Preparation of graphene-loaded nanoscale zero-valent iron and application of graphene-loaded nanoscale zero-valent iron in chromium-containing wastewater treatment

Abstract

The invention relates to preparation of graphene-loaded nano zero-valent iron and application of the graphene-loaded nano zero-valent iron in chromium-containing wastewater treatment. The preparation method comprises the following steps: preparing 60mL of a KBH4 solution with the concentration of 0.5 mol / L as a solution A and 60mL of a FeSO4. 7H2O solution with the concentration of 0.1 mol / L as a solution B, adding 0.25 g of a single-layer graphene oxide dispersion liquid into the solution B, stirring for 30 minutes, recording as a solution C, slowly dripping the solution A into the solution C, performing suction filtration separation on powder C, and drying to obtain nZVI-coated GO. The graphene is loaded with nZVI to adsorb chromium in chromium-containing wastewater, and nZVI-GO-Cr formed after wastewater treatment can be used as an auxiliary tanning agent for leather tanning or retanning sections and has good recyclability.

Description

Technical Field

[0001] This invention relates to the field of chromium-containing wastewater treatment technology, and in particular to the preparation of graphene-supported nano-zero-valent iron and its application in chromium-containing wastewater treatment. Background Technology

[0002] Chromium-containing wastewater is a typical pollutant discharged during industrial processes such as electroplating, leather making, and dyeing. The chromium element, especially hexavalent chromium (Cr), is present in this wastewater. 6+ Due to its high toxicity, strong carcinogenicity, and excellent environmental mobility, hexavalent chromium poses a serious potential threat to ecosystems and human health. It can accumulate through the food chain, and long-term exposure can cause health problems such as gene mutations and organ damage, and even induce malignant tumors. With increasingly stringent environmental regulations, the efficient and compliant treatment of chromium-containing wastewater has become a core issue in industrial pollution control.

[0003] Currently, the main treatment methods for chromium-containing wastewater in this field include chemical precipitation, adsorption, ion exchange, and biological reduction. However, these methods generally have technical shortcomings. 1. Chemical precipitation method: Although the operation process is simple, it is easy to generate a large amount of hazardous chromium-containing sludge, and the subsequent sludge disposal is prone to secondary pollution risks; 2. Adsorption method: The adsorbent has poor regeneration performance, resulting in high treatment costs, and it is difficult to consistently control the chromium concentration in the effluent below the limit of 0.5 mg / L specified in the "Integrated Wastewater Discharge Standard" (GB 8978-1996); 3. Ion exchange method: has problems such as easy resin poisoning and deactivation, and complex operation and maintenance procedures; 4. Biological reduction method: Due to the limitations of microbial growth conditions (such as temperature and pH), the treatment efficiency is prone to fluctuation, making it difficult to apply on a large scale in industry.

[0004] With increasingly stringent environmental regulations and the widespread adoption of green manufacturing concepts, there is an urgent need in this field to develop a new chromium removal technology for chromium-containing wastewater that combines high treatment efficiency, low operating costs, and good effluent stability, in order to meet the actual needs of industrial wastewater discharge compliance and resource reuse. Summary of the Invention

[0005] This invention provides a method for preparing graphene-supported nano-zero-valent iron and its application in the treatment of chromium-containing wastewater, in order to solve the aforementioned problems in existing chromium-containing wastewater treatment methods.

[0006] The present invention adopts the following technical solution: The preparation of graphene-supported nano-zero-valent iron includes the following steps: Step 1: Prepare 60 mL of 0.5 mol / L KBH4 solution as solution A, and 60 mL of 0.1 mol / L FeSO4·7H2O solution as solution B; Step 2: Under magnetic stirring, add 0.25g of monolayer graphene oxide dispersion (Shanghai Maclean Biochemical Technology Co., Ltd., average radial size: 5-8μm, thickness: 1nm, 2mg / mL, dispersion in H2O) to solution B, stir for 30min, and record as solution C; Step 3: Slowly add solution A dropwise to solution C, maintaining the reaction temperature at 23-28℃; Step 4: Continue stirring for 30 minutes. The solution will change from light green to black, producing black powder C. Step 5: Separate powder C by filtration, wash it three times with ethanol and water alternately, and dry it to obtain graphene-supported nano-zero valent iron (nZVI@GO), denoted as powder D.

[0007] An application of graphene-supported nano-zero valent iron in the treatment of chromium-containing wastewater: The pH of the chromium-containing wastewater is adjusted to 3.5-4, 500 mg of the above-mentioned powder D is added to 1000 mL of chromium-containing wastewater, and the mixture is shaken at 25-30℃ for 30-120 min to complete the treatment of chromium-containing wastewater by nZVI.

[0008] As can be seen from the above description of the structure of the present invention, compared with the prior art, the present invention has the following advantages: 1. The nZVI prepared by the chemical reduction method of this invention is prone to agglomeration, which will reduce the specific surface area of ​​nZVI and affect the removal rate of chromium; Graphene (GO), as a functional material, can effectively remove pollutants from wastewater. However, previous studies have shown that graphene has a low removal rate of chromium in chromium-containing wastewater. Therefore, graphene was used as a carrier to uniformly load nZVI, which can effectively disperse easily aggregated nZVI, resulting in nZVI@GO, and achieving a synergistic effect with nZVI.

[0009] 2. Anti-agglomeration and stability: The two-dimensional structure of graphene disperses nZVI particles, inhibiting the easy agglomeration of nZVI, suppressing oxidation and passivation, increasing the specific surface area of ​​the reaction, and improving the dechromium removal efficiency.

[0010] 3. Synergistic adsorption-reduction mechanism: Cr(VI) is selectively adsorbed by functional groups (-OH, -COOH) on the graphene surface, and nZVI is targeted for reduction, with a removal rate of over 95% and excellent regeneration performance.

[0011] 4. Recyclability: After graphene is loaded with nZVI, it adsorbs chromium in chromium-containing wastewater. The nZVI@GO@Cr formed after wastewater treatment can be used as an auxiliary tanning agent in leather tanning or retanning processes, and has good recyclability. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating the technical process of the present invention.

[0013] Figure 2 These are sample photographs of powder B (nZVI) and powder D (nZVI@GO) of the present invention. Detailed Implementation

[0014] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0015] The preparation of nano-zero-valent iron includes the following process steps: Step 1: Prepare 60 mL (0.5 mol / L) of KBH4 (Shanghai Aladdin Biochemical Technology, ≥97%) solution as solution A, and 60 mL (0.1 mol / L) of FeSO4·7H2O (Shanghai Aladdin Biochemical Technology, ≥99%) solution as solution B; Step 2: Under magnetic stirring, slowly add solution A dropwise to solution B, maintaining the reaction temperature at 23-28℃; Step 3: Continue stirring for 30 minutes. The solution will change from light green to black, producing black powder A. Step 4: Separate powder A by filtration, wash it three times with ethanol and water alternately, and dry it to obtain nZVI, which is denoted as powder B.

[0016] An application of graphene-supported nano-zero valent iron in the treatment of chromium-containing wastewater: The pH of the chromium-containing wastewater is adjusted to 3.5-4, 500 mg of powder B is added to 1000 mL of chromium-containing wastewater, and the mixture is shaken at 25-30℃ for 30-120 min to complete the treatment of chromium-containing wastewater by nZVI.

[0017] The preparation of graphene-supported nano-zero-valent iron includes the following steps: Step 1: Prepare 60 mL (0.5 mol / L) of KBH4 solution as solution A and 60 mL (0.1 mol / L) of FeSO4·7H2O solution as solution B; Step 2: Under magnetic stirring, add 0.25g of monolayer graphene oxide dispersion (Shanghai Maclean Biochemical Technology Co., Ltd., average radial size: 5-8μm, thickness: 1nm, 2mg / mL, dispersion in H2O) to solution B, stir for 30min, and record as solution C; Step 3: Slowly add solution A dropwise to solution C, maintaining the reaction temperature at 23-28℃; Step 4: Continue stirring for 30 minutes. The solution will change from light green to black, producing black powder C. Step 5: Separate powder C by filtration, wash it three times with ethanol and water alternately, and dry it to obtain nZVI@GO, which is denoted as powder D; An application of graphene-supported nano-zero valent iron in the treatment of chromium-containing wastewater: The pH of the chromium-containing wastewater is adjusted to 3.5-4, 500 mg of powder D is added to 1000 mL of chromium-containing wastewater, and the mixture is shaken at 25-30℃ for 30-120 min to complete the treatment of chromium-containing wastewater by nZVI.

[0018] Table 1 Chromium content in wastewater before and after treatment

[0019] Table 1 shows the chromium content in the wastewater before and after treatment. Graphene has the ability to remove chromium, but its chromium removal efficiency is slightly lower than that of nZVI.

[0020] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for preparing graphene-supported nano-zero-valent iron, characterized in that, Includes the following steps: Step 1: Prepare 60 mL of 0.5 mol / L KBH4 solution as solution A, and 60 mL of 0.1 mol / L FeSO4·7H2O solution as solution B; Step 2: Under magnetic stirring, add 0.25g of monolayer graphene oxide dispersion to solution B and stir for 30min. This solution is then labeled as solution C. Step 3: Slowly add solution A dropwise to solution C, maintaining the reaction temperature at 23-28℃; Step 4: Continue stirring for 30 minutes. The solution will change from light green to black, producing black powder C. Step 5: Separate powder C by filtration, wash it three times with ethanol and water alternately, and dry it to obtain graphene-supported nano-zero-valent iron, which is denoted as powder D.

2. The application of graphene-supported nano-zero-valent iron in the treatment of chromium-containing wastewater as described in claim 1, characterized in that: Adjust the pH of the chromium-containing wastewater to 3.5-4, add 500 mg of the powder D to 1000 mL of the chromium-containing wastewater, and shake at 25-30℃ for 30-120 min to complete the treatment of the chromium-containing wastewater by nZVI.

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