A beryllium (II) mineralization reagent and a method for deep purification of beryllium-containing wastewater

Abstract

The invention discloses a beryllium (II) mineralization reagent and a method for deep purification of beryllium-containing wastewater. The beryllium (II) mineralizing reagent mainly comprises a calcium-containing compound and a phosphate-containing compound. The beryllium (II) mineralizing reagent can mineralize free beryllium ions in an aqueous solution into stable mineral precipitates such as calcium phosphate beryllite [CaBe2(PO4)2] and calcium hydroxyphosphate beryllite [CaBe(PO4)(OH)], thereby achieving highly selective deep purification of beryllium ions in beryllium-containing wastewater to eliminate beryllium pollution in the water environment. The beryllium-containing wastewater treatment reagent is particularly suitable for the treatment of beryllium-containing wastewater generated in the smelting process of non-ferrous metals such as beryllium, lithium, lead, and zinc. The beryllium concentration in the beryllium-containing wastewater can be reduced to below 0.002 mg / L, which is lower than the 5 μg / L discharge standard specified in the "National Integrated Wastewater Discharge Standard (GB8978-1996)", and has the advantages of low cost, no toxicity, simple construction process, high purification efficiency, good long-term stability of precipitated slag, and no secondary pollution.

Description

Technical Field

[0001] The invention relates to a beryllium (II) mineralization reagent and also to a method for deep purification of beryllium-containing wastewater, in particular to a method for deep purification of beryllium-containing wastewater generated in the smelting process of non-ferrous metals such as beryllium, lithium and zinc, and belongs to the technical field of beryllium pollution prevention and control. Background Art

[0002] Beryllium is widely used in the fields of nuclear industry, aerospace, electronic components and petrochemical industry due to its advantages such as small thermal neutron cross section, high strength, low specific gravity and high melting point. With the rapid development of the above industries, the demand for beryllium has increased year by year; but beryllium is extremely toxic and can easily cause damage to the human respiratory system and cause diseases. The "Comprehensive Sewage Discharge Standard" (GB8978-1996) stipulates that the maximum allowable emission mass concentration of beryllium per unit of water pollutant is 5μg / L, which is a Class I pollutant. Therefore, it is of great significance to take effective measures to reduce beryllium's pollution to the environment and harm to the human body.

[0003] There are two main sources of beryllium in process wastewater: one is that beryllium minerals formed by crushing during ore dressing enter the wash water, and the other is that beryllium enters the solution in the form of ions during the smelting process. At present, there have been some studies on the treatment of beryllium-containing wastewater, but they all have certain limitations. For example, the alkali precipitation-ferrite precipitation method has a good effect on beryllium removal, but it requires the addition of more reagents, which can easily cause other ions to exceed the standard; the lime neutralization method has good economic efficiency, but the treatment effect on beryllium is not ideal. In response to the problems of using the lime neutralization method alone, some researchers have improved it and successively developed the lime neutralization-tailings dam precipitation method and the lime neutralization-biological purification method. These methods have improved the treatment effect of beryllium in wastewater, but it is still higher than the discharge standard, and further flocculation treatment with flocculants is required to achieve standard discharge. Therefore, the treatment of beryllium-containing wastewater requires mineralization reagents and supporting processes with higher purification depth, appropriate dosage, and no secondary hazards. Summary of the invention

[0004] In view of the pollution problem of beryllium-containing wastewater generated in non-ferrous metal smelting and other processes, the first object of the present invention is to provide a beryllium (II) mineralization reagent, which can mineralize free beryllium (II) ions in aqueous solution into stable Hurlbutite [CaBe 2 (PO 4 ) 2 ] and hyroxylherderite [CaBe(PO 4 )(OH)] and other mineral precipitation to achieve long-term ultra-stable mineralization of free beryllium in aqueous solution, which is particularly suitable for deep mineralization of low-concentration beryllium (II) in aqueous solution and prevention of beryllium pollution in water environment.

[0005] The second object of the present invention is to provide a method for deep purification of beryllium-containing wastewater. The method converts beryllium anions in the wastewater, uses a beryllium (II) mineralization reagent for deep mineralization, and combines a flocculant for flocculation and sedimentation and removal of residual agents to achieve deep purification of beryllium in the beryllium-containing wastewater, meet national emission standards, and do not cause secondary pollution. The method is simple to operate, low-cost, and is conducive to large-scale promotion and use.

[0006] In order to achieve the above technical purpose, the present invention provides a beryllium (II) mineralization reagent, which comprises a calcium-containing compound and a phosphate-containing compound.

[0007] The beryllium (II) mineralization reagent provided by the technical solution of the present invention comprises a phosphate-containing compound and a calcium-containing compound. In the aqueous solution, the phosphate-containing compound mainly provides phosphate ions, while the calcium-containing compound mainly provides calcium ions. The phosphate and calcium ions play a role in synergistically mineralizing beryllium (II), and can mineralize free beryllium (II) into stable hurlibutite [CaBe 2 (PO 4 ) 2 ] and hyroxylherderite [CaBe(PO 4 Therefore, by selecting calcium-containing compounds and phosphate-containing compounds for use in combination, deep purification of beryllium-containing wastewater can be achieved.

[0008] As a preferred solution, the phosphate-containing compound includes at least one of sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium phosphate, ammonium phosphate, and phosphoric acid. These phosphate-containing compounds can ionize phosphate in water.

[0009] As a preferred solution, the calcium-containing compound includes at least one of calcium oxide, calcium carbonate, calcium hydroxide, calcium chloride, and calcite (added in powder form). The preferred calcium compound can release or slowly release free calcium ions in aqueous solution.

[0010] As a preferred solution, the mass ratio of the phosphate-containing compound to the calcium-containing compound is 1:1.5-5. The amount of the phosphate-containing compound is determined according to the free beryllium (II) content in the aqueous solution, and the amount of the calcium-containing compound is excessive relative to the phosphate-containing compound. The phosphate-containing compound can convert beryllium (II) into beryllium phosphate or hydroxy beryllium phosphate. The stability of beryllium phosphate or hydroxy beryllium phosphate is relatively poor. When the calcium-containing compound is introduced, the phosphate-containing compound can react with beryllium (II) and the calcium-containing compound to convert into more stable calcium phosphate beryllium [CaBe 2 (PO 4 ) 2] If the amount of calcium-containing compound added is too low, most of the beryllium (II) is converted into beryllium phosphate or beryllium hydroxyphosphate, which have relatively poor stability, and excessive phosphate is also introduced into the solution, which is unfavorable.

[0011] As a more preferred solution, the beryllium (II) mineralization reagent contains a fluorine-containing compound. The fluorine-containing compound includes at least one of sodium fluoride, calcium fluoride, natural fluorite powder, and ammonium bifluoride. These fluorine-containing compounds can release fluoride ions. By introducing a small amount of fluorine-containing compounds, it can be used in combination with calcium compounds and phosphate-containing compounds to mineralize free beryllium (II) into more stable herderite [CaBePO 4 F].

[0012] As a preferred solution, the mass ratio of the fluorine-containing compound to the inorganic calcium-containing compound is 1:3 to 20. The amount of the fluorine-containing compound should not be too much, as excessive fluorine-containing compounds will cause secondary pollution to the wastewater, and the calcium-containing compound is also greatly excessive relative to the fluorine-containing compound, mainly to control the concentration of residual fluoride ions in the solution system.

[0013] The present invention also provides a method for deep purification of beryllium-containing wastewater, which comprises adjusting the pH of the beryllium-containing wastewater to 4-9, first adding the beryllium (II) mineralizing reagent for mineralization reaction, and then adding a flocculant for flocculation and sedimentation to obtain beryllium-removed purified water.

[0014] The technical solution of the present invention first adjusts the pH of the beryllium-containing wastewater to 4-9, mainly to reduce the BO 4 2- The beryllium anion is converted to Be 2+ cation, and then add beryllium (II) mineralization reagent to convert Be 2+ The cations are mineralized into stable calcium berylite [CaBe 2 (PO 4 ) 2 ]、CaBe(PO 4 )F] and hydroxyapatite [CaBe(PO 4 )(OH)] and other minerals, and then add flocculants to accelerate the flocculation and precipitation of these minerals through complexation. At the same time, these flocculants can also adsorb and remove excess phosphate and fluoride ions, greatly reducing the residual amount of phosphate and fluoride ions in the solution and avoiding secondary pollution.

[0015] As a preferred solution, the amount of the beryllium (II) mineralizing agent added is 2 to 10 times the theoretical molar amount required to convert the beryllium (II) mineral into a water-insoluble mineral. More specifically, the amount of the beryllium (II) mineralizing agent added is such that the beryllium in the beryllium-containing wastewater is converted into calcium phosphate beryllite [CaBe 2 (PO4 ) 2 ]、CaBe(PO 4 )F] and hydroxyapatite [CaBe(PO 4 The molar amounts of phosphate-containing compounds, calcium-containing compounds and fluorine-containing compounds required for minerals such as )(OH)] are measured.

[0016] As a preferred solution, during the mineralization reaction, the components of the beryllium (II) mineralizing reagent except the inorganic calcium-containing compound are first added to the beryllium-containing wastewater, and after stirring, the organic calcium-containing compound is added and stirred for mineralization reaction. During the mineralization reaction, phosphate-containing compounds and / or fluoride-containing compounds and calcium-containing compounds can be added at the same time, but the effect of this addition method is relatively poor, mainly based on the competitive relationship between calcium ions and beryllium cations, and calcium ions will be converted into precipitations such as calcium fluoride and calcium phosphate with fluoride ions and phosphate radicals, consuming the added fluoride ions and phosphate ions. During the mineralization reaction, it is preferred to add phosphate-containing compounds and / or fluoride-containing compounds, and then add calcium-containing compounds to avoid this phenomenon. During the mineralization reaction, after each reagent is added, stir for at least 5 minutes before adding the next agent.

[0017] As a preferred solution, during the mineralization reaction, the temperature is 0-80°C and the time is more than 5 minutes. The higher the temperature during the mineralization reaction, the faster the reaction rate. The beryllium (II) mineralization reagent of the present invention can achieve a good mineralization effect at room temperature, so the preferred mineralization reaction temperature is preferably 20-40°C. Generally, a good mineralization effect can be achieved within 5 minutes of the mineralization reaction time, and the longer the time, the more stable the mineralization effect.

[0018] As a more preferred solution, the pH of the beryllium-containing wastewater is adjusted to 4.5-8.5.

[0019] As a preferred solution, the flocculant includes at least one of activated aluminum hydroxide, polyaluminum chloride, polyaluminum ferric chloride, polyaluminum sulfate, and polyferric sulfate. After the mineralization reaction is completed, most of the excess phosphate ions and fluoride ions are converted into precipitates by calcium-containing compounds, while a small amount of phosphate ions and fluoride ions remaining in the water is unfavorable and cannot meet the discharge standard. Further addition of flocculants such as activated aluminum hydroxide, polyaluminum chloride, polyaluminum ferric chloride, polyaluminum sulfate, and polyferric sulfate can deeply purify and remove the residual phosphate ions and fluoride ions. At the same time, the flocculant can agglomerate the mineralization products into large particles, accelerate purification, and improve filtration performance. The amount of flocculant added is 0.1 to 5 g / L, and stirring is performed for about 30 minutes after adding the flocculant.

[0020] The beryllium-containing wastewater of the present invention often contains organic components, such as oxalate, naphthol and other complexing agents, which can make beryllium ions complexed. Therefore, the beryllium-containing wastewater needs to be subjected to conventional oxidation treatment, such as adding oxidizing agents such as hydrogen peroxide to carry out oxidation reaction to convert complexed beryllium into free beryllium.

[0021] The beryllium (II) mineralization reagent of the present invention can be in the form of powder, solution or slurry. The mineralization effect will be better if the solution or slurry is prepared in advance.

[0022] After the mineralization reaction and flocculation sedimentation of the present invention, static sedimentation or filtration operation is carried out. The supernatant or filtrate produced after solid-liquid separation is the qualified water body after purification and beryllium removal. The dense underflow or filter cake is the beryllium-containing sludge, which needs to be centrally disposed.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] 1) The technical solution of the present invention utilizes the combination of common phosphate-containing compounds, calcium-containing compounds and fluoride-containing compounds in the prior art to efficiently mineralize free beryllium in aqueous solution into stable calcium phosphate beryllium [CaBe 2 (PO 4 ) 2 ]、CaBe(PO 4 )F] and hydroxyapatite [CaBe(PO 4 )(OH)] and other minerals are particularly suitable for the treatment of beryllium-containing wastewater generated during the smelting of non-ferrous metals such as beryllium, lithium, lead, and zinc. It can reduce the beryllium concentration in the beryllium-containing wastewater to below 0.002 mg / L, which is lower than the 5μg / L emission standard specified in the "National Integrated Wastewater Discharge Standard (GB8978-1996)" and does not cause secondary pollution.

[0025] 2) Compared with the prior art, the technical solution of the present invention has the advantages of a purification process for beryllium-containing wastewater, high purification depth, small reagent dosage, and wide applicability.

[0026] 3) The technical solution of the present invention proposes that the beryllium (II) mineralization reagent is a conventional chemical product, which has the advantages of being cheap, easy to obtain, easy to store and use, and having no secondary pollution.

[0027] 4) The method for deep purification of beryllium-containing wastewater proposed in the technical solution of the present invention has a simple and efficient construction process, does not require complex and expensive equipment and instruments, and the overall operation process has the advantages of being economical, efficient, and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the Raman spectrum of the precipitate produced by treating beryllium-containing wastewater in Example 2. DETAILED DESCRIPTION

[0029] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0030] Example 1

[0031] The method of the present invention is used to treat the supernatant of the tailings reservoir of the beryllium smelting industry. The supernatant of the tailings reservoir contains an average of 32.4 mg / L of beryllium, a pH value between 8.5 and 9.2, and a beryllium concentration exceeding the national standard of 0.005 mg / L. The treatment process flow of purifying and removing beryllium from the supernatant of the beryllium smelting tailings reservoir is briefly described as follows: extract the supernatant of the tailings reservoir to the 1# stirred reaction tank, add phosphoric acid solution in advance to adjust the pH to 6.5, and then add a 15% sodium hydrogen phosphate aqueous solution and a 12% calcium fluoride slurry to make their concentrations in the reaction tank reach 6.5 g / L and 1.0 g / L respectively, and the stirring reaction time is 30 minutes; the 1# post-reaction liquid is extracted to the 2# reaction tank, and a 15% calcium carbonate slurry is added, and the concentration of calcium carbonate in the reaction tank is 12 g / L. , and ensure that the pH of the reaction solution is not higher than 8.5 (if the pH is higher than 8.5, add appropriate amount of phosphoric acid to adjust the pH), and the stirring reaction time is more than 45 minutes; the 2# reaction liquid is extracted to the 3# reaction tank, and 1g / L of active aluminum hydroxide and 1.5g / L of polyaluminum sulfate are added successively, and the slight stirring reaction time is more than 30 minutes; the 3# reaction tank is extracted to the dense sedimentation tank for static sedimentation, and an appropriate amount of polyacrylamide is added to strengthen the flocculation sedimentation. The dense overflow is the liquid that meets the beryllium removal standards, and the dense bottom flow is washed and dehydrated by a belt filter and then entrusted to centralized disposal.

[0032] The following table is an analysis table of key element contents in solutions during different operation processes (Example 1):

[0033]

[0034] Example 2

[0035] The method of the invention is used to treat the leachate after the roasted clinker leaching operation in the lithium smelting industry. The leachate contains an average of 16.2 mg / L of beryllium, a pH value between 6.5 and 8.3, and a beryllium concentration exceeding the national standard of 0.005 mg / L. The treatment process for purifying and removing beryllium from lithium smelting leachate is briefly described as follows: 1L of lithium smelting leachate is transferred to a 2L beaker, the leachate is mechanically stirred at 100rpm, and a 20% sodium dihydrogen phosphate aqueous solution is slowly added to make its concentration in the leachate reach 2.7g / L, and the reaction is stirred for 10 minutes; then a 15% calcium hydroxide slurry is added, the concentration of calcium hydroxide in the reaction tank is 5g / L, and the pH of the reaction solution is controlled not to be higher than 8.5 (if the pH is higher than 8.5, an appropriate amount of phosphoric acid needs to be added to adjust the pH), and the reaction is stirred for 30 minutes; then 1.0g / L of polyaluminum ferric chloride is added, and the reaction is reacted at a stirring speed of 30rpm for 30 minutes; after the reaction is completed, it is filtered and washed by a vacuum filtration device, and the key element content analysis table of each solution in different operation processes is analyzed (Example 2):

[0036]

[0037] Example 3

[0038] The method of the invention is used for treating zinc sulfate solution after high-acid leaching of zinc roasted sand and iron removal by goethite method in zinc smelting industry. The zinc sulfate solution contains an average of 0.5 mg / L of beryllium, has a pH value of about 5.0, and the beryllium exceeds the national standard of 0.005 mg / L. The treatment process flow of zinc high acid leachate purification and beryllium removal is briefly described as follows: 1L of zinc high acid leachate is transferred to a 2L beaker, the leachate is mechanically stirred at 100rpm, and a 15% sodium phosphate aqueous solution is slowly added to make its concentration in the leachate reach 1.2g / L, and the reaction is stirred for 10 minutes; then a 20% calcium oxide slurry is added, the concentration of calcium oxide in the reaction tank is 4g / L, and the pH of the reaction solution is controlled to reach 6.5, and the reaction is stirred for 30 minutes; then 1.0g / L of polyferric sulfate is added, and the reaction is carried out at a stirring speed of 30rpm for 30 minutes; after the reaction is completed, it is filtered and washed by a vacuum filtration device, and the key element content analysis table of each solution in different operation processes is analyzed (Example 3):

[0039]

Claims

1. A method for deep purification of beryllium-containing wastewater, characterized in that: After adjusting the pH of beryllium-containing wastewater to 4-9, firstly adding a beryllium (II) mineralization reagent to carry out a mineralization reaction, and then adding a flocculant to carry out flocculation and sedimentation, thereby obtaining beryllium-free purified water; the beryllium (II) mineralization reagent comprises a calcium-containing compound, a phosphate-containing compound and a fluorine-containing compound; The mass ratio of the phosphate-containing compound to the calcium-containing compound is 1:1.5-5; the mass ratio of the fluorine-containing compound to the calcium-containing compound is 1:3-20.

2. The method for deep purification of beryllium-containing wastewater according to claim 1, characterized in that: The phosphate-containing compound includes at least one of sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium phosphate, ammonium phosphate, and phosphoric acid; The calcium-containing compound includes at least one of calcium oxide, calcium carbonate, calcium hydroxide, calcium chloride and calcite.

3. The method for deep purification of beryllium-containing wastewater according to claim 1, characterized in that: The fluorine-containing compound includes at least one of sodium fluoride, calcium fluoride, natural fluorite powder and ammonium bifluoride.

4. The method for deep purification of beryllium-containing wastewater according to claim 1, characterized in that: The amount of the beryllium (II) mineralizing agent added is 2 to 10 times the theoretical molar amount required to convert the beryllium (II) mineral into a water-insoluble mineral.

5. The method for deep purification of beryllium-containing wastewater according to claim 1, characterized in that: During the mineralization reaction, the components of the beryllium (II) mineralization reagent except the calcium-containing compound are first added to the beryllium-containing wastewater, and after being stirred evenly, the calcium-containing compound is added and stirred to carry out the mineralization reaction.

6. A method for deep purification of beryllium-containing wastewater according to claim 1 or 5, characterized in that: During the mineralization reaction, the temperature is 0-80°C and the reaction time is more than 5 minutes.

7. The method for deep purification of beryllium-containing wastewater according to claim 1, characterized in that: The flocculant includes at least one of activated aluminum hydroxide, polyaluminum chloride, polyaluminum ferric chloride, polyaluminum sulfate, and polyferric sulfate.

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