Preparation method of porous calcium-aluminum hydrotalcite and application of porous calcium-aluminum hydrotalcite in sewage lead removal

Abstract

The invention relates to the technical field of heavy metal wastewater treatment, and discloses a preparation method of porous calcium-aluminum hydrotalcite and application of the porous calcium-aluminum hydrotalcite in wastewater lead removal. According to the specific scheme, an ionic liquid aqueous solution is used as a reaction solvent and a template agent, aluminum, calcium and sodium compounds are used as solutes, the porous aluminum-calcium hydrotalcite with uniform pore diameter and high adsorption capacity is synthesized, and the lead removal rate of the porous calcium-aluminum hydrotalcite can reach 98% or above. Compared with a traditional mode, the adopted preparation method is higher in efficiency, industrialization development of the porous material is facilitated, and a more excellent material can be provided for heavy metal removal.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal wastewater treatment, and specifically relates to a preparation method of porous calcium aluminum hydrotalcite and application thereof in lead removal from sewage. Background Art

[0002] With the acceleration of industrialization and the advancement of urbanization, the problem of heavy metal pollution in water bodies is becoming increasingly serious. Heavy metal pollution poses a serious threat to human health and the environment, among which lead is one of the common heavy metal pollutants. Lead has high toxicity and chronic hazards. Long-term exposure to or ingestion of lead can lead to a variety of health problems, such as nervous system damage, liver damage, and kidney dysfunction. Therefore, effectively removing lead pollution from water bodies has become an important issue in current environmental protection and water resources management. Adsorption is a simple and efficient water treatment technology that has been widely used in the removal of heavy metal pollutants. Hydrotalcite is a common adsorbent with a high specific surface area and abundant active sites, which can be used to adsorb heavy metal ion lead in water.

[0003] As an excellent adsorbent, hydrotalcite (LDH) is a non-toxic and harmless material that does not pollute the environment and meets the requirements of green environmental protection. It has high adsorption efficiency because hydrotalcite (LDH) has a layered structure, which gives it a large number of cation exchange sites and can effectively adsorb heavy metal ions in water; LDH has good selectivity and strong controllability, and can be regulated by changing its synthesis conditions, composition and surface modification to achieve efficient adsorption of different heavy metal ions; in addition, LDH is also regenerable, and the heavy metals adsorbed by LDH can be desorbed by adjusting the pH value or other methods to achieve the recycling of heavy metals; it is suitable for use in water treatment, wastewater treatment, soil remediation and other fields, and is of great significance to the control of heavy metal pollution.

[0004] Traditional lead pollution control technologies include precipitation, ion exchange and membrane separation, but these methods have problems such as high cost, complex operation and difficulty in wastewater treatment. Therefore, it is particularly important to find an efficient, low-cost and easy-to-operate lead pollution control technology. Summary of the invention

[0005] The current method has the problems of high cost, complicated operation and difficulty in wastewater treatment. The present invention provides a method for preparing porous calcium aluminum hydrotalcite and its application in wastewater lead removal. The removal rate of the porous aluminum calcium hydrotalcite synthesized by the method can reach more than 98%.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing porous calcium aluminum hydrotalcite comprises the following steps: using an ionic liquid aqueous solution as a reaction solvent and a template, completely dissolving a calcium compound, an aluminum compound and a sodium compound as solutes according to a mass ratio, adjusting the pH value, mixing evenly, hydrothermally reacting, centrifuging and washing, and drying to obtain a porous calcium aluminum hydrotalcite product.

[0008] Furthermore, in the above-mentioned preparation method, the ionic liquid is [C n mim]Br, wherein n=8-12.

[0009] Furthermore, in the above preparation method, the concentration of the ionic liquid aqueous solution is 1-2 wt %.

[0010] Furthermore, in the above-mentioned preparation method, the calcium compound, aluminum compound, and sodium compound are calcium nitrate, aluminum nitrate, and sodium nitrate, respectively.

[0011] Furthermore, in the above preparation method, the mass ratio of calcium nitrate, aluminum nitrate and sodium nitrate is 6-8:2-4:1-3.

[0012] Furthermore, in the above preparation method, the pH value is 10-12.

[0013] Furthermore, in the above-mentioned preparation method, the hydrothermal reaction time is 24-36 hours.

[0014] Furthermore, in the above-mentioned preparation method, the drying condition is drying at 60° C. for 24 hours.

[0015] The porous calcium aluminum hydrotalcite prepared by any of the preparation methods described above is used as an adsorbent in removing lead from sewage.

[0016] Furthermore, the above application is carried out as follows: porous calcium aluminum hydrotalcite is added to a lead ion solution, and the mixture is shaken and reacted at a speed of 200 r / min for 30-90 minutes.

[0017] The beneficial effects of the present invention are as follows: the present invention provides a method for preparing porous calcium aluminum hydrotalcite and its application in lead removal from sewage, and successfully prepares porous calcium aluminum hydrotalcite by an ionic liquid method to form a new porous adsorption material, thereby solving the problem of low adsorption efficiency of adsorption materials prepared by traditional methods in lead removal from sewage. In addition, the preparation method is simple, low in cost, easy to recycle, recyclable, and has little environmental pollution, and can generate huge economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD pattern of porous calcium aluminum hydrotalcite.

[0019] Figure 2 This is the SEM image of porous calcium aluminum hydrotalcite.

[0020] Figure 3 This is the infrared spectrum of porous calcium aluminum hydrotalcite. DETAILED DESCRIPTION

[0021] It should be noted that the following embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that the present invention may still be modified or replaced by equivalents; and all solutions and improvements that do not depart from the spirit and technical scope of the present invention should be included in the scope of the present invention.

[0022] Example 1

[0023] 1) Preparation of hydrotalcite

[0024] Preparation of conventional calcium aluminum hydrotalcite: First, weigh 7 parts of calcium nitrate and 3 parts of aluminum nitrate as raw materials, weigh 2 parts of sodium nitrate, and completely dissolve them in 50 parts of deionized water, then adjust the pH to 11 with sodium hydroxide solution to keep the solution alkaline, and pour the obtained mixture into a high-pressure reactor and keep it at a temperature of 100°C for 36 hours. After the reaction, the mixture is centrifuged at high speed, and the lower precipitate is the calcium aluminum hydrotalcite product, which is washed 3 times. During the washing process, the residual salts must be fully removed to ensure the purity and quality of the product. The washed product is dried at 60°C for 24 hours to finally obtain the CaAl-LDH product.

[0025] Preparation of porous calcium aluminum hydrotalcite: 7 parts of calcium nitrate, 3 parts of aluminum nitrate, and 2 parts of sodium nitrate were weighed as raw materials and mixed in 50 parts of 1.5 wt% [C 12 mim ] Br ionic liquid aqueous solution was completely dissolved, and the pH value was adjusted to 11 with NaOH solution. The obtained mixture was transferred to a magnetic stirrer and mixed evenly. After hydrothermal reaction at 30°C for 36 hours, it was centrifuged and washed 3 times, and dried at 60°C for 24 hours to obtain the CaAl-LDH (IL) product.

[0026] 2) Adsorption method

[0027] Add 20 mL of Pb(II) ion solution to a 50 mL centrifuge tube, then add 0.02 g of adsorbent, place the centrifuge tube in a constant temperature oscillating box and oscillate at a speed of 200 r / min for 60 minutes. After the reaction stops, place the centrifuge tube in a centrifuge (8000 r / min) for centrifugal separation and check the lead content.

[0028] The maximum adsorption capacity of CaAl-LDH and CaAl-LDH(IL) prepared in this example as adsorbents for Pb(II) is 551 mg / g and 768 mg / g, respectively, and the adsorption rates are as high as 95.4% and 98.1%.

[0029] Example 2

[0030] 1) Preparation of hydrotalcite

[0031] Preparation of conventional calcium aluminum hydrotalcite: First, weigh 7.5 parts of calcium nitrate and 3 parts of aluminum nitrate as raw materials, weigh 2.5 parts of sodium nitrate, and completely dissolve them in 50 parts of deionized water, then adjust the pH to 11 with sodium hydroxide solution to keep the solution alkaline, and pour the obtained mixture into a high-pressure reactor and keep it at 100°C for 36 hours. After the reaction, the mixture is centrifuged at high speed, and the lower precipitate is the calcium aluminum hydrotalcite product, which is washed 3 times. During the washing process, the residual salts must be fully removed to ensure the purity and quality of the product. The washed product is dried at 60°C for 24 hours to finally obtain the CaAl-LDH product.

[0032] Preparation of porous calcium aluminum hydrotalcite: 7.5 parts of calcium nitrate, 3 parts of aluminum nitrate, and 2.5 parts of sodium nitrate were weighed as raw materials and mixed in 50 parts of 1.5 wt% [C 12 mim ] Br ionic liquid aqueous solution was completely dissolved, and the pH value was adjusted to 11 with NaOH solution. The obtained mixture was transferred to a magnetic stirrer and mixed evenly. After hydrothermal reaction at 30°C for 36 hours, it was centrifuged and washed 3 times, and dried at 60°C for 24 hours to obtain the CaAl-LDH (IL) product.

[0033] 2) Adsorption method

[0034] Add 20 mL of Pb(II) ion solution to a 50 mL centrifuge tube, then add 0.02 g of adsorbent, place the centrifuge tube in a constant temperature oscillating box and oscillate at a speed of 200 r / min for 60 minutes. After the reaction stops, place the centrifuge tube in a centrifuge (8000 r / min) for centrifugal separation and check the lead content.

[0035] The maximum adsorption capacity of CaAl-LDH and CaAl-LDH(IL) prepared in this example as adsorbents for Pb(II) is 573 mg / g and 786 mg / g, respectively, and the adsorption rates are as high as 95.9% and 98.5%.

[0036] Example 3

[0037] 1) Preparation of hydrotalcite

[0038] Preparation of conventional calcium aluminum hydrotalcite: First, weigh 8 parts of calcium nitrate and 3.5 parts of aluminum nitrate as raw materials, weigh 2.5 parts of sodium nitrate, and completely dissolve them in 50 parts of deionized water, then adjust the pH to 11 with sodium hydroxide solution to keep the solution alkaline, and pour the obtained mixture into a high-pressure reactor and keep it at 100°C for 36 hours. After the reaction, the mixture is centrifuged at high speed, and the lower precipitate is the calcium aluminum hydrotalcite product, which is washed 2-3 times. During the washing process, the residual salts must be fully removed to ensure the purity and quality of the product. The washed product is dried at 60°C for 24 hours to finally obtain the CaAl-LDH product.

[0039] Preparation of porous calcium aluminum hydrotalcite: 8 parts of calcium nitrate, 3.5 parts of aluminum nitrate, and 2.5 parts of sodium nitrate were weighed as raw materials and mixed in 50 parts of 2 wt% [C 12 mim ] Br ionic liquid aqueous solution was completely dissolved and the pH value was adjusted to 11 with NaOH solution. The obtained mixture was transferred to a magnetic stirrer and mixed evenly. After hydrothermal reaction at 30°C for 36 hours, it was centrifuged and washed three times. After drying at 60°C for 24 hours, the CaAl-LDH (IL) product was obtained.

[0040] 2) Adsorption method

[0041] Add 20 mL of Pb(II) ion solution to a 50 mL centrifuge tube, then add 0.02 g of adsorbent, place the centrifuge tube in a constant temperature oscillating box and oscillate at a speed of 200 r / min for 60 minutes. After the reaction stops, place the centrifuge tube in a centrifuge (8000 r / min) for centrifugal separation and check the lead content.

[0042] The maximum adsorption capacity of CaAl-LDH and CaAl-LDH(IL) prepared in this example as adsorbents for Pb(II) is 568 mg / g and 795 mg / g, respectively, and the adsorption rates are as high as 95.8% and 98.7%.

Claims

1. A method for preparing porous calcium aluminum hydrotalcite, characterized in that: The method comprises the following steps: using an ionic liquid aqueous solution as a reaction solvent and a template agent, completely dissolving a calcium compound, an aluminum compound and a sodium compound as solutes according to a mass ratio, adjusting the pH value, mixing evenly, performing a hydrothermal reaction, centrifuging and washing, and drying to obtain a porous calcium aluminum hydrotalcite product.

2. The preparation method according to claim 1, characterized in that: The ionic liquid is [C n mim]Br, wherein n=8-12.

3. The preparation method according to claim 1, characterized in that: The concentration of the ionic liquid aqueous solution is 1-2 wt %.

4. The preparation method according to claim 1, characterized in that: The calcium compound, aluminum compound and sodium compound are calcium nitrate, aluminum nitrate and sodium nitrate respectively.

5. The preparation method according to claim 4, characterized in that: The mass ratio of calcium nitrate, aluminum nitrate and sodium nitrate is 6-8:2-4:1-3.

6. The preparation method according to claim 1, characterized in that: The pH value is 10-12.

7. The preparation method according to claim 1, characterized in that: The hydrothermal reaction time is 24-36h.

8. The preparation method according to claim 1, characterized in that: The drying condition is 60° C. for 24 hours.

9. Use of the porous calcium aluminum hydrotalcite prepared by the preparation method according to any one of claims 1 to 8 as an adsorbent in removing lead from sewage.

10. The use according to claim 9, characterized in that: The method is as follows: porous calcium aluminum hydrotalcite is added to a lead ion solution, and the solution is shaken at a speed of 200 r / min for 30-90 minutes.

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