Barium slag harmless treatment method and application

Abstract

The invention provides a barium slag harmless treatment method which comprises the following steps: mixing barium slag and desulfurized waste gypsum, adding water, beating into slurry, adding diluted industrial acid, stirring, acidifying, and heating, so that most of barium in the slurry forms BaSO4; adding a coupling agent, stirring, and carrying out coupling and competitive coordination reaction with free barium ions and barium salt in the product; adding a sulfate solution, and carrying out double decomposition reaction with the chelate barium to generate a non-toxic BaSO4 precipitate; and adding a ferrous sulfate solution to combine the rest of ferrous ions and sulfur ions in the product to form an iron sulfide precipitate, carrying out filter pressing to obtain filter residues with the water content of 20-30%, and drying. According to the method, toxic metal barium in the barium slag can be converted into nontoxic barium sulfate, and sulfur ions are converted into stable ferric sulfate, so that the barium ions, sulfide and corrosive pH value in the treated product all reach the national general solid waste first-class slag standard. The invention also provides an application of the barium slag treated by the method in building and building material industries.

Description

Technical Field

[0001] The invention relates to the technical field of industrial waste residue treatment, and in particular to a method for harmless treatment of barium residue and application thereof. Background Art

[0002] Barium carbonate is an important chemical substance obtained from barite. It is mainly produced by carbonization reduction method. The waste generated by barium compounds in the process of carbon thermal reduction and water / acid leaching is called "barium slag". Barium slag is a solid residue produced in the process of producing barium carbonate and thiourea by carbonization reduction method in the chemical industry. Barium slag contains barium (Ba), magnesium (Mg), silicon (Si), oxygen (O), sulfur (S) and other elements. The barium slag produced by barium salt enterprises mainly exists in the form of barium carbonate, barium sulfate in unreacted barite and unleached barium sulfide. In order to realize the recycling of barium elements in barium slag in the prior art, strong acid leaching is often used, that is, by adding hydrochloric acid, nitric acid and sulfuric acid to the barium slag to obtain corresponding barium chloride, barium nitrate, barium sulfate and other products. However, acid leaching not only consumes a large amount of strong acid, but also causes a large amount of acid mist to appear in the on-site environment, which seriously threatens the safety of workers and pollutes the surrounding environment. In addition, in the process of extracting barium from barium slag by acid leaching, since barium slag also contains barium sulfide, the reaction of barium sulfide with acid will produce a large amount of hydrogen sulfide gas, which further deteriorates the on-site environment and the surrounding environment, further exacerbates the threat to the physical and mental health of workers, and also causes a waste of sulfur resources, making the sulfur ions (S 2- ) cannot be better utilized and processed.

[0003] Barium slag is a hazardous waste listed in the National List of Hazardous Wastes. Since barium slag contains water-soluble barium and acid-soluble barium, the barium ions (Ba 2+ ) concentration exceeds the national standard concentration limit by more than ten times, and the pH value in the barium slag is close to or exceeds the standard limit (12.5), which is alkaline and corrosive. As we all know, barium is a heavy metal element that is harmful to human life and health. Inhalation through the respiratory tract or ingestion through the digestive tract can cause acute barium poisoning. If barium slag is accumulated for a long time and occupies a large amount of land resources, it will also pollute the environment. When the temperature is high, the sulfur element in the barium slag will have a stronger destructive effect on the human body and the environment, and will spontaneously combust and release SO2 gas. The barium slag is washed by rainwater, and the toxic wastewater containing sulfides directly poisons the surface water and groundwater. As it flows into rivers and reservoirs, it seeps into groundwater, threatening the drinking water health of residents. At the same time, the barium ions (Ba 2+ ) has a cumulative effect, enters the human body through the food chain, and causes irreversible damage to the natural environment and human life; in addition, the alkaline components and BaS present in barium slag will also cause soil salinization, and it is a hazardous waste explicitly listed in the "National List of Hazardous Wastes".

[0004] At present, the annual discharge of barium slag in my country exceeds 1 million tons, and the total accumulated stockpile has exceeded 10 million tons. Barium slag contains a large amount of soluble barium, which is toxic and corrosive to strong alkalis. Its leaching rate is as high as 92.8%, and the lethal dose of barium ion solution is 0.8-0.9 grams, which poses a potential toxic risk to plants and animals.

[0005] Therefore, how to treat barium slag harmlessly, remove toxicity and avoid environmental pollution is a problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and firstly provide a method for harmless treatment of barium slag.

[0007] The method for harmless treatment of barium slag provided by the present invention comprises the following steps:

[0008] S1 Mix the barium slag and desulfurization waste gypsum with water to make a slurry, add diluted industrial acid to the slurry, stir and acidify, and then heat to reduce the pH value of the slurry to 6-9, and initially remove most of the barium ions Ba in the barium slag after acidification. 2+ With sulfate ion SO4 in desulfurized waste gypsum 2- The reaction forms non-toxic BaSO4 which is insoluble in water; S2. Add a coupling agent to the product obtained in step S1 and stir to allow the coupling agent to couple with the free barium ions and barium salts in the product and to compete for coordination reaction; S3: adding a sulfate solution to the product obtained in step S2, stirring and heating, so that the sulfate and the chelated barium in the product undergo double decomposition reaction to generate water-insoluble non-toxic BaSO4; S4 Add ferrous sulfate solution to the product obtained in step S3 and continue stirring to make the remaining sulfide ions S 2- and ferrous ions Fe in ferrous sulfate 2+ The iron sulfide precipitate is formed by combination, and the filter residue with a moisture content of 20-30% is obtained by filter pressing and then dried.

[0009] The present application also provides an application of the barium slag treated by the above-mentioned barium slag harmless treatment method in the construction and building materials industries.

[0010] The present invention mixes barium slag and desulfurized gypsum, crushes them, and acidifies and heats them to remove barium ions, so that most of the barium ions (Ba 2+ ) and sulfate ions (SO4 2-) reaction to form water-insoluble non-toxic BaSO4, which is then coupled and coordinated with a coupling agent, and then heated by the waste heat of the rotary kiln flue gas to perform a double decomposition reaction, which double decomposes the soluble barium into water-insoluble barium sulfate and converts the toxic metallic barium into insoluble non-toxic barium sulfate, so that the barium ions in the barium slag are completely detoxified. At the same time, ferrous sulfate is added to convert the sulfur ions (S 2- ) is converted into a stable ferric sulfate precipitate. After filtration and drying, the barium ion, sulfide and corrosive pH value of the product can meet the national general solid waste class I slag standards.

[0011] The harmless treatment method of barium slag of the present application can reduce the cost of barium slag treatment, solve the problem of environmental pollution, especially water pollution, and can also utilize the barium slag as a resource, thereby achieving comprehensive economic and environmental benefits of waste treatment and comprehensive utilization of solid waste. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0013] The method for harmless treatment of barium slag provided by the present invention comprises the following steps:

[0014] S1 Mix barium slag and desulfurization waste gypsum with water to make slurry, add diluted acid solution to the slurry, stir and acidify, and then heat to reduce the pH value of the slurry to 6-9, and initially make most of the barium ions (Ba 2+ ) and sulfate ions (SO4 2- ) reacts to form non-toxic BaSO4 which is insoluble in water.

[0015] The stirring and acidification time is 15 to 30 minutes, and the heating temperature is 40 to 85° C. for 20 to 60 minutes.

[0016] Barium slag is a by-product of the barium salt production industry. Its main components are BaCO3, BaSO3, BaO, SiO2, Al2O3, Fe2O3, S, H2O, etc. The harmful component is Ba 2+ , S 2- Its corrosiveness is reflected in the ultra-high pH.

[0017] Desulfurized waste gypsum is a solid byproduct obtained by desulfurizing and purifying the flue gas generated by the combustion of sulfur-containing fuels (coal, oil, etc.) using the limestone-gypsum method in the production process of barium salt enterprises. Its main component is CaSO4·2H2O.

[0018] The barium slag and desulfurization waste gypsum need to be crushed and ground to a particle size of 1 to 10 mm.

[0019] The heat source for heating in this step can come from the waste heat of rotary kiln flue gas in the production process of the barium salt enterprise, further reducing the cost of harmless treatment of barium slag.

[0020] The percentage of each raw material in this step is: Barium slag: 55%~70%; desulfurization waste gypsum: 5%~20%; acid: 0.5%~5%; water: 20%~30%.

[0021] The industrial acid is either industrial sulfuric acid or industrial hydrochloric acid, and the acid concentration is 5-20%.

[0022] This step is the preliminary treatment of barium slag. The barium slag is mixed with desulfurized waste gypsum and water is added to form a slurry. The slurry is stirred with a relatively low concentration of industrial sulfuric acid or industrial hydrochloric acid solution to fully mix the raw materials in the slurry and promote rapid acidification of the slurry. The pH concentration in the mixed slurry is reduced to 6-9, which is beneficial to the sulfate ion (SO4 2- ) and soluble barium ions (Ba 2+ ) is combined to initially generate water-insoluble and non-toxic BaSO4. In this way, the sulfate ions (SO4 2- ) and barium ions (Ba 2+ ) reaction, which reduces the cost of harmless treatment of barium slag and makes the corrosive index of barium slag reach pH 6-9, meeting the optimal conditions for double decomposition reaction, and makes the corrosive index of the treated barium slag meet the first-class slag standard of general solid waste standards, effectively realizing the waste recycling of barium salt production enterprises and avoiding secondary pollution to the environment caused by desulfurization waste gypsum solid waste.

[0023] S2: Add a coupling agent to the product obtained in step S1 and stir for 5 to 30 minutes to allow the coupling agent to couple and compete with the free barium ions and barium salts such as BaCO3, BaSO3, and BaO in the product.

[0024] This step is to remove the remaining barium ions (Ba 2+ ) is further chelated and enriched. The (-CSSH) in the coupling agent molecular structure can form a network chelate on the outer layer of the S atom, and -SH can compete with the low molecular weight and unstable barium complex to capture the barium ion (Ba 2+ ), or directly with barium ions (Ba 2+ ) coordination enrichment, creating better conditions for double decomposition reactions.

[0025] The coupling agent is any one of sodium dimethyldithiocarbamate (SDMC) or sodium diethyldithiocarbamate (DDTC), and the mass percentage of the added coupling agent is 0.1% to 2% of the total mass of the product in step S1.

[0026] S3: adding sulfate solution to the product obtained in step S2, stirring, and heating to allow the sulfate to undergo double decomposition reaction with the chelated barium in the product to generate water-insoluble non-toxic BaSO4.

[0027] The sulfate is selected from any one of sodium bisulfate (NaHSO4), Na2SO4, K2SO4, KHSO4, (NH4)2SO4, and the mass percentage of the added sulfate is 0.3% to 2% of the total mass of the product of step S1.

[0028] The double decomposition reaction time is 60min to 180min, and the reaction temperature is 40°C to 85°C.

[0029] This step is to perform a double decomposition reaction on the chelated enriched barium chelate. Under the condition of pH 6-9, sodium bisulfate (NaHSO4) and potassium bisulfate (KHSO4) are added, which can be completely ionized in the solution to produce H + and SO4 2- Sodium sulfate (Na2SO4), potassium sulfate (K2SO4), and ammonium sulfate ((NH4)2SO4) produce SO4 in solution 2- When barium carbonate, barium sulfite or barium oxide is mixed with sodium bisulfate, potassium bisulfate, sodium sulfate, potassium sulfate or ammonium sulfate, it is stirred thoroughly to make the sulfate ions (SO4 2- ) and the barium ions (Ba 2+ ) to undergo double decomposition reaction to form non-toxic barium sulfate precipitation. Heating is performed while reacting to promote the reaction process, increase the reaction speed, shorten the reaction time, and save the steps and long time of stuffing required in traditional room temperature reactions.

[0030] A small amount of toxic gas will be produced during the above reaction process. However, since most of the barium ions have been solidified in step S1, the toxic gas content formed in this step is relatively small and can be discharged after recovery and purification without polluting the surrounding environment.

[0031] S4 Add ferrous sulfate solution to the product obtained in step S3 and continue stirring for 10 to 30 minutes to make the remaining ferrous ions (Fe 2+ ) and sulfide ions in ferrous sulfate (S 2-) combines to form iron sulfide (FeS) precipitation, and filter press to remove excess water from the dissolved liquid and water for pulping to obtain a filter residue with a moisture content between 30% and 50%, which is then dried to a moisture content between 10% and 20%.

[0032] The mass percentage of the added ferrous sulfate is 1.0% to 3.0% of the total mass of the product in step S1.

[0033] Since sodium bisulfate, potassium bisulfate, sodium sulfate, potassium sulfate, and ammonium sulfate will be completely ionized into Na + , K + , H + and SO4 2- During the reaction of sulfate with BaCO3, BaSO3, and BaO, the main reaction is to produce water-insoluble non-toxic barium sulfate, and some excess sulfur ions (S 2- ) reacts with the added ferrous sulfate and the chemical equation is: Fe 2+ (aq)+S 2- (aq)→FeS(s). In this reaction, the ferrous ion (Fe 2+ ) and sulfide ions (S 2- ) combine to form a stable iron sulfide (FeS) precipitate.

[0034] The chemical reaction formula is: 2Fe3 + + S 2- = 2Fe 2+ + S↓ Or: Fe 2+ + S 2- = FeS↓

[0035] In this way, the added ferrous sulfate can remove the sulfur ions (S 2- ).

[0036] After the reaction is completed, filter press is used to obtain filter residue with a moisture content of 20-30%. After drying, according to Article 6.1 of GB5085.7-2007 "Identification Standards for Hazardous Wastes - Identification of Leaching Toxicity", "Waste treated with hazardous wastes having one or more hazardous characteristics such as toxicity (including leaching toxicity, acute toxicity and other toxicity) and infectivity is still hazardous waste, unless otherwise provided by relevant national laws and regulations and standards", the treated recycled barium slag shall be subjected to full category testing with reference to "Identification Standards for Hazardous Wastes - Identification of Leaching Toxicity" (GB5085.3-2007). Only after all categories and all indicators meet the standards of general solid waste Class I slag by 100% can subsequent resource utilization be carried out. If the toxicity identification does not meet the standards of general solid waste Class I slag, it must be returned for detoxification and regeneration until the toxicity identification does not meet the standards of general solid waste Class I slag.

[0037] The method for harmless treatment of barium slag provided by the present application, wherein the barium ions (Ba 2+ ) content is far lower than the leaching toxicity identification standard value of 100mg / L in the "Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB5085.3-2007); the pH value meets the pH value requirements of the leachate in the "Hazardous Waste Identification Standard Corrosiveness Identification" (GB5085.1-2007): 6.0≤pH≤9.0; sulfide (S 2- ) is lower than the standard value of 1.0 mg / L in "Determination of Sulfide in Soil and Sediment" (HJ883-2017). Other indicators meet the standards of Class I general solid waste slag before harmless treatment. Therefore, all categories of barium slag that have undergone harmless treatment meet the standards of Class I general solid waste slag.

[0038] The barium slag regenerated by the above-mentioned harmless treatment method can be used as the main raw material in the construction, building materials and other industries, such as cement, bricks, concrete, etc., turning waste into treasure, realizing the resource utilization of barium slag, and reducing the production cost of construction, building materials and other materials.

[0039] The above-mentioned barium slag harmless treatment method is further described in detail below in conjunction with specific embodiments. Embodiment 1:

[0040] S1 Weigh 650g of barium slag and 125g of desulfurized waste gypsum, mix them, add 220ml of water and make a slurry;

[0041] Take 5g of industrial sulfuric acid, add 50ml of water and stir to make a sulfuric acid dilution, add it into the slurry, stir and acidify for 15min, then heat to 85℃ for 20min;

[0042] S2: Weigh 5.0 g of sodium dimethyldithiocarbamate (SDMC), add 80 ml of water to dissolve it, and then add it to the product obtained in step S1, and stir for 10 minutes to allow some unreacted barium ions in the product to undergo coupling and competitive coordination reactions to generate water-insoluble non-toxic BaSO4;

[0043] S3 weigh 15g of sodium bisulfate, add 100ml of water to dissolve it, and then add it to the product obtained in step S2, and perform double decomposition reaction for 60min at 75°C to generate water-insoluble non-toxic BaSO4;

[0044] S4 Weigh 20g of ferrous sulfate, add 100ml of water to dissolve it, and then add it to the product obtained in step S3, stir for 10min, and remove the remaining sulfide ions (S 2-) combines to form iron sulfide (FeS) precipitation, and finally filter presses to remove excess water from the dissolved liquid and pulping water to obtain filter residue with a moisture content of about 30%, which is then dried in an oven at 100°C to a moisture content of about 18%, thus obtaining barium slag after harmless treatment, which is suitable for subsequent resource processing.

[0045] The product treated in this example was subjected to the toxicity pH, barium ion and sulfide determination of the leachate according to the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB 5085.3-2007) and the "Hazardous Waste Identification Standard - Corrosiveness Identification" (GB 5085.3-2007). The pH was 7.5, the barium ion concentration was 1.23 mg / L, and the sulfide concentration was 0.38 mg / L (see Table 1). The concentration of hazardous components in the leachate was much lower than the standard value and pH value requirements. All categories of the barium slag that had been harmlessly treated met the standards for Class I slag of general solid waste. Embodiment 2:

[0046] S1 Weigh 600g of barium slag and 154g of desulfurized waste gypsum in sequence, mash and mix, add 240ml of water, and make into slurry;

[0047] Take 10g of industrial sulfuric acid, add 50ml of water and stir to make a sulfuric acid dilution solution, add it into the slurry, stir and acidify for 20min, then heat to 75℃ for 45min;

[0048] S2: Weigh 3.0 g of aminodithiocarbamate (DTCR), add 50 ml of water, dissolve it, add it to the product obtained in step S1, and stir for 20 minutes to allow some unreacted barium ions in the product to undergo coupling and competitive coordination reactions to generate water-insoluble non-toxic BaSO4;

[0049] S3: Weigh 10g potassium hydrogen sulfate, add 50ml water, stir to dissolve, then add to the product obtained in step S2, and perform double decomposition reaction for 120min at 85℃ to generate water-insoluble non-toxic BaSO4;

[0050] S4 Weigh 15g of ferrous sulfate, add 40ml of water, dissolve it and add it to the product obtained in step S3, stir for 15min, and remove the remaining sulfide ions (S 2- ) combines to form iron sulfide (FeS) precipitation, and finally filter presses to remove excess water from the dissolved liquid and pulping water to obtain a filter residue with a moisture content of about 28%, which is then dried in an oven at 100°C to a moisture content of about 15%, thus obtaining the harmless barium slag, which is suitable for subsequent resource processing.

[0051] The product treated in this example was subjected to leachate toxicity pH, barium ion and sulfide determination according to the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB 5085.3-2007) and the "Hazardous Waste Identification Standard - Corrosiveness Identification" (GB 5085.3-2007). The pH was 7.85, the barium ion concentration was 1.78 mg / L, and the sulfide concentration was 0.49 mg / L (see Table 1). The concentration of hazardous components in the leachate was much lower than the standard value and pH value requirements. All categories of the barium slag that had been harmlessly treated met the standards for Class I slag of general solid waste. Embodiment 3:

[0052] S1 Weigh 630g of barium slag and 125g of desulfurized waste gypsum, mash and mix, add 230ml of water, and make into slurry;

[0053] Take 15g of industrial sulfuric acid, add 100ml of water and stir to make a sulfuric acid dilution solution, add it into the slurry, stir and acidify for 25min, then heat to 40℃ for 60min;

[0054] S2: Weigh 1.0 g of sodium diethyldithiocarbamate (DDTC), add 50 ml of water, dissolve it, add it to the product obtained in step S1, and stir for 10 minutes to allow the unreacted barium in the product to undergo coupling and competitive coordination reactions to generate water-insoluble non-toxic BaSO4;

[0055] S3: Weigh 16g potassium sulfate, add 80ml water, stir to dissolve, then add to the product obtained in step S2, double decomposition reaction for 150min at 60℃ to generate water-insoluble non-toxic BaSO4;

[0056] S4 Weigh 18g of ferrous sulfate, add 100ml of water, dissolve it and add it to the product obtained in step S3, stir for 30min, and remove the remaining sulfide ions (S 2- ) combines to form iron sulfide (FeS) precipitation, and finally filter presses to remove excess water from the dissolved liquid and pulping water to obtain filter residue with a moisture content of about 25%, which is then dried in an oven at 100°C to a moisture content of about 15%, thus obtaining barium slag after harmless treatment, which is suitable for subsequent resource treatment.

[0057] The product treated in this example was subjected to leachate toxicity pH, barium ion and sulfide determination according to the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB 5085.3-2007) and the "Hazardous Waste Identification Standard - Corrosiveness Identification" (GB 5085.3-2007). The pH was 8.8, the barium ion concentration was 3.23 mg / L, and the sulfide concentration was 0.82 mg / L (see Table 1). The concentration of hazardous components in the leachate was much lower than the standard value and pH value requirements. All categories of the barium slag that had been harmlessly treated met the standards for Class I slag of general solid waste. Embodiment 4:

[0058] S1 Weigh 700g of barium slag and 140g of desulfurized waste gypsum in turn, mash and mix, add 250ml of water, and make into slurry;

[0059] Take 10g of industrial sulfuric acid, add 50ml of water and stir to make a sulfuric acid dilution, add it into the slurry, stir and acidify for 30min, then heat to 60℃ for 45min;

[0060] S2: Weigh 10.0 g of sodium dimethyldithiocarbamate (SDMC), add 100 ml of water, dissolve it, add it to the product obtained in step S1, and stir for 10 minutes to allow some unreacted barium ions in the product to undergo coupling and competitive coordination reactions to generate water-insoluble non-toxic BaSO4;

[0061] S3: Weigh 20g of sodium bisulfate, add 100ml of water, stir to dissolve, then add to the product obtained in step S2, and perform double decomposition reaction for 180min at 40°C to generate water-insoluble non-toxic BaSO4;

[0062] S4 Weigh 16g of ferrous sulfate, add 50ml of water, dissolve it and add it to the product obtained in step S3, stir for 20min, and remove the remaining sulfide ions (S 2- ) combines to form iron sulfide (FeS) precipitation, and finally filter presses to remove excess water from the dissolved liquid and pulping water to obtain filter residue with a moisture content of about 23%, which is then dried in an oven at 100°C to a moisture content of about 14%, thus obtaining barium slag after harmless treatment, which is suitable for subsequent resource processing.

[0063] The product treated in this example was subjected to leachate toxicity pH, barium ion and sulfide determination according to the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB 5085.3-2007) and the "Hazardous Waste Identification Standard - Corrosiveness Identification" (GB 5085.3-2007). The pH was 8.5, the barium ion concentration was 2.28 mg / L, and the sulfide concentration was 0.65 mg / L (see Table 1). The concentration of hazardous components in the leachate was much lower than the standard value and pH value requirements. All categories of the barium slag that had been harmlessly treated met the standards for Class I slag of general solid waste.

[0064] Table 1

[0065] The above-mentioned embodiments of the present invention are only part of the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made by those skilled in the art without departing from the essence of the present invention are within the protection scope of the present invention.

Claims

1. A method for harmless treatment of barium slag, characterized in that: The steps include: S1 Mix the barium slag and desulfurization waste gypsum with water to make a slurry, add diluted industrial acid to the slurry, stir and acidify, and then heat to reduce the pH value of the slurry to 6-9, and initially remove most of the barium ions Ba in the barium slag after acidification. 2+ With sulfate ion SO4 in desulfurized waste gypsum 2- The reaction forms non-toxic BaSO4 which is insoluble in water; S2 Add a coupling agent to the product obtained in step S1 and stir to allow the coupling agent to react with the free barium ions Ba in the product. 2+ and barium salts for coupling and competitive coordination reactions; S3: adding a sulfate solution to the product obtained in step S2, stirring and heating, so that the sulfate and the chelated barium in the product undergo double decomposition reaction to generate water-insoluble non-toxic BaSO4; S4 Add ferrous sulfate solution to the product obtained in step S3 and continue stirring to make the remaining sulfide ions S 2- and ferrous ions Fe in ferrous sulfate 2+ Combine to form iron sulfide precipitate, filter press to obtain filter residue with a moisture content between 20% and 30%, and then dry it.

2. The method for harmless treatment of barium slag according to claim 1, characterized in that: The mass percentage of the raw materials in step S1 is: Barium slag 55%-70%; desulfurization waste gypsum 5%-20%; acid 0.5%-5%; water 20%-30%.

3. The method for harmless treatment of barium slag according to claim 1, characterized in that: The sulfate is any one of NaHSO4, Na2SO4, K2SO4, KHSO4, and (NH4)2SO4.

4. The method for harmless treatment of barium slag according to claim 1, characterized in that: The coupling agent is any one of sodium dimethyldithiocarbamate or sodium diethyldithiocarbamate.

5. The method for harmless treatment of barium slag according to claim 1, characterized in that: In the step S1, the stirring acidification time is 15 min to 30 min, the heating temperature is 40° C. to 85° C., and the heating time is 20 to 60 min.

6. The method for harmless treatment of barium slag according to claim 1, characterized in that: In the step S2, the coupling agent is added and stirred for 5 to 30 minutes.

7. The method for harmless treatment of barium slag according to claim 1, characterized in that: In the step S3, under the condition of pH 6 to 9, the double decomposition reaction time is 60 min to 180 min, and the reaction temperature is 40° C. to 85° C.

8. The method for harmless treatment of barium slag according to claim 1, characterized in that: In the step S4, after adding the ferrous sulfate solution, stirring is continued for 10 min to 30 min.

9. Application of the barium slag treated by the method according to any one of claims 1 to 8 in the construction and building materials industries.

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