Sodium borohydride modified coal gangue and application thereof in Cr (VI) sewage treatment

Abstract

The invention discloses sodium borohydride modified coal gangue and application of the sodium borohydride modified coal gangue in Cr (VI) sewage treatment. According to the modified coal gangue, sodium borohydride is used as a reducing agent to carry out reduction treatment on an iron element in the coal gangue to form metal sites with high reaction activity, and then chromium ion curing is carried out, so that the adsorption and reduction capacities of the coal gangue are effectively improved, and the application effect of the modified coal gangue in Cr (VI)-containing sewage is remarkably improved; meanwhile, the modified coal gangue can be repeatedly used, the sewage treatment cost is reduced, high economical efficiency and sustainability are achieved, a novel, efficient and economical material is provided for treatment of Cr (VI)-containing sewage, and wide application prospects are achieved.

Description

Technical Field

[0001] The invention relates to the field of removal and solidification treatment of heavy metal ions, and in particular to sodium borohydride-modified coal gangue and application thereof in Cr(VI) sewage treatment. Background Art

[0002] Chromium salt is one of the main products of the inorganic chemical industry and is widely used in leather making, metallurgy, spices, dyes, wood preservation, ceramics, metal surface treatment, chemical reagents, medicine and military industry. As an important strategic resource for my country's economic development, the demand for chromium salt is huge, and about 10% of commodities are closely related to it. However, the natural release of chromium and its use in industrial applications have led to the aggravation of water pollution problems. Especially Cr(VI), which is difficult to degrade in water bodies, has extremely high fluidity, toxicity and carcinogenicity, and has long-term effects on aquatic organisms and human health, causing irreversible harm. Therefore, how to effectively remove Cr(VI) has become an environmental problem that needs to be solved urgently.

[0003] Solidification technology is currently an economical and effective method for treating heavy metal pollutants, with the advantages of short treatment time, low cost, good effect, and wide application range. However, cement, as the most commonly used solidifying agent, has certain limitations in solidifying chromium pollution. At the same time, the cement industry is facing pressure to reduce energy consumption and greenhouse gas emissions, and urgently needs to find alternative materials for cement.

[0004] Gangue, as solid waste generated during coal mining, is rich in mineral components, among which the content of iron is relatively high. Since the iron minerals in gangue mainly exist in the form of iron oxide, these oxides have strong stability and are difficult to react or solidify effectively with chromium ions. Therefore, the iron element in gangue is not reducible enough, which limits its application effect in chromium pollution control. Trace iron elements and sulfide and other reducing components in gangue play a key role in the control process of Cr(VI). These reducing components can convert Cr(VI) into less toxic Cr(III) through chemical reduction reactions, thereby reducing the harm of chromium. Therefore, in order to improve the reaction activity of gangue in chromium ion solidification, it is first necessary to reduce the iron oxide in the gangue.

[0005] Although some studies have explored the resource utilization of coal gangue and heavy metal solidification technology, there is still a lack of systematic research on how to effectively improve the application effect of coal gangue in chromium ion solidification, especially to enhance the activity of coal gangue through chemical reduction. Summary of the invention

[0006] In view of the shortcomings of existing lithium recovery technology, the present invention proposes a sodium borohydride modified coal gangue and its application in the treatment of Cr(VI) wastewater. The modified coal gangue uses sodium borohydride as a reducing agent to reduce the iron element in the coal gangue to form metal sites with high reactivity, and then solidifies the chromium ions, which effectively improves the adsorption and reduction capabilities of the coal gangue and significantly improves its application effect in Cr(VI)-containing wastewater. In addition, the modified coal gangue can be reused, which reduces the cost of sewage treatment and has high economy and sustainability. This provides a new, efficient and economical material for the treatment of Cr(VI)-containing wastewater and has broad application prospects.

[0007] A sodium borohydride modified coal gangue, the preparation method of which comprises the following steps:

[0008] S1: Grinding and screening the coal gangue raw material to obtain coal gangue powder;

[0009] S2: adding the gangue powder obtained in step S1 into a hydrochloric acid solution at a mass volume ratio of 1:8-1:20, stirring at 30-60° C. to remove soluble salts in the gangue powder, and obtaining a gangue suspension;

[0010] S3: adding the gangue suspension obtained in step S2 into a sodium borohydride solution, wherein the mass ratio of sodium borohydride to the gangue suspension is 1:5-1:25, and reacting at room temperature to generate active metal sites on the surface of the gangue to obtain modified gangue.

[0011] Furthermore, in the step S1, the gangue is sieved through 160 meshes, and the grinding time is 30-180 minutes.

[0012] Furthermore, in step S2, the concentration of the hydrochloric acid solution is 1-6 mol / L, and the stirring time is 30-180 min.

[0013] Furthermore, in step S3, the concentration of the sodium borohydride solution is 0.15 mol / L, and the reaction time is 1-5 h.

[0014] Another object of the present invention is to provide an application of the sodium borohydride modified coal gangue in the treatment of Cr(VI) wastewater, wherein the modified coal gangue is used for the treatment of Cr(VI)-containing wastewater without filtering, and is directly mixed with the Cr(VI)-containing wastewater and stirred for 3-6 hours to achieve the immobilization of Cr(VI).

[0015] Furthermore, in the coal gangue material after the Cr(VI) immobilization treatment, chromium ions exist in a stable solid form and have high dissolution resistance and environmental stability.

[0016] Furthermore, the modified coal gangue has a Cr(VI) removal rate of up to 87%.

[0017] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0018] The beneficial effects of the present invention are:

[0019] 1. Efficient solidification of chromium ions: Sodium borohydride can effectively reduce iron oxide in coal gangue and convert it into low-valent iron (such as Fe 2+ ), significantly enhancing the surface chemical reactivity of coal gangue, playing a better role in the subsequent chromium ion solidification process, significantly improving the removal efficiency and fixation effect of chromium, with a removal rate of up to 87%;

[0020] 2. Good stability: The solidified chromium ions exist in a stable solid form, showing excellent anti-solubility and environmental stability, which greatly reduces the harm of chromium ions to the environment;

[0021] 3. Low cost and environmental protection: The treatment method of the present invention does not require complicated equipment or chemical reagents. It utilizes coal gangue, a low-cost and environmentally friendly waste material, and can achieve efficient chromium-contaminated wastewater treatment through simple modification treatment, which has broad application prospects;

[0022] 4. Simple operation process: Compared with the traditional method, the present invention does not require complicated filtering steps, simplifies the operation process, reduces the processing cost, and has strong practical application advantages;

[0023] 5. Broad application prospects: This method is suitable for the treatment of chromium-contaminated wastewater, which can make it play a stronger solidification function in the treatment of chromium pollution. It has important application value, especially in the field of industrial wastewater treatment, and becomes an innovative environmental protection technology. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 30 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0027] Removal of soluble salts: Prepare 1 mol / L hydrochloric acid solution for later use. Weigh 5 g of gangue powder and add 40 mL of hydrochloric acid solution. Place in a 30°C constant temperature water bath and stir the mixture with a magnetic stirrer for 30 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0028] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, and the mass ratio of sodium borohydride to coal gangue is 1:25. This reaction is carried out at room temperature for 1 hour. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0029] Direct treatment of Cr(VI) wastewater: Add the modified coal gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to stir them for 3 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified coal gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​coal gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of coal gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 87%.

[0030] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0031] Example 2

[0032] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 60 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0033] Removal of soluble salts: Prepare 2 mol / L hydrochloric acid solution for later use. Weigh 10 g of gangue powder and add 100 mL of hydrochloric acid solution. Place in a 30°C constant temperature water bath and stir the mixture with a magnetic stirrer for 60 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0034] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, with the mass ratio of sodium borohydride to coal gangue being 1:20. The reaction is carried out at room temperature for 2 hours. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0035] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to fully stir for 3.5 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 81%.

[0036] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0037] Example 3

[0038] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 90 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0039] Removal of soluble salts: Prepare 3 mol / L hydrochloric acid solution for later use. Weigh 20 g of gangue powder and add 300 mL of hydrochloric acid solution. Place in a 30°C constant temperature water bath and stir the mixture with a magnetic stirrer for 90 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0040] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, and the mass ratio of sodium borohydride to coal gangue is 1:15. This reaction is carried out at room temperature for 3.5 hours. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0041] Direct treatment of Cr(VI) wastewater: Add the modified coal gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to fully stir for 4 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified coal gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​coal gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of coal gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 78%.

[0042] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0043] Example 4

[0044] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 150 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reactivity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0045] Removal of soluble salts: Prepare 5 mol / L hydrochloric acid solution for later use. Weigh 30 g of gangue powder and add 540 mL of hydrochloric acid solution. Place in a 30°C constant temperature water bath and stir the mixture with a magnetic stirrer for 150 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0046] Sodium borohydride modification treatment: Add the gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, with the mass ratio of sodium borohydride to gangue being 1:10. The reaction is carried out at room temperature for 4 hours. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of the gangue and increase its adsorption capacity for chromium ions.

[0047] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to stir them thoroughly for 5 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 84%.

[0048] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0049] Example 5

[0050] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 180 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0051] Removal of soluble salts: Prepare 6 mol / L hydrochloric acid solution for later use. Weigh 40 g of gangue powder and add 800 mL of hydrochloric acid solution. Place in a 30°C constant temperature water bath and stir the mixture with a magnetic stirrer for 180 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0052] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, with the mass ratio of sodium borohydride to coal gangue being 1:5. The reaction is carried out at room temperature for 5 hours. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0053] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to fully stir for 6 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 76%.

[0054] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0055] Example 6

[0056] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 30 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0057] Removal of soluble salts: Prepare 1 mol / L hydrochloric acid solution for later use. Weigh 5 g of gangue powder and add 40 mL of hydrochloric acid solution. Place in a constant temperature water bath at 45°C and stir the mixture with a magnetic stirrer for 30 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0058] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, and the mass ratio of sodium borohydride to coal gangue is 1:25. The reaction is carried out at 45°C for 1 hour. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0059] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to fully stir for 3 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 85%.

[0060] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0061] Example 7

[0062] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 30 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0063] Removal of soluble salts: Prepare 1 mol / L hydrochloric acid solution for later use. Weigh 5 g of gangue powder and add 40 mL of hydrochloric acid solution. Place in a 60°C constant temperature water bath and stir the mixture with a magnetic stirrer for 30 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0064] Sodium borohydride modification treatment: The gangue suspension after impurities are removed is added to a 0.15 mol / L sodium borohydride solution, and the mass ratio of sodium borohydride to gangue is 1:25. The reaction is carried out at 60°C for 1 hour. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of the gangue and increase its adsorption capacity for chromium ions.

[0065] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to fully stir for 3 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 82%.

[0066] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0067] Example 8

[0068] Gangue treatment: First, put the gangue into the ball mill for grinding, and set the grinding time to 180 minutes. This process helps to achieve the homogenization and full refinement of the gangue particles, and improve their surface area and reaction activity. After grinding, the gangue powder is sieved through a 160-mesh sieve to remove larger particles and obtain gangue powder with uniform particle size and appropriate fineness.

[0069] Removal of soluble salts: Prepare 6 mol / L hydrochloric acid solution for later use. Weigh 40 g of gangue powder and add 800 mL of hydrochloric acid solution. Place in a 50°C constant temperature water bath and stir the mixture with a magnetic stirrer for 180 minutes. This process helps to remove soluble salts and impurities on the surface of gangue, ensuring that the modification effect of gangue will not be interfered with in the subsequent treatment process.

[0070] Sodium borohydride modification treatment: Add the coal gangue suspension after impurities are removed into a 0.15 mol / L sodium borohydride solution, with the mass ratio of sodium borohydride to coal gangue being 1:5. The reaction is carried out at 50°C for 5 hours. Sodium borohydride, as a strong reducing agent, reacts with metal oxides or other active groups in the coal gangue to generate highly reactive metal sites, such as Fe, Mn, etc. The generated active metal sites can significantly enhance the surface activity of coal gangue and increase its adsorption capacity for chromium ions.

[0071] Direct treatment of Cr(VI) wastewater: Add the modified gangue to the wastewater containing Cr(VI), mix them according to a certain solid-liquid ratio, and use a stirring device to stir them for 6 hours. During the stirring process, the active metal sites (such as Fe, Mn, etc.) generated on the surface of the modified gangue undergo redox reactions with Cr(VI) ions, reducing Cr(VI) to low-toxic Cr(III). In addition, the porous structure and large specific surface area of ​​the gangue provide effective adsorption sites for Cr(III) ions. Electrostatic effects, complexation, and precipitation reactions are used to further fix Cr(III) on the surface or in the pores of the gangue, thereby achieving the removal and solidification of Cr(VI). The solidification rate measured by XRF is 80%.

[0072] After treatment, the concentration of Cr(VI) in the sewage was significantly reduced, reaching the environmental discharge standard, and the treatment effect was good. The modified coal gangue showed high treatment efficiency and good stability, and could maintain good performance after multiple cycles.

[0073] Comparative Example 1

[0074] In order to verify the effect of sodium borohydride modification treatment, a comparative experiment was conducted to treat the same Cr(VI) wastewater without using sodium borohydride to modify coal gangue.

[0075] Treatment process: The control group experiment used unmodified coal gangue powder, which was directly mixed with Cr(VI)-containing wastewater after grinding, screening and hydrochloric acid washing and stirred for 6 hours.

[0076] Comparison of results: Examples 1-5 optimize the curing effect by adjusting the grinding time, reaction time and ingredient ratio, while Examples 6-8 focus on the effect of reaction temperature on curing performance. The results show that these optimized conditions significantly improve the curing effect, which is better than Comparative Example 1. Example 1 achieves the highest Cr(VI) curing rate (87%). In Comparative Example 1, due to the lack of sufficient active metal sites on the surface of the gangue, its adsorption capacity for Cr(VI) ions is significantly lower than that of the modified gangue. In addition, the reduction efficiency of Cr(VI) in Comparative Example 1 is low, and the concentration of Cr(VI) in the sewage has not been significantly reduced, with a removal rate of only 25%.

[0077] Specifically, as the grinding time increases, the gangue particles become more uniform and refined, thereby improving the reaction activity, but if the grinding time is too long, it may cause agglomeration between particles and reduce the curing effect. The increase in hydrochloric acid concentration and pickling time helps to remove impurities more thoroughly, but after exceeding a certain range (such as Example 5 and Example 8), the curing rate of Cr (VI) is not significantly improved. Higher hydrochloric acid concentrations and long-term pickling excessively deplete the active surface of gangue and reduce efficiency. The increase in reaction temperature (such as Example 6 and Example 7) enhances the adsorption and reduction ability of gangue to Cr (VI), but too high a temperature can lead to instability of certain structures.

[0078]

[0079] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A sodium borohydride modified coal gangue, characterized in that: The preparation method thereof comprises the following steps: S1 Gangue processing: Grinding and screening the gangue raw materials to obtain gangue powder; S2: removing soluble salts: adding the gangue powder in step S1 to a hydrochloric acid solution at a mass volume ratio of 1:8-20, stirring at 30-60° C., removing soluble salts in the gangue powder, and obtaining a gangue suspension; S3 sodium borohydride modification treatment: adding the gangue suspension obtained in step S2 into a sodium borohydride solution, wherein the mass ratio of sodium borohydride to the gangue suspension is 1:5-25, and reacting at room temperature to generate active metal sites on the surface of the gangue to obtain modified gangue.

2. The sodium borohydride modified coal gangue according to claim 1, characterized in that: In the step S1, the gangue is sieved through a 160-mesh screen, and the grinding time is 30-180 minutes.

3. The sodium borohydride modified coal gangue according to claim 1, characterized in that: The concentration of the hydrochloric acid solution in step S2 is 1-6 mol / L, and the stirring time is 30-180 min.

4. The sodium borohydride modified coal gangue according to claim 1, characterized in that: The concentration of the sodium borohydride solution in step S3 is 0.15 mol / L, and the reaction time is 1-5 h.

5. The application of sodium borohydride modified coal gangue in Cr(VI) wastewater treatment according to claim 1, characterized in that: The modified coal gangue is used for the treatment of wastewater containing Cr(VI) without filtering, and is directly mixed with the wastewater containing Cr(VI) and stirred for 3-6 hours to achieve the immobilization of Cr(VI).

6. The use of sodium borohydride modified coal gangue in Cr(VI) wastewater treatment according to claim 5, characterized in that: After the Cr(VI) immobilization treatment, the modified coal gangue has chromium ions in a stable solid form and has high dissolution resistance and environmental stability.

7. The use of sodium borohydride modified coal gangue in Cr(VI) wastewater treatment according to claim 5, characterized in that: The modified coal gangue has a Cr(VI) removal rate of up to 87%.

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