeline after the outlet of the shearing machine 8 in the embodiment, and the circulating pump 10 can also be arranged on the pipeline before the shearing machine feeding port 7 in actual use.

[0049] The external shearing circulation technology is adopted in the embodiment, and the shearing equipment is produced by Shanghai Xinle Machine Electrical Technology Co., Ltd. and the model is SZ1-1.5. Internal shearing can also be adopted in specific implementation, that is, a shearing device is arranged in the reaction tank 3 to realize shearing reaction.

Claims

1. A method for selectively removing thallium from a solution containing thallium, characterized by, It comprises the following steps: (1) heating the solution to a set temperature; (2) immediately after the solution reaches the set temperature, shearing treatment is performed on the solution, and ozone is introduced into the solution during shearing to achieve sufficient mixing of gas and liquid; when a predetermined time is reached, shearing and ozone introduction are stopped; (3) separation of the thallium-containing precipitate from the solution is achieved through liquid-solid separation.

2. The method for selectively removing thallium from a solution containing thallium according to claim 1, characterized in that, The set temperature in step (1) is 25-65 ℃.

3. The method for selectively removing thallium from a solution containing thallium according to claim 1, characterized in that, The shearing mode in step (2) is one or a combination of internal shearing and / or external shearing.

4. The method for selectively removing thallium from a solution containing thallium according to claim 3, characterized in that, The shearing rate in step (2) is 1000-10000 r / min.

5. The method for selectively removing thallium from a solution containing thallium according to claim 1 or 3 or 4, characterized in that, The pH during the reaction in step (2) is not lower than 0.

9.

6. The method for selectively removing thallium from a solution containing thallium according to claim 5, wherein When the thallium-containing solution contains Fe 2+ or Fe 3+ , in the solution system, if the cooperative removal of thallium and iron is to be achieved, the pH is controlled at 3.5~4.0; if the single removal of thallium is to be achieved, the pH is controlled at 0.9~2.

5.

7. The method for selectively removing thallium from a solution containing thallium according to claim 1 or 3 or 4, characterized in that, The ozone concentration in step (2) is above 1%; the ozone introduction rate is to increase the concentration of Tl in the solution. + Oxidized to Tl 3+ 0.5 to 10 times the theoretical amount required.

8. The method for selectively removing thallium from a solution containing thallium according to claim 1, wherein The flow rate of ozone introduced in step (2) is above 10 mL / min.

9. The method for selectively removing thallium from a solution containing thallium according to claim 1, wherein The predetermined time in step (2) is above 5 min.

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