Efficient recovery treatment process for steel slag

Abstract

The invention discloses an efficient steel slag recovery treatment process, and relates to the technical field of steel slag treatment, the treatment process comprises the following steps: adding a modifier into molten steel slag for modification treatment; cooling the modified steel slag, grinding, crushing, adding into deionized water, and adding the modified charcoal for adsorption leaching treatment; treating the slurry to obtain phosphorus-rich biochar and dephosphorized residues; according to the recycling process, the steel slag and the agricultural straw are cooperatively treated, valuable elements such as phosphorus and iron in the steel slag are recycled through a green process and efficient physical separation, and the valuable elements are converted into high-value products such as slow-release phosphate fertilizer, ironmaking raw materials and building materials; according to the scheme, waste is turned into wealth, complete recycling of solid waste is achieved, a substance circulation closed-loop industrial chain free of secondary pollution is constructed, and economic and environmental benefits are remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of steel slag treatment, and in particular to a high-efficiency steel slag recovery and treatment process. Background Art

[0002] The steel industry is a key pillar of my country's national economy, but its production process produces a large amount of steel slag as a byproduct. With the continued growth of my country's steel production, annual slag output has exceeded 100 million tons. This storage not only occupies a significant amount of valuable land resources, but also contains unstable mineral phases and heavy metals, which pose a risk of soil and groundwater contamination through rainwater leaching, placing a heavy burden on the ecological environment.

[0003] However, steel slag is not entirely useless waste. It is essentially a man-made mineral resource rich in valuable elements such as calcium, silicon, iron, magnesium, and phosphorus. The phosphorus and iron contained in it, in particular, have high recycling value. Therefore, effectively treating steel slag and realizing its resourceful and high-value utilization is not only an urgent need to address environmental issues, but also a key step in promoting "waste-free" green and circular development in the steel industry.

[0004] Currently, steel slag treatment and utilization methods are primarily divided into two categories: direct utilization and separation, extraction, and reuse. Direct utilization primarily involves using it as roadbed material, cement admixture, and construction aggregate. While this method consumes some steel slag, it fails to effectively recover valuable components like phosphorus and iron, resulting in extremely low added value and failing to fundamentally address the massive slag backlog.

[0005] In order to improve economic benefits, researchers have developed a variety of high-value utilization technologies aimed at recovering valuable elements. For example, strong acids (such as sulfuric acid and hydrochloric acid) are used to wet-leach steel slag to recover phosphorus. CN119464589A discloses a method for diversified utilization of steel slag resources, which belongs to the field of metallurgical resource recycling technology. The present invention conducts acid leaching separation and precipitation on steel slag, and sequentially changes the leachate to obtain different precipitation products, effectively separating different elements of converter steel slag. However, this method has the following disadvantages that are difficult to overcome, such as high acid consumption, severe equipment corrosion, poor leaching selectivity (a large number of impurity ions will be dissolved at the same time), and the generation of a large amount of acidic wastewater causing secondary pollution.

[0006] In addition, there are also studies that attempt to use adsorption methods to recover phosphorus from steel slag, such as using materials such as biochar. However, the adsorption capacity of traditional biochar for phosphorus is limited, and its mechanism of action can only passively adsorb phosphate that has been dissolved from the steel slag, and cannot actively promote the decomposition and release of stable solid-phase phosphorus minerals in the steel slag, resulting in low overall dephosphorization efficiency. More importantly, after the adsorption is completed, the light biochar that has adsorbed phosphorus is evenly mixed with the remaining heavy steel slag powder. There is a lack of effective and low-cost industrial separation methods to separate the two, resulting in the inability to obtain pure products of high-value phosphorus-rich biochar and dephosphorized steel slag, which seriously restricts the practical application of this route.

[0007] In summary, existing slag treatment technologies generally suffer from one or more issues, including complex process flows, high energy consumption, high costs, environmental unfriendliness, low recovery efficiency, and difficulty in product separation. Therefore, the development of a new technology with mild process conditions, environmental friendliness, and the ability to efficiently and synergistically leaching and recover valuable elements such as phosphorus from slag, while achieving complete separation and high-value utilization of the product components, is of great practical significance and has broad application prospects. Summary of the Invention

[0008] In order to address the deficiencies in the prior art, the present invention aims to provide a highly efficient steel slag recovery and treatment process, which synergistically treats steel slag and agricultural straw. Through green technology and efficient physical separation, valuable elements such as phosphorus and iron in the steel slag are recovered and converted into high-value products such as slow-release phosphate fertilizer, ironmaking raw materials and building materials. This solution turns waste into treasure, realizes the complete resource utilization of solid waste, and constructs a closed-loop material circulation industry chain without secondary pollution, with significant economic and environmental benefits.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A high-efficiency steel slag recovery and treatment process comprises the following steps: adding a modifier to molten steel slag for modification; cooling the modified steel slag, grinding and crushing it, adding it to deionized water, and adding modified biochar for adsorption and leaching treatment; and treating the slurry to obtain phosphorus-rich biochar and dephosphorization residue.

[0011] Preferably, the slurry treatment method is: pumping the obtained slurry into a hydrocyclone for classification, obtaining a dephosphorization residue from the underflow port, and obtaining a modified biochar suspension from the overflow port; further separating the dephosphorization residue through a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; filtering, washing and drying the modified biochar suspension to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0012] Preferably, the modified steel slag is crushed to a particle size of less than 0.3 mm; the dosage ratio of modified steel slag, deionized water, and modified biochar is 10 g: 1000-3000 mL: 0.5-3 g; the adsorption leaching conditions are leaching at 25-35 ° C and 200-800 r / min for 30-90 min, and the system pH is maintained at 4-7.

[0013] Preferably, the modifier is SiO2, the addition amount is 10-20wt% of the steel slag, and the particle size is below 150 mesh.

[0014] Preferably, the modified biochar is prepared by the following steps:

[0015] (1) Cut corn stalks into sections, wash and dry them, perform anaerobic pyrolysis, crush and grind them to obtain biochar, disperse the biochar into deionized water, perform ultrasonic treatment to obtain a suspension, then slowly add potassium periodate, stir and react in the dark, centrifuge the product, wash it to neutrality, and dry it to obtain oxidized biochar;

[0016] Preparation of oxidized biochar: Biochar's surface contains chemical groups derived from plant fibers. Potassium periodate (KIO4), a strong oxidant, oxidizes these surface alcoholic hydroxyl groups (-OH) to aldehyde groups (-CHO), or further to carboxyl groups (-COOH) under mild conditions. This process introduces these chemically active oxygen-containing functional groups into the porous framework of the biochar, providing the necessary foundation for the subsequent grafting of other functional molecules.

[0017] Preferably, in step (1), the powder is ground to 100-200 mesh, and the anaerobic pyrolysis conditions are anaerobic pyrolysis at 300-500° C. for 0.5-2 h.

[0018] Preferably, in step (1), the ratio of biochar, deionized water, and potassium periodate is 10 g: 300-500 mL: 10-22 g; the ultrasonic treatment time is 20-40 min; and the stirring reaction conditions are 30-60° C. and 12-24 h.

[0019] (2) dispersing the oxidized biochar into a borate buffer solution, uniformly dispersing it by ultrasonication, then adding polylysine, stirring the reaction, centrifuging, washing, and drying the product to obtain an intermediate;

[0020] Grafted polylysine: Polylysine is a long-chain molecule with numerous amino groups (-NH2) on its side chains. In the slightly alkaline environment provided by the borate buffer, the aldehyde groups on the biochar surface react with the amino groups of polylysine through a nucleophilic addition-dehydration reaction, forming a Schiff base (-C=N-). Through this reaction, a large number of polylysine molecules are grafted onto the biochar surface, forming an intermediate.

[0021] Preferably, in step (2), the pH of the borate buffer solution is 7.5-8.5, and the usage ratio of the oxidized biochar, borate buffer solution, and polylysine is 10 g: 100-200 mL: 5-15 g.

[0022] Preferably, in step (2), the stirring reaction condition is 25-40° C. for 12-24 h.

[0023] Preferably, in step (2), the molecular weight of polylysine is 1000 to 4000 Da.

[0024] (3) The intermediate is dispersed in deionized water, and calcium chloride solution and hydrogen peroxide solution are added dropwise simultaneously under vigorous stirring. The stirring reaction is continued, and the product is centrifuged, washed, and dried to obtain modified biochar.

[0025] Generation of modified biochar: The large number of free amino groups on the polylysine molecular chain grafted in the previous step are alkaline, and the generation of calcium peroxide (CaO2) requires alkaline conditions (Ca 2+ +H2O2+2OH-→CaO2↓+2H2O), thus triggering the reaction and confining it to the surface of the biochar. Ultimately, the in-situ generation and loading of nanoscale calcium peroxide particles on the carrier was achieved, resulting in modified biochar.

[0026] Preferably, in step (3), the concentration of the calcium chloride solution is 0.1-0.5 mol / L, the concentration of the hydrogen peroxide solution is 0.1-0.5 mol / L, and the dosage ratio of the intermediate, deionized water, calcium chloride solution, and hydrogen peroxide solution is 10 g: 500-1000 mL: 30-150 mL: 30-150 mL.

[0027] Preferably, in step (3), the calcium chloride solution and the hydrogen peroxide solution are added dropwise over 1 to 3 hours; and the stirring reaction conditions are 25 to 40° C. and 2 to 8 hours.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention proposes a highly efficient steel slag recovery and treatment process. All chemical reactions in the wet leaching and adsorption process are carried out under mild conditions at room temperature and pressure, with the advantages of low energy consumption, simple equipment requirements, and high operational safety. The slurry treatment utilizes the significant density difference between modified biochar and steel slag. First, a hydrocyclone is used to achieve efficient pre-separation of the light and heavy phases, separating the majority of the biochar from the steel slag. Subsequently, the separated dephosphorization residue is subjected to magnetic separation to obtain three products: phosphorus-rich biochar fertilizer, magnetic material that can be returned to the furnace for ironmaking, and non-magnetic slag that can be used as building materials. This forms a complete closed-loop material cycle with significant economic and environmental benefits.

[0030] 2. The present invention provides a modified biochar that integrates the functions of "leaching" and "adsorption". First, porous biochar is used as a basic platform with a high specific surface area, and a large number of aldehyde groups and carboxyl groups are introduced on its surface through oxidation, which provides the necessary foundation for the firm grafting of subsequent functional molecules. Secondly, the grafted polylysine is protonated in large quantities under the weakly acidic environment of the leaching system to form positively charged ammonium groups (-NH3 + ), thereby constructing a cationic charge layer on the biochar surface, which has a strong electrostatic attraction and capture ability for the negatively charged phosphate anions released from the steel slag. Finally, the in-situ loaded nano-calcium peroxide can continuously and slowly release weakly acidic hydrogen peroxide, creating an acidic environment to efficiently decompose the solid phosphate rock phase and release phosphate ions from the steel slag. These liberated phosphate ions can be quickly and firmly "captured" and locked by the polylysine layer through electrostatic attraction, fundamentally solving the problem of phosphorus leaching and recovery, thereby efficiently generating a high-value-added phosphorus-rich biochar product. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0032] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0033] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0034] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 300-500°C in the absence of oxygen for 0.5-2h, grind them to 100-200 mesh to obtain biochar, disperse 10g of biochar into 300-500mL of deionized water, ultrasonicate them for 20-40min to obtain a suspension, then slowly add 10-22g of potassium periodate, stir and react at 30-60°C in the dark for 12-24h, centrifuge the product, wash it to neutrality, and dry it to obtain oxidized biochar;

[0035] (2) Disperse 10 g of oxidized biochar into 100-200 mL of borate buffer (pH = 7.5-8.5), disperse uniformly by ultrasonication, then add 5-15 g of polylysine, stir and react at 25-40 ° C for 12-24 h, centrifuge, wash, and dry the product to obtain an intermediate;

[0036] (3) Disperse 10 g of the intermediate into 500-1000 mL of deionized water, and simultaneously add 30-150 mL of 0.1-0.5 mol / L calcium chloride solution and 30-150 mL of 0.1-0.5 mol / L hydrogen peroxide solution dropwise under vigorous stirring. The addition is completed over 1-3 h, and the mixture is stirred at 25-40 ° C for 2-8 h. The product is centrifuged, washed, and dried to obtain modified biochar;

[0037] (4) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 10-20wt% of the steel slag; cooling the modified steel slag, grinding it to a particle size of less than 0.3mm, adding it to deionized water, adding modified biochar, and adsorbing and leaching it at 25-35°C and 200-800r / min for 30-90min, maintaining the pH of the system at 4-7, and the amount ratio of modified steel slag, deionized water, and modified biochar is 10g:1000-3000mL:0.5-3g; pumping the obtained slurry into a hydrocyclone for classification, obtaining a dephosphorization residue from the bottom flow port, and obtaining a modified biochar suspension from the overflow port; further separating the dephosphorization residue by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; filtering, washing, and drying the modified biochar suspension to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0038] In the following examples, the steel slag was obtained from Wuhan Iron and Steel Co., Ltd., and its chemical composition is shown in Table 1.

[0039] Table 1 Chemical composition of steel slag (%)

[0040] CaO <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> MgO <![CDATA[P2O5]]> <![CDATA[Al2O3]]> <![CDATA[MnO2]]> other 44.25 16.42 25.4 4.15 2.72 2.3 2.1 2.66

[0041] The present invention will be further described below with reference to specific examples.

[0042] Example 1

[0043] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0044] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, slowly add 22 g of potassium periodate, stir and react at 60°C in the dark for 12 h, centrifuge the product, wash it until it is neutral, and dry it to obtain oxidized biochar;

[0045] (2) Disperse 10 g of oxidized biochar into 150 mL of borate buffer (pH = 8.0) and disperse uniformly by ultrasonication. Then, add 15 g of polylysine and stir the mixture at 40 °C for 12 h. The product is centrifuged, washed, and dried to obtain an intermediate.

[0046] (3) Disperse 10 g of the intermediate into 1000 mL of deionized water, and add 150 mL of 0.1 mol / L calcium chloride solution and 150 mL of 0.1 mol / L hydrogen peroxide solution dropwise simultaneously under vigorous stirring over a period of 3 h. Stir and react at 40 °C for 2 h. Centrifuge, wash, and dry the product to obtain modified biochar.

[0047] (4) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and modified biochar is added, and adsorption leaching is carried out at 30°C and 800r / min for 30min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:3000mL:3g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a modified biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the modified biochar suspension is filtered, washed and dried to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0048] Example 2

[0049] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0050] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, 18 g of potassium periodate was slowly added, and the mixture was stirred and reacted at 50°C in the dark for 16 h. The product was centrifuged, washed until neutral, and dried to obtain oxidized biochar.

[0051] (2) 10 g of oxidized biochar was dispersed in 150 mL of borate buffer (pH = 8.0) and dispersed evenly by ultrasonication. Then, 12 g of polylysine was added and stirred at 35 °C for 16 h. The product was centrifuged, washed, and dried to obtain an intermediate.

[0052] (3) Disperse 10 g of the intermediate into 800 mL of deionized water, and add 120 mL of 0.2 mol / L calcium chloride solution and 120 mL of 0.2 mol / L hydrogen peroxide solution dropwise simultaneously under vigorous stirring over a period of 2 h. Stir and react at 35 °C for 4 h. Centrifuge, wash, and dry the product to obtain modified biochar.

[0053] (4) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and modified biochar is added, and adsorption leaching is carried out at 30°C and 600r / min for 50min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:2500mL:2.5g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a modified biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the modified biochar suspension is filtered, washed and dried to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0054] Example 3

[0055] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0056] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, 14 g of potassium periodate was slowly added, and the mixture was stirred and reacted at 40°C in the dark for 20 h. The product was centrifuged, washed until neutral, and dried to obtain oxidized biochar.

[0057] (2) 10 g of oxidized biochar was dispersed in 150 mL of borate buffer (pH = 8.0) and dispersed evenly by ultrasonication. Then, 8 g of polylysine was added and stirred at 30 °C for 20 h. The product was centrifuged, washed, and dried to obtain an intermediate.

[0058] (3) Disperse 10 g of the intermediate into 600 mL of deionized water, and add 80 mL of 0.3 mol / L calcium chloride solution and 80 mL of 0.3 mol / L hydrogen peroxide solution dropwise simultaneously under vigorous stirring. The addition is completed over 2 h. Stir and react at 30 °C for 6 h. The product is centrifuged, washed, and dried to obtain modified biochar.

[0059] (4) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and modified biochar is added, and adsorption leaching is carried out at 30°C and 400r / min for 70min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:1500mL:1.5g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a modified biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the modified biochar suspension is filtered, washed and dried to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0060] Example 4

[0061] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0062] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, slowly add 10 g of potassium periodate, stir and react at 30°C in the dark for 24 h, centrifuge the product, wash it until it is neutral, and dry it to obtain oxidized biochar;

[0063] (2) Disperse 10 g of oxidized biochar into 150 mL of borate buffer (pH = 8.0) and disperse uniformly by ultrasonication. Then, add 5 g of polylysine and stir the mixture at 25 °C for 24 h. The product is centrifuged, washed, and dried to obtain an intermediate.

[0064] (3) Disperse 10 g of the intermediate into 500 mL of deionized water, and add 30 mL of 0.5 mol / L calcium chloride solution and 30 mL of 0.5 mol / L hydrogen peroxide solution dropwise simultaneously under vigorous stirring. The addition is completed over 1 h. Stir and react at 25 °C for 8 h. The product is centrifuged, washed, and dried to obtain modified biochar.

[0065] (4) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and modified biochar is added, and adsorption leaching is carried out at 30°C and 200r / min for 90min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:1000mL:0.5g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a modified biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the modified biochar suspension is filtered, washed and dried to obtain a phosphorus-rich biochar product that can be used as a slow-release phosphate fertilizer.

[0066] Comparative Example 1

[0067] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0068] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, slowly add 22 g of potassium periodate, stir and react at 60°C in the dark for 12 h, centrifuge the product, wash it until it is neutral, and dry it to obtain oxidized biochar;

[0069] (2) Disperse 10 g of oxidized biochar into 150 mL of borate buffer (pH = 8.0) and disperse uniformly by ultrasonication. Then, add 15 g of polylysine and stir the mixture at 40 °C for 12 h. The product is centrifuged, washed, and dried to obtain an intermediate.

[0070] (3) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; after cooling the modified steel slag, grind it to a particle size of less than 0.3mm, add it to deionized water, add the intermediate, and perform adsorption leaching at 30°C and 800r / min for 30min, the pH of the system is maintained at 4-6, and the dosage ratio of modified steel slag, deionized water, and modified biochar is 10g:3000mL:3g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the biochar suspension is filtered, washed and dried to obtain a biochar product.

[0071] Comparative Example 2

[0072] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0073] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, slowly add 22 g of potassium periodate, stir and react at 60°C in the dark for 12 h, centrifuge the product, wash it until it is neutral, and dry it to obtain oxidized biochar;

[0074] (2) Disperse 10 g of oxidized biochar into 1000 mL of deionized water, and add 150 mL of 0.1 mol / L calcium chloride solution and 150 mL of 0.1 mol / L hydrogen peroxide solution dropwise simultaneously under vigorous stirring for 3 h. Stir and react at 40 °C for 2 h. Centrifuge, wash, and dry the product to obtain modified biochar.

[0075] (3) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and modified biochar is added, and adsorption leaching is carried out at 30°C and 800r / min for 30min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:3000mL:3g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the biochar suspension is filtered, washed and dried to obtain a biochar product.

[0076] Comparative Example 3

[0077] A high-efficiency steel slag recovery and treatment process comprises the following steps:

[0078] (1) Cut corn stalks into sections, wash and dry them, pyrolyze them at 400°C for 1.5 h in the absence of oxygen, grind them into 150 mesh to obtain biochar, disperse 10 g of biochar into 400 mL of deionized water, and ultrasonicate them for 30 min to obtain a suspension. Then, slowly add 22 g of potassium periodate, stir and react at 60°C in the dark for 12 h, centrifuge the product, wash it until it is neutral, and dry it to obtain oxidized biochar;

[0079] (2) Adding a modifier SiO2 (less than 150 mesh) to the molten steel slag for modification treatment, the addition amount is 15wt% of the steel slag; the modified steel slag is cooled and ground to a particle size of less than 0.3mm, added to deionized water, and oxidized biochar is added, and adsorption leaching is carried out at 30°C and 800r / min for 30min, and the pH of the system is maintained at 4-6. The amount ratio of modified steel slag, deionized water, and modified biochar is 10g:3000mL:3g; the obtained slurry is pumped into a hydrocyclone for classification, and a dephosphorization residue is obtained from the bottom flow port, and a biochar suspension is obtained from the overflow port; the dephosphorization residue is further separated by a wet magnetic separator to obtain a magnetic iron-rich component that can be returned to the metallurgical process and a non-magnetic component that can be used as a building material; the biochar suspension is filtered, washed and dried to obtain a biochar product.

[0080] The magnetic iron-rich components obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were ball-milled and passed through a 200-mesh sieve. After drying, the pellets were pressed and subjected to XRF testing. The iron and phosphorus contents in the samples were tested (the average value of 5 samples was taken), and the phosphorus removal rate and the percentage increase in iron grade were calculated. The specific data are shown in Table 2.

[0081] Table 2 Recovery process effects

[0082]

[0083] *Based on the chemical composition of steel slag, the original iron content of steel slag is 17.77% and the original phosphorus content is 1.19%.

[0084] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A high-efficiency steel slag recovery and treatment process, characterized in that: The method comprises the following steps: adding a modifier to molten steel slag for modification treatment; cooling the modified steel slag, grinding and crushing it, adding it to deionized water, adding modified biochar for adsorption and leaching treatment; and treating the slurry to obtain phosphorus-rich biochar and dephosphorization residue.

2. The high-efficiency steel slag recovery process according to claim 1, characterized in that: The modified biochar is prepared by the following steps: (1) Cut corn stalks into sections, wash and dry them, perform anaerobic pyrolysis, crush and grind them to obtain biochar, disperse the biochar into deionized water, perform ultrasonic treatment to obtain a suspension, then slowly add potassium periodate, stir and react in the dark, centrifuge the product, wash it to neutrality, and dry it to obtain oxidized biochar; (2) dispersing the oxidized biochar into a borate buffer solution, uniformly dispersing it by ultrasonication, then adding polylysine, stirring the reaction, centrifuging, washing, and drying the product to obtain an intermediate; (3) The intermediate is dispersed in deionized water, and calcium chloride solution and hydrogen peroxide solution are added dropwise simultaneously under vigorous stirring. The stirring reaction is continued, and the product is centrifuged, washed, and dried to obtain modified biochar.

3. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (1), the powder is ground into 100-200 mesh, and the anaerobic pyrolysis condition is anaerobic pyrolysis at 300-500° C. for 0.5-2 h.

4. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (1), the ratio of biochar, deionized water, and potassium periodate is 10 g: 300-500 mL: 10-22 g; the ultrasonic treatment time is 20-40 min; and the stirring reaction conditions are 30-60° C. and 12-24 h.

5. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (2), the pH of the borate buffer solution is 7.5-8.5, and the usage ratio of the oxidized biochar, the borate buffer solution, and the polylysine is 10 g: 100-200 mL: 5-15 g.

6. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (2), the stirring reaction condition is 25-40° C. for 12-24 h.

7. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (3), the concentration of the calcium chloride solution is 0.1-0.5 mol / L, the concentration of the hydrogen peroxide solution is 0.1-0.5 mol / L, and the usage ratio of the intermediate, deionized water, calcium chloride solution, and hydrogen peroxide solution is 10 g: 500-1000 mL: 30-150 mL: 30-150 mL.

8. The high-efficiency steel slag recovery process according to claim 2, characterized in that: In step (3), the calcium chloride solution and the hydrogen peroxide solution are added dropwise over 1 to 3 hours; and the stirring reaction conditions are 25 to 40° C. and 2 to 8 hours.

9. The high-efficiency steel slag recovery process according to claim 1, characterized in that: The modified steel slag is crushed to a particle size of less than 0.3 mm; the dosage ratio of modified steel slag, deionized water, and modified biochar is 10 g: 1000-3000 mL: 0.5-3 g; the adsorption leaching conditions are 25-35 ° C, 200-800 r / min, leaching for 30-90 min, and the system pH is maintained at 4-7.

10. The high-efficiency steel slag recovery process according to claim 1, characterized in that: The modifier is SiO2, the addition amount of which is 10-20wt% of the steel slag, and the particle size is below 150 meshes.

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