Curing and stabilizing method for beryllium slag

Abstract

The invention discloses a solidification and stabilization method of beryllium slag. The method comprises the following steps: firstly, adjusting the water content of the beryllium slag to 15-30%; adding insoluble phosphate seed crystals, controlling the adding amount of the insoluble phosphate seed crystals to be 0.5-2% of the mass of the dry beryllium slag, and mixing and stirring to obtain beryllium slag-phosphate mixed precipitate; then soluble phosphate and an aluminum-containing regulator are added for a conversion reaction, the adding amount of the soluble phosphate is controlled to be 2%-8% of the mass of the dry beryllium slag, the adding amount of the aluminum-containing regulator is controlled to be 0%-0.5% of the mass of the dry beryllium slag, mixing and stirring are conducted, and converted beryllium slag is obtained; finally, Portland cement is added, the adding amount of the cement is controlled to be 3%-12% of the mass of the dry beryllium slag, and stable curing is conducted to obtain the beryllium slag solidified body. According to the method, the stable beryllium slag solidified body is obtained through water content adjustment, induced adsorption precipitation of the insoluble phosphate seed crystal, deep coordination conversion coprecipitation of the soluble phosphate and the aluminum-containing regulator and hydration and gel solidification reaction of the cement, the beryllium slag solidification stability is improved, and the treatment cost and the compatibilization ratio are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of harmless treatment and disposal of beryllium-containing waste residues, and in particular to a solidification and stabilization method for beryllium slag. Background Art

[0002] Beryllium is a grayish-white alkaline earth metal with extensive applications in numerous scientific and technological fields due to its outstanding physical, thermal, electrical, mechanical, and nuclear properties. Its metal, alloys, and oxides are widely used in industries such as atomic energy, rockets, missiles, satellites, aviation, aerospace, electronics, instrumentation, petrochemicals, and ceramics. Due to its global industrial and strategic significance, beryllium and beryllium-containing materials are designated as critical elements with high supply risk and high economic importance, which has driven related mining and recycling activities.

[0003] Beryllium slag originates from beryllium smelting, production and processing, and the scrapping of beryllium products. Beryllium oxide is primarily smelted using beryl as the raw material, employing a sulfuric acid extraction process (i.e., flux smelting). Extraction proceeds through smelting, acid leaching, aluminum removal, iron removal, crystallization, and calcination. This extraction process produces waste slag containing beryllium. A smelter's beryllium-containing industrial wastewater is treated with lime and biological agents. The resulting environmentally friendly filter press residue contains silicon, iron, calcium, and a small amount of heavy metal beryllium (approximately 0.4%). Beryllium metal processing, such as beryllium forming (forging, rolling, etc.) and machining (cutting, drilling, etc.), generates waste and slag. Beryllium slag is also produced during the disassembly of retired aerospace components, including surface coatings and damaged parts. Currently, the world's undisposed beryllium slag stockpile is approximately 15,000 kg, and this stockpile is increasing at a rate of 600 kg per year. Beryllium and its compounds are highly toxic, even at low concentrations (<0.004 mg / L) to plants and animals. The World Health Organization's International Agency for Research on Cancer lists beryllium as a Group 1 human carcinogen. Therefore, the proper disposal of beryllium slag is crucial.

[0004] Currently, limited research exists on solidification technologies for Be-containing waste residues, both domestically and internationally. The main reported solidification and stabilization methods include mixing red mud with concrete blocks and casting them into blocks to immobilize Be. Other studies have found that fly ash (CFA), synthetic zeolite (SynZ), and chitosan-modified zeolite can be used as modifiers to immobilize Be, highlighting the effectiveness of synthetic zeolite (SynZ) for environmentally friendly Be immobilization. Other studies have confirmed that Be is strongly adsorbed in cement systems under argon, with the gel system formed by calcium silicate hydrate (CSH) being the primary adsorption site for Be. Beryllium is adsorbed onto the CSH surface via calcium bridges, providing a scientific basis for the development of geochemical models. Domestic research has successfully solidified / stabilized Be-containing waste residues using a composite stabilization agent based on Portland cement supplemented with calcium oxide, fly ash, and sodium sulfide. However, the above treatment methods all have disadvantages such as large amount of curing agent, high disposal cost, poor long-term stability and large volume expansion ratio. There is an urgent need to screen a curing agent with low cost, small dosage, good stability and high safety to meet the safe disposal of beryllium slag. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and propose a solidification and stabilization method for beryllium slag to solve the problems of large amount of curing agent, high disposal cost, poor long-term stability and large volume expansion ratio in the current solidification of beryllium slag.

[0006] To achieve the above technical objectives, the technical solution of the present invention provides a method for solidifying and stabilizing beryllium slag, comprising the following steps:

[0007] 1) Adjust the moisture content of beryllium slag to 15% to 30% by adding water or air drying;

[0008] 2) adding insoluble phosphate seed crystals to the beryllium slag, controlling the addition amount of the insoluble phosphate seed crystals to be 0.5% to 2% of the mass of the dry beryllium slag, and mixing and stirring to obtain a beryllium slag-phosphate mixed precipitate;

[0009] 3) adding soluble phosphate and aluminum-containing regulator to the beryllium slag-phosphate mixed precipitate to carry out conversion reaction, controlling the addition amount of soluble phosphate to be 2% to 8% of the mass of the dry beryllium slag, and the addition amount of aluminum-containing regulator to be 0% to 0.5% of the mass of the dry beryllium slag, and mixing and stirring to obtain converted beryllium slag;

[0010] 4) Adding silicate cement to the converted beryllium slag, controlling the cement dosage to be 3% to 12% of the mass of the dry beryllium slag, and performing stable curing to obtain a solidified beryllium slag.

[0011] The key to this invention lies in its approach, based on the geochemical principles of beryllium, to achieve a stable solidified beryllium slag through moisture content adjustment, induced adsorption and precipitation of sparingly soluble phosphate seed crystals, deep coordination conversion and co-precipitation of soluble phosphates and an aluminum-containing modifier, and cement hydration and gel curing reactions. This improves the solidification stability of the beryllium slag. Furthermore, the synergistic effect of the phosphate and aluminum-containing modifier effectively reduces the amount of cement and other reagents used, lowering processing costs and reducing the volume expansion ratio of the cement solidified body.

[0012] The geochemical properties of beryllium show that it is easy for oxygen to coordinate with beryllium to form stable [BeO4] 6- The tetrahedral structure ultimately exists stably in the form of minerals such as beryl, hydroxyl beryllite, calcium phosphate beryllite ([CaBe(PO4)OH]), and beryllite. Therefore, the present invention primarily utilizes the aforementioned properties of beryllium, relying on principles such as seed adsorption and co-precipitation, to convert beryllium slag into stable beryllium-like minerals at room temperature and in a relatively short period of time, thereby achieving safe disposal of the beryllium slag.

[0013] In step 1), the moisture content of the beryllium slag is first controlled to ensure that the beryllium slag has good fluidity and mobility, thereby creating conditions for the mixing reaction in the subsequent steps.

[0014] Due to the low Be content in beryllium slag, as well as its low activity and mobility, it is difficult to increase the effective Be fixation rate in the beryllium slag. The stability of the beryllium slag after solidification using traditional methods is poor. Therefore, the present invention proposes first performing seed-induced adsorption precipitation. In step 2), the addition of sparingly soluble phosphate seed crystals serves as a nucleation surface for Be adsorption in the beryllium slag. Through the adsorption, enrichment, and co-precipitation of Be by the seed crystals, the problem of poor Be precipitation efficiency with a single soluble phosphate is addressed. The phosphorus-containing groups on the sparingly soluble phosphate seed crystals are primarily negatively charged, while Be is positively charged, achieving Be adsorption by the seed crystals. The concentration, activity, and mobility of Be adsorbed on the surface of the sparingly soluble phosphate seed crystals are effectively improved. Some Be can also co-precipitate directly on the seed crystal surface, forming stable beryllium-containing minerals such as calcium phosphate beryllite (CaBe(PO4)OH). This achieves pre-solidification and pre-adsorption enrichment of Be. The dosage of insoluble phosphate seed crystals is controlled to be 0.5% to 2% of the mass of dry beryllium slag, so as to ensure the adsorption and co-precipitation effect of Be while avoiding the increase of reagent cost and the increase of total slag volume.

[0015] In step 3), soluble phosphate and aluminum-containing regulator are added to deeply solidify and stabilize the remaining Be in the beryllium slag. 2+ With PO4 3- Formation of stable beryllium phosphate precipitate, and some Be 2+ With PO4 3-Forming stable complexes, such as BeHPO4 and Be(H2PO4)2. Then combining with Ca in beryllium slag, it forms precipitation in the form of CaBe(PO4)OH, which improves the curing effect of Be. Aluminum-containing regulators can co-precipitate with the original Al and Si in beryllium slag and Si in cement to obtain stable Al-Si-Be precipitates, such as Be3Al2Si6O 18 , achieving the goal of further improving the solidification stability of Be. The dosage of soluble phosphate is controlled to 2% to 8% of the mass of the dry beryllium slag, and the dosage of aluminum-containing regulator is controlled to 0% to 0.5% of the mass of the dry beryllium slag, ensuring the precipitation and coordination solidification effects of Be while avoiding an increase in reagent costs.

[0016] In step 4), Portland cement is added to form a hard calcium silicate hydrate (CSH) gel, ettringite, and other minerals, encapsulating and consolidating the low-solubility stabilized products (e.g., beryllium phosphate precipitates and aggregates) and other components formed in steps 2 and 3) within a dense matrix. The cement dosage is controlled to 3% to 12% of the dry beryllium slag mass to ensure densification and stable encapsulation of the slag, while minimizing excessive reagent costs and excessive volume expansion.

[0017] As a preferred embodiment, the main components of beryllium slag, calculated on a dry basis, are as follows: Ca (mass fraction) 10% to 25%, Si (mass fraction) 10% to 25%, Be (mass fraction) 0.05% to 0.40%, O (mass fraction) 35% to 55%, S (mass fraction) 5% to 15%, and Al (mass fraction) 0.3% to 1.0%. Beryllium slag is generally neutral or alkaline.

[0018] As a preferred solution, the mixing time in step 2) is 1 h to 3 h, and the mixing temperature is 5°C to 35°C. The mixing time in step 3) is 3 h to 6 h, and the mixing temperature is 5°C to 35°C.

[0019] As a preferred solution, the sparingly soluble phosphate seed crystals in step 2) are one or more of Ca3(PO4)2, Ca5(PO4)3OH, CaHPO4, and CaHPO4·2H2O.

[0020] As a preferred solution, the amount of sparingly soluble phosphate seed crystals added in step 2) is 0.6% to 1% of the mass of the dry beryllium slag, and the particle size of the sparingly soluble phosphate seed crystals is 20 to 60 μm. The amount and particle size of the sparingly soluble phosphate seed crystals are controlled to provide sufficient and effective Be adsorption surface.

[0021] As a preferred solution, the amount of soluble phosphate added in step 3) is 2.5% to 4% of the mass of the dry beryllium slag.

[0022] As a preferred solution, the soluble phosphate in step 3) is one or more of KH2PO4, K2HPO4, K3PO4, NaH2PO4, Na2HPO4, Na3PO4, NH4H2PO4, and (NH4)2HPO4.

[0023] As a preferred embodiment, the aluminum-containing modifier in step 3) is one or more of AlCl₃, Al₂(SO₄)₃, polyaluminum sulfate, polyaluminum chloride, and Al(OH)₃. When the molar ratio of Al to Be in the beryllium slag (dry basis) is greater than or equal to 1:1, the dosage of the aluminum-containing modifier is 0% to 0.5% of the dry beryllium slag mass. The addition of an additional aluminum-containing modifier can be selected based on actual conditions. If not added, the dosage is 0%. If added to enhance the solidification and stabilization of Be, the dosage is 0.1% to 0.5%. When the molar ratio of Al to Be in the beryllium slag (dry basis) is less than 1:1, the dosage of the aluminum-containing modifier is 0.1% to 0.5% of the dry beryllium slag mass.

[0024] As a preferred solution, the silicate cement in step 4) includes one or more of P·O42.5, P·O42.5R, P·O52.5, P·O52.5R, P·S32.5, P·S32.5R, P·S42.5, P·S42.5R, P·S52.5, and P·S52.5R.

[0025] As a preferred solution, in step 4), the moisture content of the converted beryllium slag when mixed with cement is controlled to be 20% to 30%, the mixing time is 0.5h to 1h, and the stabilization curing time is not less than 7 days.

[0026] Compared with the existing technology, the technical solution of the present invention has the following beneficial effects:

[0027] 1. Seed-induced Be adsorption and precipitation: Insoluble phosphate seeds and soluble phosphates are added step by step. Through adsorption, enrichment, coordination, co-precipitation and other mechanisms, the low Be concentration and difficult Be migration and transformation in beryllium slag are solved. Natural mineral-like precipitates with strong stability and low solubility, such as CaBe(PO4)OH, are formed, which reduces the solubility and leaching concentration of Be in beryllium slag and effectively improves the Be solidification stability.

[0028] 2. Use aluminum-containing regulators to promote the flocculation and stability of beryllium phosphate precipitation, forming Al-Si-Be co-precipitates with low solubility, further improving the Be solidification stability effect.

[0029] 3. Based on the geochemical principle of beryllium, the Be in the beryllium slag can be converted into a stable mineral-like precipitate at room temperature in a relatively short period of time. Then, an appropriate amount of cement is added. Relying on the effects of hydration and CSH gelation, the stability of the solidified body is ensured, and the amount of cement and other curing agents is significantly reduced, thus solving the problems of high curing cost and large volume expansion ratio of beryllium slag after curing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0031] Figure 1 This is a process flow chart of a beryllium slag solidification and stabilization method according to an embodiment of the present invention;

[0032] Figure 2 These are SEM (electron microscope) photos of samples of beryllium slag before and after solidification in Examples 1 and 2 of the present invention. Sample numbers: (a) beryllium slag before solidification, (b) Example 1, (c) Example 2;

[0033] Figure 3 is the XRD (X-ray diffraction) spectrum of the beryllium slag samples after solidification in Example 1 and Example 2 of the present invention;

[0034] Figure 4 FTIR (infrared) spectra of beryllium slag before and after solidification in Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The present invention provides a method for solidifying and stabilizing beryllium slag, comprising the following steps:

[0037] 1) Adjust the moisture content of beryllium slag to 15% to 30% by adding water or air drying;

[0038] 2) adding insoluble phosphate seed crystals to the beryllium slag, controlling the addition amount of the insoluble phosphate seed crystals to be 0.5% to 2% of the mass of the dry beryllium slag, and mixing and stirring to obtain a beryllium slag-phosphate mixed precipitate;

[0039] 3) adding soluble phosphate and aluminum-containing regulator to the beryllium slag-phosphate mixed precipitate to carry out conversion reaction, controlling the addition amount of soluble phosphate to 2% to 8% of the mass of the dry beryllium slag, and controlling the addition amount of aluminum-containing regulator to 0% to 0.5% of the mass of the dry beryllium slag, and mixing and stirring to obtain converted beryllium slag;

[0040] 4) Adding silicate cement to the converted beryllium slag, controlling the cement dosage to be 3% to 12% of the mass of the dry beryllium slag, and performing stable curing to obtain a solidified beryllium slag.

[0041] A solidification and stabilization method for beryllium slag of the present invention:

[0042] In step 1), the main purpose is to control the moisture content of the beryllium slag to ensure that the beryllium slag has an appropriate physical state, neither too dry to cause poor fluidity and slow ion migration, nor too wet to cause difficulty in slurry mixing, thereby creating conditions for efficient mixing and reaction of the reagent and beryllium slag in subsequent steps.

[0043] In step 2), the added sparingly soluble phosphate seed crystals can provide seed crystals (adsorption nucleation surface) for the solidification and stabilization of Be in the beryllium slag.

[0044] In an aqueous solution system, the reaction between phosphate and Be is relatively easy to proceed, but the mobility and activity of Be in beryllium slag are relatively low. The effect of relying solely on the precipitation reaction between phosphate and Be to achieve the solidification and stabilization of Be is not ideal.

[0045] In the present invention, it is proposed to first use insoluble phosphate seeds to provide adsorption nucleation surfaces. The phosphorus-containing groups (such as HPO4) on the insoluble phosphate seeds are mainly negatively charged. 3- As a typical multidentate ligand, the multiple oxygen atoms around the phosphorus atom have the ability to provide lone pair electrons. 2+ The ionic radius is smaller and it is easier to react with PO4 3- The presence of phosphate facilitates the adsorption of beryllium (electrostatic attraction and coordination), promoting its adsorption and co-precipitation, and forming a stable, low-solubility Ca-P-Be precipitate, which can provide microcrystalline nuclei for the subsequent formation of C-S-H gel.

[0046] Specifically, the addition of insoluble phosphate seeds can achieve the adsorption of Be by the insoluble phosphate seeds, forming a Be-phosphate composite precipitate, as shown in formula (1) to formula (4):

[0047] Ca3(PO4)2 + 3Be 2+ + 3OH - + PO4 3- = 3CaBe(PO4)OH↓ (1)

[0048] Ca5(PO4)3OH + 5Be 2+ + 4OH - + 2PO4 3- = 5CaBe(PO4)OH↓ (2)

[0049] 3CaHPO4 + 3Be 2+ + 6OH - = 3CaBe(PO4)OH↓ + 3H2O (3)

[0050] 3CaHPO4·2H2O + 3Be 2+ + 6OH - = 3CaBe(PO4)OH↓ + 9H2O (4)

[0051] On the other hand, the activity and mobility of Be adsorbed on the phosphate surface are effectively improved, and the concentration of Be on the surface of the phosphate precipitate is increased through enrichment, which can create favorable conditions for the subsequent efficient solidification reaction of soluble phosphate, aluminum-containing regulator and Be.

[0052] In step 2), the amount of sparingly soluble phosphate seed crystals added is controlled to be between 0.5% and 2% of the mass of the dry beryllium slag, specifically 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2.0%. Too little sparingly soluble phosphate seed crystals weakens their adsorption and coprecipitation of Be, preventing effective Be enrichment and solidification. Too much sparingly soluble phosphate seed crystals unnecessarily increases the total amount of beryllium slag and the cost of the sparingly soluble phosphate seed crystal reagent.

[0053] In step 3), the addition of soluble phosphate and aluminum-containing regulator can further achieve the solidification and stabilization of Be.

[0054] Among them, soluble phosphates provide a large amount of phosphate ions (PO4 3- ). PO4 3- Be in beryllium slag 2+ The reaction generates a beryllium phosphate precipitate with extremely low solubility and very stable chemical properties, converting soluble / leachable beryllium into insoluble stable minerals, promoting the solidification and stabilization of Be. The reaction is shown in Equation (5):

[0055] 3Be 2+ + 2PO4 3- = Be3(PO4)2↓ (5)

[0056] The addition of soluble phosphate can also promote the formation of stable complexes between Be and P. - Two mononuclear complexes can be formed, namely BeHPO4 and Be(H2PO4)2. Since beryllium slag contains a large amount of Ca, Ca can react with complexes such as BeHPO4 and Be(H2PO4)2 to form low-solubility precipitates in the form of CaBe(PO4)OH, making the solidification effect of beryllium more stable and providing microcrystalline nuclei for the subsequent formation of C-S-H gel. The reactions are shown in Equations (6) to (7):

[0057] BeHPO4 + Ca 2+ +2OH - = CaBe(PO4)OH↓ + H2O (6)

[0058] Be(H2PO4)2 + Ca 2+ +2OH - = CaBe(PO4)OH↓ + H3PO4 +H2O (7)

[0059] Adding aluminum-containing regulator to beryllium slag can react with the original Al, Si (SiO2, SiO3 2- ) and the subsequent Si added to the cement undergoes adsorption and co-precipitation reaction to obtain Al-Si-Be co-precipitates with low solubility, such as Be3Al2Si6O 18 Or 2Al(OH)3·3Be(OH)2·6SiO2 precipitation. The reaction is shown in equations (8) to (11):

[0060] 3Be 2+ + 2Al 3+ + 6SiO2 + 12OH - = Be3Al2Si6O 18 ↓ + 6H2O (8)

[0061] 3Be 2+ + 2Al 3+ + 6SiO2 + 12OH - = 2Al(OH)3·3Be(OH)2·6SiO2↓(9)

[0062] 3Be 2+ + 2Al(OH)3 + 6SiO2 + 6OH - = Be3Al2Si6O 18 ↓ + 6H2O (10)

[0063] 3Be 2++ 2Al(OH)3 + 6SiO2 + 6OH - = 2Al(OH)3·3Be(OH)2·6SiO2↓(11)

[0064] In addition, the aluminum-containing regulator hydrolyzes to produce hydroxyl complexes or polymers, which promote the aggregation and flocculation growth of fine beryllium phosphate particles and other colloidal particles through adsorption, electrical neutralization, net capture and sweeping, forming denser and easier to settle / filter aggregates, reducing the risk of subsequent leaching.

[0065] In step 3), the amount of soluble phosphate added is controlled to be 2% to 8% of the mass of the dry beryllium slag, specifically 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, and 8%. Too little soluble phosphate addition will result in PO4 3- If the concentration is too low, the precipitation reaction and coordination reaction with Be will be limited, which is not conducive to the precipitation and coordination solidification of Be. If the amount of soluble phosphate added is too high, it will lead to unnecessary increase in reagent costs.

[0066] The dosage of aluminum-containing regulator is controlled to be 0% to 0.5% of the mass of dry beryllium slag, specifically 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%.

[0067] In step 4), the purpose of adding silicate cement is to form hard calcium silicate hydrate (CSH) gel, ettringite and other minerals, which wrap and consolidate the low-solubility stabilized products (such as beryllium phosphate precipitates and their aggregates) formed in steps 2) and 3) and other components in a dense matrix.

[0068] Cement hydration produces a strong alkaline environment (pH>12.5). According to equations (1) to (4) and (6) to (11), alkaline conditions are conducive to promoting the formation of CaBe(PO4)OH, Be3Al2Si6O 18 Furthermore, even if a small amount of incompletely solidified beryllium remains, it tends to precipitate as less soluble beryllium hydroxide (Be(OH)2). Through these steps, deep solidification and stabilization of beryllium are ultimately achieved.

[0069] In step 4), the cement dosage should be controlled between 3% and 12% of the dry beryllium slag mass, specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, and 12%. Too low a cement dosage will hinder the formation of minerals such as calcium silicate hydrate (CSH) gel and ettringite, preventing densification and stable encapsulation of the beryllium slag. This can lead to excessive Be leaching concentrations. Too low a cement dosage will lead to unnecessary increases in reagent costs and an increase in the volume and mass of the beryllium slag (increased volume expansion ratio), resulting in excessively high overall treatment and disposal costs for the beryllium slag.

[0070] Beryllium slag, calculated on a dry basis, contains the following main components: Ca (10% to 25%), Si (10% to 25%), Be (0.05% to 0.40%), O (35% to 55%), S (5% to 15%), and Al (0.3% to 1.0%). Beryllium slag is generally neutral or alkaline, with gypsum (CaSO₄·2H₂O) and silicon dioxide (SiO₂) as its primary mineral components.

[0071] The mixing and stirring time in step 2) is 1 to 3 hours, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. The mixing and stirring temperature is 5°C to 35°C, specifically 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, or 35°C. The mixing and stirring time in step 3) is 3 to 6 hours, specifically 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours. The mixing and stirring temperature is 5°C to 35°C, specifically 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, or 35°C. The adsorption and precipitation reactions in steps 2) and 3) can be completed at room temperature (5°C to 35°C) with a relatively short reaction time. High temperatures and prolonged reaction times are not required to form a beryllium-containing precipitate similar to natural calcium phosphate beryllite ([CaBe(PO4)OH]), creating favorable conditions for the application of the technology.

[0072] The sparingly soluble phosphate seed crystals in step 2) are one or more of Ca₃(PO₄)₂, Ca₅(PO₄)₃OH, CaHPO₄, and CaHPO₄·2H₂O. The sparingly soluble phosphate seed crystals are derived from common calcium-phosphate precipitates and can be artificially synthesized or naturally occurring minerals containing these components, such as leucodesprite, hydroxyapatite, monetite, and brushite.

[0073] In step 2), the amount of sparingly soluble phosphate seed crystals added is 0.6% to 1% of the mass of the dry beryllium slag. The particle size of the sparingly soluble phosphate seed crystals is 20 to 60 μm, specifically 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, and 60 μm. Controlling the amount of sparingly soluble phosphate seed crystals is crucial for ensuring adsorption and co-precipitation effectiveness while reducing processing costs. The particle size of the sparingly soluble phosphate seed crystals is designed to optimize their specific surface area and effectiveness, thereby improving adsorption and precipitation efficiency. If the particle size of the sparingly soluble phosphate seed crystals is too small, the precipitate will easily agglomerate, hindering ion migration and reaction, and reducing adsorption and precipitation efficiency. If the particle size of the sparingly soluble phosphate seed crystals is too large, the specific surface area of ​​the seed crystals will decrease, correspondingly reducing adsorption and precipitation efficiency.

[0074] In step 3), the dosage of soluble phosphate is 2.5% to 4% of the dry beryllium slag mass. By controlling the dosage of soluble phosphate, processing costs can be reduced while ensuring the precipitation and coordination effects.

[0075] In step 3), the soluble phosphate is one or more of KH2PO4, K2HPO4, K3PO4, NaH2PO4, Na2HPO4, Na3PO4, NH4H2PO4, (NH4)2HPO4. The soluble phosphate has a large solubility in the water system, which is beneficial to PO4 3- Migration and reaction in beryllium slag.

[0076] The aluminum-containing modifier in step 3) is one or more of AlCl₃, Al₂(SO₄)₃, polyaluminum sulfate, polyaluminum chloride, and Al(OH)₃. The aluminum-containing modifier is an aluminum-containing compound or precipitate. Under alkaline conditions, the aluminum-containing modifier undergoes a co-precipitation reaction with Si and Be to produce a stable Al-Si-Be precipitate. The dosage of the aluminum-containing modifier is controlled to ensure the co-precipitation effect while reducing processing costs. When the molar ratio of Al to Be in the beryllium slag (dry basis) is greater than or equal to 1:1, the dosage of the aluminum-containing modifier is 0% to 0.5% of the dry beryllium slag mass. For example, if the mass fraction of Al in the beryllium slag is greater than 0.6% and the mass fraction of Be is less than 0.2%, the addition of the aluminum-containing modifier is unnecessary. If a better solidification and stabilization effect of Be is desired, the aluminum-containing modifier may be added, with the dosage controlled to 0.1% to 0.5% of the dry beryllium slag mass. If the molar ratio of Al to Be in the beryllium slag (dry basis) is less than 1:1, the dosage of the aluminum-containing regulator should be controlled to 0.1% to 0.5% of the dry beryllium slag mass. If the dosage of the aluminum-containing regulator is too large, the reagent cost will increase, the volume and mass of the beryllium slag will increase, and the final disposal cost of the beryllium slag will increase.

[0077] The Portland cement in step 4) includes one or more of P·O42.5, P·O42.5R, P·O52.5, P·O52.5R, P·S32.5, P·S32.5R, P·S42.5, P·S42.5R, P·S52.5, and P·S52.5R. The Portland cement meets the requirements of GB175-2023 "General Portland Cement," where P·O represents ordinary Portland cement and P·S represents slag Portland cement.

[0078] In step 4), the moisture content of the converted beryllium slag during mixing with cement is controlled to be 20% to 30%, the mixing time is 0.5h to 1h, and the stabilization curing time is not less than 7 days. Controlling the moisture content during mixing with cement and maintaining an alkaline aqueous environment in the solidification system for a certain period of time is conducive to the complete reaction of equations (1) to (11), further promoting the co-precipitation and solidification of Be. Finally, through stabilization curing for not less than 7 days, a monolithic block with high mechanical strength and low permeability is obtained, achieving efficient and low-cost solidification and stabilization of the final beryllium slag, and laying the foundation for subsequent disposal such as transportation and landfill.

[0079] The present invention has no particular limitation on the sources of the above raw materials, and general commercial products can be selected.

[0080] In order to further illustrate the present invention, a method for solidifying and stabilizing beryllium slag provided by the present invention is described in detail below with reference to the following examples and comparative examples, but they should not be construed as limiting the scope of protection of the present invention.

[0081] In the following examples (1 to 4) and comparative examples provided by the present invention, the treated beryllium slag was taken from a beryllium smelter in Hunan Province. The moisture content of the beryllium slag was 12%. The main components of the beryllium slag (dry basis) are shown in Table 1.

[0082] Table 1 Main components of beryllium slag (dry basis) by mass percentage, % Ca Si Be As O Cu S Mg Al 18.85 16.64 0.20 0.11 42.70 0.13 10.15 0.54 0.57

[0083] In the following examples (5-6) provided by the present invention, the treated beryllium slag was taken from a beryllium smelter in Hunan Province. The moisture content of the beryllium slag was 12%. The main components of the beryllium slag (dry basis) are shown in Table 2.

[0084] Table 2 Main components of beryllium slag (dry basis) by mass percentage, % Ca Si Be As O Cu S Mg Al 18.66 16.51 0.15 0.11 42.77 0.12 10.39 0.55 0.65

[0085] Example 1

[0086] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0087] Place 100 g of beryllium slag in a plastic container and add an appropriate amount of water to adjust the moisture content of the beryllium slag to 18%. Add 0.5 g of Ca₃(PO₄)₂ with a particle size of 20 μm to the beryllium slag and stir at 20°C for 3 hours to obtain a beryllium slag-phosphate mixed precipitate. Add 2.5 g of KH₂PO₄ and 0.3 g of Al₂(SO₄)₃ to the beryllium slag-phosphate mixed precipitate and stir at 20°C for 3 hours to obtain converted beryllium slag. Add 3 g of P·O₄2.5 cement to the converted beryllium slag and add an appropriate amount of water to control the moisture content of the converted beryllium slag and cement to 20%. Stir for 1 hour and allow to stabilize and cure for 28 days to obtain a solidified beryllium slag.

[0088] SEM image of the solid body ( Figure 2 ) shows that the overall structure of beryllium slag before solidification is loose, with many large pores and channels. After solidification, the solidified body is fully hydrated, the gelled products increase and cross-link and grow with each other, the microstructure becomes denser, and the pore size and connectivity are significantly reduced. The large amount of highly active PO4 contained in phosphate 3- It reacts rapidly with Ca(OH)2, providing microcrystalline nuclei for the subsequent formation of C-S-H gel. The presence of Ca(OH)2 makes the system alkaline, which facilitates silicate hydration. Phosphate, cement, and beryllium slag form a synergistic coupling, fostering the formation of a dense network structure and achieving solidification and stabilization of beryllium.

[0089] XRD Figure 3 ) The results show that the diffraction peak at 2θ of 31.2° in Example 1 is attributed to Be3Al2Si6O 18 (PDF#00-009-0430), and the diffraction peak at 2θ of 23.45° is attributed to CaBe(PO4)OH (PDF#00-006-0338), indicating that the increase in the use of phosphate and aluminum-containing regulators promotes the conversion of Be in beryllium slag into stable mineral-like precipitates, thereby promoting the solidification and stabilization of beryllium.

[0090] FTIR spectrum ( Figure 4 ) showed that before solidification, the beryllium slag had a stretching vibration peak of Si—O bonds in the 1020–1090 cm⁻¹ region. After solidification, this peak significantly weakened. The addition of phosphate altered the electron cloud distribution of the groups, resulting in a shift in their absorption frequency, indicating the formation of beryllium-containing silicon precipitates. Before solidification, a stretching vibration peak of Be—O bonds was present in the 510–600 cm⁻¹ region. After solidification, this characteristic peak significantly broadened, indicating the formation of a new solidified product.

[0091] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.05 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0092] Example 2

[0093] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0094] Place 100 g of beryllium slag in a plastic container and add an appropriate amount of water to adjust the moisture content of the beryllium slag to 15%. Add 2 g of Ca5(PO4)3OH with a particle size of 30 μm to the beryllium slag and stir at 5°C for 2 hours to obtain a beryllium slag-phosphate mixed precipitate. Add 2 g of NaH2PO4 and 0.2 g of AlCl3 to the beryllium slag-phosphate mixed precipitate and stir at 5°C for 4 hours to obtain converted beryllium slag. Add 5 g of P·O52.5 cement to the converted beryllium slag and add an appropriate amount of water to control the moisture content of the converted beryllium slag and cement to 25%. Stir for 0.5 hour and allow to stabilize and cure for 7 days to obtain a solidified beryllium slag.

[0095] Electron micrograph of the solidified body ( Figure 2 )、XRD pattern( Figure 3 )、FTIR spectrum( Figure 4 ) all prove that solidification forms a stable beryllium-containing mineral precipitate, the solidified body has a denser structure and better physical and chemical stability.

[0096] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.07 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0097] Example 3

[0098] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0099] Place 100 g of beryllium slag in a plastic container and add an appropriate amount of water to adjust the moisture content of the beryllium slag to 30%. Add 0.6 g of CaHPO₄ with a particle size of 45 μm to the beryllium slag and stir at 25°C for 1 hour to obtain a beryllium slag-phosphate mixed precipitate. Add 4 g of K₂HPO₄ and 0.5 g of polyaluminum sulfate to the beryllium slag-phosphate mixed precipitate and stir at 25°C for 6 hours to obtain converted beryllium slag. Add 8 g of P·S₄2.5 cement to the converted beryllium slag and add an appropriate amount of water to adjust the moisture content of the converted beryllium slag and cement to 30%. Stir for 0.5 hour and allow to stabilize for 7 days to obtain a solidified beryllium slag.

[0100] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.09 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0101] Example 4

[0102] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0103] Place 100 g of beryllium slag in a plastic container and add an appropriate amount of water to adjust the moisture content to 25%. Add 1.0 g of CaHPO4·2H2O with a particle size of 60 μm to the beryllium slag and stir at 35°C for 1 hour to obtain a beryllium slag-phosphate mixed precipitate. Add 8 g of NH4H2PO4 and 0.4 g of polyaluminum chloride to the beryllium slag-phosphate mixed precipitate and stir at 35°C for 5 hours to obtain converted beryllium slag. Add 12 g of P·S52.5 cement to the converted beryllium slag and add an appropriate amount of water to control the moisture content of the converted beryllium slag and cement to 25%. Stir for 1 hour and allow to stabilize and cure for 14 days to obtain a solidified beryllium slag.

[0104] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.06 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0105] Example 5

[0106] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0107] The difference from Example 1 is that the composition of the beryllium slag (dry basis) is shown in Table 2.

[0108] Place 100 g of beryllium slag in a plastic container and add an appropriate amount of water to adjust the moisture content of the beryllium slag to 18%. Add 0.5 g of Ca₃(PO₄)₂ with a particle size of 20 μm to the beryllium slag and stir at 20°C for 3 hours to obtain a beryllium slag-phosphate mixed precipitate. Add 2.5 g of KH₂PO₄ to the beryllium slag-phosphate mixed precipitate and stir at 20°C for 3 hours to obtain converted beryllium slag. Add 3 g of P·O₄2.5 cement to the converted beryllium slag and add an appropriate amount of water to control the moisture content of the converted beryllium slag and cement to 20%. Stir for 1 hour and allow to stabilize for 28 days to obtain a solidified beryllium slag.

[0109] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.12 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0110] It can be seen that when the mass fraction of Al in the beryllium slag is higher than 0.6% and the mass fraction of Be is lower than 0.2%, that is, when the molar ratio of Al to Be in the beryllium slag is greater than or equal to 1:1, there is no need to add additional aluminum-containing regulator, and the solidified beryllium leaching concentration can meet the national standard requirements.

[0111] Example 6

[0112] A method for solidification and stabilization of beryllium slag, the process flow chart is as follows Figure 1 shown.

[0113] The difference from Example 1 is that the composition of the beryllium slag (dry basis) is shown in Table 2.

[0114] 0.5g of Ca₃(PO₄)₂ with a particle size of 20μm was added to the beryllium slag and stirred at 20°C for 3 hours to obtain a beryllium slag-phosphate mixed precipitate. 2.5g of KH₂PO₄ and 0.3g of Al₂(SO₄)₃ were added to the beryllium slag-phosphate mixed precipitate and stirred at 20°C for 3 hours to obtain converted beryllium slag. 3g of P·O₄2.5 cement was added to the converted beryllium slag. An appropriate amount of water was added to control the moisture content of the converted beryllium slag and cement to 20% during mixing. The mixture was stirred for 1 hour and then cured for 28 days to obtain a solidified beryllium slag.

[0115] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.06 mg / L, which meets the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0116] It can be seen that when the molar ratio of Al to Be in the beryllium slag is greater than or equal to 1:1, the beryllium leaching concentration of the solidified body can be further reduced if an additional aluminum-containing regulator is added.

[0117] Comparative Example 1

[0118] The difference from Example 1 is that the insoluble phosphate seed crystals Ca3(PO4)2 are not added.

[0119] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.72 mg / L, which does not meet the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0120] Comparative Example 2

[0121] The difference from Example 1 is that the added amount of Ca3(PO4)2 is 0.3 g and the particle size is 10 μm.

[0122] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.37 mg / L, which does not meet the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0123] Comparative Example 3

[0124] The difference from Example 1 is that the particle size of Ca3(PO4)2 is 80 μm.

[0125] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.29 mg / L, which does not meet the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0126] Comparative Example 4

[0127] The difference from Example 1 is that the aluminum-containing regulator Al2(SO4)3 is not added.

[0128] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.25 mg / L, which does not meet the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0129] It can be seen that when the molar ratio of Al to Be in beryllium slag is lower than 1:1, if no additional aluminum-containing regulator is added, the beryllium leaching concentration of the solidified body cannot meet the national standard requirements.

[0130] Comparative Example 5

[0131] The difference from Example 1 is that the amount of soluble phosphate KH2PO4 added is 0.5 g.

[0132] Empirical measurements show that the mass concentration of beryllium leaching in the solidified body is 0.41 mg / L, which does not meet the limit requirement of 0.20 mg / L in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019).

[0133] Comparative Example 6

[0134] The difference from Example 1 is that the insoluble phosphate seed crystals Ca3(PO4)2 are not added, and the amount of cement added is 20g.

[0135] Empirical measurements show that the beryllium leaching concentration in the solidified material is 0.16 mg / L, which meets the 0.20 mg / L limit stipulated in the "Hazardous Waste Landfill Pollution Control Standard" (GB 18598-2019). However, excessive cement addition increases the solidified material volume by 40%, significantly increasing both the cost of the reagent (cement) and the cost of disposing of the solidified material.

[0136] Combining Examples 1 to 6 and Comparative Examples 1 to 5, it can be seen that if the method and conditions of the present invention are not adopted, the beryllium concentration leached from the beryllium slag solid body cannot be guaranteed to meet the 0.20 mg / L requirement of the "Hazardous Waste Landfill Pollution Control Standard" GB 18598-2019. Combining Example 1 and Comparative Example 6, it can be seen that if the method and conditions of the present invention are not adopted, increasing the cement addition amount can make the Be leaching concentration of the solid body meet the national standard requirements, but the solid body volume expansion ratio is significantly increased, resulting in increased processing costs.

[0137] The above description of the disclosed embodiments is intended to enable one skilled in the art to experiment with or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for solidification and stabilization of beryllium slag, characterized in that: The following steps are involved: (1) Adjust the moisture content of beryllium slag to 15% to 30% by adding water or air drying; (2) adding insoluble phosphate seed crystals to the beryllium slag, controlling the addition amount of the insoluble phosphate seed crystals to be 0.5% to 2% of the mass of the dry beryllium slag, and mixing and stirring to obtain a beryllium slag-phosphate mixed precipitate; (3) adding soluble phosphate and aluminum-containing regulator to the beryllium slag-phosphate mixed precipitate to carry out conversion reaction, controlling the addition amount of soluble phosphate to 2% to 8% of the mass of the dry beryllium slag, and controlling the addition amount of aluminum-containing regulator to 0% to 0.5% of the mass of the dry beryllium slag, and mixing and stirring to obtain converted beryllium slag; (4) Add silicate cement to the converted beryllium slag, control the cement dosage to 3% to 12% of the dry mass of the beryllium slag, and perform stable curing to obtain a solidified beryllium slag.

2. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The beryllium slag has the following main components, calculated on a dry basis: a mass fraction of Ca of 10% to 25%, a mass fraction of Si of 10% to 25%, a mass fraction of Be of 0.05% to 0.40%, a mass fraction of O of 35% to 55%, a mass fraction of S of 5% to 15%, and a mass fraction of Al of 0.3% to 1.0%.

3. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The mixing and stirring time in step (2) is 1 h to 3 h, and the mixing and stirring temperature is 5° C. to 35° C.; the mixing and stirring time in step (3) is 3 h to 6 h, and the mixing and stirring temperature is 5° C. to 35° C.

4. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The sparingly soluble phosphate seed crystals in step (2) are one or more of Ca3(PO4)2, Ca5(PO4)3OH, CaHPO4, and CaHPO4·2H2O.

5. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: In the step (2), the amount of the sparingly soluble phosphate seed crystals added is 0.6% to 1% of the mass of the dry beryllium slag, and the particle size of the sparingly soluble phosphate seed crystals is 20 to 60 μm.

6. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: In step (3), the amount of soluble phosphate added is 2.5% to 4% of the mass of the dry beryllium slag.

7. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The soluble phosphate in step (3) is one or more of KH2PO4, K2HPO4, K3PO4, NaH2PO4, Na2HPO4, Na3PO4, NH4H2PO4, and (NH4)2HPO4.

8. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The aluminum-containing regulator in step (3) is one or more of AlCl3, Al2(SO4)3, polyaluminum sulfate, polyaluminum chloride, and Al(OH)3. When the molar ratio of Al to Be in the beryllium slag (dry basis) is greater than or equal to 1:1, the amount of the aluminum-containing regulator added is 0% to 0.5% of the mass of the dry beryllium slag. When the molar ratio of Al to Be in the beryllium slag (dry basis) is less than 1:1, the amount of the aluminum-containing regulator added is 0.1% to 0.5% of the mass of the dry beryllium slag.

9. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: The silicate cement in step (4) includes one or more of P·O42.5, P·O42.5R, P·O52.5, P·O52.5R, P·S32.5, P·S32.5R, P·S42.5, P·S42.5R, P·S52.5, and P·S52.5R.

10. The method for solidification and stabilization of beryllium slag according to claim 1, characterized in that: In the step (4), the moisture content of the converted beryllium slag when mixed with cement is controlled to be 20% to 30%, the mixing time is 0.5h to 1h, and the stable curing time is not less than 7 days.

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