Method for treating arsenic-containing wastewater in a tungsten smelting process

Abstract

The present application provides a kind of tungsten smelting process arsenic-containing wastewater treatment method, comprising (1) analyzing the arsenic concentration in wastewater, calculating the amount of arsenic in wastewater;(2) preparation of black tungsten slag slurry, add acid to make it dissolve, obtain black tungsten slag dissolution solution and a small amount of dissolved slag;(3) the black tungsten slag dissolution solution and a small amount of dissolved slag are reacted with wastewater, a small amount of acid is added to react, stirring, to obtain filtrate and waste residue.(4) after analyzing the arsenic concentration of filtrate, the arsenic removal rate can reach ≥90%.The present application utilizes the waste black tungsten slag generated in tungsten smelting to treat wastewater, changes waste into treasure, treats waste with waste, and the cost of arsenic removal is low and the operation is simple.

Description

Technical Field

[0001] This invention relates to the field of tungsten smelting technology, and in particular to a method for treating arsenic-containing wastewater in the tungsten smelting process. Background Technology

[0002] With the continuous exploitation of tungsten resources, the grade of usable tungsten ore is declining, and the content of impurities in various tungsten ores, including phosphorus, arsenic, and silicon, is increasing significantly. These elements are leached into the leachate along with the tungsten during the alkaline leaching process, becoming a serious source of arsenic pollution. The leachate undergoes ion exchange to remove impurities and transform it into an ammonium tungstate solution with low impurity content, which is then used in subsequent processes to produce APT (acetic acid petroleum ether). However, the arsenic pollutants in the leachate enter the wastewater along with the ion exchange solution during the tungsten ion exchange process. Generally, the concentration of arsenic in APT production wastewater can exceed the "Integrated Wastewater Discharge Standard" by several times. Arsenic and most of its compounds are highly toxic and have been included in the first batch of toxic and hazardous water pollutants by my country's Ministry of Environmental Protection.

[0003] Existing technologies for treating arsenic-containing wastewater have been extensively researched. The most commonly used industrial methods include: ion exchange, which is suitable for low-concentration arsenic-containing wastewater, but for complex arsenic-containing wastewater from tungsten smelting processes, the exchange resin is prone to failure and the cost is too high; adsorption, which uses appropriate adsorbents such as zeolite, clay minerals, and activated carbon, utilizing adsorption and ion exchange mechanisms to fix arsenic in the water onto the adsorbent surface through the interaction between arsenic compounds and the adsorbent, thereby achieving arsenic removal; this method is suitable for water bodies with low arsenic content, but its effectiveness is less stable when the wastewater volume is large; and coagulation sedimentation, which involves adding appropriate amounts of iron or aluminum salt coagulants to the water. The coagulants react with trivalent and pentavalent arsenic to form precipitates or complexes. This method is simple and widely used, but the amount of coagulant used is large, resulting in high costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of high cost, large volume of wastewater to be treated and complex operation, and to provide a method for treating arsenic-containing wastewater in the tungsten smelting process.

[0005] In this invention, the tungsten minerals are mainly wolframite and scheelite. Wolframite has the molecular formula (Fe, Mn)WO4, which is a homogeneous mixture of iron tungstate and manganese tungstate. Under high-temperature alkaline boiling, the WO3 in the wolframite is converted to sodium tungstate and enters the aqueous solution, while iron, manganese, and calcium are separated from the tungsten in the form of insoluble FeO, Ca(OH)2, and Mn(OH)2, etc., entering the slag phase. The waste wolframite slag is dissolved in acid to obtain iron salt, calcium salt, and manganese salt solutions. When mixed with alkaline wastewater from tungsten smelting, the forms of iron and manganese in the water vary with the pH of the solution. As the pH decreases to 7-9, the iron and manganese salts form colloids. At this point, arsenic anions form complexes with these colloids or adsorb onto the colloid surface, coagulating and precipitating. After clarification and filtration, the wastewater is discharged, thus achieving the effect of removing arsenic from the wastewater.

[0006] The specific plan is as follows:

[0007] A method for treating arsenic-containing wastewater from tungsten smelting processes includes the following steps:

[0008] (1) Take a certain amount of the arsenic-containing wastewater, analyze the arsenic concentration in the arsenic-containing wastewater, and calculate the mass of arsenic in the arsenic-containing wastewater;

[0009] Furthermore, the arsenic-containing wastewater in step (1) is obtained by treating tungsten ore with an alkaline boiling process, and the pH of the arsenic-containing wastewater is 7-14, preferably 7-10.

[0010] Furthermore, in step (1), the arsenic concentration is 0.01–1000 mg / L, preferably 0.01–500 mg / L, and more preferably 0.01–100 mg / L;

[0011] (2) Take 500 to 1000 times the mass of arsenic in the arsenic-containing wastewater, add water to the arsenic slag to prepare a slurry, add acid A while stirring to obtain a arsenic slag solution;

[0012] Preferably, the tungsten slag in step (2) is a solid waste obtained after tungsten ore has been treated by an alkaline boiling process at 100-400℃, and the tungsten slag contains at least one element among iron, manganese and calcium.

[0013] Preferably, in step (2), the slurry prepared by adding water to the black tungsten slag has a mass concentration of 10-40%.

[0014] Preferably, acid A includes at least one of nitric acid, hydrochloric acid, and sulfuric acid. Acid A is added until the pH of the solution is 0.5-2, at which point the addition of acid A is stopped to obtain a black tungsten slag solution.

[0015] (3) Mix the acidic black tungsten slag solution with the arsenic-containing wastewater in step (1), add acid B, measure the pH value of the mixture, stop adding acid B when the pH value of the mixture drops to 7-9, stir the reaction and filter to obtain filtrate and waste residue.

[0016] Preferably, the mixing and stirring time is 10 to 30 minutes;

[0017] Preferably, the acid B added in step (3) includes at least one of nitric acid, hydrochloric acid, and sulfuric acid.

[0018] Furthermore, the filtrate obtained after treatment by the above-mentioned method for treating arsenic-containing wastewater has an arsenic concentration of 0.01–0.50 mg / L.

[0019] Preferably, the arsenic concentration in the filtrate is 0.21–0.28 mg / L.

[0020] Furthermore, the filtrate obtained after treatment by the above-mentioned method for treating arsenic-containing wastewater has an arsenic removal rate of ≥90%.

[0021] Beneficial effects: This invention utilizes waste tungsten slag from tungsten smelting for arsenic removal from wastewater, turning waste into a valuable resource. It achieves low arsenic removal costs and simple operation, with an arsenic removal rate >90%, making it of great significance for the treatment of arsenic-containing wastewater. Detailed Implementation

[0022] The embodiments of the present invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0023] The tungsten slag used in the following examples is a solid waste obtained after tungsten ore has been treated by an alkaline boiling process at 100-400℃. The elemental composition of the tungsten slag is shown in Table 1.

[0024] Table 1. Composition of black tungsten slag

[0025]

[0026]

[0027] The wastewater used in the following examples is obtained by treating tungsten ore with an alkaline boiling process. The specific composition, pH and other indicators of the arsenic-containing wastewater are shown in Table 2.

[0028] The wastewater has a complex composition and no fixed indicators.

[0029] Example 1

[0030] (1) Take 1L of arsenic-containing wastewater with pH=10.3. The arsenic concentration in the arsenic-containing wastewater is 18.5mg / L. Calculate the mass of arsenic in the wastewater as 18.5mg.

[0031] (2) Take 18.5g of black tungsten slag (which is 1000 times the mass of arsenic in the arsenic-containing wastewater), add 50mL of water to the black tungsten slag to make a slurry, add hydrochloric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0032] (3) Slowly add the acidic black tungsten slag solution and a small amount of undissolved slag from step (2) to the alkaline wastewater from step (1) and stir to react. After the addition is complete, slowly add a small amount of hydrochloric acid. Use a pH meter to measure the pH value of the wastewater. Stop when the pH value of the wastewater drops to 7. After stirring and reacting for 10 minutes, filter to obtain filtrate and waste residue.

[0033] (4) The arsenic concentration of the obtained filtrate was 0.28 mg / L, and the arsenic removal rate was calculated to be 98.5%.

[0034] Example 2

[0035] (1) Take 1L of arsenic-containing wastewater with pH=14. Analyze the arsenic concentration in the wastewater and find it to be 5mg / L. Calculate the mass of arsenic in the wastewater to be 5mg.

[0036] (2) Take 2.5g of black tungsten slag (which is 500 times the mass of arsenic in the arsenic-containing wastewater), add 25mL of water to the black tungsten slag to make a slurry, add nitric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0037] (3) Slowly add the acidic black tungsten slag solution and a small amount of undissolved slag from step (2) to the alkaline wastewater from step (1) and stir to react. After the addition is complete, slowly add a small amount of sulfuric acid. Use a pH meter to measure the pH value of the wastewater. Stop when the pH value of the wastewater drops to 9. After stirring and reacting for 30 minutes, filter to obtain filtrate and waste residue.

[0038] (4) The arsenic concentration of the obtained filtrate was 0.26 mg / L, and the arsenic removal rate was calculated to be 94.8%.

[0039] Example 3

[0040] (1) Take 1L of arsenic-containing wastewater with pH=12.1. The arsenic concentration in the arsenic-containing wastewater is 2.3mg / L. Calculate the mass of arsenic in the wastewater as 2.3mg.

[0041] (2) Take 2g of black tungsten slag (which is 870 times the mass of arsenic in the arsenic-containing wastewater), add 10mL of water to the black tungsten slag to make a slurry, add hydrochloric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0042] (3) Slowly add the acidic black tungsten slag solution and a small amount of undissolved slag from step (2) to the alkaline wastewater from step (1) and stir to react. After the addition is complete, slowly add a small amount of hydrochloric acid. Use a pH meter to measure the pH value of the wastewater. Stop when the pH value of the wastewater drops to 8. After stirring and reacting for 20 minutes, filter to obtain filtrate and waste residue.

[0043] (4) The arsenic concentration of the obtained filtrate was 0.21 mg / L, and the arsenic removal rate was calculated to be 90.9%.

[0044] Comparative Example 1

[0045] (1) Take 1L of arsenic-containing wastewater with pH=14. The arsenic concentration in the wastewater is 10.1mg / L. Calculate the mass of arsenic in the wastewater as 10.1mg.

[0046] (2) Take 4g of black tungsten slag (which is 396 times the mass of arsenic in the arsenic-containing wastewater), add 10mL of water to the black tungsten slag to make a slurry, add hydrochloric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0047] (3) Slowly add the acidic black tungsten slag solution and a small amount of undissolved slag from step (2) to the alkaline wastewater from step (1) and stir to react. After the addition is complete, slowly add a small amount of hydrochloric acid. Use a pH meter to measure the pH value of the wastewater. Stop when the pH value of the wastewater drops to 9. After stirring and reacting for 30 minutes, filter to obtain filtrate and waste residue.

[0048] (4) The arsenic concentration of the obtained filtrate was 2.5 mg / L, and the arsenic removal rate was calculated to be 75.2%.

[0049] The results indicate that the arsenic removal rate of wastewater is related to the amount of black tungsten slag added; when the amount added is small, the arsenic removal rate is low.

[0050] Comparative Example 2

[0051] (1) Take 1L of arsenic-containing wastewater with pH=9.2. The arsenic concentration in the arsenic-containing wastewater is 8.6mg / L. Calculate the mass of arsenic in the wastewater as 8.6mg.

[0052] (2) Take 8g of black tungsten slag (which is 930 times the mass of arsenic in the arsenic-containing wastewater), add 40mL of water to the black tungsten slag to make a slurry, add hydrochloric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0053] (3) Slowly add the acidic black tungsten slag solution and a small amount of undissolved slag from step (2) to the alkaline wastewater from step (1) and stir to react. After the addition is complete, slowly add a small amount of hydrochloric acid. Use a pH meter to measure the pH value of the wastewater. Stop when the pH value of the wastewater drops to 6.5. After stirring and reacting for 30 minutes, filter to obtain filtrate and waste residue.

[0054] (4) The arsenic concentration of the obtained filtrate was 5.1 mg / L, and the arsenic removal rate was calculated to be 40.7%.

[0055] The results indicate that pH is very important in the process of arsenic removal from wastewater. When the reaction pH value is <7, the arsenic removal rate is low.

[0056] Comparative Example 3

[0057] A soluble arsenic salt solution was used to simulate an acidic wastewater containing arsenic (pH<7), with Example 1 serving as a control group. (1) 1L of arsenic-containing wastewater with pH=6.5 was taken, and the arsenic concentration in the wastewater was analyzed to be 18.5mg / L. The mass of arsenic in the wastewater was calculated to be 18.5mg.

[0058] (2) Take 18.5g of black tungsten slag (which is 1000 times the mass of arsenic in the arsenic-containing wastewater), add 50mL of water to the black tungsten slag to make a slurry, add hydrochloric acid to dissolve it while stirring, and stop adding acid when the pH value is 1, to obtain black tungsten slag solution and a small amount of undissolved slag.

[0059] (3) The acidic black tungsten slag solution and a small amount of undissolved slag in step (2) are slowly added to the acidic wastewater in step (1) and stirred to react. The pH value of the wastewater is measured to be 2.3 using a pH meter. After stirring for 10 minutes, the filtrate and waste residue are obtained by filtration.

[0060] (4) The arsenic concentration of the obtained filtrate was 18.3 mg / L.

[0061] The results showed that the proposed method had virtually no effect on arsenic removal. This was mainly because the acidic wastewater, when mixed with an acidic wollastonite slag dissolution solution, resulted in a solution with a pH of 2.3. Under these pH conditions, iron salts did not react with arsenic, thus failing to remove arsenic.

[0062] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0063] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for treating arsenic-containing wastewater, characterized in that, Includes the following steps: (1) Take a certain amount of the arsenic-containing wastewater, analyze the arsenic concentration in the arsenic-containing wastewater, and calculate the mass of arsenic in the arsenic-containing wastewater; (2) Take 500 to 1000 times the mass of arsenic in the arsenic-containing wastewater, add water to the arsenic slag to prepare a slurry, add acid A while stirring until the pH of the solution is 0.5-2, and then stop adding acid A to obtain arsenic slag solution; (3) Mix the black tungsten slag solution with the arsenic-containing wastewater in step (1), add acid B, measure the pH value of the mixture, stop adding acid B when the pH value of the mixture drops to 7, stir the reaction and filter to obtain filtrate and waste residue.

2. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The arsenic-containing wastewater in step (1) is obtained by treating tungsten ore with an alkaline boiling process, and the pH of the arsenic-containing wastewater is 7~14.

3. The method for treating arsenic-containing wastewater according to claim 2, characterized in that, The pH of the arsenic-containing wastewater is 7~10.

4. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, Step (1) The arsenic concentration is 0.01~1000 mg / L.

5. The method for treating arsenic-containing wastewater according to claim 4, characterized in that, Step (1) The arsenic concentration is 0.01~500 mg / L.

6. The method for treating arsenic-containing wastewater according to claim 4, characterized in that, Step (1) The arsenic concentration is 0.01~100 mg / L.

7. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The black tungsten slag mentioned in step (2) is a solid waste obtained after black tungsten ore has been treated by an alkaline boiling process at 100-400 ℃. The black tungsten slag contains at least one element among iron, manganese and calcium.

8. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The black tungsten slag described in step (2) is mixed with water to form a slurry with a mass concentration of 10-40%.

9. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The acid A mentioned in step (2) includes at least one of nitric acid, hydrochloric acid and sulfuric acid.

10. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The mixing time in step (3) is 10~30 min.

11. The method for treating arsenic-containing wastewater according to claim 1, characterized in that, The acid B added in step (3) includes at least one of nitric acid, hydrochloric acid and sulfuric acid.

12. The method for treating arsenic-containing wastewater according to any one of claims 1-11, characterized in that: The arsenic concentration in the filtrate in step (3) is 0.01~0.50 mg / L.

13. The method for treating arsenic-containing wastewater according to claim 12, characterized in that, The arsenic concentration in the filtrate in step (3) is 0.21~0.28 mg / L.

14. The method for treating arsenic-containing wastewater according to any one of claims 1-11, characterized in that: The arsenic removal rate of the filtrate in step (3) is ≥90%.

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