Barium chloride production waste residue treatment method

Abstract

The invention provides a barium chloride production waste residue treatment method, and relates to the technical field of barium chloride production waste residue treatment, and the barium chloride production waste residue treatment method comprises the following steps: S1, carrying out ball milling on waste residues containing barium sulfate and barium sulfide, and then carrying out pre-oxidation and hydration treatment to obtain a barium hydroxide-containing turbid liquid; s2, dehydrating and drying the turbid liquid in the S1; s3, mixing and calcining the dried material and sodium carbonate to obtain a calcined product containing barium carbonate; s4, the calcined product is subjected to hot water leaching to remove soluble sodium salt, and water leaching residues are obtained; s5, first-stage acid leaching is conducted on the water leaching residues through low-concentration hydrochloric acid, and first-stage leaching liquid and first-stage filter residues are obtained through filtering; performing second-stage acid leaching on the first-stage filter residue by using high-concentration hydrochloric acid, and filtering to obtain a second-stage leaching solution; and S6, combining the first-stage leaching solution and the second-stage leaching solution, adjusting the pH value to 4.0-5.0, filtering and separating precipitates, and concentrating and crystallizing to obtain a barium chloride product. According to the method, efficient conversion and resource utilization of barium in the waste residues are achieved through the processes of pre-oxidation toxicity control, calcination conversion, gradient acid leaching and deep purification.

Description

Technical Field

[0001] This application relates to the field of barium chloride production waste residue treatment technology, and in particular to a method for treating barium chloride production waste residue. Background Technology

[0002] The production of barium chloride generates industrial waste residue, primarily composed of insoluble barium sulfate (BaSO4), barium sulfide (BaS), and barium silicate salts. The long-term accumulation of this waste residue poses a serious environmental crisis: barium ions (Ba... 2+ Through continuous leaching by rainwater, barium sulfide will cause heavy metal pollution in soil and groundwater. Simultaneously, barium sulfide components will release highly toxic hydrogen sulfide gas (H2S) during acid leaching or in humid environments, directly endangering the lives of workers. Even more seriously, 15–30% of recyclable barium resources in the waste residue are discarded, resulting in tens of thousands of tons of barium compounds being unusable annually, creating a dual burden of resource waste and environmental risks.

[0003] In existing technologies, such as the patent with publication number CN120271022B, a method for preparing barium chloride from barium slag is disclosed. This method achieves barium recovery through staged roasting (dehydration + chlorination) combined with graded leaching (hot water leaching + dilute hydrochloric acid leaching). Although this method has a certain effect on the conversion of barium sulfate, it has obvious defects when treating mixed waste residue containing barium sulfide. First, barium sulfide easily reacts with oxygen to generate barium oxide and sulfur dioxide during the roasting stage, or is converted into calcium sulfide (CaS) by calcium chloride. However, the decomposition rate of calcium sulfide is insufficient in the subsequent low-concentration hydrochloric acid leaching, resulting in a significant decrease in barium recovery rate. Second, the molten calcium sulfide formed in the high-temperature stage will coat unreacted barium compound particles, blocking the acid mass transfer path and causing a large amount of barium resources to remain. Third, the insufficiently decomposed calcium sulfide continuously releases H2S gas during acid leaching, requiring an additional tail gas purification system to meet safety production requirements, which significantly increases the processing cost.

[0004] Current barium chloride waste residue treatment processes generally have low recovery efficiency. For waste residues with complex compositions (such as those containing barium sulfate, barium sulfide, and aluminosilicates simultaneously), traditional methods fail to achieve sufficient barium recovery rates. This is mainly attributed to the conflicting conversion conditions of various forms of barium compounds (such as barium sulfate and barium sulfide) in the waste residue, making it difficult to achieve the desired results with a single process parameter. This leads to the ineffective conversion of some components, exacerbating resource waste and forcing some companies to abandon waste residue resource recovery in favor of lower-cost landfill disposal, further increasing the environmental burden. Summary of the Invention

[0005] In view of this, this application proposes a method for treating barium chloride production waste residue to solve the problems of low efficiency in barium resource recovery from barium sulfide conversion, high risk of hydrogen sulfide release during acid leaching, and poor impurity removal in existing barium chloride waste residue treatment technologies.

[0006] The technical solution of this application is implemented as follows: This application provides a...

[0007] On the one hand, this application discloses a method for treating waste residue from barium chloride production, including the following steps: S1. The waste residue containing barium sulfate and barium sulfide is ball-milled, then pre-oxidized and hydrated to obtain a suspension containing barium hydroxide.

[0008] This step addresses the issue of hydrogen sulfide generation from direct acid leaching of barium sulfide. Pre-oxidation reduces the risk and is a prerequisite for all subsequent processes.

[0009] Specifically, the waste residue is first treated using a ball milling process to increase its specific surface area and activity, thereby improving the efficiency of subsequent reaction conversion. In the pre-oxidation stage, under controlled oxygen conditions (such as limited air supply), barium sulfide (BaS), which is highly toxic and easily decomposes into H2S, is oxidized to barium oxide (BaO), with the reaction formula: 2BaS + 3O2 → 2BaO + 2SO2.

[0010] During the hydration stage, barium oxide reacts with water to transform into barium hydroxide (Ba(OH)2), which is more readily involved in subsequent reactions. The reaction equation is: BaO + H2O → Ba(OH)2.

[0011] By setting up step S1, the BaS in the waste residue is converted into stable Ba(OH)2 at the source, completely eliminating the risk of generating highly toxic H2S gas in the subsequent acid leaching step. Secondly, after pre-oxidation hydration treatment, the waste residue is transformed from the original barium sulfate (BaSO4), barium sulfide (BaS), and aluminosilicates into a complex mixture of barium hydroxide solid particles, unreacted barium sulfate, silicate impurities, and other components dispersed in water. This complex mixture is a suspension, and the Ba(OH)2 in the suspension more readily participates in subsequent reactions.

[0012] S2. Dehydrate and dry the suspension from step S1.

[0013] This step can be carried out by mechanical dehydration and thermal drying. Mechanical dehydration methods include centrifugal separation or pressure filtration, while thermal drying can be carried out using methods such as rotary dryers or fluidized bed dryers.

[0014] Step S2 is designed to avoid the waste of energy in evaporating water caused by directly calcining the suspension. It also prevents the wet material from softening and sticking together at high temperatures, forming large lumps or a kiln crust that prevents sufficient contact between the material inside and the sodium carbonate, leading to incomplete reaction and a significant reduction in conversion rate. Furthermore, it avoids unnecessary side reactions between high-temperature steam and reactants or products. For example, it might promote the hydrolysis of sodium carbonate (Na₂CO₃) or react with certain impurities to form difficult-to-handle compounds.

[0015] S3. The dried material is mixed with sodium carbonate and then calcined to obtain a calcined product containing barium carbonate.

[0016] In this step, barium hydroxide and sodium carbonate in the material react at high temperature to produce barium carbonate and sodium hydroxide. The reaction formula is: Ba(OH)₂ + Na₂CO₃ → BaCO₃ + 2NaOH. The NaOH gas generated at high temperature can be recovered. Simultaneously, barium sulfate and sodium carbonate in the material react at high temperature to produce barium carbonate and sodium sulfate. The reaction formula is: BaSO₄ + Na₂CO₃ → BaCO₃ + Na₂SO₄.

[0017] In step S3, barium sulfate and barium hydroxide can be converted into barium carbonate (BaCO3), which is easier to extract with acid. Compared with Ba(OH)2 or BaSO4, BaCO3 has a higher dissolution rate and efficiency in acid. This step is designed to create optimal conditions for efficient acid leaching and recovery of barium.

[0018] S4. The calcined product is leached with hot water to remove soluble sodium salts, and the water-leached residue is obtained.

[0019] This step utilizes differences in solubility for preliminary separation and purification. Na₂SO₄ and unreacted Na₂CO₃ sodium salts, byproducts of calcination, are readily soluble in hot water, while barium carbonate and unreacted aluminosilicates are poorly soluble. Separating and removing soluble sodium salts prevents large amounts of sodium ions from entering the subsequent acid leaching system, reducing acid consumption and the burden on subsequent purification processes, improving the efficiency of subsequent steps, and lowering processing costs. The resulting "water-leached residue," primarily composed of barium carbonate and silicates, improves the raw material grade for subsequent acid leaching.

[0020] S5. The water-leached residue is first subjected to a first-stage acid leaching with low-concentration hydrochloric acid, and then filtered to obtain a first-stage leachate containing barium chloride and a first-stage filter residue; then the first-stage filter residue is subjected to a second-stage acid leaching with high-concentration hydrochloric acid, and then filtered to obtain a second-stage leachate containing barium chloride.

[0021] The primary acid leaching process uses low-concentration hydrochloric acid to dissolve barium carbonate in the water-leached residue. The reaction equation is: BaCO3 + 2HCl → BaCl2 + CO2 + H2O. The reaction product yields a primary leachate mainly containing barium chloride (BaCl2), while simultaneously generating a large amount of carbon dioxide bubbles. The primary filter residue mainly consists of undissolved barium silicate, barium silicate, and aluminosilicate. Primary acid leaching efficiently recovers the main barium source and preferentially dissolves the main product (BaCO3) generated during calcination, resulting in a relatively pure barium chloride solution. Furthermore, it inhibits the leaching of impurities: under low acidity conditions, the leaching rate of impurities such as iron and aluminum is low, reducing the burden on subsequent purification.

[0022] The secondary acid leaching process uses high-concentration hydrochloric acid to dissolve barium silicate in the primary filter residue. The reaction formula is: BaSiO3 + 4HCl → BaCl2 + Si(OH)4, where Si(OH)4 condenses to form SiO2·nH2O (flocculated silica gel). The reaction product yields a secondary leachate mainly containing barium chloride (BaCl2) and a large amount of silica gel. Secondary acid leaching effectively dissolves insoluble barium salts (such as BaSiO3), improving barium recovery, and concentrates insoluble impurities such as iron and aluminum in a smaller liquid volume, facilitating subsequent centralized processing.

[0023] It should be noted that the barium compounds in the waste residue have drastically different chemical properties and solubilities. Using a single concentration of acid for treatment cannot simultaneously achieve both high efficiency and economy, presenting a trade-off. If a high-concentration acid is used throughout the process, although it can dissolve all barium compounds, it will cause a large amount of impurities such as silicon, aluminum, and iron to dissolve rapidly and simultaneously, severely polluting the leachate and greatly increasing the difficulty and cost of subsequent purification. If a low-concentration acid is used throughout the process, it can only dissolve easily reactive barium carbonate (BaCO3), but cannot dissolve sparingly soluble barium salts such as barium silicate (BaSiO3), resulting in a significant decrease in barium recovery rate.

[0024] Therefore, the "gradient acid leaching" (lower acid leaching first, then higher acid leaching) design in step S5 of this application is the optimal solution to the contradiction between "recovery rate" and "purity", and achieves graded selective dissolution of barium compounds with different properties.

[0025] S6. Combine the primary and secondary leachates, adjust the pH to 4.0-5.0, filter to separate the precipitate, and concentrate and crystallize to obtain barium chloride product.

[0026] The primary and secondary leachates are combined to collect all dissolved barium elements, forming a solution with a high barium concentration and uniform composition. This provides feed for the subsequent concentration and crystallization process, improving production efficiency. The combined leachate mainly contains BaCl2, with the core impurities being silica gel (SiO2·nH2O) produced by the secondary acid leaching and trace amounts of dissolved metal ions (such as Fe). 3+ Al3 + pH adjustment is a precise method for removing these impurities.

[0027] In practice, the pH value of the mixed leachate is adjusted by adding an alkaline solution (such as NaOH) to the combined leachate.

[0028] The removal of colloids is accomplished through a colloidal aggregation mechanism. The mechanism is as follows: silica gel particles carry a negative charge on their surface, which causes them to repel each other and remain in stable suspension. At pH 4-5, their surface zeta potential approaches the isoelectric point (≈0), the electrostatic repulsion disappears, and the colloidal particles rapidly collide and aggregate into large flocs (agglomerates).

[0029] For the removal of metal ions (such as Fe) 3+ The removal is accomplished through a hydrolysis-precipitation mechanism, and its removal mechanism is as follows: Fe 3+ When pH > 3.5, it begins to hydrolyze to form a flocculent precipitate of Fe(OH)3, which can trap and adsorb other trace impurities and settle together.

[0030] Adjusting the pH to 4.0-5.0 is necessary to achieve silica flocculation and Fe... 3+ The common optimal range for hydrolysis precipitation is determined. After this operation, most impurities can be removed in solid form by filtration, resulting in a pure barium chloride solution. Finally, high-purity barium chloride product can be obtained by concentration and crystallization.

[0031] Based on the above technical solution, preferably, in step S1, the ball milling treatment includes: ball milling the waste residue at 20-25℃ for 1-2 hours, and controlling the particle size of the pretreated barium slag to be ≤200 mesh.

[0032] Based on the above technical solution, preferably, the pre-oxidation in step S1 is carried out at 300-400°C by introducing oxygen-containing gas, and the oxygen concentration of the oxygen-containing gas is controlled at 5%-8%.

[0033] By limiting the pre-oxidation temperature, with a lower limit of 300℃, the oxidation reaction of barium sulfide (BaS) is ensured to start (2BaS + 3O2 → 2BaO + 2SO2). Below this temperature, the reaction rate is too low and the efficiency is not up to standard. The upper limit of 400℃ prevents over-oxidation of barium sulfide (BaS) to form difficult-to-handle BaSO4 (side reaction: BaS + 2O2 → BaSO4), while also avoiding material sintering. In addition, excessive oxygen concentration will promote the direct oxidation of BaO to BaSO4, while insufficient oxygen will lead to incomplete oxidation of BaS, and the residual BaS will release H2S during subsequent acid leaching. Based on the above technical solution, preferably, the low-concentration hydrochloric acid in step S5 is 1-2 mol / L hydrochloric acid, and the high-concentration hydrochloric acid is 4-6 mol / L hydrochloric acid.

[0034] Based on the above technical solution, preferably, in step S3, a catalyst is added simultaneously when the dried material is mixed with sodium carbonate. The catalyst includes zinc oxide and calcium fluoride, and the amount added is based on the mass of the dried material, with zinc oxide at 0.7%-2.0% and calcium fluoride at 0.3%-1.0%. The mass ratio of the dried material to sodium carbonate is 1:(0.5-0.6).

[0035] The zinc oxide and calcium fluoride exhibit a significant synergistic catalytic effect under the low-temperature calcination conditions of this invention. As a solid acid catalyst, zinc oxide's surface acidic sites can adsorb carbonate ions (CO3-). 2- This weakens the lattice energy of barium sulfate (BaSO4) and lowers the activation energy of the reaction. Calcium fluoride can form a trace liquid phase at 650-750℃, which is a source of ions (such as O) in solid-phase reactions. 2- CO3 2- This provides a rapid migration pathway. Together, these two processes enable the efficient conversion of barium sulfate to barium carbonate at temperatures significantly lower than those of traditional processes (650-750℃ vs. 1100-1200℃).

[0036] The calcination temperature in step S3 is 650-750℃, and the calcination time is 1-2 hours.

[0037] Specifically, during the calcination stage, the solid-state reaction between barium sulfate (BaSO4) and sodium carbonate (Na2CO3) typically requires a calcination temperature of 1100℃-1200℃, resulting in high energy consumption. Furthermore, at high temperatures, the materials are prone to sintering and forming rings, which can encapsulate unreacted raw materials, leading to uneven reaction and a decrease in conversion rate.

[0038] This application introduces a catalyst during the calcination stage, wherein ZnO acts as a solid acid catalyst, adsorbing CO3 through its surface acidic sites. 2- The presence of ions weakens the Ba-O bond strength in the BaSO4 lattice, thus lowering the activation energy of the reaction. CaF2 melts at 650-750℃ to form a eutectic liquid phase, accelerating the reaction. 2- and CO3 2- Ion migration enhances the reaction rate. By adding two catalysts, the calcination temperature can be reduced from 1100℃ to 650℃-700℃, thereby increasing the conversion rate of BaSO4.

[0039] The treatment plan for catalyst residues is as follows: In a high-concentration hydrochloric acid environment, some ZnO rapidly dissolves to form a soluble zinc salt: ZnO + 2HCl → ZnCl₂ + H₂O. After the reaction, Zn... 2+Upon entering the solution, it becomes an ionic impurity in the secondary leachate. During the pH adjustment stage in step S6, Zn(OH)2 colloid is generated at pH = 4.0-5.0. 2+ +2OH - →Zn(OH)2↓, and is simultaneously captured and co-precipitated by Fe(OH)3 flocs.

[0040] CaF2 is chemically very stable and remains essentially unchanged at calcination temperatures. As an inert substance, CaF2 is sparingly soluble in water but soluble in strong acids. Under secondary high-concentration hydrochloric acid leaching conditions, the following reaction occurs: CaF2 + 2HCl → CaCl2 + 2HF↑. The generated HF (hydrogen fluoride) is a gas and can be collected for alkaline treatment. Calcium is converted from solid CaF2 to soluble CaCl2 and enters the solution. The secondary leaching solution containing CaCl2 is combined with the primary leaching solution in step S6. Under strict control of the crystallization process (such as cooling rate, stirring speed, and seed crystal addition), barium chloride crystals will precipitate first, while calcium chloride will remain more in the mother liquor. The calcium-rich mother liquor can be partially recycled or centrally treated (e.g., precipitation) to prevent the unlimited accumulation of calcium ions in the product and ensure the purity of the final barium chloride product.

[0041] In the above treatment process, the pH of the combined leachate is adjusted to 4.0-5.0. Under these weakly acidic conditions, some heavy metal ions in the solution will form hydroxide precipitates or basic salt precipitates, such as ferric ions (Fe3+). 3+ ) and trivalent aluminum ions (Al 3+ ).

[0042] However, divalent heavy metal ions: such as Cu 2+ (copper), Pb 2+ (Lead), Cd 2+ (Cadmium), etc. These ions have a high pH threshold for forming hydroxides (usually pH > 6.0). Under conditions of pH 4.0-5.0, the vast majority of them remain in solution in ionic form and cannot be effectively precipitated and removed. They will eventually enter the concentration and crystallization process, resulting in a decrease in product purity.

[0043] Therefore, based on the above technical solution, this application further adds sodium thiosulfate in the secondary acid leaching step S5. The amount added is 1.1-1.3 times the molar amount of heavy metal ions in the water-leached residue. The sodium thiosulfate is added in stages. First, the water-leached residue is mixed with high-concentration hydrochloric acid to maintain the pH of the system <1.0. Then, an 8%-10% sodium thiosulfate solution is slowly added dropwise at a rate of 3-5 L / min·m³ to control the final pH to 1.5-2.0.

[0044] During the secondary acid leaching process, when the pH is less than 1.0, sodium thiosulfate is not added initially. At this stage, the silicate dissolves rapidly. After a period of reaction, an alkaline solution is added to the solution. Under acidic conditions with a controlled pH of 1.5-2.0, sodium thiosulfate is slowly added, releasing thiosulfate ions (S₂O₃). 2- It will decompose and react with other metal ions. Its core impurity removal mechanism lies in the fact that the active sulfur species (such as S, H2S) produced by the decomposition of thiosulfate ions react with copper (Cu) in the solution. 2+ ), lead (Pb) 2+ Heavy metal ions such as Cu2S, CuS, and PbS react preferentially to form extremely insoluble sulfide precipitates (such as Cu2S, CuS, and PbS), thereby achieving selective removal of heavy metals.

[0045] The specific chemical reaction is: S2O3 2- + 2H + → SO2↑ + S↓ + H2O; 2Cu 2+ + 2S2O3 2- + 2H₂O → Cu₂S↓ + S↓ + 4H + + 2SO4 2- ; Pb 2+ + S2O3 2- + H2O → PbS↓ + SO4 2- + 2H + .

[0046] The secondary leachate is mainly a solution containing barium chloride (BaCl2), while the secondary filter residue is a precipitate of sulfides of all heavy metals (CuS, PbS, etc.).

[0047] The secondary acid leaching in step S5 is carried out in a closed reactor. After the secondary acid leaching is completed, sulfur-containing colloids are separated by adding 0.1-0.2 wt% polyacrylamide for flocculation. The generated tail gas is treated by an alkaline absorption tower.

[0048] After the secondary acid leaching is completed, polyacrylamide flocs can flocculate elemental sulfur into sulfur colloids, which can be filtered and separated. The generated SO2 gas can be treated harmlessly through an alkaline absorption tower.

[0049] It is worth noting that Zn 2+ No ZnS precipitate is formed at pH 1.5-2.0 (pH > 3.0 is required), therefore no S2O3 is consumed. 2- ZnO dissolves rapidly at pH less than 1.0 to form soluble zinc salts, and after the reaction, Zn... 2+ It enters the solution, becomes an ionic impurity in the secondary leachate, and generates Zn(OH)2 colloid in the pH adjustment stage of step S6.

[0050] In addition, the HF (hydrogen fluoride) gas generated by the reaction of CaF2 with hydrochloric acid can also be absorbed simultaneously by the alkaline absorption tower.

[0051] In step S6, the pH value is precisely adjusted to 4.0-5.0 by adding an alkaline solution to the mixture of the primary and secondary leachates, and air is introduced for aeration. When the pH > 4.0, Fe... 2+ Hydrolysis begins to form Fe(OH)2 precipitate. Fe(OH)2 is unstable and is rapidly oxidized in the air to form the more stable Fe(OH)3 precipitate. At the same time, these Fe(OH)3 precipitates capture Zn(OH)2 colloids, accelerating the precipitation. Finally, the Fe(OH)3 precipitate is filtered off to obtain a clear and pure barium chloride solution. The filtrate is evaporated, concentrated, cooled, and crystallized to obtain a high-purity barium chloride product.

[0052] It is noteworthy that no side reactions occurred in the catalyst (ZnO / CaF2) in the sodium thiosulfate system, and ZnO was converted to Zn. 2+ Through S6 hydrolysis precipitation for deep removal, CaF2 decomposes into Ca. 2+ / HF, through crystallization recovery and regeneration reuse to achieve a closed loop, sodium thiosulfate focuses on removing heavy metals (Cu). 2+ / Pb 2+ ), and does not interfere with the products dissolved by the catalyst.

[0053] Based on the above technical solution, preferably, the hot water immersion temperature in step S4 is 80-90℃. By limiting the water immersion temperature, the calcined product containing Na2SO4 and unreacted Na2CO3 can be fully dissolved in water to quickly remove sodium salts, while BaCO3 will not hydrolyze due to excessively high water immersion temperature, thus avoiding barium loss.

[0054] This application has the following advantages over the prior art: This application successfully addresses two core pain points of existing technologies through a synergistic technical approach of "pre-oxidation for toxicity control - calcination conversion - gradient acid leaching - deep purification": First, the pre-oxidation step transforms unstable sulfides into safe compounds at the source, completely eliminating the risk of releasing highly toxic hydrogen sulfide during acid leaching; second, the gradient acid leaching technology enables the classification, complete dissolution, and recovery of different forms of barium compounds, ultimately yielding high-value barium chloride products through targeted purification, significantly improving the recovery efficiency and purity of barium resources. This solution ensures production safety while achieving high-value-added resource utilization of waste residue, combining environmental and economic benefits.

[0055] By leaching the calcined product with hot water, soluble sodium salts are separated and removed, avoiding a large amount of sodium ions from entering the subsequent acid leaching system, reducing acid consumption and subsequent purification burden, improving the efficiency of subsequent processes, and reducing processing costs.

[0056] By adding a composite catalyst of zinc oxide and calcium fluoride, the calcination conversion process achieves low-temperature, high-efficiency synergy. Zinc oxide significantly reduces the reaction energy barrier by activating the crystal lattice, while calcium fluoride forms ion transport channels to accelerate solid-phase ion exchange, greatly increasing the rate of conversion of barium sulfate to barium carbonate, thereby improving the efficiency of waste residue conversion and recovery.

[0057] By slowly adding sodium thiosulfate during a two-stage acid leaching process under controlled acidic conditions, heavy metals can be efficiently removed through a directional precipitation mechanism. In a precisely controlled acidic environment, thiosulfate ions (S₂O₃²⁻) are released into the atmosphere. 2- It specifically binds to heavy metal ions such as copper and lead to form stable sulfide precipitates (such as Cu2S and PbS), thereby achieving targeted removal of heavy metals and improving the purity of barium chloride. Detailed Implementation

[0058] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0059] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0060] The waste residue generated during the production of barium chloride has the following main metal components and their mass fractions: barium sulfate 45%, barium sulfide 15%, aluminosilicate 22%, aluminum 3.5%, iron 5.2%, copper 0.8%, lead 1.5%, and the balance being other impurities.

[0061] Example 1 This embodiment provides a method for treating waste residue from barium chloride production, including the following steps: S1. The waste residue is fed into a ball mill and milled at 25℃ for 1.5 hours with a ball-to-material ratio of 4.5:1. The milling media is zirconium balls, and the particle size of the treated waste residue is controlled to be ≤200 mesh. 500g of the treated waste residue is then fed into a rotary kiln and pre-oxidized for 1 hour at 350℃ by introducing a nitrogen-oxygen mixture with an oxygen concentration of 6% by volume (gas flow rate of 10m³ / h). The pre-oxidized material is then transferred to a reaction vessel, 1.5L of deionized water is added, and the mixture is stirred at 80℃ for hydration treatment for 2 hours, finally yielding a suspension containing barium hydroxide.

[0062] S2. Dehydrate the suspension obtained in step S1 using a plate and frame filter press until the moisture content is ≤25%, and then send it to a dryer to dry at 150°C for 1 hour. S3. Take 100g of the dried material and mix it evenly with 55g of sodium carbonate, 1.3g of zinc oxide and 0.6g of calcium fluoride. Place the mixture in a muffle furnace and calcine at 700℃ for 1.5 hours to obtain a calcined product containing barium carbonate.

[0063] S4. Add the calcined product to hot water at 85℃ (solid-liquid ratio 1:5) and stir for 40 minutes. Filter to separate, wash the filter residue twice with hot water, combine the filtrates (to recover sodium salt), and obtain the water-leached residue.

[0064] S5. Add 1.5 mol / L hydrochloric acid (solid-liquid ratio 1:4) to the water-leached residue and stir at 60℃ for 2 hours. Filter to obtain a primary leachate containing barium chloride and a primary filter residue. Transfer the primary filter residue to a closed reactor, add 5 mol / L hydrochloric acid, and maintain pH < 1.0 for 30 minutes. Add 5% NaOH solution to control the final pH = 1.8, and add 9% sodium thiosulfate solution dropwise at a rate of 4 L / min·m³. Continue the reaction for 1 hour. The tail gas (containing SO2 and HF) is introduced into a 10% NaOH absorption tower for treatment. After the reaction is completed, add 0.15% polyacrylamide solution for flocculation, and filter by pressure to obtain a secondary leachate and a filter residue containing heavy metal sulfides. S6. Combine the primary and secondary leachates, adjust the pH to 4.5 with 20% NaOH solution, stir and mature for 30 minutes, then filter. Concentrate the filtrate to a BaCl2 concentration ≥ 300 g / L, cool to crystallize, centrifuge, and dry to obtain barium chloride product.

[0065] Example 2 S1. The waste residue is fed into a ball mill and milled at 25℃ for 1 hour with a ball-to-material ratio of 5:1 and zirconium balls as the milling media. The particle size of the treated waste residue is controlled to be ≤200 mesh. 500g of the treated waste residue is then fed into a rotary kiln and pre-oxidized at 300℃ by introducing a nitrogen-oxygen mixture with an oxygen concentration of 5% by volume (gas flow rate of 10m³ / h). The pre-oxidized material is then transferred to a reaction vessel, 1.5L of deionized water is added, and the mixture is stirred at 75℃ for hydration treatment for 2 hours, ultimately yielding a suspension containing barium hydroxide.

[0066] S2. Dehydrate the suspension obtained in step S1 using a plate and frame filter press until the moisture content is ≤25%, and then send it to a dryer to dry at 100°C for 1 hour. S3. Take 100g of the dried material and mix it evenly with 50g of sodium carbonate, 0.7g of zinc oxide and 0.3g of calcium fluoride. Place the mixture in a muffle furnace and calcine at 650℃ for 1.5 hours to obtain a calcined product containing barium carbonate.

[0067] S4. Add the calcined product to hot water at 80℃ (solid-liquid ratio 1:5) and stir for 40 minutes. Filter and separate the residue. Wash the residue twice with hot water and combine the filtrates (to recover sodium salt) to obtain the water-leached residue.

[0068] S5. Add 1 mol / L hydrochloric acid to the water-leached residue (solid-liquid ratio 1:4), stir and react at 60℃ for 2 hours, filter to obtain primary leachate containing barium chloride and primary filter residue; transfer the primary filter residue to a closed reactor, add 4 mol / L hydrochloric acid, maintain pH < 1.0 and react for 30 minutes. Add 5% NaOH solution to control the final pH = 1.5, add 8% sodium thiosulfate solution dropwise at a rate of 4 L / min·m³, continue the reaction for 1 hour, and introduce the tail gas (containing SO2 and HF) into a 10% NaOH absorption tower for treatment. After the reaction is completed, add 0.1% polyacrylamide solution for flocculation, and filter by pressure to obtain secondary leachate and filter residue containing heavy metal sulfides; S6. Combine the primary and secondary leachates, adjust the pH to 4 with 20% NaOH solution, stir and mature for 30 minutes, then filter. Concentrate the filtrate to a BaCl2 concentration ≥ 300 g / L, cool to crystallize, centrifuge, and dry to obtain barium chloride product.

[0069] Example 3 S1. The waste residue is fed into a ball mill and milled at 25℃ for 2 hours with a ball-to-material ratio of 4:1 and zirconium balls as the milling media. The particle size of the treated waste residue is controlled to be ≤200 mesh. 500g of the treated waste residue is then fed into a rotary kiln and pre-oxidized at 400℃ by introducing a nitrogen-oxygen mixture with an oxygen concentration of 8% by volume (gas flow rate of 10m³ / h). The pre-oxidized material is then transferred to a reaction vessel, 1.5L of deionized water is added, and the mixture is stirred at 85℃ for hydration treatment for 2 hours, ultimately yielding a suspension containing barium hydroxide.

[0070] S2. Dehydrate the suspension obtained in step S1 using a plate and frame filter press until the moisture content is ≤25%, and then send it to a dryer to dry at 200℃ for 1 hour. S3. Take 100g of the dried material and mix it evenly with 60g of sodium carbonate, 2.0g of zinc oxide and 1.0g of calcium fluoride. Place the mixture in a muffle furnace and calcine at 750℃ for 1.5 hours to obtain a calcined product containing barium carbonate.

[0071] S4. Add the calcined product to hot water at 90℃ (solid-liquid ratio 1:5) and stir for 40 minutes. Filter to separate, wash the filter residue twice with hot water, combine the filtrates (to recover sodium salt), and obtain the water-leached residue.

[0072] S5. Add 2 mol / L hydrochloric acid to the water-leached residue (solid-liquid ratio 1:4), stir and react at 60℃ for 2 hours, filter to obtain primary leachate containing barium chloride and primary filter residue; transfer the primary filter residue to a closed reactor, add 6 mol / L hydrochloric acid, maintain pH < 1.0 and react for 30 minutes. Add 5% NaOH solution to control the final pH = 2.0, add 8% sodium thiosulfate solution dropwise at a rate of 4 L / min·m³, continue the reaction for 1 hour, introduce the tail gas (containing SO2 and HF) into a 10% NaOH absorption tower for treatment, after the reaction is completed, add 0.2% polyacrylamide solution for flocculation, and filter by pressure to obtain secondary leachate and filter residue containing heavy metal sulfides; S6. Combine the primary and secondary leachates, adjust the pH to 5.0 with 20% NaOH solution, stir and mature for 30 minutes, then filter. Concentrate the filtrate to a BaCl2 concentration ≥ 300 g / L, cool to crystallize, centrifuge, and dry to obtain barium chloride product.

[0073] To verify the key impact of pre-oxidation oxygen concentration on barium conversion rate and by-product control, the applicant conducted a comparative experiment. 500g of waste residue from the same source was pre-oxidized at 350℃ for 1 hour using oxygen concentrations of 3%, 6%, 10%, and 21% (air), respectively. Subsequent steps were the same as in Example 1. The content of residual barium sulfide (BaS) and generated barium sulfate (BaSO4) in the pre-oxidized material was measured, and the barium recovery rate of the final product was calculated. The results are shown in Table 1 below.

[0074] Results Analysis: When the oxygen concentration is below 5% (e.g., 3%), BaS oxidation is incomplete, resulting in high residual levels. This leads to a risk of H2S release during subsequent acid leaching and a decrease in recovery rate. When the oxygen concentration is above 8% (e.g., 10% and 21%), an over-oxidation side reaction occurs (BaS + 2O2 → BaSO4), generating a large amount of BaSO4 that is difficult to convert in subsequent calcination, significantly reducing the final barium recovery rate. Therefore, controlling the oxygen concentration within the range of 5%-8% is the optimal choice for achieving efficient pre-oxidation while balancing safety and conversion rate.

[0075] Comparative Example 1 This comparative example provides a method for treating waste residue from barium chloride production, specifically the same as in Example 1, except that a catalyst is not added in step S3. Specifically, it includes: S3. Take 100g of dried material and mix it evenly with 55g of sodium carbonate. Place the mixture in a muffle furnace and calcine it at 1100℃ for 1.5 hours.

[0076] Comparative Example 2 This comparative example provides a method for treating waste residue from barium chloride production, specifically the same as in Example 1, except that calcium fluoride from the catalyst is not added in step S3. Specifically, it includes: S3. Take 100g of dry material, mix it evenly with 55g of sodium carbonate and 1.2g of zinc oxide, and calcine it at 700℃ for 1.5 hours.

[0077] Comparative Example 3 This comparative example provides a method for treating waste residue from barium chloride production, specifically the same as in Example 1, except that zinc oxide from the catalyst is not added in step S3. Specifically, it includes: S3. Take 100g of dry material, mix it evenly with 55g of sodium carbonate and 0.8g of calcium fluoride, and calcine it at 700℃ for 1.5 hours.

[0078] Comparative Example 4 This comparative example provides a method for treating waste residue from barium chloride production, which is the same as in Example 1, except that sodium thiosulfate and polyacrylamide solution are not added in step S5. Specifically, it includes: S5. Add 1.5 mol / L hydrochloric acid (solid-liquid ratio 1:4) to the water-leached residue, stir and react at 60℃ for 2 hours, filter to obtain primary leachate containing barium chloride and primary filter residue; transfer the primary filter residue to a closed reaction vessel, add 5 mol / L hydrochloric acid, maintain pH < 1.0 and react for 30 minutes, introduce the tail gas (containing HF) into a 10% NaOH absorption tower for treatment, and filter by pressure to obtain secondary leachate and filter residue containing heavy metal sulfides.

[0079] Performance testing The purity, barium ion recovery rate, and content of key impurity elements of barium chloride were tested according to the relevant requirements of GB / T 1617-2014 "Industrial Barium Chloride". The barium ion recovery rate is the percentage of barium content in the actual recovered barium chloride compared to the total barium content in the waste residue. Simultaneously, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the residual amounts of zinc (Zn) and calcium (Ca) elements introduced by the catalyst in the product to verify the deep purification effect. The test results are shown in Table 2.

[0080]

[0081] As shown in Table 2, the experimental data indicate that: The barium ion recovery rate in Examples 1-3 was higher than 94%, and the main barium chloride content exceeded 99.5%, which fully demonstrates the high efficiency and stability of the entire process chain of "pre-oxidation-catalytic calcination-gradient acid leaching-deep purification".

[0082] The content of heavy metal impurities such as Fe, Cu, and Pb in the products of the examples was significantly lower than that of the comparative examples. In particular, the Cu content of the comparative example 4 (without sodium thiosulfate treatment) was 3.7 times that of the example 1. This strongly demonstrates the key role of adding sodium thiosulfate in the secondary acid leaching process for targeted removal of heavy metals.

[0083] As shown in the last two columns of Table 2, “Zn Residue” and “Ca Residue”, the levels of zinc and calcium residues introduced by the catalyst detected in the product of the example are extremely low (Zn < 5 ppm, Ca < 20 ppm). This data is crucial: it demonstrates that although the catalyst (ZnO, CaF2) is introduced into the system during calcination and acid leaching, the pH adjustment, Fe(OH)3 flocculation co-precipitation, and subsequent concentration and crystallization optimization control in step S6 of this invention effectively prevent the enrichment of these introduced impurity elements in the product, ensuring the high purity of the final product. This fully reveals the final fate of the catalyst elements, proving that the process has a powerful deep purification capability.

[0084] In Comparative Example 2 (without CaF2) and Comparative Example 3 (without ZnO), the barium recovery rate decreased significantly and the impurity content increased in the absence of one catalyst, confirming the synergistic necessity of zinc oxide and calcium fluoride in low-temperature catalytic conversion.

[0085] In summary, the experimental data in Table 2 fully and clearly demonstrate the synergistic effect between the various technical features of this invention. It not only achieves efficient recovery of barium resources, but also ensures production safety while achieving a deep purification effect on various impurities (including foreign catalyst elements), ultimately obtaining high-quality barium chloride products.

[0086] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for treating waste residue from barium chloride production, characterized in that, Includes the following steps: S1. The waste residue containing barium sulfate and barium sulfide is ball-milled, then pre-oxidized and hydrated to obtain a suspension containing barium hydroxide. S2. Dehydrate and dry the suspension from step S1; S3. The dried material is mixed with sodium carbonate and then calcined to obtain a calcined product containing barium carbonate. S4. The calcined product is leached with hot water to remove soluble sodium salts, and the water-leached residue is obtained. S5. The water-leached residue is first subjected to a first-stage acid leaching with low-concentration hydrochloric acid, and then filtered to obtain a first-stage leachate containing barium chloride and a first-stage filter residue; then the first-stage filter residue is subjected to a second-stage acid leaching with high-concentration hydrochloric acid, and then filtered to obtain a second-stage leachate containing barium chloride. S6. Combine the primary and secondary leachates, adjust the pH to 4.0-5.0, filter to separate the precipitate, and concentrate and crystallize to obtain barium chloride product.

2. The method for treating barium chloride production waste residue as described in claim 1, characterized in that: In step S1, the ball milling process includes: ball milling the waste residue at 20-25℃ for 1-2 hours, and controlling the particle size of the pretreated barium slag to be ≤200 mesh.

3. The method for treating barium chloride production waste residue as described in claim 1, characterized in that: The pre-oxidation in step S1 is carried out at 300-400°C by introducing oxygen-containing gas, and the oxygen concentration of the oxygen-containing gas is controlled at 5%-8%.

4. The method for treating barium chloride production waste residue as described in claim 1, characterized in that: The low-concentration hydrochloric acid mentioned in step S5 is 1-2 mol / L hydrochloric acid, and the high-concentration hydrochloric acid is 4-6 mol / L hydrochloric acid.

5. The method for treating barium chloride production waste residue as described in claim 1, characterized in that: In step S3, a catalyst is added simultaneously when the dried material is mixed with sodium carbonate. The catalyst includes zinc oxide and calcium fluoride. The amount added is based on the mass of the dried material, with zinc oxide at 0.7%-2.0% and calcium fluoride at 0.3%-1.0%. The mass ratio of the dried material to sodium carbonate is 1:(0.5-0.6).

6. The method for treating barium chloride production waste residue as described in claim 5, characterized in that: In the secondary acid leaching of step S5, sodium thiosulfate is also added. The amount added is 1.1-1.3 times the molar amount of heavy metal ions in the water-leached residue. The sodium thiosulfate is added in stages. First, the water-leached residue is mixed with high-concentration hydrochloric acid to maintain the pH of the system <1.

0. Then, an 8%-10% sodium thiosulfate solution is slowly added dropwise at a rate of 3-5 L / min·m³ to control the final pH to 1.5-2.

0.

7. The method for treating barium chloride production waste residue as described in claim 6, characterized in that: The secondary acid leaching in step S5 is carried out in a closed reactor. After the secondary acid leaching is completed, sulfur-containing colloids are separated by adding 0.1-0.2 wt% polyacrylamide for flocculation. The generated tail gas is treated by an alkaline absorption tower.

8. The method for treating barium chloride production waste residue as described in claim 5, characterized in that: The calcination temperature in step S3 is 650-750℃, and the calcination time is 1-2 hours.

9. The method for treating barium chloride production waste residue as described in claim 1, characterized in that: The temperature of the hot water immersion in step S4 is 80-90℃.

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