A method for treating vanadium-containing wastewater by using organic amine flue gas desulfurization residue

Abstract

The present application belongs to the technical field of solid waste resource and wastewater treatment, and particularly relates to a method for treating chromium-containing wastewater by using organic amine flue gas desulfurization residue. In the method, the organic amine flue gas desulfurization residue is used as a reducing agent, and the pH of the wastewater is controlled by phosphoric acid under acidic conditions to reduce hexavalent chromium to trivalent chromium and convert the desulfurization ash into melamine phosphate flame retardant material. The trivalent chromium is separated from the water in the form of precipitation under neutral conditions. The precipitate is calcined to obtain high-purity chromium sesquioxide powder. The residual ammonia nitrogen in the wastewater and the added magnesium salt and residual phosphoric acid in the water form struvite precipitation to remove the ammonia nitrogen in the water. The struvite can be used as a slow-release fertilizer raw material. The present application significantly reduces the treatment cost of vanadium extraction wastewater and flue gas desulfurization residue, fully recovers valuable elements, and realizes the resource utilization of flue gas desulfurization waste in a waste treatment mode.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and wastewater treatment technology, specifically relating to a method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag. Background Technology

[0002] Vanadium is a high-melting-point rare metal. Due to its excellent alloying properties and catalytic activity, it has become an important strategic resource, often referred to as a "metallic vitamin." In vanadium production, the sodium roasting-water leaching-acidic ammonium salt precipitation method is commonly used to separate vanadium from the leaching solution. The precipitate is then roasted to obtain vanadium pentoxide, and the supernatant is the vanadium extraction wastewater. Vanadium extraction wastewater is a typical high-concentration heavy metal wastewater, characterized by strong acidity and high concentrations of heavy metal pollutants. The main pollutants include hexavalent chromium (2000-5000 mg / L), vanadium (45 mg / L), and ammonia nitrogen (1500-3500 mg / L), posing a high risk of harm and exhibiting poor biodegradability. Chemical precipitation is commonly used to treat high-concentration chromium-containing wastewater, but this method consumes large amounts of reagents and is costly. Therefore, there is a need to develop efficient, stable, and low-cost treatment methods. Summary of the Invention

[0003] This invention provides a method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag. The method uses the organic amine flue gas desulfurization slag as a reducing agent, and phosphoric acid is used to control the pH of the wastewater under acidic conditions to reduce hexavalent chromium to trivalent chromium, while simultaneously converting the desulfurization ash into melamine phosphate flame retardant material. Trivalent chromium is separated from the water as a precipitate under neutral conditions. The precipitate is calcined to obtain high-purity chromium trioxide powder. Residual ammonia nitrogen in the wastewater, along with added magnesium salts and residual phosphoric acid, forms struvite precipitate, thereby reducing ammonia nitrogen levels in the water. Struvite can be used as a raw material for slow-release fertilizer. This invention significantly reduces the cost of treating vanadium extraction wastewater and flue gas desulfurization slag, fully recovers valuable elements, and achieves resource utilization of flue gas desulfurization waste through a waste-to-waste approach.

[0004] 1. A method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag, characterized by the following steps: (1) Reduction stage: Vanadium extraction wastewater is introduced into the reduction tank and the wastewater temperature is kept not lower than 90℃. Desulfurization slag with a mass of about 5-15 times that of hexavalent chromium in the wastewater is added to the tank. The mixture is stirred continuously and the pH is adjusted to 1.0-3.0 with phosphoric acid. The mixture is stirred continuously for 1.0-3.0h and allowed to stand for 0.5-1.0h to settle. The supernatant and precipitate are separated by filtration. The melamine phosphate obtained after washing and drying the precipitate can be used to prepare flame retardant materials. The supernatant enters the neutralization sedimentation tank. (2) Neutralization and precipitation stage: The supernatant is introduced into the neutralization and precipitation tank, the pH is adjusted to 7.0~8.0 and stirred continuously for 10~30 min, and allowed to settle for 0.5~3.0 h. The supernatant and the precipitate are separated by filtration. The precipitate is washed three times with clean water and dried at 80℃. The dried precipitate is ground and crushed, and then calcined at 900~1200℃ for 2.0 h to obtain chromium trioxide. The supernatant enters the ammonia nitrogen precipitation tank. (3) Ammonia nitrogen precipitation stage: Add easily soluble magnesium salts to the ammonia nitrogen precipitation tank at 1.1 to 1.3 times the molar amount of ammonia nitrogen in the water, adjust the pH to 8.0 to 11.0, stir continuously for 5 to 30 minutes, let it stand for 10 to 30 minutes to settle, filter and separate the supernatant from the precipitate, the precipitate is struvite, and the supernatant is mixed with domestic sewage for further treatment.

[0005] The flue gas desulfurization residue refers to the desulfurizing agent that has become ineffective after fully circulating and absorbing sulfur dioxide in the flue gas using melamine as a desulfurizing agent. Its main components are melamine sulfite and a small amount of melamine sulfate and unreacted melamine.

[0006] The vanadium extraction wastewater is generated from the sodium roasting, water leaching vanadium extraction, and acidic ammonium salt precipitation processes. The main pollutants have a hexavalent chromium concentration of 2000~5000 mg / L, a vanadium concentration of 45 mg / L, and an ammonia nitrogen concentration of 1500~3500 mg / L, and the temperature is approximately 95℃.

[0007] During the reduction stage, the temperature is not lower than 90℃, and the amount of organic amine flue gas desulfurization residue added is 5-15 times the mass of hexavalent chromium in the wastewater; the pH of the wastewater needs to be adjusted to 1.0-3.0 with phosphoric acid, and the reaction time is 1.0-3.0h.

[0008] During the reduction stage, the desulfurization residue of the organic amine flue gas is converted into melamine phosphate while reducing hexavalent chromium, which can be used to prepare flame retardant materials.

[0009] During the ammonia nitrogen precipitation stage, magnesium salt can be added at 1.1 to 1.3 times the molar amount of ammonia nitrogen in the water; no additional phosphorus is required. Attached Figure Description

[0010] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0011] The methods and techniques described in this invention are illustrated below through examples, but in practical applications, they are not limited to these examples. Example 1

[0012] This embodiment describes a method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag, characterized by the following steps: (1) Reduction stage: 200 mL of vanadium extraction wastewater (hexavalent chromium concentration of 3750 mg / L, total chromium concentration of 3980 mg / L, vanadium concentration of 57 mg / L, and ammonia nitrogen concentration of 2650 mg / L) was introduced into the reduction tank. The temperature was maintained at 90℃ by water bath heating. Desulfurization residue with a mass of about 10 times that of hexavalent chromium in the wastewater was added to the tank. The mixture was stirred continuously and the pH was adjusted to 2.5 with phosphoric acid. The mixture was stirred continuously for 2.0 h and allowed to settle for 0.5 h. The supernatant and precipitate were separated by filtration. The precipitate was washed and dried to obtain melamine phosphate. The supernatant was then introduced into the neutralization sedimentation tank. (2) Neutralization and precipitation stage: The supernatant is introduced into the neutralization and precipitation tank, the pH is adjusted to 7.5, and the mixture is stirred for 20 min and allowed to stand for 0.5 h to settle. The supernatant and the precipitate are separated by filtration. The precipitate is washed three times with clean water and then dried at 80°C. The dried precipitate is ground and crushed and then calcined at 900°C for 2.0 h to obtain chromium trioxide (83%). The supernatant is then introduced into the ammonia nitrogen precipitation tank. (3) Ammonia nitrogen precipitation stage: Add easily soluble magnesium salt to the ammonia nitrogen precipitation tank at 1.3 times the molar amount of ammonia nitrogen in the water, adjust the pH to 9.0, stir continuously for 5 minutes, let it stand for 10 minutes to settle, filter and separate the supernatant from the precipitate, the precipitate is struvite, and the supernatant is mixed with domestic sewage for further treatment. The treated wastewater contained 0.27 mg / L hexavalent chromium, 0.35 mg / L total chromium, 0.26 mg / L vanadium, 250 mg / L ammonia nitrogen, and 0.5 mg / L total phosphorus. Example 2

[0013] This embodiment describes a method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag, characterized by the following steps: (1) Reduction stage: 200 mL of vanadium extraction wastewater (hexavalent chromium concentration of 3500 mg / L, total chromium concentration of 3740 mg / L, vanadium concentration of 39 mg / L, and ammonia nitrogen concentration of 2300 mg / L) was introduced into the reduction tank. The temperature was maintained at 90℃ by water bath heating. Desulfurization residue with a mass of about 15 times that of hexavalent chromium in the wastewater was added to the tank. The mixture was stirred continuously and the pH was adjusted to 2.0 with phosphoric acid. The mixture was stirred continuously for 2.0 h and allowed to settle for 0.5 h. The supernatant and precipitate were separated by filtration. The precipitate was washed and dried to obtain melamine phosphate. The supernatant was then introduced into the neutralization sedimentation tank. (2) Neutralization and precipitation stage: The supernatant is introduced into the neutralization and precipitation tank, the pH is adjusted to 7.5, and the mixture is stirred for 25 min and allowed to stand for 0.5 h to settle. The supernatant and the precipitate are separated by filtration. The precipitate is washed three times with clean water and then dried at 80°C. The dried precipitate is ground and crushed and then calcined at 900°C for 2.0 h to obtain chromium trioxide (83%). The supernatant is then introduced into the ammonia nitrogen precipitation tank. (3) Ammonia nitrogen precipitation stage: Add easily soluble magnesium salt to the ammonia nitrogen precipitation tank at 1.2 times the molar amount of ammonia nitrogen in the water, adjust the pH to 9.05, stir continuously for 15 minutes, let it stand for 15 minutes to settle, filter and separate the supernatant from the precipitate, the precipitate is struvite, and the supernatant is mixed with domestic sewage for further treatment. The treated wastewater contained 0.22 mg / L hexavalent chromium, 0.29 mg / L total chromium, 0.17 mg / L vanadium, 200 mg / L ammonia nitrogen, and 0.47 mg / L total phosphorus.

[0014] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag, characterized in that... Follow these steps: (1) Reduction stage: Vanadium extraction wastewater is introduced into the reduction tank and the wastewater temperature is kept not lower than 90℃. Desulfurization slag with a mass of 5-15 times that of hexavalent chromium in the wastewater is added to the tank. The mixture is stirred continuously and the pH is adjusted to 1.0-3.0 with phosphoric acid. The mixture is stirred continuously for 1.0-3.0 h and allowed to stand for 0.5-1.0 h. The supernatant and precipitate are separated by filtration. The melamine phosphate obtained after washing and drying the precipitate can be used to prepare flame retardant materials. The supernatant enters the neutralization precipitation tank. (2) Neutralization and precipitation stage: The supernatant is introduced into the neutralization and precipitation tank, the pH is adjusted to 7.0-8.0 and stirred continuously for 10-30 min, and the sediment is allowed to stand for 0.5-3.0 h. The supernatant and sediment are separated by filtration. The sediment is washed three times with clean water and dried at 80℃. The dried sediment is ground and crushed, and then calcined at 900-1200℃ for 2.0 h to obtain chromium trioxide. The supernatant enters the ammonia nitrogen precipitation tank. (3) Ammonia nitrogen precipitation stage: Add easily soluble magnesium salts to the ammonia nitrogen precipitation tank at 1.1-1.3 times the molar amount of ammonia nitrogen in the water, adjust the pH to 8.0-11.0, stir continuously for 5-30 min, let it stand for 10-30 min to settle, filter and separate the supernatant from the precipitate, the precipitate is struvite, and the supernatant is mixed with domestic sewage for further treatment. Flue gas desulfurization residue refers to the desulfurizing agent that has become ineffective after fully circulating and absorbing sulfur dioxide in the flue gas using melamine as a desulfurizing agent. Its main components are melamine sulfite and a small amount of melamine sulfate and unreacted melamine. The vanadium extraction wastewater is generated from sodium roasting, water leaching vanadium extraction, and acidic ammonium salt precipitation processes. The concentration of hexavalent chromium is 2000-5000 mg / L, the concentration of vanadium is 45 mg / L, the concentration of ammonia nitrogen is 1500-3500 mg / L, and the temperature is 95℃.

2. The method for treating vanadium extraction wastewater using organic amine flue gas desulfurization slag according to claim 1, characterized in that... During the ammonia nitrogen precipitation stage, magnesium salt can be added at 1.1-1.3 times the molar amount of ammonia nitrogen in the water; no additional phosphorus is required.

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