Treatment method of high-concentration ammonia-containing wastewater generated in smelting of rare and precious metals

Abstract

The invention relates to a rare and noble metal smelting high-concentration ammonia-containing wastewater treatment method which comprises the following steps: adding concentrated sulfuric acid into wastewater to be treated, and adjusting the pH value to 9-10.5; adding sodium hydrogen phosphate into the solution obtained in the step S1, and stirring until the sodium hydrogen phosphate is dissolved; adding magnesium chloride into the solution obtained in the step S2, and stirring; and filtering the solution obtained in the step S3. According to the method, ammonia nitrogen in the ammonia-containing wastewater is converted into the fertilizer, the environmental protection and economic benefits of a smeltery are improved, the method is convenient to operate, high in automation degree, safe and reliable, the method can be carried out by utilizing original equipment without newly adding equipment, no wastewater and waste residues are generated, the ammonia-containing wastewater realizes whole-process circulation, and the method is suitable for industrial production. And the problem that ammonia nitrogen exceeds the standard in the rare and noble metal wastewater treatment process is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of disposal of high-concentration ammonia-containing wastewater in rare and precious metal smelting, and particularly relates to a method for treating high-concentration ammonia-containing wastewater in rare and precious metal smelting. Background Art

[0002] Some copper smelters adopt the processes of sulfation roasting + acid leaching for copper separation + chlorination for gold separation + ammonia leaching for silver separation to comprehensively recover rare and precious metals in copper anode slime. During the ammonia leaching for silver separation, silver is converted into silver ammonia complex ions and enters the solution, thus realizing the separation of silver from impurity elements; after the silver ammonia solution is reduced by hydrazine hydrate, crude silver powder is formed, and a large amount of ammonia still remains in the filtered solution and enters the wastewater. A large amount of ammonia nitrogen can cause eutrophication of water bodies, result in black and smelly water bodies, damage the ecological balance, and ultimately endanger the health of animals and humans. In severe cases, it will endanger human life. Therefore, it is necessary to dispose of high-concentration ammonia-containing wastewater in rare and precious metal smelting and recover the ammonia nitrogen therein.

[0003] Currently, the air oxidation method is generally used to treat high-concentration ammonia-containing wastewater in rare and precious metal smelting. During the treatment process, part of the ammonia gas escapes, resulting in a poor on-site environment, and the removal rate of ammonia nitrogen can only reach 20 - 28%, with poor effects and it is difficult to meet the environmental protection requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for treating high-concentration ammonia-containing wastewater in rare and precious metal smelting, which can optimize the on-site environment for treating high-concentration ammonia-containing wastewater during the rare and precious metal smelting process, reduce ammonia escape, and be able to recover ammonia nitrogen.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for treating high-concentration ammonia-containing wastewater in rare and precious metal smelting, comprising the following steps:

[0007] S1. Add concentrated sulfuric acid to the wastewater to be treated and adjust the pH value to 9 - 10.5;

[0008] S2. Add sodium hydrogen phosphate to the solution obtained in step S1 and stir until the sodium hydrogen phosphate is dissolved;

[0009] S3. Add magnesium chloride to the solution obtained in step S2 and stir;

[0010] S4. Filter the solution obtained in step S3, and the filter residue becomes magnesium ammonium phosphate fertilizer, and the filtrate is sent back for reuse in the rare and precious metal recovery process.

[0011] Preferably, the addition amount of sodium hydrogen phosphate in step S2 is 16 - 19 times the weight of ammonia in the wastewater to be treated.

[0012] Preferably, the addition amount of magnesium chloride in step S3 is 11 to 13.5 times the weight of ammonia in the wastewater to be treated.

[0013] Preferably, the stirring time in step S3 is 15 to 30 min.

[0014] In the present invention, by converting ammonia nitrogen in ammonia-containing wastewater into fertilizer, the environmental protection and economic benefits of the smelter are improved. This method has convenient process operation, high automation, is safe and reliable, and can be carried out using the original equipment without adding new equipment. There is no generation of wastewater and waste residue, and the ammonia-containing wastewater realizes full-process circulation, reducing the problem of ammonia nitrogen exceeding the standard caused during the disposal of dilute precious metal wastewater.

[0015] Since the dilute precious metal high-concentration ammonia-containing wastewater is alkaline, in the present invention, concentrated sulfuric acid is used to neutralize the free ammonia in the wastewater, converting it into ammonium ions NH4+, enriching the ammonium ions in the ammonia-containing wastewater, providing raw materials for subsequent reactions, and during the production process of magnesium ammonium phosphate, the released H+ is neutralized by the alkaline environment, which can promote the forward progress of the reaction. Specific Embodiments

[0016] The following further describes the present invention in conjunction with specific embodiments.

[0017] Example 1:

[0018] A method for treating dilute precious metal smelting high-concentration ammonia-containing wastewater includes the following steps:

[0019] S1. Under normal temperature conditions, that is, at 25°C, 5 L of dilute precious metal high-concentration ammonia-containing wastewater is taken and added to a reaction tank, and 98% concentrated sulfuric acid is slowly added to adjust the pH value to 9.8. By using concentrated sulfuric acid to neutralize the free ammonia in the wastewater, it is converted into ammonium ions NH 4 + , enriching the ammonium ions in the ammonia-containing wastewater and providing raw materials for subsequent reactions;

[0020] S2. Through a dosing hopper, solid sodium hydrogen phosphate 16.9 times the weight of ammonia in the dilute precious metal high-concentration ammonia-containing wastewater is added to the solution obtained in step S1, and continuously stirred until the sodium hydrogen phosphate dissolves;

[0021] S3. Solid magnesium chloride 11.7 times the weight of ammonia in the dilute precious metal high-concentration ammonia-containing wastewater is added to the solution obtained in step S2, and stirred for 20 min. By using sodium hydrogen phosphate to provide HPO 4 2- , and magnesium chloride to provide Mg 2+ , Mg 2+ , NH 4 + 4 2- ​Combined under alkaline conditions to form magnesium ammonium phosphate precipitate, and the released H⁺ is neutralized by the alkaline environment, promoting the forward reaction;

[0022] S4. Use a slurry pump to pump the solution obtained in step S3 into a filter press for filtration operation. The ammonia nitrogen in the high-concentration ammonia-containing wastewater enters the filter residue to become magnesium ammonium phosphate fertilizer, and the filtrate is sent back to the precious and rare metal recovery process for reuse through a recycled water pump.

[0023] Example 2:

[0024] A treatment method for high-concentration ammonia-containing wastewater in precious and rare metal smelting, comprising the following steps:

[0025] S1. At 25 °C, take 5 L of high-concentration ammonia-containing wastewater from precious and rare metals and add it to a reaction tank, and slowly add 98% concentrated sulfuric acid to adjust the pH value to 10;

[0026] S2. Add solid sodium hydrogen phosphate, which is 18.5 times the weight of ammonia in the high-concentration ammonia-containing wastewater from precious and rare metals, to the solution obtained in step S1 through a dosing hopper, and continuously stir until the sodium hydrogen phosphate dissolves;

[0027] S3. Add solid magnesium chloride, which is 12.9 times the weight of ammonia in the high-concentration ammonia-containing wastewater from precious and rare metals, to the solution obtained in step S2, and stir for 25 min;

[0028] S4. Use a slurry pump to pump the solution obtained in step S3 into a filter press for filtration operation. The ammonia nitrogen in the high-concentration ammonia-containing wastewater enters the filter residue to become magnesium ammonium phosphate fertilizer, and the filtrate is sent back to the precious and rare metal recovery process for reuse through a recycled water pump.

[0029] Example 3:

[0030] A treatment method for high-concentration ammonia-containing wastewater in precious and rare metal smelting, comprising the following steps:

[0031] S1. At 25 °C, take 5 L of high-concentration ammonia-containing wastewater from precious and rare metals and add it to a reaction tank, and slowly add 98% concentrated sulfuric acid to adjust the pH value to 10.4;

[0032] S2. Add solid sodium hydrogen phosphate, which is 18.7 times the weight of ammonia in the high-concentration ammonia-containing wastewater from precious and rare metals, to the solution obtained in step S1 through a dosing hopper, and continuously stir until the sodium hydrogen phosphate dissolves;

[0033] S3. Add solid magnesium chloride, which is 13.5 times the weight of ammonia in the high-concentration ammonia-containing wastewater from precious and rare metals, to the solution obtained in step S2, and stir for 25 min;

[0034] S4. Use a slurry pump to pump the solution obtained in step S3 into a filter press for filtration. The ammonia nitrogen in the high-concentration ammonia-containing wastewater enters the filter residue to become magnesium ammonium phosphate fertilizer, and the filtrate is sent to the dilute precious metal recovery process for reuse through a recycled water pump.

Claims

1. A method for treating high-concentration ammonia-containing wastewater from rare and precious metal smelting, characterized in that: The following steps are involved: S1. Add concentrated sulfuric acid to the wastewater to be treated and adjust the pH value to 9-10.5; S2, adding sodium hydrogen phosphate to the solution obtained in step S1, and stirring until the sodium hydrogen phosphate is dissolved; S3, adding magnesium chloride to the solution obtained in step S2, and stirring; S4, filtering the solution obtained in step S3.

2. The method for treating high-concentration ammonia-containing wastewater from rare and precious metal smelting according to claim 1, characterized in that: The amount of sodium hydrogen phosphate added in step S2 is 16 to 19 times the weight of ammonia in the wastewater to be treated.

3. The method for treating high-concentration ammonia-containing wastewater from rare and precious metal smelting according to claim 1, characterized in that: The amount of magnesium chloride added in step S3 is 11 to 13.5 times the weight of ammonia in the wastewater to be treated.

4. The method for treating high-concentration ammonia-containing wastewater from rare and precious metal smelting according to claim 1, characterized in that: The stirring time in step S3 is 15 to 30 minutes.