Beryllium (II) mineralization reagent and deep purification method for beryllium-containing wastewater

Abstract

Disclosed in the present invention are a beryllium (II) mineralization reagent and a deep purification method for beryllium-containing wastewater. The beryllium (II) mineralization reagent mainly comprises a calcium-containing compound and a phosphate-containing compound, and can mineralize free beryllium ions in an aqueous solution into stable mineral precipitates, such as hurlbutite [CaBe2(PO4)2] and hydroxyl herderite [CaBe(PO4)(OH)], thereby achieving the high-selectivity deep purification of beryllium ions in beryllium-containing wastewater, so as to eliminate beryllium pollution in a water environment. The beryllium (II) mineralization reagent is particularly suitable for the treatment of beryllium-containing wastewater generated during the smelting process of non-ferrous metals, such as beryllium, lithium, lead and zinc, and can reduce the beryllium concentration in the beryllium-containing wastewater to 0.002 mg / L or below, which is lower than the discharge standard of 5 μg / L specified in the National Comprehensive Wastewater Discharge Standard (GB8978-1996). In addition, the beryllium (II) mineralization reagent has the advantages of low costs, no toxicity, a simple construction process, a high purification efficiency, good long-acting stability of precipitated slag, no secondary pollution, etc.

Description

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

[0001] The present invention relates to a beryllium (II) mineralization reagent and 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, belonging to the technical field of beryllium pollution prevention and control. Background Art

[0002] Beryllium, due to its advantages such as a small thermal neutron cross-section, high strength, low specific gravity, and high melting point, is widely used in the nuclear industry, aerospace, electronic components, and petrochemicals. With the rapid development of these industries, demand for beryllium has increased annually. However, beryllium is extremely toxic and can easily damage the human respiratory system and cause illness. The "Comprehensive Sewage Discharge Standard" (GB8978-1996) stipulates that the maximum permissible beryllium discharge concentration per unit of water pollutant is 5μg / L, making it a Category 1 pollutant. Therefore, it is important to take effective measures to reduce beryllium's environmental pollution and harm to humans. Technical issues

[0003] Beryllium in process wastewater primarily originates from two sources: beryllium ore, crushed during beneficiation, enters the wash water, and beryllium enters the solution as ions during the smelting process. While some research has focused on treating beryllium-containing wastewater, these methods all have limitations. For example, alkaline precipitation with ferrite precipitation is effective for beryllium removal, but requires the addition of a large amount of reagents, which can easily lead to excessive levels of other ions. Lime neutralization is economical but ineffective for beryllium treatment. To address the challenges of using lime neutralization alone, researchers have developed improvements, including lime neutralization with tailings dam precipitation and lime neutralization with biological purification. These methods have improved beryllium treatment in wastewater, but levels remain above discharge standards, requiring further coagulation with flocculants to achieve standard discharge. Therefore, the treatment of beryllium-containing wastewater requires mineralizing reagents and supporting processes that achieve a higher purification depth, require appropriate dosage, and avoid secondary hazards. Technical Solutions

[0004] In response to the problem of beryllium-containing wastewater pollution generated by processes such as non-ferrous metal smelting, the first object of the present invention is to provide a beryllium (II) mineralization reagent that can mineralize free beryllium (II) ions in aqueous solution into stable mineral precipitates such as hurlbutite [CaBe2(PO4)2] and hyroxylherderite [CaBe(PO4)(OH)], thereby achieving long-term and ultra-stable mineralization of free beryllium in aqueous solution. The reagent is particularly suitable for deep mineralization of low-concentration beryllium (II) in aqueous solution and preventing and controlling beryllium pollution in the water environment.

[0005] A 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, then 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 objectives, 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 an 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 mineral precipitates such as hurlbutite [CaBe2(PO4)2] and hyroxylherderite [CaBe(PO4)(OH)]. Therefore, by selecting the calcium-containing compound and the phosphate-containing compound 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 into phosphate in water.

[0009] As a preferred embodiment, 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 embodiment, 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 based on 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 beryllium hydroxyphosphate, which are relatively unstable. When the calcium-containing compound is introduced, the phosphate-containing compound can react with beryllium (II) and the calcium-containing compound to form the more stable calcium phosphate beryllite [CaBe2(PO4)2]. If the amount of the calcium-containing compound added is too low, most of the beryllium (II) is converted into beryllium phosphate or beryllium hydroxyphosphate, which are relatively unstable, and excessive phosphate is also introduced into the solution, which is disadvantageous.

[0011] As a preferred embodiment, the beryllium (II) mineralization reagent comprises a fluorine-containing compound. The fluorine-containing compound includes at least one of sodium fluoride, calcium fluoride, natural fluorspar powder, and ammonium bifluoride. These fluorine-containing compounds can release fluoride ions. By introducing a small amount of the fluorine-containing compound, it can be used in conjunction with a calcium-containing compound and a phosphate-containing compound to mineralize free beryllium (II) into the more stable herderite [CaBePO4F].

[0012] As a preferred embodiment, 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 large, as excessive fluorine-containing compounds can cause secondary pollution to the wastewater. The calcium-containing compound is also greatly excessive relative to the fluorine-containing compound, primarily 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. The method comprises the following steps: adjusting the pH of the beryllium-containing wastewater to 4-9, first adding the beryllium (II) mineralization reagent to carry out a mineralization reaction, and then adding a flocculant to carry out flocculation and sedimentation to obtain beryllium-removed purified water.

[0014] The technical solution of the present invention first adjusts the pH of beryllium-containing wastewater to 4-9, mainly by reducing the BO4 2- The beryllium anion is converted to Be 2+ cations, and then add beryllium (II) mineralization reagent to Be 2+ The cations are mineralized into stable minerals such as calcium phosphate beryllite [CaBe2(PO4)2], calcium fluoride beryllite [CaBe(PO4)F] and calcium hydroxy beryllite [CaBe(PO4)(OH)]. Flocculants are then added 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 embodiment, the amount of the beryllium (II) mineralizing reagent 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 reagent added is measured based on the molar amounts of the phosphate-containing compound, calcium-containing compound, and fluorine-containing compound required to convert beryllium in the beryllium-containing wastewater into minerals such as calceite [CaBe2(PO4)2], calceite [CaBe(PO4)F], and calceite [CaBe(PO4)(OH)].

[0016] As a preferred solution, during the mineralization reaction, the components of the beryllium (II) mineralization reagent, excluding the inorganic calcium-containing compound, are first added to the beryllium-containing wastewater and stirred evenly. The organic calcium-containing compound is then added and stirred to carry out the mineralization reaction. During the mineralization reaction, phosphate-containing compounds and / or fluoride-containing compounds can be added simultaneously with the calcium-containing compound. However, this method of addition is relatively ineffective due to the competitive relationship between calcium ions and beryllium cations. Calcium ions react with fluoride ions and phosphate ions to form precipitates such as calcium fluoride and calcium phosphate, which consume the added fluoride and phosphate ions. This phenomenon can be avoided by preferably adding the phosphate-containing compound and / or fluoride-containing compound before adding the calcium-containing compound during the mineralization reaction. During the mineralization reaction, after each reagent is added, stir for at least 5 minutes before adding the next reagent.

[0017] As a preferred embodiment, the mineralization reaction temperature is 0-80°C and the reaction time is 5 minutes or longer. The higher the temperature during the mineralization reaction, the faster the reaction rate. Since the beryllium (II) mineralization reagent of the present invention can achieve excellent mineralization effects at room temperature, the preferred mineralization reaction temperature is 20-40°C. A mineralization reaction time of 5 minutes generally achieves excellent mineralization effects, and longer reaction times result in more stable mineralization effects.

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

[0019] As a preferred embodiment, 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 remain in the water, which is disadvantageous and does not 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 mineralized products into large particles, accelerate purification, and improve filtration performance. The amount of flocculant added is 0.1 to 5 g / L, and the mixture is stirred for about 30 minutes after the addition of 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 complex beryllium ions. Therefore, the beryllium-containing wastewater needs to be subjected to conventional oxidation treatment, such as adding an oxidizing agent such as hydrogen peroxide to carry out an oxidation reaction to convert the complexed beryllium into free beryllium.

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

[0022] After the mineralization reaction and flocculation sedimentation of the present invention, static sedimentation or filtration operation is performed. 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 of. Beneficial effects

[0023] 1) The technical solution of the present invention utilizes a combination of common phosphate-containing compounds, calcium-containing compounds and fluoride-containing compounds in the prior art, and can efficiently mineralize free beryllium in aqueous solution into stable minerals such as calcium phosphate beryllite [CaBe2(PO4)2], calcium fluoride beryllite [CaBe(PO4)F] and calcium hydroxy beryllite [CaBe(PO4)(OH)]. It 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. It can reduce the beryllium concentration in the beryllium-containing wastewater to below 0.002 mg / L, which is lower than the 5 μg / L emission standard specified in the "National Integrated Wastewater Discharge Standard (GB8978-1996)" and does not cause secondary pollution.

[0024] 2) Compared with the existing technology, 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.

[0025] 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, easily available, easy to store and use, and having no secondary pollution.

[0026] 4) The deep purification method for 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

[0027] FIG1 is a Raman spectrum of the precipitate produced by treating beryllium-containing wastewater in Example 2. Modes for Carrying Out the Invention

[0028] 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.

[0029] Example 1

[0030] The method of the present invention is used to treat the supernatant of the beryllium smelting industry tailings pond. The average beryllium content of the supernatant of the tailings pond is 32.4 mg / L, the pH value is between 8.5 and 9.2, and the beryllium concentration exceeds the national standard of 0.005 mg / L. The treatment process flow for purifying and removing beryllium from the supernatant of the beryllium smelting tailings pond is briefly described as follows: the supernatant of the tailings pond is extracted to the 1# stirred reaction tank, phosphoric acid solution is added in advance to adjust the pH to 6.5, and then a 15% aqueous solution of disodium hydrogen phosphate and a 12% slurry of calcium fluoride are added respectively 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# 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 no higher than 8.5 (if the pH is higher than 8.5, add an appropriate amount of phosphoric acid to adjust the pH), stirring the reaction for at least 45 minutes; the liquid after the 2# reaction is pumped to the 3# reaction tank, where 1g / L of activated aluminum hydroxide and 1.5g / L of polyaluminum sulfate are added successively, with gentle stirring for at least 30 minutes; the liquid from the 3# reaction tank is pumped to a thickening sedimentation tank for static sedimentation, and an appropriate amount of polyacrylamide is added to enhance flocculation and sedimentation. The thick overflow is the liquid that meets the standards for beryllium removal, and the thick bottom flow is washed and dehydrated by a belt filter before being outsourced for centralized disposal. The following table is an analysis of the key element content in the solution during different operation processes (Example 1):

[0031]

[0032] Example 2

[0033] The method of the present 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, has a pH value between 6.5 and 8.3, and the beryllium concentration exceeds the national standard of 0.005 mg / L. The process flow for purifying and removing beryllium from lithium smelting leachate is briefly described as follows: 1 L of lithium smelting leachate is transferred to a 2 L beaker, the leachate is mechanically stirred at 100 rpm, and a 20% aqueous sodium dihydrogen phosphate solution is slowly added to reach a concentration of 2.7 g / L in the leachate, and the mixture is stirred for 10 minutes; then a 15% calcium hydroxide slurry is added, the concentration of calcium hydroxide in the reaction tank is 5 g / L, and the pH of the reaction solution is controlled to be no 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 mixture is stirred for 30 minutes; then 1.0 g / L of polyaluminum ferric chloride is added, and the mixture is stirred at 30 rpm for 30 minutes; after the reaction, the mixture is filtered and washed by a vacuum filtration device, and the key element content of each solution in different operation processes is analyzed (Example 2):

[0034]

[0035] Example 3

[0036] The method of the present invention is used to treat zinc sulfate solution after high-acid leaching of zinc roasted sand and iron removal by the goethite method in the zinc smelting industry. The zinc sulfate solution contains an average beryllium content of 0.5 mg / L and a pH of approximately 5.0, exceeding the national standard of 0.005 mg / L. The process flow for purifying and removing beryllium from zinc high-acid leachate is briefly described as follows: 1 L of zinc high-acid leachate is transferred to a 2 L beaker, the leachate is mechanically stirred at 100 rpm, and a 15% sodium phosphate aqueous solution is slowly added to a concentration of 1.2 g / L in the leachate. The solution is stirred and reacted for 10 minutes. A 20% calcium oxide slurry is then added to a concentration of 4 g / L in the reaction tank. The pH of the reaction solution is controlled to 6.5, and the solution is stirred and reacted for 30 minutes. 1.0 g / L of polyferric sulfate is then added, and the reaction is carried out at a stirring speed of 30 rpm for 30 minutes. After the reaction is completed, the solution is filtered and washed using a vacuum filtration device. The key element content of each solution during different operation processes is analyzed (Example 3):

[0037]

[0038] In summary, the beryllium (II) mineralization reagent and method of the present invention can reduce the beryllium concentration in beryllium-containing wastewater 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)".

Claims

1. A beryllium (II) mineralization reagent, characterized in that: Contains calcium-containing compounds and phosphate-containing compounds.

2. A beryllium (II) mineralization reagent 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. A beryllium (II) mineralization reagent according to claim 1 or 2, characterized in that: The mass ratio of the phosphate-containing compound to the calcium-containing compound is 1:1.5-5.

4. A beryllium (II) mineralization reagent according to claim 1 or 2, characterized in that: Contains fluorine-containing compounds; the fluorine-containing compounds include at least one of sodium fluoride, calcium fluoride, natural fluorite powder, and ammonium bifluoride.

5. A beryllium (II) mineralization reagent according to claim 4, characterized in that: The mass ratio of the fluorine-containing compound to the calcium-containing compound is 1:3-20.

6. A method for deep purification of beryllium-containing wastewater, characterized in that: After the pH of beryllium-containing wastewater is adjusted to 4-9, the beryllium (II) mineralization reagent described in any one of claims 1-5 is first added to carry out a mineralization reaction, and then a flocculant is added to carry out flocculation and sedimentation to obtain beryllium-removed purified water.

7. A method for deep purification of beryllium-containing wastewater according to claim 6, 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.

8. The method for deep purification of beryllium-containing wastewater according to claim 6, 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.

9. A method for deep purification of beryllium-containing wastewater according to claim 6 or 8, characterized in that: During the mineralization reaction, the temperature is 0-80°C and the reaction time is more than 5 minutes.

10. The method for deep purification of beryllium-containing wastewater according to claim 6, 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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