Method for synthesizing Schwertmannite with strong adsorption capacity on lead by using waste chemical milling liquid

Abstract

According to the method for synthesizing the Schwertmannite with the high lead adsorption capacity through the waste chemical milling liquid, aviation industry waste, namely the scrapped chemical milling liquid, is used for synthesizing the Schwertmannite with the lead adsorption capacity at the normal temperature, the maximum lead adsorption capacity of the Schwertmannite can reach 286 mg g <-1 >, compared with traditional Schwertmannite, the adsorption efficiency of the Schwertmannite on the lead is improved by about 26%, and the Schwertmannite can be used for preparing the Schwertmannite with the high lead adsorption capacity. The specific surface area is 44.291 m < 2 > g <-1 >, which is far greater than the specific surface area of 16.881 m < 2 > g <-1 > of pure Schwertmannite. The method is simple in preparation step, mild in condition and low in cost, the prepared Schwertmannite is an excellent lead adsorption material, the treatment cost of wastewater containing heavy metal ions is greatly reduced, the environmental protection target of treating waste with waste is achieved, and the method has wide application prospects in the fields of water treatment and mine remediation.

Description

Technical Field

[0001] The invention relates to a schreberite mineral having a strong adsorption capacity for lead synthesized by utilizing waste milling fluid, and specifically belongs to the technical field of development of new environmental restoration / resource recovery materials. Background Art

[0002] The aerospace industry is an important manifestation of the country's comprehensive strength. Aluminum alloy, as the main structural material, plays an indispensable role in this field. Chemical milling fluid plays an important role in the chemical milling of aluminum alloys and other materials. It removes excess metal from the surface of parts by chemical corrosion, especially in removing trace metal on the surface. However, during the processing, aluminum and its alloys will dissolve in the strong alkaline chemical milling fluid to form sodium aluminate. When the mass concentration of aluminum ions accumulates to 70~80 g / L, the chemical milling fluid will not meet the requirements of chemical milling and will be scrapped. This scrapped chemical milling fluid not only leads to a waste of resources, but also has higher economic costs in industrial scrap treatment, harmless treatment and hazardous waste recycling due to its strong alkalinity and complex chemical composition.

[0003] At present, the common treatment methods for chemical milling fluid include physicochemical crystallization and biochemical treatment. The physicochemical crystallization method can effectively reduce the aluminum ion concentration in the chemical milling fluid by means of dilution and standing, so that it can reach the standard of reusability. However, this method requires a large amount of water resources for dilution. In addition, although the physicochemical crystallization method can achieve the purification of solutes, its disadvantages are that the generation rate is slow and the growth conditions are difficult to control. The biochemical treatment method uses the metabolism of microorganisms to decompose harmful components in the chemical milling fluid to achieve the purpose of purification. However, this method takes a long time to process and requires precise control of the processing environment to ensure that the microorganisms can grow and metabolize effectively. In addition, improper storage of chemical milling fluid can easily cause bacteria and other microorganisms to grow and multiply in large numbers, causing the oil substances in it to decompose and become smelly due to biochemical decomposition, which will greatly affect the recycling of chemical milling fluid.

[0004] Schroederite is a low-crystallinity secondary iron hydroxysulfate mineral. It has a unique pore structure and a large specific surface area, and exhibits good adsorption properties for heavy metal ions. Heavy metal ions in aqueous solution exist in various forms, usually in the form of oxygen-containing anions. These ions are mainly adsorbed by electrostatic adsorption and by sulfate ions (SO4 2- ) to achieve adsorption through ion exchange. In addition, there are a certain number of hydroxyl groups (-OH) and sulfate groups (SO4 2- ), some heavy metal ions can combine with the surface hydroxyl groups through complexation, or with the surface SO4 2-The groups exchange ions to achieve the purpose of adsorption. Based on the above adsorption mechanism, Schroeder mineral can effectively remove heavy metal ions in water.

[0005] At present, the research on the removal of anionic pollutants by Schroeder mineral is relatively extensive at home and abroad, but the research on the removal of cationic pollutants such as lead by Schroeder mineral is relatively small. Due to the unique pore structure of Schroeder mineral, its adsorption effect on lead is not ideal. Therefore, it is particularly necessary to develop a low-cost and efficient synthesis method to prepare a new type of Schroeder mineral with stronger lead adsorption capacity.

[0006] The invention uses the Schmidtite synthesized from the discarded chemical milling fluid, which effectively consumes the difficult-to-treat industrial waste on the one hand, and significantly enhances the adsorption capacity of lead on the other hand. The discarded chemical milling fluid is an industrial waste generated after the material processing in the aerospace field. The invention makes resource utilization of the discarded chemical milling fluid, which not only greatly reduces the processing cost, but also realizes the recycling of the waste, achieves the purpose of treating waste with waste, and thus realizes the efficient utilization of waste resources. Summary of the invention

[0007] Aiming at the current utilization status of waste chemical milling fluid, the present invention utilizes the chemical milling fluid as a resource to synthesize a new type of Schmidt mineral at room temperature.

[0008] The invention uses waste chemical milling fluid to synthesize a schreberite with strong lead adsorption capacity. The waste chemical milling fluid is used to synthesize the schreberite with lead adsorption performance at room temperature. The specific steps are as follows: Step 1: dissolve ferrous sulfate heptahydrate in pure water and ultrasonically vibrate for 20 min to obtain a ferrous sulfate solution; Step 2: In the ferrous sulfate solution, add hydrogen peroxide and waste milling liquid according to the proportion every 30 minutes and mix them evenly, and adjust the pH value of the mixed solution between 2.4 and 2.6; Step 3: The mixture obtained in step 2 was heated at 500 r min -1 The mixture was stirred at room temperature for 24 h at a speed of 1000 rpm to obtain a suspension; Step 4: The suspension in step 3 was allowed to settle for 3 h, the precipitate was washed twice with H2SO4 at pH = 2, and then washed twice with deionized water, and the solid was obtained by centrifugation; Step 5: After freeze-drying the solid for 24 h, grind it and sieve it through 100-mesh and 200-mesh sieves to obtain Schroeder mineral with lead adsorption capacity.

[0009] In the mixed solution, the ratio of the molar mass of iron to the molar mass of hydrogen peroxide is 32:47, and the ratio of the molar mass of iron to the molar mass of aluminum in the waste milling liquid is 18:1.

[0010] Beneficial effects of the present invention: The present invention utilizes the scrapped chemical milling fluid of the aviation industry to synthesize the lead-adsorbing schreiterite at room temperature, and the maximum lead adsorption capacity thereof can reach 286 mg g -1 Compared with traditional Schroeder mineral, the adsorption efficiency of lead is increased by about 26%, and the specific surface area is 44.291 m 2 g -1 , much larger than the pure Schroeder mineral 16.881 m 2 g -1 The preparation process of the present invention is simple, the conditions are mild, and the cost is low. The prepared schreberite is an excellent lead adsorption material, which not only greatly reduces the treatment cost of wastewater containing heavy metal ions, but also achieves the environmental protection goal of "treating waste with waste", and has broad application prospects in the fields of water treatment and mine restoration. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1-1 : XRD pattern of the Schmidtite prepared in Example 1 of the present invention; Figure 1-2 : BET diagram of the Schmidtite prepared in Example 1 of the present invention; Figure 1-3 : Average pore size distribution diagram of the Schmidtite prepared in Example 1 of the present invention; Figure 2 : Isothermal absorption curve of lead of the Schwarzschild mineral prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0012] Example 1 The specific steps of synthesizing the schreberite with strong adsorption capacity for lead by using waste milling fluid are as follows: Step 1: Dissolve 22.24 g of ferrous sulfate heptahydrate evenly in 0.5 L of pure water and ultrasonically vibrate for 20 min to obtain a ferrous sulfate solution; Step 2: Add 12 mL of hydrogen peroxide (19.94 mmol L -1 , 30 wt%), divided into 6 equal parts, added 1 part (2 mL) every 30 min and mixed evenly; at the same time, prepared 12 mL of 10% (V / V) chemical milling solution, divided the solution into 6 equal parts (2 mL each), and the operation was the same as hydrogen peroxide, adding one part of chemical milling solution to the reaction system every 30 min and mixing evenly. During the whole operation, the pH value of the mixed solution was adjusted between 2.4 and 2.6; Step 3: The solution obtained in step 2 was heated at 500 r min -1 The suspension was obtained by stirring at room temperature for 24 h at a speed of 1000 rpm; Step 4: let the suspension stand for 3 hours, wash the precipitate twice with H2SO4 (pH=2), and then wash it twice with deionized water to obtain a washed solid; Step 5: freeze-dry the solid washed in step 4 for 24 h, grind it after drying, and sieve it through 100-mesh and 200-mesh sieves respectively to obtain milling liquid-modified Schweiner mineral.

[0013] Figure 1-1 The XRD pattern of the Schreiber mineral prepared in this example shows that the crystallinity of the Schreiber mineral is very low. The XRD spectrum of the Schreiber mineral synthesized by the chemical milling fluid is basically consistent with that of the pure Schreiber mineral, indicating that the quantitative use of the chemical milling fluid to synthesize the new Schreiber mineral in this study has no significant effect on the mineral phase.

[0014] Figure 1-2 This is the BET diagram of the Schmidtite prepared in this example. It can be seen from the BET that the specific surface area of ​​the Schmidtite synthesized by the chemical milling fluid is 44.291 m 2 g -1 , which is much larger than the specific surface area of ​​pure Schroeder mineral (16.881 m 2 g -1 ), indicating that the Schmidtite synthesized by chemical milling fluid can provide more active sites and contact areas, thereby improving the adsorption capacity of the material. Figure 1-3 The average pore size distribution diagram of the Schreiber mineral prepared in this embodiment shows that the average pore size of the two adsorption materials has only slightly changed (the average pore size of pure Schreiber mineral is 8.8588 nm, and the average pore size of the Schreiber mineral synthesized by chemical milling liquid is 8.8289 nm). The pore size is almost unchanged, indicating that the pore structure of the material remains stable to a certain extent, and no significant pore expansion or contraction occurs, which means that the preparation process of the material optimizes the pore structure, so that it increases the specific surface area while maintaining the pore size stability, thereby improving the adsorption efficiency.

[0015] Example 2 This example is to study the adsorption of different initial concentrations by conducting a series of adsorption experiments at the same temperature. Isothermal adsorption experiment of lead by synthesized Schmidtite with chemical milling fluid. The specific process is as follows: Seven different initial concentrations were prepared, each with a concentration of 10 mg L -1 , 20 mg L -1 , 40 mg L -1 、80 mg L -1 , 120 mgL -1 , 160 mg L -1 , 200 mg L -1 , 300 mg L -1, 400 mg L -1 and 600 mg L -1 of divalent lead ion solution; A total of 20 polypropylene tubes were prepared and divided into 2 groups, corresponding to 2 different adsorption materials, with 10 polypropylene tubes in each group. The 10 polypropylene tubes in each group were added with 20 mg of the same adsorption material, but 20 mL of 10 different initial concentrations of divalent lead ion solutions were added respectively.

[0016] The polypropylene tube was placed in a constant temperature shaking box at a temperature of 25 °C and a speed of 180 rpm min -1 The solution was shaken continuously for 24 h under the condition of 40 °C. After the adsorption experiment, the lead concentration in the solution with different initial concentrations was measured by flame atomic absorption spectrophotometer.

[0017] Figure 2 This is the isothermal adsorption curve of the Schmidtite prepared in Example 1 for divalent lead ions.

[0018] pass Figure 2 It can be seen that the maximum adsorption capacity of pure Schroeder mineral for divalent lead ions is 227 mg g -1 The maximum adsorption capacity of Schroeder mineral synthesized by chemical milling fluid for divalent lead ions is 286 mg g -1 The test results show that the Schmidtite synthesized from waste milling fluid has a high adsorption capacity for divalent lead ions. Compared with traditional Schmidtite, the adsorption efficiency is increased by about 26%.

Claims

1. A method for synthesizing a Schmidtite mineral having a strong adsorption capacity for lead by using waste milling fluid, characterized in that: The Schmidt mineral is synthesized at room temperature using waste milling fluid to have lead adsorption properties. The specific steps are as follows: Step 1: dissolve ferrous sulfate heptahydrate in pure water and ultrasonically vibrate for 20 min to obtain a ferrous sulfate solution; Step 2: In the ferrous sulfate solution, add hydrogen peroxide and waste milling liquid according to the proportion every 30 minutes and mix them evenly, and adjust the pH value of the mixed solution between 2.4 and 2.6; Step 3: The mixture obtained in step 2 was heated at 500 r min -1 The mixture was stirred at room temperature for 24 h at a speed of 1000 rpm to obtain a suspension; Step 4: The suspension in step 3 was allowed to settle for 3 h, the precipitate was washed twice with H2SO4 at pH = 2, and then washed twice with deionized water, and the solid was obtained by centrifugation; Step 5: After freeze-drying the solid for 24 h, grind it and sieve it through 100-mesh and 200-mesh sieves to obtain Schroeder mineral with lead adsorption capacity.

2. The method of synthesizing the Schmidtite with strong lead adsorption capacity by using waste milling fluid according to claim 1, characterized in that: In the mixed solution, the ratio of the molar mass of iron to the molar mass of hydrogen peroxide is 32:47, and the ratio of the molar mass of iron to the molar mass of aluminum in the waste milling liquid is 18:1.

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