A method for preparing zeolite using waste milling fluid as raw material

Abstract

The present invention discloses a method for preparing zeolite using waste milling fluid as raw material. This method utilizes the alkali and aluminum in the waste milling fluid as resources, and uses original soil as a silicon source to prepare zeolite through a hydrothermal reaction. This method realizes the resource utilization of waste milling fluid, and the preparation process is simple, energy-efficient, and cost-effective. The zeolite of the present invention has excellent adsorption performance for heavy metal ions, with the maximum adsorption capacity for lead and copper ions reaching 413 mg g, respectively. ‑1 and 231 mg g ‑1 It has a large adsorption capacity and can be recycled and reused with good repeatability and stability. It greatly reduces the cost of treating wastewater containing heavy metal ions and achieves the goal of "treating waste with waste". It is a water treatment adsorbent with great application prospects.

Description

Technical Field

[0001] The invention relates to a method for preparing zeolite by using waste milling fluid as raw material, and specifically belongs to the technical field of development of new environmental restoration / resource recovery materials. Background Art

[0002] Chemical milling is a key aluminum alloy processing method widely used in the aerospace industry. During the milling process, aluminum dissolves in a highly alkaline milling fluid and forms sodium aluminate. As the milling process progresses, the sodium aluminate accumulates until the fluid loses its effectiveness. When the aluminum ion concentration reaches 70-80 g / L, the milling fluid fails to meet production requirements and is scrapped, resulting in significant waste of chemical raw materials and high end-of-pipe treatment costs, placing both financial and environmental pressures on the company. The milling fluid contains a high concentration of sodium hydroxide, a highly alkaline solution. Upon entering the environment, it rapidly alters the pH of water and soil, turning it alkaline, posing a significant threat to life in the environment.

[0003] At present, most of the methods used in China to recycle waste milling fluids are to reduce the content of dissolved aluminum in the fluids. For example, aluminum hydroxide crystals are added to the fluids to induce the dissolved aluminum to precipitate in the form of aluminum hydroxide, thereby reducing the concentration of aluminum ions and reusing the waste milling fluids. However, this method takes a long time and is not very efficient. However, the highly toxic substance cetyltrimethylammonium bromide (CTAB) needs to be added during the preparation process.

[0004] Zeolite is a porous natural mineral or synthetic material primarily composed of silicates. Its porous structure gives it a large specific surface area and pore volume, providing abundant adsorption sites. Heavy metal ions exist as cations in aqueous solutions and bind to the pores and surface potentials of the zeolite. This binding occurs through ion exchange, coordination bonds, and electrostatic interactions. Zeolite's ion exchange capacity is a key mechanism for heavy metal adsorption. Cations (such as sodium ions) within the zeolite framework can exchange with heavy metal ions in solution. Zeolite also possesses specialized chemical sites, such as hydroxyl (-OH) groups and silicon-oxygen (Si-O-Si) bonds. These sites can bind to heavy metal ions through coordination bonds or electrostatic interactions, resulting in adsorption. Through these adsorption mechanisms, zeolite can effectively remove heavy metal ions, such as copper, lead, cadmium, and chromium, from water.

[0005] Natural zeolite has low adsorption efficiency for heavy metals due to its low purity, poor crystallinity, insufficient adsorption sites, and mismatched pore structure characteristics. Therefore, high-purity zeolite needs to be artificially synthesized. However, the cost of artificially synthesizing zeolite is expensive, so a synthesis method with low synthesis cost and high purity is needed.

[0006] Scrapped milling fluid is seriously harmful and difficult to handle, but it contains rich aluminum resources and has huge resource potential. The present invention uses scrapped milling fluid to synthesize zeolite and use it for heavy metal removal, which can not only greatly reduce the cost of treatment, but also achieve "waste treatment with waste" and realize the efficient utilization of waste resources. Summary of the Invention

[0007] Aiming at the current utilization status of waste milling fluid, the present invention utilizes alkali and aluminum in the waste milling fluid as resources and prepares zeolite for wastewater treatment through hydrothermal reaction with soil.

[0008] The present invention discloses a method for preparing zeolite using waste milling fluid as raw material, which utilizes the alkali and aluminum in the waste milling fluid as resources, and uses original soil as a silicon source to prepare zeolite through a hydrothermal reaction. The specific steps are as follows:

[0009] Step 1: The original soil was sieved with a 40-mesh sieve and then dried at 30°C for 12 hours. The soil was then crushed with a ball mill and sieved with a 100-mesh sieve to obtain soil with a particle size less than 100 mesh.

[0010] Step 2: Mix the soil with a mesh size smaller than 100, the waste milling fluid, sodium silicate, sodium hydroxide and deionized water in proportion;

[0011] Step 3: stirring the mixture obtained in step 2 at a speed of 500 r / min for 8 hours to obtain a silica-alumina gel;

[0012] Step 4: The silica-alumina gel of step 3 was transferred to a reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. The product was centrifuged and the obtained filter cake was added to deionized water, stirred for 15 minutes, and then centrifuged again. The deionized water washing and centrifugation were repeated 3 to 4 times to obtain a washed filter cake.

[0013] Step 5: The filter cake washed in step 4 was placed in 0.1 M HCl and stirred for 15 minutes, followed by centrifugation. The resulting filtered product was washed with deionized water until the pH of the filtrate reached neutral.

[0014] Step 6: The filtered product whose acidity and alkalinity reach neutral in step 5 is dried at 70° C. for 12 hours, and then ground and passed through a 100-mesh sieve to obtain zeolite.

[0015] The ratio of liquid volume to solid mass of the mixed solution is 3 ml / g, the molar ratio of silicon to aluminum is 1.5, and the molar ratio of sodium hydroxide to silicon and aluminum is 3.

[0016] Beneficial effects of the present invention: The present invention utilizes the high alkalinity and high aluminum content in waste milling fluid to prepare zeolite through hydrothermal reaction with soil, thus realizing resource utilization of waste milling fluid. The preparation process is simple, energy-saving and cost-effective. The zeolite of the present invention has excellent adsorption performance for heavy metal ions, and the maximum adsorption capacity for lead ions and copper ions reaches 413 mg g -1 and 231 mg g -1 It has a large adsorption capacity and can be recycled and reused with good repeatability and stability. It greatly reduces the cost of treating wastewater containing heavy metal ions and achieves the goal of "treating waste with waste". It is a water treatment adsorbent with great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : XRD pattern of the zeolite prepared by the present invention;

[0018] Figure 2-1 : Isothermal adsorption test data of lead by the zeolite of Example 2 of the present invention;

[0019] Figure 2-2 : Isothermal adsorption test data of copper by the zeolite of Example 2 of the present invention;

[0020] Figure 3 : Repeatability experimental data diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0021] Example 1 The method for preparing zeolite from waste milling fluid and original soil is as follows:

[0022] Step 1: The original soil was first sieved with a 40-mesh sieve. The soil with a mesh size smaller than 40 was dried at 30°C for 12 hours. The dried soil was crushed with a ball mill and then sieved with a 100-mesh sieve to obtain soil with a mesh size smaller than 100 for subsequent zeolite synthesis.

[0023] Step 2: Add 74 ml of deionized water to 5 g of original soil, 7.8 ml of waste milling fluid, 15 g of sodium hydroxide, and 7.1 g of sodium silicate, and stir to mix. The liquid volume / solid mass ratio of the resulting mixture is 3 ml / g, the molar ratio of silicon to aluminum is 1.5, and the molar ratio of sodium hydroxide to silicon and aluminum is 3.

[0024] Step 3: Place the mixed solution obtained in step 2 on a magnetic stirrer and stir at 500 r / min for 8 h to obtain silica-alumina gel.

[0025] Step 4: The silica-alumina gel of step 3 was transferred to a reactor and subjected to hydrothermal reaction at 120°C for 12 hours. The product was centrifuged and the obtained filter cake was added to deionized water, stirred and washed for 15 minutes, and then centrifuged. The deionized water washing and centrifugation were repeated 3 to 4 times to obtain the washed filter cake.

[0026] Step 5: The filter cake washed in step 4 was placed in 0.1 M HCl and stirred for 15 minutes, followed by centrifugation. The filtered product was washed with deionized water until the acidity and alkalinity of the filtrate reached neutrality.

[0027] Step 6: The filtered product whose acidity and alkalinity have reached neutrality in step 5 is dried at 70° C. for 12 hours, and then ground and passed through a 100-mesh sieve to obtain zeolite.

[0028] Figure 1 2 is the XRD pattern of zeolite. It can be seen from the XRD that the crystallinity of the zeolite is very high, which indicates that the zeolite is successfully synthesized using the waste milling fluid and the original soil in this embodiment.

[0029] Example 2 The isothermal adsorption performance of the zeolite synthesized in Example 1 for divalent lead ions and divalent copper ions was studied by performing a series of adsorptions at different initial concentrations at the same temperature. The specific process is as follows:

[0030] Different initial concentrations of 100 mg / L were prepared. -1 , 200mgL -1 , 225mgL -1 , 250mgL -1 , 275mgL -1 、300mgL -1 、 325mgL -1 、350mgL -1 and 400mgL -1 divalent lead ion solution; then prepare different initial concentrations of 50mgL -1 、75 mgL -1 、100 mgL -1 、125 mgL -1 、150 mgL -1 、175 mgL -1 , 200 mgL -1 , 250 mgL -1 、300 mgL -1 of divalent copper ion solution.

[0031] Prepare 18 Erlenmeyer flasks, 9 flasks in each group, divided into 2 groups, corresponding to 38 ml of the above-mentioned divalent lead ion and copper ion solutions respectively, and then add 19 mg of zeolite to each Erlenmeyer flask.

[0032] The above conical flask was placed in a constant temperature shaking box at a temperature of 25 ° C and a speed of 180 rpm min -1 The mixture was shaken continuously for 24 hours under the conditions of 40 °C. After the adsorption was completed, the concentration of heavy metal ions in the solutions with different initial concentrations was measured using a flame atomic absorption spectrophotometer.

[0033] Figure 2-1 and 2-2 is the isothermal adsorption test data of zeolite for divalent lead ions and divalent copper ions. Figure 2-1 is the isothermal adsorption test data of divalent lead ions, Figure 2-2 This is the isothermal adsorption test data of divalent copper ions.

[0034] pass Figure 2-1 and Figure 2-2 It can be seen that the maximum adsorption capacity of zeolite for divalent lead ions is 413 mg g -1 The maximum adsorption capacity for divalent copper ions is 231 mg g -1 The test results show that the zeolite synthesized from waste milling fluid and original soil has a high adsorption capacity for divalent lead ions and divalent copper ions.

[0035] Example 3 This example conducts a repeatability test to evaluate the durability of the zeolite synthesized in Example 1. The specific process is as follows:

[0036] Add 200 mg of zeolite to 200 ml of 100 mgL -1 of divalent copper ions or 200 mgL -1 The adsorption test of divalent lead ions was carried out for 24 h; the zeolite separated by filtration after adsorption was eluted with saturated NaCl solution until no lead ions or copper ions were detected in the filtrate. The eluted zeolite was then dried and used for the next adsorption test, and the adsorption-desorption process was repeated 5 times under the same conditions.

[0037] Figure 3 The data are the test data of the repetitive adsorption test of divalent lead ions and divalent copper ions by zeolite after elution treatment. The removal rate of divalent lead ions and divalent copper ions in the first cycle adsorption test was close to 100%. After five adsorption-desorption tests, the removal efficiency of divalent lead ions and divalent copper ions by zeolite was as high as more than 80%, indicating that the zeolite after elution treatment has good reusability and stability.

Claims

1. A method for preparing zeolite using waste milling fluid as raw material, characterized in that: The method utilizes alkali and aluminum in waste milling fluid as resources, uses original soil as silicon source, and prepares zeolite through hydrothermal reaction. The specific steps are as follows: Step 1: The original soil was sieved with a 40-mesh sieve and then dried at 30°C for 12 hours. The soil was then crushed with a ball mill and sieved with a 100-mesh sieve to obtain soil with a particle size less than 100 mesh. Step 2: Mix the soil with a mesh size smaller than 100, the waste milling fluid, sodium silicate, sodium hydroxide and deionized water in proportion; Step 3: stirring the mixture obtained in step 2 at a speed of 500 r / min for 8 hours to obtain a silica-alumina gel; Step 4: The silica-alumina gel of step 3 was transferred to a reactor and subjected to a hydrothermal reaction at 120°C for 12 hours. The product was centrifuged and the obtained filter cake was added to deionized water, stirred for 15 minutes, and then centrifuged again. The deionized water washing and centrifugation were repeated 3 to 4 times to obtain a washed filter cake. Step 5: The filter cake washed in step 4 was placed in 0.1 M HCl and stirred for 15 minutes, followed by centrifugation. The resulting filtered product was washed with deionized water until the pH of the filtrate reached neutral. Step 6: The filtered product whose acidity and alkalinity reach neutral in step 5 is dried at 70° C. for 12 hours, and then ground and passed through a 100-mesh sieve to obtain zeolite.

2. The method for preparing zeolite using waste milling fluid as raw material according to claim 1, characterized in that: The ratio of liquid volume to solid mass in the mixed solution was 3 ml / g, the molar ratio of silicon to aluminum was 1.5, and the molar ratio of sodium hydroxide to silicon and aluminum was 3.

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