Method for deeply removing fluorine and chlorine in lead-zinc smelting wastewater

Abstract

The invention discloses a method for deeply removing fluorine and chlorine in lead-zinc smelting wastewater, which is characterized in that the method for deeply removing fluorine and chlorine in lead-zinc smelting wastewater comprises the steps of defluorination and neutralization dechlorination, and specifically comprises the following steps: adding an aluminum salt defluorination agent into lead-zinc smelting wastewater to be treated for defluorination to obtain defluorination liquid a and defluorination residue b, the defluorination slag b enters a slag yard to be piled up; zinc oxide powder is added into the defluorinated liquid a for a neutralization reaction until the pH value of the solution is 2-3, a neutralized liquid c and neutralized slag d are obtained, and the neutralized slag d is returned to lead pyrometallurgy; and dechlorinating the neutralized liquid c by adopting a molecular sieve to obtain a purified liquid e and high-chlorine wastewater f, and introducing the high-chlorine wastewater f into a lead smelting water-quenched slag flushing step. According to the method, fluorine and chlorine can be deeply removed from the lead and zinc smelting wastewater in a grading manner, the fluorine removal rate reaches 82% or above, the chlorine removal rate reaches 95% or above, the fluorine content of the solution is reduced to 120 mg / l or below, the chlorine content is reduced to 235 mg / l, and the conditions of lead and zinc smelting production and recycling are completely met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for deeply removing fluorine and chlorine from lead and zinc smelting wastewater. Background Art

[0002] The lead and zinc smelting production process produces a large amount of acidic wastewater, which contains a variety of impurities, such as arsenic, fluorine, chlorine, etc. These impurities are highly polluting to humans and nature. The wastewater needs to be deeply purified to remove fluorine and chlorine before it can be returned to the process for reuse. The fluorine and chlorine content in the wastewater is relatively high. Fluorine and chloride ions are highly corrosive, causing equipment corrosion, resulting in high equipment maintenance costs, and even affecting the organization of normal production. The high chlorine content in the new electrolytic solution will corrode the anode and reduce the service life of the anode, ultimately leading to reduced quality of zinc ingot products. In addition, the chloride ions in the acidic solution can enhance the corrosion ability of the acid solution, and can even corrode and destroy the passivation film on the surface of alloys, stainless steel and metals, causing corrosion to metallurgical equipment and metal parts, and frequent replacement of equipment and parts, increasing production costs. Therefore, it is very necessary to develop a method that can solve the above technical problems. Summary of the invention

[0003] The object of the present invention is to provide a method for deeply removing fluorine and chlorine from lead and zinc smelting wastewater.

[0004] The object of the present invention is achieved by comprising the steps of defluorination, neutralization and dechlorination, specifically comprising: A. Defluorination: Aluminum salt defluorinating agent is added to the lead-zinc smelting wastewater to be treated for defluorination to obtain defluorinated liquid a and defluorinated slag b, and the defluorinated slag b is stored in the slag yard; The aluminum salt defluorination agent is iron-free aluminum sulfate (purity is 99.99%) + polyacrylamide (flocculant); Iron-free aluminum sulfate: The basic component is Al2(SO4)3.2H2O, the iron content is extremely low (usually less than 0.005%), the solid product is white granular or blocky, the chemical properties are stable, and it is not easy to decompose and oxidize. After dissolving in water, it can quickly hydrolyze to produce aluminum hydroxide colloid, and the reaction speed with fluoride ions is relatively fast, which can achieve a good defluorination effect in a short time. No iron ions are introduced when treating the solution, and the color and odor of the water are less affected, and it will not cause water discoloration or produce odor.

[0005] Ordinary aluminum sulfate: The main component is Al2(SO4)3.XH2O, which contains a certain amount of iron. It contains low-valent iron salts and has a light green color. The surface turns yellow due to the oxidation of low-valent iron salts, and the stability is relatively poor. Because it contains iron elements, its hydrolysis process is relatively complicated. In addition to the hydrolysis of aluminum ions, iron ions will also undergo hydrolysis reactions, which may affect the formation speed and structure of aluminum hydroxide colloids, resulting in a slower reaction speed with fluoride ions. A longer reaction time is required to achieve a better defluorination effect. Because it contains iron elements, the treated water will have a certain color, and when the iron ion content is high, it will produce a rusty smell.

[0006] Experimental studies have shown that when the same amount of iron-free aluminum sulfate and ordinary aluminum sulfate are used to remove fluorine from the solution, the removal rate of iron-free aluminum sulfate can reach more than 75%, while the removal rate of ordinary aluminum sulfate can only reach more than 40%.

[0007] B. Neutralization: Add zinc oxide powder to the defluorinated liquid a for neutralization reaction until the pH value of the solution is 2-3 to obtain neutralized liquid c and neutralized slag d, and the neutralized slag d is returned to lead pyrometallurgy; C. Dechlorination: The neutralized liquid c is dechlorinated by molecular sieve to obtain purified liquid e and high-chlorine wastewater f, and the high-chlorine wastewater f enters the dry water quenching and slag flushing step.

[0008] The specific operations are as follows: The process includes the following steps: 1) removing fluorine from the solution with an aluminum salt defluorinating agent; 2) adjusting the pH value of the solution with zinc oxide powder; 3) removing chlorine from the solution with a molecular sieve physical method, wherein: Aluminum salt defluorination agent removes fluorine from the solution: Aluminum salt defluorination agent is added to the lead-zinc smelting wastewater containing acid: 5-6g / l, fluorine: 950-1150mg / l, chlorine: 3950-4800mg / l, Zn: 0.5-0.8g / l. The aluminum salt defluorination agent is 20-25g / m 3 , the temperature is controlled at 25-30℃, the stirring paddle is turned on, the time is controlled at 0.8-1h, the fluorine removal rate reaches more than 82%, and the fluorine content of the solution is reduced to below 120mg / l.

[0009] The principle of defluorination by aluminum salt defluorination agent: aluminum salt is de-enriched and added to the solution, and then the aluminum salt is hydrolyzed to produce [Al(H2O)6] 3+ [Al(OH),(H2O)5] 2+ [Al2(OH)2, (H2O)8] 4+ 、[Al3(OH)5(H2O)9] 4+ 、[Al3(OH)4] 5+ 、[Al7(OH) 17 ] 4+ 、[Al 13 O4(OH) 17 ]7+ Various high-valent cations such as F2+ and F3+ can be adsorbed from zinc sulfate solution by electrostatic action. - The hydrolysis product of aluminum sulfate, Al(OH)3, is a colloid with a large surface area and can adsorb F - In addition, F in the solution - With the addition of Al 3+ A chemical reaction occurs to form a compound composed of the elements F and Al.

[0010] Positively charged aluminum ions have a strong electrical neutralization and adsorption effect on fluoride ions with small ion radius and strong negative charge, which causes the fluorine in the solution to be electrically neutralized and then collide with each other under the action of Brownian motion. The adsorption capacity of aluminum hydroxide is better than that of flocculants, which cause them to flocculate together to form a precipitate.

[0011] Zinc oxide powder is used to adjust the pH value of the solution: the defluorinated liquid is added with zinc oxide powder to adjust the pH value of the solution. The end point pH value is controlled between 2 and 3. The amount of zinc oxide powder added is 5 to 7 g / l.

[0012] Molecular sieve physical method to remove chlorine from the solution: take the volume of the defluorinated solution and pass it through the molecular sieve dechlorination system, control the solution endpoint pH value at 2.0-3.0, control the time for 36-40h, and achieve a solution chlorine removal rate of more than 95%, and the chlorine in the solution is reduced to below 235mg / l. The fluorine and chlorine values ​​of the treated water fully meet the conditions for reuse in lead and zinc smelting production.

[0013] The principle of molecular sieve physical method to remove chlorine from solution: The working principle of molecular sieve is based on the characteristics of molecular size, shape and polarity, and separation and screening are achieved through the diffusion and adsorption of molecules in the pores. When the mixture passes through the molecular sieve, the molecules interact with the molecular sieve according to their size and hydrophilic and hydrophobic properties. Smaller molecules can diffuse freely in the pores of the molecular sieve and thus pass the screening process. Larger molecules cannot enter the pores due to the limitation of the pore size and are therefore excluded.

[0014] The physical separation principle of molecular sieve is to separate large molecular weight zinc sulfate from small molecular weight chlorine. It is a purely physical separation. The process does not introduce impurities, does not bring new hazards to zinc electrolysis, does not affect product quality, does not generate new calcium sulfate hazardous waste residue, is easy to operate, and has cost advantages compared with other methods.

[0015] The hydrolysis of iron-free aluminum sulfate will also generate a series of aluminum hydroxide colloids with flocculation effect. These colloidal particles have a large specific surface area and can adsorb fluoride ion complexes and other impurity particles in the solution. As the colloidal particles continue to aggregate, they are combined with flocculants for flocculation and coprecipitation to form larger flocs, which eventually settle down, thereby achieving the separation of fluoride ions from the solution.

[0016] Iron-free aluminum sulfate: The basic component is Al2(SO4)3.2H2O, the iron content is extremely low (usually less than 0.005%), the solid product is white granular or blocky, the chemical properties are stable, and it is not easy to decompose and oxidize. After dissolving in water, it can quickly hydrolyze to produce aluminum hydroxide colloid, and the reaction speed with fluoride ions is relatively fast, which can achieve a good defluorination effect in a short time. No iron ions are introduced when treating the solution, and the color and odor of the water are less affected, and it will not cause water discoloration or produce odor.

[0017] Ordinary aluminum sulfate: The main component is Al2(SO4)3.XH2O, which contains a certain amount of iron. It contains low-valent iron salts and has a light green color. The surface turns yellow due to the oxidation of low-valent iron salts, and the stability is relatively poor. Because it contains iron elements, its hydrolysis process is relatively complicated. In addition to the hydrolysis of aluminum ions, iron ions will also undergo hydrolysis reactions, which may affect the formation speed and structure of aluminum hydroxide colloids, resulting in a slower reaction speed with fluoride ions. A longer reaction time is required to achieve a better defluorination effect. Because it contains iron elements, the treated water will have a certain color, and when the iron ion content is high, it will produce a rusty smell.

[0018] The present invention adopts a method combining aluminum salt defluorinating agent + molecular sieve physical and chemical methods to achieve graded and deep removal of fluorine and chlorine from lead-zinc smelting wastewater, with a fluorine removal rate of more than 82%, a chlorine removal rate of more than 95%, a fluorine content in the solution reduced to less than 120 mg / l, and a chlorine content reduced to 235 mg / l, fully meeting the conditions for lead-zinc smelting production reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0021] The method for deep removal of fluorine and chlorine from lead and zinc smelting wastewater of the present invention comprises defluorination, neutralization and dechlorination steps, specifically comprising: A. Defluorination: Aluminum salt defluorinating agent is added to the lead-zinc smelting wastewater to be treated for defluorination to obtain defluorinated liquid a and defluorinated slag b, and the defluorinated slag b is stored in the slag yard; The aluminum salt defluorination agent is iron-free aluminum sulfate (purity is 99.99%) + polyacrylamide (flocculant); Iron-free aluminum sulfate: The basic component is Al2(SO4)3.2H2O, the iron content is extremely low (usually less than 0.005%), the solid product is white granular or blocky, the chemical properties are stable, and it is not easy to decompose and oxidize. After dissolving in water, it can quickly hydrolyze to produce aluminum hydroxide colloid, and the reaction speed with fluoride ions is relatively fast, which can achieve a good defluorination effect in a short time. No iron ions are introduced when treating the solution, and the color and odor of the water are less affected, and it will not cause water discoloration or produce odor.

[0022] Ordinary aluminum sulfate: The main component is Al2(SO4)3.XH2O, which contains a certain amount of iron. It contains low-valent iron salts and has a light green color. The surface turns yellow due to the oxidation of low-valent iron salts, and the stability is relatively poor. Because it contains iron elements, its hydrolysis process is relatively complicated. In addition to the hydrolysis of aluminum ions, iron ions will also undergo hydrolysis reactions, which may affect the formation speed and structure of aluminum hydroxide colloids, resulting in a slower reaction speed with fluoride ions. A longer reaction time is required to achieve a better defluorination effect. Because it contains iron elements, the treated water will have a certain color, and when the iron ion content is high, it will produce a rusty smell.

[0023] Experimental studies have shown that when the same amount of iron-free aluminum sulfate and ordinary aluminum sulfate are used to remove fluorine from the solution, the removal rate of iron-free aluminum sulfate can reach more than 75%, while the removal rate of ordinary aluminum sulfate can only reach more than 40%.

[0024] B. Neutralization: Add zinc oxide powder to the defluorinated liquid a for neutralization reaction until the pH value of the solution is 2-3 to obtain neutralized liquid c and neutralized slag d, and the neutralized slag d is returned to lead pyrometallurgy; C. Dechlorination: The neutralized liquid c is dechlorinated by molecular sieve to obtain purified liquid e and high-chlorine wastewater f, and the high-chlorine wastewater f enters the dry water quenching and slag flushing step.

[0025] The amount of aluminum salt defluorinating agent added in step A is 20~25g / m 3 .

[0026] The defluorination temperature in step A is 25~30℃.

[0027] The present invention is further described below with specific implementation cases: Example 1

[0028] Aluminum salt defluorination agent removes fluorine from the solution: Aluminum salt defluorination agent is added to the lead and zinc smelting wastewater containing acid: 5g / l, fluorine: 950mg / l, chlorine: 3950mg / l, Zn: 0.5g / l, and iron-free aluminum sulfate is added 20g / m 3, add 1.5 ml of polyacrylamide (agent No. 3) (concentration 2 g / l), control the temperature at 25°C, turn on the stirring paddle, control the time for 0.8 h, the fluorine removal rate reaches 85%, and the fluorine content of the solution is reduced to 120 mg / l.

[0029] Zinc oxide powder is used to adjust the pH value of the solution: the defluorinated liquid is added with zinc oxide powder to adjust the pH value of the solution. The end point pH value is controlled at 2.0, and the amount of zinc oxide powder added is 5g / l.

[0030] Molecular sieve physical method to remove chlorine from the solution: the volume of the defluorinated solution is passed through the molecular sieve dechlorination system, the solution endpoint pH value is controlled at 2.0, the control time is 36h, the solution chlorine removal rate reaches 95%, and the chlorine in the solution is reduced to 235mg / l. The fluorine and chlorine values ​​of the treated water fully meet the conditions for lead and zinc smelting production reuse.

[0031] Example 2

[0032] Aluminum salt defluorination agent removes fluorine from the solution: Aluminum salt defluorination agent is added to the lead and zinc smelting wastewater containing acid: 6g / l, fluorine: 1000mg / l, chlorine: 4000mg / l, Zn: 0.6g / l, and iron-free aluminum sulfate is added 25g / m 3 , add 2 ml of polyacrylamide (agent No. 3) (concentration 2 g / l), control the temperature at 25°C, turn on the stirring paddle, control the time for 0.9 h, the fluorine removal rate reaches 86%, and the fluorine content of the solution is reduced to 115 mg / l.

[0033] Zinc oxide powder is used to adjust the pH value of the solution: the defluorinated liquid is added with zinc oxide powder to adjust the pH value of the solution. The end point pH value is controlled at 2.5, and the amount of zinc oxide powder added is 6g / l.

[0034] Molecular sieve physical method to remove chlorine from the solution: the volume of the defluorinated solution is passed through the molecular sieve dechlorination system, the solution endpoint pH value is controlled at 2.5, the control time is 38h, the solution chlorine removal rate reaches 97%, and the chlorine in the solution is reduced to 215mg / l. The fluorine and chlorine values ​​of the treated water fully meet the conditions for lead and zinc smelting production reuse.

[0035] Example 3

[0036] Aluminum salt defluorination agent removes fluorine from the solution: Aluminum salt defluorination agent is added to the lead and zinc smelting wastewater containing acid: 7g / l, fluorine: 1150mg / l, chlorine: 4800mg / l, Zn: 0.58g / l, and iron-free aluminum sulfate is added 25g / m 3 , add 2.5 ml of polyacrylamide (agent No. 3) (concentration 2 g / l), control the temperature at 30°C, turn on the stirring paddle, control the time for 1 hour, the fluorine removal rate reaches 87%, and the fluorine content of the solution is reduced to 115 mg / l.

[0037] Zinc oxide powder is used to adjust the pH value of the solution: the defluorinated liquid is added with zinc oxide powder to adjust the pH value of the solution. The end point pH value is controlled at 3.0, and the amount of zinc oxide powder added is 7g / l.

[0038] Molecular sieve physical method to remove chlorine from the solution: the volume of the defluorinated solution is passed through the molecular sieve dechlorination system, the solution endpoint pH value is controlled at 3.0, the control time is 40h, and the solution chlorine removal rate reaches 97.5%. The chlorine in the solution is reduced to 205mg / l. The fluorine and chlorine values ​​of the treated water fully meet the conditions for lead and zinc smelting production reuse.

Claims

1. A method for deeply removing fluorine and chlorine from lead and zinc smelting wastewater, characterized in that: The method for deeply removing fluorine and chlorine from lead and zinc smelting wastewater includes defluorination, neutralization and dechlorination steps, specifically including: A. Defluorination: Aluminum salt defluorinating agent is added to the lead-zinc smelting wastewater to be treated for defluorination to obtain defluorinated liquid a and defluorinated slag b, and the defluorinated slag b is stored in the slag yard; The aluminum salt defluorination agent is composed of iron-free aluminum sulfate and polyacrylamide; B. Neutralization: Add zinc oxide powder to the defluorinated liquid a for neutralization reaction until the pH value of the solution is 2-3 to obtain neutralized liquid c and neutralized slag d, and the neutralized slag d is returned to lead pyrometallurgy; C. Dechlorination: The neutralized liquid c is dechlorinated by molecular sieve to obtain purified liquid e and high-chlorine wastewater f, and the high-chlorine wastewater f enters the dry water quenching and slag flushing step.

2. The method for deep removal of fluorine and chlorine from lead and zinc smelting wastewater according to claim 1, characterized in that: The amount of aluminum salt defluorinating agent added in step A is 20~25g / m 3 .

3. The method for deep removal of fluorine and chlorine from lead and zinc smelting wastewater according to claim 1, characterized in that: The defluorination temperature in step A is 25-30°C.

4. The method for deep removal of fluorine and chlorine from lead and zinc smelting wastewater according to claim 1, characterized in that: The mass ratio of the iron-free aluminum sulfate and polyacrylamide is (1-3): (1-3).

5. The method for deep removal of fluorine and chlorine from lead and zinc smelting wastewater according to claim 1 or 4, characterized in that: The mass ratio of the iron-free aluminum sulfate and polyacrylamide is 1:1.

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