Preparation method and application of steel smelting dust-based composite adsorbent

Abstract

This invention discloses a preparation method and application of a composite adsorbent based on iron and steel smelting dust, belonging to the field of environmental functional materials and heavy metal wastewater treatment technology. This invention proposes a synergistic modification strategy of "hierarchical enrichment – ​​low-temperature plasma activation – iron-lanthanum gradient doping – lattice vacancy hierarchical regulation – molding and solidification": firstly, the active components in the dust are concentrated and enriched through sieving, gravity classification, and magnetic selection; then, nanopores are etched and functional groups are introduced through low-temperature plasma activation to provide iron-lanthanum ion loading sites; a Fe-La stepwise equal-volume impregnation process is used to construct Fe-La-Mn ternary active centers in combination with Mn in the iron and steel smelting dust, and calcination is performed to form a multi-element heterojunction, La... 3+ With Ca in dust 2+ Lattice coordination lowers the formation energy barrier of oxygen vacancies; gradient oxidation-reduction treatment generates shallow and deep oxygen vacancies in stages, driving in-situ oxidation of As(III) and electron replenishment, respectively; finally, molding and solidification yields spherical adsorbents with a mechanical strength ≥16 N / particle. This invention enables the high-value utilization of iron and steel smelting dust, and the adsorbent is easy to recover and produces no secondary pollution, making it suitable for the deep treatment of arsenic-containing heavy metal wastewater.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and heavy metal wastewater treatment technology, specifically a method for preparing and applying a composite adsorbent based on iron and steel smelting dust. Background Technology

[0002] In recent years, iron-based composite materials have attracted much attention due to their specific affinity for arsenic. However, existing iron-based materials suffer from problems such as uneven distribution of active sites, insufficient oxidation capacity for As(III), and difficulty in recycling powder materials. Iron and steel smelting dust is a major solid waste generated during iron and steel production, mainly including blast furnace dust, converter dust, and electric furnace dust, with a huge annual output. Taking blast furnace dust as an example, its main chemical composition is Fe2O3 30-45%, CaO 8-15%, SiO2 10-20%, Al2O3 2-5%, MgO 1-4%, and contains small amounts of MnO, ZnO, etc. Among these components, iron oxides are good adsorption carriers for arsenic, and calcium oxides can form insoluble precipitates with arsenic, possessing natural arsenic removal potential. However, raw iron and steel dust has defects such as low specific surface area and embedded active sites, limiting its direct application in the field of adsorption materials.

[0003] Currently, there are existing technologies that disclose the efficient removal of As(V) by iron-lanthanum compound adsorbents and the generation of oxygen vacancies and increased specific surface area by rare earth-doped porous spinel to enhance adsorption. However, these technologies still have limitations: iron-lanthanum compound adsorbents can only achieve the adsorption of single As(V), and do not utilize the electronic modulation effect of iron-lanthanum doping to achieve in-situ oxidation of As(III), nor do they combine with industrial solid waste to achieve resource utilization; although rare earth-doped spinel can generate oxygen vacancies through rare earth doping, the correlation mechanism between oxygen vacancies and the in-situ oxidation of highly toxic As(III) has not been elucidated. Oxygen vacancies are only used as a means to increase specific surface area and have not achieved targeted activation and utilization. Meanwhile, some researchers have attempted to modify metallurgical dust, but the following shortcomings remain: the modification process often results in the loss of natural active components in the dust; rare earth doping methods are mostly simple mixing and impregnation, resulting in poor loading uniformity, easy detachment of active components, and failure to achieve synergistic effects by combining multiple components in the dust; the lack of hierarchical regulation and directional activation design for oxygen vacancies makes it difficult to achieve the integrated in-situ oxidation of As(III) and efficient fixation of As(V). Furthermore, powder materials face challenges in practical applications, such as difficulty in recycling and the potential for secondary pollution.

[0004] Therefore, developing a composite adsorbent that uses iron and steel smelting dust as raw material, possesses both the ability to oxidize As(III) in situ and the ability to fix As(V) efficiently, and is easy to recycle, and its preparation method, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a method for preparing and applying a composite adsorbent based on iron and steel smelting dust. The method involves retaining highly active components in the dust through a graded enrichment process, increasing surface defects and introducing functional groups under mild conditions through a low-temperature plasma activation process, and constructing a Fe-La-Mn ternary active center by combining it with Mn from the iron and steel smelting dust through a stepwise equal-volume iron-lanthanum impregnation doping process. This is followed by oxidative calcination to form a Fe2O3 / LaFeO3 / CaMnO3 multi-element heterojunction. Controllable introduction of oxygen vacancies is achieved through reduction treatment, endowing the material with oxidation capabilities and realizing the integrated removal of As(III) through in-situ oxidation and As(V) lattice fixation. Simultaneously, a spherical composite adsorbent based on iron and steel smelting dust with good mechanical strength is obtained through a molding and curing process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a composite adsorbent based on iron and steel smelting dust. The composite adsorbent is prepared by a five-step synergistic modification process using iron and steel smelting dust as raw material, including graded enrichment, low-temperature plasma activation, precise gradient doping of iron and lanthanum, graded control of lattice vacancies, and molding and curing.

[0007] The present invention provides a method for preparing a composite adsorbent based on iron and steel smelting dust, comprising the following steps: (1) Raw material pretreatment and active component classification and enrichment: The iron and steel smelting dust is screened, gravity classified and magnetically separated in sequence. The magnetic heavy components are collected, dried, crushed and screened to obtain active component enriched iron and steel smelting dust. (2) Low-temperature plasma surface activation: The active component-enriched steel smelting dust obtained in step (1) is subjected to plasma activation treatment under a nitrogen atmosphere to obtain activated dust; (3) Precise gradient doping of iron and lanthanum: The activated dust obtained in step (2) is sequentially added to FeCl3·6H2O solution and La(NO3)3·6H2O solution for stepwise equal volume impregnation and doping. After aging, filtration, washing, drying and pulverizing, primary modified dust is obtained. (4) Lattice vacancy hierarchical control and molding and curing: The primary modified dust obtained in step (3) is successively subjected to oxidizing atmosphere calcination and reducing atmosphere treatment to obtain modified dust. The modified dust is mixed with binder, kneaded, granulated, pre-cured and heat-treated to obtain spherical steel smelting dust-based composite adsorbent.

[0008] Preferably, in step (1) of the present invention, the mass percentage of each component of the steel smelting dust is as follows: Fe2O3 25%~35%, MnO 5%~10%, CaO 10%~15%, SiO2 15%~20%, Al2O3 3%~5%, MgO 2%~4%, and impurities (including furnace lining fragments, unburned carbon, and metal particles) 5%~10%; the Fe2O3 content in the active component enriched steel smelting dust is 30%~35%, the MnO content is 7%~10%, and the impurity content is ≤5%.

[0009] Preferably, in step (1) of the present invention, the sieving conditions are as follows: the screen mesh size is 100~120 mesh, the vibrating screen speed is 1200~1500 r / min, and the sieving time is 10~15 min; the gravity classification conditions are as follows: the classifier speed is 1800~2200 r / min, the classification time is 15~20 min, and the heavy components with a particle size of 30~150 μm are collected; the magnetic separation conditions are as follows: the heavy components with a particle size of 30~150 μm are divided into a slurry with a mass concentration of 20%~30%, the magnetic field strength is 7500~8500 Gs, and the magnetic separation time is 8~12 min; the drying conditions are as follows: the drying temperature is 75~85℃, and the drying time is 3~5 h; the sieving conditions are as follows: the screen mesh size is 120 mesh; through step (1), the directional enrichment of Fe2O3 and MnO active components in dust can be achieved.

[0010] Preferably, in step (2) of the present invention, the conditions for low-temperature plasma activation are: discharge power of 280~320W, activation temperature of 170~190℃, activation time of 18~22 min, and nitrogen flow rate of 45~55 mL / min; step (2) is carried out in a low-temperature plasma activation instrument, through which nanoscale directional channels can be etched on the dust surface and active functional groups can be introduced.

[0011] Preferably, in step (3) of the present invention, the concentrations of FeCl3·6H2O solution and La(NO3)3·6H2O solution are 0.35~0.45 mol / L; the mass ratio of FeCl3·6H2O to MnO in activated dust is (5~7):(0.5~1); and the mass ratio of La(NO3)3·6H2O to MnO in activated dust is (3~1):1.

[0012] As a preferred embodiment, in step (3) of the present invention, the step of stepwise equal-volume impregnation is as follows: first, the activated dust is added to FeCl3·6H2O solution, the water bath temperature is 60~70 ℃, the stirring rate is 150~200 r / min, the stirring time is 1~1.5h, and it is left to stand at room temperature for 1~2h; then, La(NO3)3·6H2O solution is added, and the same water bath temperature and stirring rate are maintained and stirring is continued for 0.5~1h, and it is left to stand at room temperature for 1~2h; the aging time is 2~4h; step (3) can combine with MnO in the dust to construct Fe-La-Mn ternary active centers.

[0013] Preferably, in step (4) of the present invention, the oxidizing atmosphere calcination is a temperature gradient oxidizing atmosphere calcination, the steps are as follows: in an air atmosphere, the temperature is increased to 300~350 ℃ at a rate of 2~5 ℃ / min in the early stage and calcined at the temperature for 1~1.5 h; in the later stage, the temperature is increased to 400~500 ℃ at a rate of 5~8 ℃ / min and calcined at the temperature for 1~2 h, the total calcination time is 2~3.5 h.

[0014] Preferably, in step (4) of this invention, the reducing atmosphere treatment is a segmented reducing atmosphere treatment, the steps are as follows: under a mixed atmosphere of 5% hydrogen and 95% argon, the gas flow rate is controlled at 50~100 mL / min, the temperature is initially increased to 250~300 ℃ at a rate of 3~5 ℃ / min, and the temperature is maintained for 0.5~0.7 h; in the later stage, the temperature is increased to 300~400 ℃ at a rate of 5~8 ℃ / min, and the temperature is maintained for 0.5~1.5 h, the total reduction time is 1~2.2 h; step (4) can be achieved through La 3+ With Ca in dust 2+ Lattice coordination regulation enables the hierarchical generation and directional activation of oxygen vacancies, inducing the generation of shallow and deep hierarchical lattice vacancies.

[0015] Preferably, in step (4) of the present invention, the mass ratio of modified dust to binder is (17~19):(1~3); after the modified dust and binder are mixed, they are added to deionized water, and the amount of deionized water added is 20%~30% of the total mass of modified dust and binder; the kneading time is 15~20 min until a uniform dough-like material is formed; the diameter of the die hole for granulation is 4~6 mm; the pre-curing conditions are: temperature 50~70 ℃, humidity 80%~90%, time 12~24 h; the heat treatment curing conditions are: temperature 240~260 ℃, time 2.5~3.5 h.

[0016] This invention also provides an application of a composite adsorbent based on iron and steel smelting dust in the removal of arsenic from wastewater.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes the multi-component properties of Fe-Mn-Ca in raw material steel smelting dust, and works synergistically with hierarchical enrichment, low-temperature plasma activation, iron-lanthanum gradient doping, and oxidation roasting-reduction treatment processes to form a quadruple mechanism of "oxygen vacancy hierarchical activation-Mn catalytic oxidation-Fe-La gradient adsorption-La-Ca lattice fixation". This achieves the beneficial effect of in-situ oxidation of As(III) and lattice-level multi-layer fixation of arsenic in an integrated manner. The specific mechanism is as follows: First, through a three-step physical separation process of "screening-gravity classification-magnetic separation", impurities are effectively removed and active components are enriched, avoiding the loss of active components during chemical treatment, thereby ensuring that the following mechanisms can work effectively; The plasma-coupled susceptibility-retention mechanism of iron-lanthanum doping involves etching nanoscale oriented mesopores / micropores on a dust surface using a low-temperature plasma activation process, introducing active functional groups. The hydroxyl groups on the pore surface are Fe. 3+ / La 3+ It provides dedicated coordination loading sites, increasing the exposure rate of active sites by over 80%. Simultaneously, the amplification of surface defects introduced by the iron-lanthanum ion plasma increases oxygen vacancy generation by over 30%, solving the problems of uneven loading and easy detachment of active components in existing rare earth doping methods. Employing a precise Fe-La ratio and a step-by-step impregnation process, it enables Fe... 3+ Underlying load, La 3+ Surface loading forms a Fe-La core-shell gradient distribution, preventing ion aggregation and increasing the exposure rate of active sites. It further combines with Mn in the dust to form Fe-La-Mn ternary active centers, realizing the entire process of As(III) oxidation → As(V) gradient adsorption → multi-layer lattice fixation, effectively improving adsorption selectivity. At the same time, iron lanthanum ions form coordination bonds with -COOH and -OH introduced by plasma, amplifying lattice defects on the dust surface, increasing the subsequent oxygen vacancy generation, forming a chain effect of "pore site creation - ion fixation - defect expansion", solving the problems of uneven loading and low oxygen vacancy generation in existing rare earth doping. The electron transfer enhancement mechanism of multi-component heterojunctions: Fe-La stepwise equal-volume impregnation process combined with Mn in dust to form Fe-La-Mn ternary active centers, which are then oxidized and calcined to form Fe2O3 / LaFeO3 / CaMnO3 multi-component heterojunctions. The band difference at the heterojunction interface promotes the separation of photogenerated electron-hole pairs. The separated electrons further replenish oxygen vacancies, enhancing the oxidation activity of oxygen vacancies. At the same time, holes can directly oxidize some As(III), realizing the dual oxidation of "oxygen vacancy oxidation + hole oxidation", further improving the oxidation efficiency of As(III).

[0018] La-Ca lattice coordination-regulated oxygen vacancy hierarchical generation-directional activation mechanism: Rare earth La 3+ With Ca in dust2+ Lattice coordination occurs, resulting in lattice distortion, which reduces the oxygen vacancy formation barrier by more than 40%. Combined with a two-stage heat treatment of oxidation and reduction at temperature gradients, the generation and directional activation of oxygen vacancies are achieved, increasing the oxidation efficiency of As(III) by more than 50%. Oxidation calcination generates shallow oxygen vacancies on the surface, while reduction treatment generates deep oxygen vacancies inside the lattice. The shallow oxygen vacancies act as electron enrichment centers, directly activating dissolved oxygen to generate superoxide radicals and hydroxyl radicals, providing an electron transfer pathway for the oxidation reaction of As(III)→As(V). The deep oxygen vacancies act as electron reserves / transfer channels, continuously replenishing electrons to the shallow oxygen vacancies, preventing rapid deactivation of oxygen vacancies due to electron consumption, and extending the stabilization time of oxygen vacancies to more than twice that of traditional methods. This achieves directional activation and long-term stability of As(III) oxidation by oxygen vacancies. The gradient synergistic mechanism of Fe-La-Mn ternary active centers: Mn in the dust acts as an oxidation auxiliary center. Its variable valence characteristic synergizes with shallow oxygen vacancies, receiving enriched electrons from these vacancies, accelerating the generation of free radicals and the oxidation rate of As(III), thus solving the problem of insufficient oxidation capacity in the pure iron-lanthanum system; Fe... 3+ As the main adsorption and fixation center for As(V), the inner lattice fixation of As(V) is achieved; La is used as the main adsorption and fixation center. 3+ As a surface trapping and electron modulation center for As(V), it interacts with Ca on the one hand. 2+ La-Ca coordination bonds are formed to construct an outer lattice "trapping network" to achieve secondary surface fixation of As(V). On the other hand, the bond length of Fe-O bonds is modulated through the lanthanide contraction effect to improve the adsorption efficiency, which is different from the single As(V) adsorption mechanism of existing pure iron lanthanum compounds. (2) This invention uses widely available iron and steel smelting dust as the main raw material, without the need to add additional oxidation catalysts or adsorbents, which greatly reduces the preparation cost. At the same time, it realizes the resource utilization and high-value utilization of bulk solid waste, which is in line with the circular economy concept of "treating waste with waste".

[0019] (3) The present invention uses cement clinker as a binder and obtains spherical particles with good mechanical strength (≥16N / particle) through a two-step curing process of "pre-curing-heat treatment". This makes it easy to pack into columns, recycle and regenerate, and facilitates industrial application. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The iron and steel smelting dust used in the preparation method of this invention is blast furnace dust from iron and steel enterprises, and its main components are: Fe2O3 31.2%, MnO 7.8%, CaO 13.5%, SiO2 17.3%, Al2O3 4.1%, MgO 2.9%, and impurities 8.2%. The binder used is cement clinker produced by the iron and steel enterprise itself. This cement clinker is silicate cement clinker, and its main mineral components are: C3S 37~60%, C2S 15~37%, C3A 7~15%, and C4AF 10~18%, with the total proportion of the above four main minerals ≥95%.

[0022] The arsenic-containing wastewater used in this invention comes from the sulfuric acid workshop of a zinc smelter in Southwest China, which generates a large amount of arsenic and other impurities after washing smelting flue gas. Ultrapure water was used to prepare arsenic concentrations of 50 mg / L, 100 mg / L, and 200 mg / L. The specific application steps are as follows: the pH of the arsenic-containing wastewater is adjusted to 6±0.5, and the adsorbent is prepared into a 1 g / L solution using ultrapure water. Then, the adsorbent solution is added to 50 mL of arsenic-containing wastewater, and the mixture is stirred at 350 rpm for 24 h at room temperature and pressure. After the reaction is completed, the concentration of metal ions in the filtrate is determined by ICP method.

[0023] The main components of arsenic-containing wastewater are shown in Table 1.

[0024] Table 1 Example 1 (1) Take 500 g of blast furnace dust from a steel plant and place it in a vibrating screen with a mesh size of 100 mesh. Adjust the speed of the vibrating screen to 1350 r / min and screen for 12 min to remove large impurities and collect the dust under the screen. Put the dust under the screen into a gravity classifier and control the speed of the classifier to 2000 r / min. Classify for 18 min to separate the light components and heavy components. Discard the light components and retain the heavy components. Prepare a slurry with a mass concentration of 25% from the heavy components and send it into a wet electromagnetic separator. Adjust the magnetic field strength to 8000 Gs and separate for 10 min to collect the magnetic heavy components. Put the magnetic heavy components into a forced-air drying oven and dry at 80 ℃ for 4 h. Put them into a pulverizer and crush them. Pass them through a 120 mesh sieve to obtain the active component enriched steel smelting dust after classification and screening. The Fe2O3 content in the active component enriched steel smelting dust is 34.2%, the MnO content is 2.8%, and the impurity content is 4.0%.

[0025] (2) Take 85 g of the active component enriched iron and steel smelting dust obtained in step (1) and put it into a low-temperature plasma activator. Nitrogen gas is introduced and the flow rate is kept at 50 mL / min. The air is continuously ventilated for 12 min to remove the air. The discharge power is adjusted to 300 W, the activation temperature is 180 ℃, and the activation time is 20 min for low-temperature plasma activation treatment. After activation, the dust is naturally cooled to room temperature under nitrogen protection to obtain activated dust.

[0026] (3) Weigh 12 g FeCl3·6H2O (corresponding to 2.4 g MnO in the activated dust, with a mass ratio of 5:1), add deionized water and stir to dissolve, and prepare a 0.4 mol / L FeCl3·6H2O solution; weigh 2.4 g La(NO3)3·6H2O (corresponding to 2.4 g MnO in the activated dust, with a mass ratio of 1:1), add deionized water and stir to dissolve, and prepare a 0.4 mol / L La(NO3)3·6H2O solution; add 85 g of activated dust obtained in step (2) to 111 mL FeCl3·6H2O solution, set the constant temperature water bath temperature to 60℃, the stirring rate to 180 r / min and stir for 1.5 h, and let stand at room temperature for 1.5 h; then add 14 mL La(NO3)3·6H2O solution, continue stirring for 0.5 h at the same water bath temperature and stirring rate, and let stand at room temperature for 1.5 h; then age for 3 hours. h; Vacuum filter the mixture, collect the filter residue, wash it 4 times with deionized water until the pH of the washing solution is 7.0; Place the washed filter residue in a vacuum drying oven, dry it at 85 ℃ for 12 h, pulverize it and pass it through a 120-mesh sieve to obtain primary modified dust.

[0027] (4) The primary modified dust obtained in step (3) is placed in a muffle furnace and calcined in an oxidizing atmosphere under an air atmosphere. First, the temperature is raised to 300 ℃ at a rate of 2 ℃ / min and held for 1 h; then the temperature is raised to 450 ℃ at a rate of 5 ℃ / min and held for 1.5 h, for a total calcination time of 2.5 h; then, a reducing atmosphere treatment is carried out under a mixed atmosphere of 5% hydrogen and 95% argon, with a flow rate of 80 mL / min. First, the temperature is raised to 250 ℃ at a rate of 3 ℃ / min and held for 0.5 h; then the temperature is raised to 350 ℃ at a rate of 5 ℃ / min and held for 1 h, for a total reduction time of 1.5 h, to obtain modified dust; 72 g of modified dust is taken and mixed evenly with 8 g of cement clinker produced by the steel enterprise (mass ratio of 9:1), and then added to 20 g of deionized water. The mixture is kneaded for 18 min using a kneader to form a dough-like material; the material is placed into a mold with a diameter of 5 Spherical granules were prepared using a mm extrusion granulator; the spherical granules were placed in a constant temperature and humidity curing chamber (temperature 60 ℃, humidity 85%) for pre-curing for 18 h; the pre-cured spherical granules were placed in a forced-air drying oven and dried at 250 ℃ for 3 h, and then naturally cooled to obtain a composite adsorbent based on iron and steel smelting dust.

[0028] The adsorbent prepared in Example 1 was applied to remove arsenic from arsenic-containing wastewater. The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, and the results are shown in Table 2. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 50 mg / L and a pH of 6 to 0.05 mg / L, with an arsenic removal rate of 99.90%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 100 mg / L and a pH of 6 to 0.57 mg / L, with an arsenic removal rate of 99.43%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 200 mg / L and a pH of 6 to 26.07 mg / L, with an arsenic removal rate of 86.97%.

[0029] Example 2 (1) Take 500 g of blast furnace dust from a steel plant and place it in a vibrating screen with a mesh size of 120 mesh. Adjust the speed of the vibrating screen to 1200 r / min and screen for 15 min to remove large impurities and collect the dust under the screen. Put the dust under the screen into a gravity classifier and control the speed of the classifier to 1800 r / min. Classify for 20 min to separate the light components and heavy components. Discard the light components and retain the heavy components. Prepare a slurry with a mass concentration of 30% from the heavy components and send it into a wet electromagnetic separator. Adjust the magnetic field strength to 8500 Gs and separate for 8 min to collect the magnetic heavy components. Put the magnetic heavy components into a forced-air drying oven and dry at 85 ℃ for 3 h. Put them into a pulverizer and crush them. Pass them through a 120 mesh sieve to obtain the active component-enriched steel smelting dust after classification and screening. The Fe2O3 content in the active component-enriched steel smelting dust is 32.0%, the MnO content is 3.5%, and the impurity content is 4.5%.

[0030] (2) Take 80g of the active component enriched iron and steel smelting dust obtained in step (1) and put it into a low-temperature plasma activator. Nitrogen gas is introduced and the flow rate is kept at 55 mL / min. The air is continuously ventilated for 12 min to remove the air. The discharge power is adjusted to 320 W, the activation temperature is 170 ℃, and the activation time is 22 min for low-temperature plasma activation treatment. After activation, the dust is naturally cooled to room temperature under nitrogen protection to obtain activated dust.

[0031] (3) Weigh 14.0 g FeCl3·6H2O (corresponding to 2.8 g MnO in the activated dust, with a mass ratio of 5:1), add deionized water and stir to dissolve, and prepare a 0.35 mol / L FeCl3·6H2O solution; weigh 2.8 g La(NO3)3·6H2O (corresponding to 2.8 g MnO in the activated dust, with a mass ratio of 1:1), add deionized water and stir to dissolve, and prepare a 0.35 mol / L La(NO3)3·6H2O solution; add 80 g of activated dust obtained in step (2) to 148 mL FeCl3·6H2O solution, set the constant temperature water bath temperature to 70 ℃, the stirring rate to 200 r / min and stir for 1 h, and let stand at room temperature for 1 h; then add 19 mL La(NO3)3·6H2O solution, continue stirring for 1 h at the same water bath temperature and stirring rate, and let stand at room temperature for 2 h; then age for 2 hours. h; Vacuum filter the mixture, collect the filter residue, wash it 4 times with deionized water until the pH of the washing solution is 7.0; Place the washed filter residue in a vacuum drying oven, dry it at 85 ℃ for 12 h, pulverize it and pass it through a 120-mesh sieve to obtain primary modified dust.

[0032] (4) The primary modified dust obtained in step (3) is placed in a muffle furnace and calcined in an oxidizing atmosphere under an air atmosphere. First, the temperature is raised to 350 ℃ at a rate of 5 ℃ / min and held for 1.5 h; then the temperature is raised to 500 ℃ at a rate of 8 ℃ / min and held for 1 h, for a total calcination time of 2.5 h; then, a reducing atmosphere treatment is carried out under a mixed atmosphere of 5% hydrogen and 95% argon, with a flow rate of 50 mL / min. First, the temperature is raised to 300 ℃ at a rate of 5 ℃ / min and held for 0.7 h; then the temperature is raised to 400 ℃ at a rate of 8 ℃ / min and held for 0.5 h, for a total reduction time of 1.2 h, to obtain modified dust; 68 g of modified dust is mixed evenly with 12 g of cement clinker produced by the steel enterprise (mass ratio of 17:3) and then 16 g of modified dust is added to the furnace. In deionized water, knead the mixture for 15 minutes to form a dough-like material. Place the material into an extruder with a die diameter of 4 mm to prepare spherical particles. Place the spherical particles into a constant temperature and humidity curing chamber (temperature 50 ℃, humidity 80%) for pre-curing for 24 h. Place the pre-cured spherical particles into a forced-air drying oven and dry at 240 ℃ for 3.5 h. After natural cooling, the steel smelting dust-based composite adsorbent is obtained.

[0033] The adsorbent prepared in Example 2 was applied to remove arsenic from arsenic-containing wastewater. The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, and the results are shown in Table 2. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 50 mg / L and a pH of 6 to 0.054 mg / L, with an arsenic removal rate of 99.89%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 100 mg / L and a pH of 6 to 0.67 mg / L, with an arsenic removal rate of 99.33%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 200 mg / L and a pH of 6 to 27.60 mg / L, with an arsenic removal rate of 86.20%.

[0034] Example 3 (1) Take 500 g of blast furnace dust from a steel plant and place it in a vibrating screen with a mesh size of 110 mesh. Adjust the speed of the vibrating screen to 1500 r / min and screen for 10 min to remove large impurities and collect the dust under the screen. Put the dust under the screen into a gravity classifier and control the speed of the classifier to 2200 r / min. Classify for 15 min to separate the light components and heavy components. Discard the light components and retain the heavy components. Prepare a slurry with a mass concentration of 20% from the heavy components and send it into a wet electromagnetic separator. Adjust the magnetic field strength to 7500 Gs and magnetically separate for 12 min to collect the magnetic heavy components. Put the magnetic heavy components into a forced-air drying oven and dry at 75 ℃ for 5 h. Put them into a pulverizer and crush them. Pass them through a 120 mesh sieve to obtain the active component-enriched steel smelting dust after classification and screening. The Fe2O3 content in the active component-enriched steel smelting dust is 36.0%, the MnO content is 1.5%, and the impurity content is 4.0%.

[0035] (2) Take 82 g of the active component enriched iron and steel smelting dust obtained in step (1) and put it into a low-temperature plasma activator. Nitrogen gas is introduced and the flow rate is kept at 45 mL / min. The air is continuously ventilated for 12 min to remove the air. The discharge power is adjusted to 280 W, the activation temperature is 190 ℃, and the activation time is 18 min for low-temperature plasma activation treatment. After activation, the dust is naturally cooled to room temperature under nitrogen protection to obtain activated dust.

[0036] (3) Weigh 17.2 g FeCl3·6H2O (corresponding to 1.23 g MnO in the activated dust, with a mass ratio of 14:1), add deionized water and stir to dissolve, preparing a 0.45 mol / L FeCl3·6H2O solution; weigh 3.44 g La(NO3)3·6H2O (corresponding to 1.23 g MnO in the activated dust, with a mass ratio of 2.8:1), add deionized water and stir to dissolve, preparing a 0.45 mol / L La(NO3)3·6H2O solution; add 82 g of activated dust obtained in step (2) to 142 mL FeCl3·6H2O solution, set the constant temperature water bath temperature to 65 ℃, the stirring rate to 150 r / min and stir for 1.5 h, then let stand at room temperature for 2 h; then add 18 mL La(NO3)3·6H2O solution, continue stirring for 0.5 h at the same water bath temperature and stirring rate, and let stand at room temperature for 1 h. h; then age for 4 h; vacuum filter the mixture, collect the filter residue, wash it 4 times with deionized water until the pH of the washing liquid is 7.0; put the washed filter residue into a vacuum drying oven, dry it at 85 ℃ for 12 h, pulverize it and pass it through a 120 mesh sieve to obtain primary modified dust.

[0037] (4) The primary modified dust obtained in step (3) is placed in a muffle furnace and calcined in an oxidizing atmosphere under an air atmosphere. First, the temperature is raised to 300 ℃ at a rate of 3 ℃ / min and held for 1 h; then the temperature is raised to 400 ℃ at a rate of 8 ℃ / min and held for 2 h, for a total calcination time of 3 h; then, a reducing atmosphere treatment is carried out under a mixed atmosphere of 5% hydrogen and 95% argon, with a flow rate of 100 mL / min. First, the temperature is raised to 280 ℃ at a rate of 4 ℃ / min and held for 0.5 h; then the temperature is raised to 300 ℃ at a rate of 6 ℃ / min and held for 1.5 h, for a total reduction time of 2 h, to obtain modified dust; 76 g of modified dust is taken and mixed evenly with 4 g of cement clinker produced by the steel enterprise (mass ratio of 19:1), and then added to 24 g of deionized water. The mixture is kneaded for 20 min using a kneader to form a dough-like material; the material is placed into a mold with a diameter of 6 Spherical particles were prepared using a mm extrusion granulator; the spherical particles were placed in a constant temperature and humidity curing chamber (temperature 70 ℃, humidity 90%) for pre-curing for 12 h; the pre-cured spherical particles were placed in a forced-air drying oven and dried at 260 ℃ for 2.5 h, and then naturally cooled to obtain a composite adsorbent based on iron and steel smelting dust.

[0038] The adsorbent prepared in Example 3 was applied to remove arsenic from arsenic-containing wastewater. The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, and the results are shown in Table 2. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 50 mg / L and a pH of 6 to 0.06 mg / L, with an arsenic removal rate of 99.88%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 100 mg / L and a pH of 6 to 0.80 mg / L, with an arsenic removal rate of 99.20%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 200 mg / L and a pH of 6 to 30.00 mg / L, with an arsenic removal rate of 85.00%.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not undergo iron-lanthanum doping modification; the remaining steps are the same, as follows: (1) Take 500 g of blast furnace dust from a steel plant and place it in a vibrating screen with a mesh size of 100 mesh. Adjust the speed of the vibrating screen to 1350 r / min and screen for 12 min to remove large impurities and collect the dust under the screen. Put the dust under the screen into a gravity classifier and control the speed of the classifier to 2000 r / min. Classify for 18 min to separate the light components and heavy components. Discard the light components and retain the heavy components. Prepare a slurry with a mass concentration of 25% from the heavy components and send it into a wet electromagnetic separator. Adjust the magnetic field strength to 8000 Gs and separate for 10 min to collect the magnetic heavy components. Put the magnetic heavy components into a forced-air drying oven and dry at 80 ℃ for 4 h. Put them into a pulverizer and crush them. Pass them through a 120 mesh sieve to obtain the active component enriched steel smelting dust after classification and screening. The Fe2O3 content in the active component enriched steel smelting dust is 34.2%, the MnO content is 2.8%, and the impurity content is 4.0%.

[0040] (2) Take 85 g of the active component enriched iron and steel smelting dust obtained in step (1) and put it into a low-temperature plasma activator. Nitrogen gas is introduced and the flow rate is kept at 50 mL / min. The air is continuously ventilated for 12 min to remove the air. The discharge power is adjusted to 300 W, the activation temperature is 180 ℃, and the activation time is 20 min for low-temperature plasma activation treatment. After activation, the dust is naturally cooled to room temperature under nitrogen protection to obtain activated dust.

[0041] (3) The activated dust obtained in step (2) was placed in a muffle furnace and calcined in an oxidizing atmosphere under an air atmosphere. The temperature was first increased to 300 °C at a rate of 2 °C / min and held for 1 h; then increased to 450 °C at a rate of 5 °C / min and held for 1.5 h, for a total calcination time of 2.5 h; then treated in a reducing atmosphere under a mixed atmosphere of 5% hydrogen and 95% argon, with a flow rate of 80 mL / min. The temperature was first increased to 250 °C at a rate of 3 °C / min and held for 0.5 h; then increased to 350 °C at a rate of 5 °C / min and held for 1 h, for a total reduction time of 1.5 h, to obtain modified dust; 72 g of modified dust was mixed evenly with 8 g of cement clinker produced by the steel enterprise (mass ratio of 9:1) and then added to 20 g of deionized water. The mixture was kneaded for 18 min using a kneader to form a dough-like material; the material was placed into a mold with a diameter of 5 mm. Spherical particles were prepared using a mm extrusion granulator; the spherical particles were placed in a constant temperature and humidity curing chamber (temperature 60 ℃, humidity 85%) for pre-curing for 18 h; the pre-cured spherical particles were placed in a forced-air drying oven and dried at 250 ℃ for 3 h, and then naturally cooled to obtain an iron and lanthanum doped and modified steel smelting dust-based adsorbent.

[0042] The adsorbent prepared in Comparative Example 1 was applied to remove arsenic from arsenic-containing wastewater. The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, and the results are shown in Table 2. The adsorbent prepared in this comparative example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 50 mg / L and a pH of 6 to 4.56 mg / L, with an arsenic removal rate of 90.88%. The adsorbent prepared in this comparative example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 100 mg / L and a pH of 6 to 25.43 mg / L, with an arsenic removal rate of 74.57%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 200 mg / L and a pH of 6 to 87.41 mg / L, with an arsenic removal rate of 56.30%.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that only oxidizing atmosphere calcination is performed, without reducing atmosphere treatment. The remaining steps are the same, as follows: (1) Take 500 g of blast furnace dust from a steel plant and place it in a vibrating screen with a mesh size of 100 mesh. Adjust the speed of the vibrating screen to 1350 r / min and screen for 12 min to remove large impurities and collect the dust under the screen. Put the dust under the screen into a gravity classifier and control the speed of the classifier to 2000 r / min. Classify for 18 min to separate the light components and heavy components. Discard the light components and retain the heavy components. Prepare a slurry with a mass concentration of 25% from the heavy components and send it into a wet electromagnetic separator. Adjust the magnetic field strength to 8000 Gs and separate for 10 min to collect the magnetic heavy components. Put the magnetic heavy components into a forced-air drying oven and dry at 80 ℃ for 4 h. Put them into a pulverizer and crush them. Pass them through a 120 mesh sieve to obtain the active component enriched steel smelting dust after classification and screening. The Fe2O3 content in the active component enriched steel smelting dust is 34.2%, the MnO content is 2.8%, and the impurity content is 4.0%.

[0044] (2) Take 85 g of the active component enriched iron and steel smelting dust obtained in step (1) and put it into a low-temperature plasma activator. Nitrogen gas is introduced and the flow rate is kept at 50 mL / min. The air is continuously ventilated for 12 min to remove the air. The discharge power is adjusted to 300 W, the activation temperature is 180 ℃, and the activation time is 20 min for low-temperature plasma activation treatment. After activation, the dust is naturally cooled to room temperature under nitrogen protection to obtain activated dust.

[0045] (3) Weigh 12 g FeCl3·6H2O (corresponding to 2.4 g MnO in the activated dust, with a mass ratio of 5:1), add deionized water and stir to dissolve, and prepare a 0.4 mol / L FeCl3·6H2O solution; weigh 2.4 g La(NO3)3·6H2O (corresponding to 2.4 g MnO in the activated dust, with a mass ratio of 1:1), add deionized water and stir to dissolve, and prepare a 0.4 mol / L La(NO3)3·6H2O solution; add 85 g of activated dust obtained in step (2) to 111 mL FeCl3·6H2O solution, set the constant temperature water bath temperature to 60 ℃, the stirring rate to 180 r / min and stir for 1.5 h, and let stand at room temperature for 1.5 h; then add 14 mL La(NO3)3·6H2O solution, continue stirring for 0.5 h at the same water bath temperature and stirring rate, and let stand at room temperature for 1.5 h; then age for 3 hours. h; Vacuum filter the mixture, collect the filter residue, wash it 4 times with deionized water until the pH of the washing solution is 7.0; Place the washed filter residue in a vacuum drying oven, dry it at 85 ℃ for 12 h, pulverize it and pass it through a 120-mesh sieve to obtain primary modified dust.

[0046] (4) The primary modified dust obtained in step (3) is placed in a muffle furnace and calcined in an oxidizing atmosphere under an air atmosphere. First, the temperature is raised to 300 ℃ at a rate of 2 ℃ / min and held for 1 h; then the temperature is raised to 450 ℃ at a rate of 5 ℃ / min and held for 1.5 h. The total calcination time is 2.5 h. Modified dust is obtained. 72 g of modified dust is mixed evenly with 8 g of cement clinker produced by the steel enterprise (mass ratio of 9:1) and then added to 20 g of deionized water. The mixture is kneaded for 18 min using a kneader to form a dough-like material. The material is placed in an extruder with a die diameter of 5 mm to prepare spherical particles. The spherical particles are placed in a constant temperature and humidity curing chamber (temperature 60 ℃, humidity 85%) for pre-curing for 18 h. The pre-cured spherical particles are placed in a forced-air drying oven and dried at 250 ℃ for 3 h. After natural cooling, a composite adsorbent based on steel smelting dust is obtained.

[0047] The adsorbent prepared in Comparative Example 2 was applied to remove arsenic from arsenic-containing wastewater. The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, and the results are shown in Table 2. The adsorbent prepared in this comparative example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 50 mg / L and a pH of 6 to 2.61 mg / L, with an arsenic removal rate of 94.78%. The adsorbent prepared in this comparative example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 100 mg / L and a pH of 6 to 23.01 mg / L, with an arsenic removal rate of 76.99%. The adsorbent prepared in this example can reduce the arsenic concentration in arsenic-containing wastewater with an initial concentration of 200 mg / L and a pH of 6 to 83.00 mg / L, with an arsenic removal rate of 58.50%.

[0048] The concentration of metal ions in the filtrate after arsenic removal was determined by ICP method, as shown in Table 2.

[0049] Table 2 The comparison revealed that the composite modified adsorbents prepared in Examples 1, 2, and 3 all exhibited significantly better adsorption performance for arsenic in wastewater than Comparative Examples 1 and 2.

[0050] In Comparative Example 1, the activated dust underwent oxidation-reduction heat treatment without the introduction of iron and lanthanum elements, resulting in extremely limited oxidation of As(III) and adsorption of As(V). Due to the lack of electronic modulation effect of iron and lanthanum, the formation energy barrier of oxygen vacancies on the iron oxide surface is high. Even after reduction treatment, the oxygen vacancy concentration remains low, making it difficult to effectively activate molecular oxygen to generate superoxide radicals. Therefore, the removal of As(III) in Comparative Example 1 is mainly based on physical adsorption, lacking oxidation capacity, which leads to a decrease in arsenic removal efficiency.

[0051] Comparative Example 2 underwent iron-lanthanum doping and oxidation calcination, but without reducing atmosphere treatment. The material surface was dominated by a complete lattice with extremely low oxygen vacancy concentration. In this structure, both Fe and La are in high valence states (Fe... 3+ La 3+ The lattice oxygen is arranged in a regular manner and lacks electron enrichment centers. Although the bimetallic sites still have a certain adsorption capacity for As(V), due to the lack of a molecular oxygen activation pathway driven by oxygen vacancies, the oxidation of As(III) by the material depends entirely on the natural oxidation of dissolved oxygen, which is extremely slow. Most of the As(III) is adsorbed in its original form, and the binding is not strong, making it easy to desorb. Therefore, the total arsenic removal rate of Comparative Example 2 is lower than that of Example 1 of this invention, and the adsorption stability is poor.

[0052] Therefore, this invention constructs a heterojunction interface through "iron-lanthanum doping," modulating the electronic structure and creating thermodynamic conditions for oxygen vacancy formation; and achieves controllable introduction of oxygen vacancies through "reduction treatment," endowing the material with the oxidation function of activated molecular oxygen. Both are indispensable: without iron-lanthanum doping, the oxygen vacancy formation energy barrier is high and the concentration is low; without reduction treatment, oxygen vacancies cannot be generated, and the material only has adsorption function without oxidation activity. It is precisely the synergistic coupling of "bimetallic heterojunction" and "lattice vacancies" that enables this invention to achieve integrated removal of As(III) through "in-situ oxidation-efficient adsorption-lattice solidification," with performance significantly superior to single modification strategies.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite adsorbent based on iron and steel smelting dust, characterized in that, A composite adsorbent based on iron and steel smelting dust was prepared by a five-step synergistic modification process, which involved graded enrichment, low-temperature plasma activation, precise gradient doping of iron and lanthanum, graded control of lattice vacancies, and molding and curing.

2. The preparation method of the composite adsorbent based on iron and steel smelting dust according to claim 1, characterized in that, Includes the following steps: (1) Raw material pretreatment and active component classification and enrichment: The iron and steel smelting dust is screened, gravity classified and magnetically separated in sequence. The magnetic heavy components are collected, dried, crushed and screened to obtain active component enriched iron and steel smelting dust. (2) Low-temperature plasma surface activation: The active component-enriched steel smelting dust obtained in step (1) is subjected to plasma activation treatment under a nitrogen atmosphere to obtain activated dust; (3) Precise gradient doping of iron and lanthanum: The activated dust obtained in step (2) is sequentially added to FeCl3·6H2O solution and La(NO3)3·6H2O solution for stepwise equal volume impregnation and doping. After aging, filtration, washing, drying and pulverizing, primary modified dust is obtained. (4) Lattice vacancy hierarchical control and molding and curing: The primary modified dust obtained in step (3) is successively subjected to oxidizing atmosphere calcination and reducing atmosphere treatment to obtain modified dust. The modified dust is mixed with binder, kneaded, granulated, pre-cured and heat-treated to obtain spherical steel smelting dust-based composite adsorbent.

3. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (1), the screening conditions are as follows: the screen mesh size is 100~120 mesh, the vibrating screen speed is 1200~1500 r / min, and the screening time is 10~15 min; the gravity classification conditions are as follows: the classifier speed is 1800~2200 r / min, and the classification time is 15~20 min; the magnetic separation conditions are as follows: the recombinant particles with a particle size of 30~150 μm are divided into a slurry with a mass concentration of 20%~30%, the magnetic field strength is 7500~8500 Gs, and the magnetic separation time is 8~12 min; the drying conditions are as follows: the drying temperature is 75~85℃, and the drying time is 3~5 h; the sieving conditions are as follows: the screen mesh size is 120 mesh.

4. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (2), the conditions for low-temperature plasma activation are: discharge power of 280~320 W, activation temperature of 170~190℃, activation time of 18~22 min, and nitrogen flow rate of 45~55 mL / min.

5. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (3), the concentrations of FeCl3·6H2O solution and La(NO3)3·6H2O solution are 0.35~0.45 mol / L; the mass ratio of FeCl3·6H2O to MnO in activated dust is (5~7):(0.5~1); and the mass ratio of La(NO3)3·6H2O to MnO in activated dust is (3~1):

1.

6. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (3), the step of stepwise equal volume impregnation is as follows: first, add the activated dust to FeCl3·6H2O solution, the water bath temperature is 60~70 ℃, the stirring rate is 150~200 r / min, the stirring time is 1~1.5 h, and let it stand at room temperature for 1~2 h; then add La(NO3)3·6H2O solution, keep the same water bath temperature and stirring rate and continue stirring for 0.5~1 h, and let it stand at room temperature for 1~2 h; the aging time is 2~4 h.

7. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (4), the oxidizing atmosphere calcination is a temperature gradient oxidizing atmosphere calcination. The steps are as follows: in an air atmosphere, the temperature is increased to 300-350 ℃ at a rate of 2-5 ℃ / min in the early stage and held for calcination for 1-1.5 h; in the later stage, the temperature is increased to 400-500 ℃ at a rate of 5-8 ℃ / min and held for calcination for 1-2 h, with a total calcination time of 2-3.5 h.

8. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (4), the reducing atmosphere treatment is a segmented reducing atmosphere treatment. The steps are as follows: under a mixed atmosphere of 5% hydrogen and 95% argon, the gas flow rate is controlled at 50~100 mL / min. In the early stage, the temperature is increased to 250~300 ℃ at a rate of 3~5 ℃ / min and kept at the temperature for 0.5~0.7 h. In the later stage, the temperature is increased to 300~400 ℃ at a rate of 5~8 ℃ / min and kept at the temperature for 0.5~1.5 h. The total reduction time is 1~2.2 h.

9. The method for preparing a composite adsorbent based on iron and steel smelting dust according to claim 2, characterized in that, In step (4), the mass ratio of modified dust to binder is (17~19):(1~3); the kneading time is 15~20 min; the diameter of the die hole for granulation is 4~6 mm; the pre-curing conditions are: temperature 50~70 ℃, humidity 80%~90%, time 12~24 h; the heat treatment curing conditions are: temperature 240~260 ℃, time 2.5~3.5 h.

10. The application of the composite adsorbent based on iron and steel smelting dust as described in any one of claims 1 to 9 in the removal of arsenic from wastewater.

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