Adsorbent for adsorbing lead ions as well as preparation method and adsorption method thereof

Abstract

The invention relates to the technical field of composite materials, in particular to an adsorbent for adsorbing lead ions as well as a preparation method and an adsorption method of the adsorbent. The adsorbent for adsorbing lead ions is prepared by a method comprising the steps of mixing raw materials, performing hot press molding and calcining, and the raw materials comprise the following components in percentage by weight: 30-60% of a polymer, 20-50% of diatomite and 12-30% of glass powder. The lead ion adsorbent is prepared by carrying out melt blending modification and calcination on the diatomite by adopting the glass powder, and the lead ion adsorbent has efficient adsorption performance and a stable structure, can be recycled, and has a wide application prospect in the field of lead ion-containing wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and particularly relates to an adsorbent for adsorbing lead ions, a preparation method thereof, and an adsorption method thereof. Background Art

[0002] Lead is a stubborn pollutant. Once it circulates from the deep layer of the earth's crust into the earth's surface layer, it will not degrade and form permanent pollution. Among the lead causing environmental pollution, 1 / 4 can be recycled by humans, and the remaining 3 / 4 remains in the environment, especially in water bodies, in different forms. Due to the increasing demand for water resources by humans, sewage must be effectively purified and reused. Methods for treating sewage include chemical sedimentation, electrochemical osmosis, adsorption method, etc. Among them, the adsorption method has received wide attention due to the low price of raw materials and remarkable adsorption effect.

[0003] Diatomite is a light yellow or light gray siliceous rock, mainly composed of amorphous SiO2. Diatomite has a small density, many internal pores, and contains a large number of hydrogen bonds and silanol groups, which greatly enhances its ability to adsorb heavy metal ions and can be used for the treatment of heavy metal sewage. However, due to the presence of a small amount of metal oxides and organic impurities in natural diatomite, the internal pores will be blocked, thereby limiting its adsorption performance. Therefore, it is necessary to modify it to improve its adsorption effect.

[0004] Zhou Huijie et al. (Study on the Adsorption Performance of Nickel-Modified Diatomite for Pb(II) in Wastewater, Journal of Inner Mongolia University of Science and Technology, 2019, 38(02): 109-112+165) evenly dispersed nickel in the internal pores through a surfactant, which played a supporting role and dredged the internal channels, thereby improving the adsorption capacity of diatomite. However, the particle size and morphology of nickel-modified diatomite are not easy to control, resulting in an uncertain specific surface area.

[0005] Luo Wenlian et al. (Study on the Adsorption Characteristics of Manganese Oxide-Modified Diatomite for Pb 2+ Journal of Central South University of Forestry and Technology, 2013, 33(11): 134-138) modified natural diatomite with manganese oxide, improved the pore structure and charged properties of diatomite, enhanced its sedimentation ability in water, and thus improved the efficiency of diatomite in removing Pb 2+ The modified diatomite particles have a higher adsorption capacity. However, due to their small particle size, they are not easy to remove after adsorption and are likely to remain in water, causing secondary pollution. Summary of the Invention

[0006] Technical problems to be solved by the present invention: Aiming at the disadvantage that modified diatomite is difficult to separate from water in the prior art, the present application provides a modified diatomite adsorbent for adsorbing lead ions, which uses low-melting glass powder to connect diatomite to form a solid and easy-to-collect massive body or granular body, and at the same time has high adsorption performance for lead ions and excellent mechanical properties.

[0007] Specifically, in order to solve the problems in the prior art, the present invention provides the following technical solutions:

[0008] The present application provides an adsorbent for adsorbing lead ions, and the adsorbent is prepared by a method including the steps of mixing raw materials, hot pressing and calcining. By weight percentage, the raw materials include the following components: 30-60% of polymer, 20-50% of diatomite, and 12-30% of glass powder.

[0009] In some embodiments of the present application, by weight percentage, the raw materials include the following components: 50-60% of polymer, 25-30% of diatomite, and 12-25% of glass powder.

[0010] In some embodiments of the present application, the sum of the weight percentages of the diatomite and the glass powder is 40-70%, preferably 40-50%; and / or,

[0011] The weight ratio of the diatomite to the glass powder is 0.5-2.5:1; preferably 1-2.5:1, more preferably 1-1.5:1.

[0012] In some embodiments of the present application, the polymer includes linear low-density polyethylene and / or ethylene-vinyl acetate copolymer, and preferably the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 30-50 wt%;

[0013] Preferably, the polymer includes linear low-density polyethylene and ethylene-vinyl acetate copolymer. Preferably, the weight percentage content of the linear low-density polyethylene is 5-15%, and the weight percentage content of the ethylene-vinyl acetate copolymer is 20-50%. Preferably, the mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:3-5; and / or,

[0014] The glass powder is low-melting glass powder, and its melting point range is 350-550 °C, and preferably the particle size range is 1000-2500 mesh.

[0015] In some embodiments of the present application, the temperature of the mixing is 150-180 °C, preferably 140-160 °C; and / or,

[0016] The temperature of the hot pressing is 160 - 180°C, preferably the unit pressure of the hot pressing is 10 - 20 MPa, more preferably the hot pressing time is 2 - 4 min; and / or,

[0017] The calcination temperature is 700 - 900°C, preferably the calcination time is 1 - 4 h.

[0018] In some embodiments of the present application, the adsorbent is in the shape of a block or a granule. Preferably, when the adsorbent is in the shape of a granule, its average diameter is 0.1 - 0.3 mm.

[0019] The present application also provides a method for preparing an adsorbent for adsorbing lead ions, comprising the following steps:

[0020] (1) Mixing each raw material, wherein the raw materials include a polymer, diatomaceous earth, and glass powder;

[0021] (2) Hot pressing the mixed raw materials into a shape;

[0022] (3) Calcining the semi-finished product formed in step (2) to obtain the adsorbent for adsorbing lead ions.

[0023] In some embodiments of the present application, in the above preparation method, the temperature of the mixing in step (1) is 150 - 180°C, preferably 140 - 160°C, more preferably the mixing time is 8 - 10 min; and / or,

[0024] The temperature of the hot pressing in step (2) is 160 - 180°C, preferably the hot pressing unit pressure is 10 - 20 MPa, more preferably the hot pressing time is 2 - 4 min; and / or,

[0025] The calcination temperature in step (3) is 700 - 900°C, preferably the calcination time is 1 - 4 h.

[0026] In some embodiments of the present application, in the above preparation method, after the calcination in step (3), there is also a step of crushing.

[0027] The present application also provides a method for adsorbing lead ions from an aqueous solution, which comprises adding the above adsorbent or the adsorbent prepared by the above preparation method into the aqueous solution for adsorption.

[0028] In some embodiments of the present application, in the above method, the pH of the aqueous solution is 7 - 11, and / or, based on the volume of the aqueous solution, the addition amount of the adsorbent is 0.2 g / 100 mL or more, preferably 0.2 - 0.25 g / 100 mL.

[0029] In some embodiments of the present application, in the above method, the adsorption time is 5 h or more, preferably 5 - 6 h.

[0030] Advantages of the present invention:

[0031] The present invention uses glass powder to carry out melt blending modification on diatomite and prepares a lead ion adsorbent through calcination. The lead ion adsorbent has high adsorption performance and stable structure, can be recycled, and has broad application prospects in the field of lead ion-containing wastewater treatment. Description of the drawings

[0032] Figure 1 Scanning electron microscope images of Examples 1, 2, and 4 and Comparative Example 1, with a magnification of 5000 times.

[0033] Figure 2 Scanning electron microscope images of Examples 5, 6, and 7 and Comparative Example 2, with a magnification of 5000 times.

[0034] Figure 3 Effect of different reaction times on the lead ion removal rate.

[0035] Figure 4 Effect of pH of different adsorption solutions on the lead ion removal rate.

[0036] Figure 5 Effect of different adsorbent dosages on the lead ion removal rate. Detailed implementation manners

[0037] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The following described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Combining the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0038] In this application, the term "linear low density polyethylene" refers to polyethylene with a density of 910 kg / m 3 or more and less than 930 kg / m 3 , which is obtained by copolymerizing ethylene with α-olefin. α-olefin refers to a monoolefin with a double bond at the end of the molecular chain, such as 1-butene, 1-hexene, or 1-octene.

[0039] In a first aspect, in a specific implementation manner of this application, this application provides an adsorbent for adsorbing lead ions. The adsorbent is prepared by a method including mixing raw materials, hot pressing, and calcining. By weight percentage, the raw materials include components: 30-60% of polymer, 20-50% of diatomite, and 12-30% of glass powder.

[0040] In some embodiments of the present application, by weight percentage, the polymer in the raw materials of the adsorbent can be 30 - 60%, 30 - 55%, 30 - 50%, 30 - 45%, 30 - 40%, 35 - 60%, 40 - 60%, 45 - 60% or 50 - 60%. In some embodiments, by weight percentage, the raw materials of the adsorbent include 30%, 35%, 40%, 45%, 50%, 55% or 60% of the polymer, or a range formed by any two of the above values as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other range.

[0041] In some embodiments of the present application, by weight percentage, the diatomaceous earth in the raw materials of the adsorbent can be 20 - 50%, 20 - 45%, 20 - 40%, 20 - 35%, 20 - 30%, 25 - 50%, 30 - 50%, 35 - 50% or 40 - 50%. In some embodiments, by weight percentage, the raw materials of the adsorbent include 20%, 25%, 28%, 30%, 35%, 40%, 42%, 45%, 49% or 50% of the diatomaceous earth, or a range formed by any two of the above values as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other range.

[0042] In some embodiments of the present application, by weight percentage, the glass powder in the raw materials of the adsorbent can be 12 - 30%, 12 - 25%, 12 - 20%, 15 - 30%, 20 - 30% or 25 - 30%. In some embodiments, the raw materials of the adsorbent include 12%, 15%, 18%, 20%, 21%, 25% or 30% of the glass powder, or a range formed by any two of the above values as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other range.

[0043] In some embodiments of the present application, the raw materials include components: 50 - 60% of the polymer, 25 - 30% of the diatomaceous earth, and 12 - 25% of the glass powder.

[0044] In some embodiments of the present application, by weight percentage, the sum of the weight percentages of diatomaceous earth and glass powder in the raw materials of the adsorbent can be 40 - 70%, 40 - 65%, 40 - 60%, 40 - 55%, 40 - 50%, 45 - 70%, 50 - 70%, 55 - 70% or 60 - 70%. In some embodiments, 40%, 45%, 50%, 55%, 60%, 65% or 70% of diatomaceous earth and glass powder in the raw materials of the adsorbent, or a range formed by any two of the above values as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other range. In some embodiments, the sum of the weight percentages of diatomaceous earth and glass powder is 40 - 70%, preferably 40 - 50%.

[0045] In some embodiments of the present application, the weight ratio of diatomaceous earth to glass powder can be 0.5 - 2.5:1, 0.5 - 2.0:1, 0.5 - 1.5:1, 1 - 2.5:1, 1.5 - 2.5:1 or 2 - 2.5:1. In some embodiments, the weight ratio of diatomaceous earth to glass powder is 0.5:1, 2:3, 1:1, 1.5:1, 2:1, 7:3 or 2.5:1, or a range formed by any two of the above values as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other range. In some embodiments, the weight ratio of diatomaceous earth to glass powder is 0.5 - 2.5:1; preferably 1 - 2.5:1, more preferably 1 - 1.5:1.

[0046] In some embodiments of the present application, the polymer includes linear low density polyethylene (LLDPE) and / or ethylene - vinyl acetate copolymer (EVA), wherein the mass content of VA in the ethylene - vinyl acetate copolymer is 30 - 50%. In some embodiments, the melt index of the ethylene - vinyl acetate copolymer under the conditions of 190°C and 2.16 kg is 2 - 6 g / 10 min, and the melt index is obtained by testing according to the ASTM D1238 method. In some embodiments, the density of the ethylene - vinyl acetate copolymer is 0.90 - 0.98 g / cm 3 。

[0047] In some embodiments, the mass fraction of α - olefin in the linear low density polyethylene copolymer is 5 - 10%, and the mass fraction of ethylene in the linear low density polyethylene copolymer is 90 - 95%. In some embodiments, the number average molecular weight of linear low density polyethylene ranges from 20,000 to 200,000. In some embodiments, the number average molecular weight of linear low density polyethylene ranges from 20,000 to 100,000. In some embodiments, the number average molecular weight of linear low density polyethylene ranges from 20,000 to 50,000.

[0048] In some embodiments of the present application, the weight percentage content of the linear low-density polyethylene is 5-15%, and the weight percentage content of the ethylene-vinyl acetate copolymer is 20-50%. Preferably, the mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:3-5.

[0049] In some embodiments of the present application, the glass powder is a low-melting-point glass powder, with a melting point range of 350-550 °C, and preferably a particle size range of 1000-2500 mesh.

[0050] In some embodiments of the present application, the temperature of the mixing is 150-180 °C, preferably 140-160 °C. In some embodiments of the present application, the temperature of the hot pressing and forming is 160-180 °C. Preferably, the unit pressure of the hot pressing and forming is 10-20 MPa, and more preferably the hot pressing time is 2-4 min. In some embodiments of the present application, the calcination temperature is 700-900 °C, and preferably the calcination time is 1-4 h.

[0051] It can be understood that the hot pressing and forming refers to a forming method in which a polymer is melted and pressed into a solid shape by using high temperature and high pressure.

[0052] In some embodiments of the present application, the adsorbent further includes a step of crushing the product obtained by calcination. Through the crushing treatment, an adsorbent product with a certain appearance size can be obtained.

[0053] In some embodiments of the present application, the shape of the adsorbent is blocky or granular. Preferably, when the adsorbent is granular, its average diameter is 0.1-0.3 mm.

[0054] On the other hand, the present application provides a method for preparing the above-mentioned adsorbent for adsorbing lead ions, which is prepared by the following steps:

[0055] (1) Mixing each raw material, where the raw materials include a polymer, diatomaceous earth, and glass powder;

[0056] (2) Hot pressing and forming the mixed raw materials;

[0057] (3) Calcining the semi-finished product formed in step (2) to obtain the above-mentioned adsorbent for adsorbing lead ions.

[0058] In some embodiments of the present application, the mixing in step (1) includes putting each raw material into a mixer for mixing. Preferably, the temperature of the mixing is 120-180 °C, more preferably 140-160 °C, and further preferably the mixing time is 8-10 min.

[0059] In some embodiments of the present application, the temperature of the hot pressing in step (2) is 150 - 180 °C; preferably 160 - 180 °C. In some embodiments, the thickness of the hot pressing is controlled to be 1 - 3 mm. In some embodiments, the unit pressure of the hot pressing is 10 - 20 MPa, preferably 14 - 16 MPa. In some embodiments, the hot pressing time of the hot pressing is 2 - 4 min.

[0060] In some embodiments of the present application, the calcination temperature in step (3) is 700 - 900 °C. In some embodiments, the calcination time is 1 - 4 h.

[0061] In some embodiments of the present application, after the calcination in step (3), there is also a step of crushing.

[0062] On the other hand, the present application also provides a method for adsorbing lead ions from an aqueous solution, which includes the step of adding the above-mentioned adsorbent for adsorbing lead ions into the aqueous solution for adsorption.

[0063] In some embodiments of the present application, the pH of the aqueous solution is 7 - 11.

[0064] In some embodiments of the present application, the concentration of lead ions in the aqueous solution is 1 - 100 mg / L.

[0065] In some embodiments of the present application, based on the volume of the aqueous solution, the addition amount of the adsorbent is 0.2 g / 100 mL or more, preferably 0.2 - 0.25 g / 100 mL.

[0066] In some embodiments of the present application, the adsorption time is 5 h or more, preferably 5 - 6 h.

[0067] Next, the preparation method and technical effects of the surface-modified alumina of the present application will be specifically described through specific examples.

[0068] The sources of raw materials and equipment used in the examples and comparative examples of the present invention are shown in Table 1.

[0069] Table 1 Sources of raw materials and equipment used in the examples and comparative examples of the present invention

[0070]

[0071]

[0072] The following method is used to test the adsorbents prepared in the examples and comparative examples:

[0073] 1. SEM analysis: The surface of the granular adsorbent sample is sputtered with gold, and then its cross-section is observed by SEM, and the acceleration voltage is 10 kV.

[0074] 2. XRD analysis: The granular adsorbent sample was crushed and tested by XRD. The scanning rate was 8 (°) / min, and 2θ was 10° - 60°.

[0075] 3. Test of flexural strength: The flexural strength of the block adsorbent was tested according to the test method for flexural strength of fine ceramics GB / T 6569 - 2006.

[0076] 4. The average diameter of the granular adsorbent was measured by an optical microscope.

[0077] Example 1

[0078] Weigh 20 g of linear low - density polyethylene, 80 g of ethylene - vinyl acetate copolymer, 70 g of diatomaceous earth and 30 g of glass powder. Put each raw material component into a mixer and mix for 10 min at a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent, and then crush the block adsorbent to obtain a granular adsorbent sample.

[0079] Example 2

[0080] Weigh 20 g of linear low - density polyethylene, 80 g of ethylene - vinyl acetate copolymer, 60 g of diatomaceous earth and 40 g of glass powder. Put each raw material component into a mixer and mix for 10 min at a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent, and then crush the block adsorbent to obtain a granular adsorbent sample.

[0081] Example 3

[0082] Weigh 20 g of linear low - density polyethylene, 80 g of ethylene - vinyl acetate copolymer, 50 g of diatomaceous earth and 50 g of glass powder. Put each raw material component into a mixer and mix for 10 min at a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent, and then crush the block adsorbent to obtain a granular adsorbent sample.

[0083] Example 4

[0084] Weigh 20 g of linear low density polyethylene, 80 g of ethylene-vinyl acetate copolymer, 40 g of diatomaceous earth and 60 g of glass powder. Put each raw material component into a mixer and mix for 10 min under the conditions of a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent. Then break the block adsorbent to obtain a granular adsorbent sample.

[0085] Example 5

[0086] Weigh 12 g of linear low density polyethylene, 48 g of ethylene-vinyl acetate copolymer, 98 g of diatomaceous earth and 42 g of glass powder. Put each raw material component into a mixer and mix for 10 min under the conditions of a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent. Then break the block adsorbent to obtain a granular adsorbent sample.

[0087] Example 6

[0088] Weigh 16 g of linear low density polyethylene, 64 g of ethylene-vinyl acetate copolymer, 84 g of diatomaceous earth and 36 g of glass powder. Put each raw material component into a mixer and mix for 10 min under the conditions of a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent. Then break the block adsorbent to obtain a granular adsorbent sample.

[0089] Example 7

[0090] Weigh 24 g of linear low density polyethylene, 96 g of ethylene-vinyl acetate copolymer, 56 g of diatomaceous earth and 24 g of glass powder. Put each raw material component into a mixer and mix for 10 min under the conditions of a temperature of 150 °C and a rotation speed of 60 r / min. Then put the mixed material into a hot press and press for 3 min at 170 °C and a unit pressure of 15 MPa to form a sheet with a thickness of 2 mm. Finally, calcine at 750 °C for 2 hours to obtain a block adsorbent for testing the flexural strength of the adsorbent. Then break the block adsorbent to obtain a granular adsorbent sample.

[0091] Comparative Example 1

[0092] Weigh 20g of linear low-density polyethylene, 80g of ethylene-vinyl acetate copolymer, 80g of diatomaceous earth and 20g of glass powder, put the raw material components into an internal mixer, mix them at a temperature of 150°C and a speed of 60r / min for 10min, then put the mixed materials into a hot press, press them at 170°C and a unit pressure of 15MPa for 3min, and press them into sheets with a thickness of 2mm. Finally, calcine them at 750°C for 2 hours to obtain a block adsorbent, which is used to test the bending strength of the adsorbent, and then crush the block adsorbent to obtain a granular adsorbent sample.

[0093] Comparative Example 2

[0094] Weigh 28g of linear low-density polyethylene, 112g of ethylene-vinyl acetate copolymer, 42g of diatomaceous earth and 18g of glass powder, put the raw material components into an internal mixer, mix them at a temperature of 150°C and a speed of 60r / min for 10min, then put the mixed materials into a hot press, press them at 170°C and a unit pressure of 15MPa for 3min, and press them into sheets with a thickness of 2mm. Finally, calcinate at 750°C for 2 hours to obtain a block adsorbent, which is used to test the bending strength of the adsorbent, and then crush the block adsorbent to obtain a granular adsorbent sample.

[0095] The results of scanning electron microscope (SEM) analysis of Example 1, Example 2 and Example 4 and Comparative Example 1 are as follows: Figure 1 As shown, (a)-(d) are photos of samples of Comparative Example 1, Example 1, Example 2 and Example 4, respectively. In Comparative Example 1, Example 1, Example 2 and Example 4, the ratio of the sum of the weight of diatomaceous earth and glass powder to the total weight of raw materials is 50%, and the difference is the ratio of diatomaceous earth to glass powder. The ratio of diatomaceous earth to glass powder in Comparative Example 1 is greater than that in Examples 1, 2 and 4, reaching 4:1. By magnifying the fracture cross section of the calcined sample by 5000 times through SEM, the internal structure of the sample under different glass powder filling and total powder amount changes can be observed. Figure 1 It can be seen that in Comparative Example 1, due to the small amount of glass powder filling, the gaps between the skeletons in the cross section of the sample are large, so a large number of holes are generated, and the cross section is uneven and the internal structure is relatively loose, making it difficult to maintain a stable structure. However, with the continuous increase in the amount of glass powder, the cross section of the sample becomes denser, especially in Example 4 when the amount of glass powder added accounts for 60% of the total amount of diatomaceous earth and glass powder, the larger holes in the cross section almost disappear and the surface is relatively flat. This is mainly because the glass powder is heated and melted during the calcination process to form a molten mobile phase that fills the gaps between the skeletons formed by the diatomaceous earth, effectively reducing the number and size of the holes.

[0096] The results of scanning electron microscope (SEM) analysis of Examples 5-7 and Comparative Example 2 are as follows: Figure 2As shown, where (a)-(d) are photos of the samples of Comparative Example 2, Example 7, Example 6, and Example 5, respectively. In Comparative Example 2, Example 5, Example 6, and Example 7, the ratios of the sum of the weights of diatomaceous earth and glass powder to the total weight of the raw materials are 30%, 70%, 60%, and 40%, respectively, and the ratio of diatomaceous earth to glass powder is 7:3. From Figure 2 it can be seen that when the proportion of the total powder volume (the sum of the weights of diatomaceous earth and glass powder) is only 30%, a large number of pores appear inside the sample, and the skeleton structure is difficult to maintain, with poor stability. However, as the proportion increases, the pores in the cross-section of the sample gradually decrease, and the pore diameter shrinks, showing good structural stability.

[0097] The test results of the flexural strength and adsorbent particles of Examples 1-7 and Comparative Examples 1-2 are shown in Table 2

[0098] Table 2 Test results of the flexural strength of the bulk adsorbent and the average diameter of the granular adsorbent

[0099] Number Flexural strength, MPa Average diameter of adsorbent particles, mm Example 1 0.18 0.2 Example 2 1.36 0.2 Example 3 0.87 0.2 Example 4 0.37 0.2 Example 5 0.17 0.2 Example 6 0.24 0.2 Example 7 0.4 0.2 Comparative Example 1 0.02 <0.005 Comparative Example 2 0.1 <0.005

[0100] As can be seen from Table 2, the flexural strength of the adsorbent samples in Examples 1-7 of this application is 0.17-1.36 MPa. Compared with Comparative Example 1, the ratios of the sum of the weights of diatomaceous earth and glass powder to the total weight of the raw materials in Examples 1-4 are the same as those in Comparative Example 1, but the addition amounts of glass powder are all higher than those in Comparative Example 1, and their flexural strengths are also higher than those in Comparative Example 1. Among them, when the proportion of glass powder is 20%, the flexural strength is the largest; when the proportion of glass powder reaches 20%, the flexural strength decreases instead. This is mainly because after too much glass powder replaces diatomaceous earth, the number of internal skeletons generated by the calcination of the sample decreases, and the strength of the amorphous silica continuous phase generated after the cooling of the mobile phase melted by the glass powder is small, and it is difficult to maintain the internal structure stability of the sample under external force, so the flexural strength decreases.

[0101] Compared with Comparative Example 2, the proportions of diatomaceous earth and glass powder in Examples 5-7 are all higher than those in Comparative Example 2, and as the ratio of the sum of the weights of diatomaceous earth and glass powder to the total weight of the raw materials increases, the flexural strength continuously increases. When the ratio of the sum of the weights of diatomaceous earth and glass powder to the total weight of the raw materials reaches 70%, the flexural strength of the sample increases from 0.1 to 0.4 MPa. This shows that when the ratio of diatomaceous earth to glass powder is fixed, the more the addition amount of diatomaceous earth and glass powder, the greater the flexural strength. This is because more diatomaceous earth forms a dense skeleton inside the sample during calcination, playing a good role in resisting external forces, and at the same time, the glass powder penetrates the pores between the skeletons during the melting and flowing process, further improving the flexural strength.

[0102] Further, in Example 2, Example 3, and Example 7, when the polymer weight percentage is 50 - 60%, and the proportion of diatomite and glass powder is 40 - 50%, where the weight percentage of glass powder is 12 - 25% and the weight percentage of diatomite is 25 - 30%, the flexural strength of the bulk adsorbent reaches 0.4 - 1.36 MPa. Further still, when the weight ratio of diatomite to glass powder in Example 2 and Example 3 is 1 - 1.5:1, the flexural strength of the bulk adsorbent reaches 0.87 - 1.36 MPa.

[0103] Experimental Example

[0104] 1. Influence of adsorption time on adsorption effect

[0105] In a sample bottle, an aqueous solution of 100 mL Pb with a concentration of 10 mg / L was prepared using lead nitrate and deionized water, and the pH was adjusted to 7. 0.2 g of the lead ion adsorbent prepared in Example 1 was added to the above sample bottle, and then the sample bottle was placed in a constant temperature shaker and shaken at 180 rpm and 23 ± 2 °C. Samples were taken at different reaction times (1 h, 2 h, 3 h, 4 h, 5 h, and 6 h), and then the concentration of Pb was measured by atomic absorption spectrophotometry according to GB / T7475 - 1987, and the lead ion removal rate was calculated. The calculation formula for the removal rate is: (concentration of lead ions in the solution before adsorption - concentration of lead ions in the solution after adsorption) / concentration of lead ions in the solution before adsorption. The results are as 2+ shown. 2+ As shown in [Figure / Table] [specific number] for the influence of different reaction times on the lead ion removal rate, it can be seen that the time for the sample to reach equilibrium in adsorbing lead ions is 5 h, and the removal rate can reach 90%. The adsorption process can be divided into two stages: rapid adsorption and slow adsorption. In the initial stage of adsorption, due to the relatively high concentration of lead ions in the solution and the relatively large number of adsorption sites inside the sample, lead ions can be adsorbed rapidly. However, as the concentration of lead ions and the number of adsorption sites continuously decrease, the adsorption amount increases gradually more slowly and finally stabilizes. Therefore, 5 h is the optimal adsorption time. Figure 3 shown.

[0106] Figure 3 As shown in [Figure / Table] [specific number] for the influence of different reaction times on the lead ion removal rate, it can be seen that the time for the sample to reach equilibrium in adsorbing lead ions is 5 h, and the removal rate can reach 90%. The adsorption process can be divided into two stages: rapid adsorption and slow adsorption. In the initial stage of adsorption, due to the relatively high concentration of lead ions in the solution and the relatively large number of adsorption sites inside the sample, lead ions can be adsorbed rapidly. However, as the concentration of lead ions and the number of adsorption sites continuously decrease, the adsorption amount increases gradually more slowly and finally stabilizes. Therefore, 5 h is the optimal adsorption time. Figure 3 As shown in [Figure / Table] [specific number] for the influence of different reaction times on the lead ion removal rate, it can be seen that the time for the sample to reach equilibrium in adsorbing lead ions is 5 h, and the removal rate can reach 90%. The adsorption process can be divided into two stages: rapid adsorption and slow adsorption. In the initial stage of adsorption, due to the relatively high concentration of lead ions in the solution and the relatively large number of adsorption sites inside the sample, lead ions can be adsorbed rapidly. However, as the concentration of lead ions and the number of adsorption sites continuously decrease, the adsorption amount increases gradually more slowly and finally stabilizes. Therefore, 5 h is the optimal adsorption time.

[0107] 2. Influence of pH of adsorption solution on adsorption effect

[0108] Six sample bottles were taken, and an aqueous solution of 100 mL Pb with a concentration of 10 mg / L was prepared using lead nitrate and deionized water in the sample bottles, and the pH was adjusted to 2+An aqueous solution with a concentration of 10 mg / L was adjusted to pH 1, 3, 5, 7, 9, and 11 with hydrochloric acid and sodium hydroxide respectively. 0.2 g of the lead ion adsorbent prepared in Example 1 was added to 6 sample bottles, and then the sample bottles were placed in a constant temperature shaker and shaken at 180 rpm and 23 ± 2 °C for 5 h to reach the adsorption and desorption equilibrium. Then, the concentration of Pb was measured by atomic absorption spectrophotometry according to GB / T7475-1987 2+ The concentration of was calculated, and the lead ion removal rate was calculated. The calculation formula for the removal rate is: (lead ion concentration in the solution before adsorption - lead ion concentration after adsorption) / lead ion concentration before adsorption. The results are as Figure 4 shown

[0109] Figure 4 The influence of the pH of different adsorption solutions on the lead ion removal rate. As can be seen from Figure 4 it, the lead ion removal rate gradually increases with the increase of the pH value. When the pH value is less than 3, the removal rate is very small, mainly because there are a large number of hydrogen ions in the solution, which will compete with lead ions for adsorption and occupy the adsorption sites in the sample, so it is not conducive to the removal of lead ions. As the pH value continues to increase, the content of hydrogen ions becomes smaller and the competitive adsorption effect weakens, so the removal rate increases rapidly. When the pH value exceeds 7, the removal rate stabilizes at about 90%. Therefore, it is more conducive to adsorption under alkaline conditions

[0110] 3. Influence of adsorbent dosage on adsorption effect

[0111] Take 5 sample bottles. Use lead nitrate and deionized water in the sample bottles to prepare 100 mL of an aqueous solution with a Pb 2+ concentration of 10 mg / L, adjust the pH value to 7, add 0.05 g, 0.1 g, 0.15 g, 0.2 g, and 0.25 g of the lead ion adsorbent prepared in Example 1 to the sample bottles respectively, and then place the sample bottles in a constant temperature shaker and shake at 180 rpm and 23 ± 2 °C for 5 h to reach the adsorption and desorption equilibrium. Then, the concentration of Pb was measured by atomic absorption spectrophotometry according to GB / T7475-1987 2+ The concentration of was calculated, and the lead ion removal rate was calculated. The calculation formula for the removal rate is: (lead ion concentration in the solution before adsorption - lead ion concentration after adsorption) / lead ion concentration before adsorption. The results are as Figure 5 shown

[0112] Figure 5 The influence of different adsorbent dosages on the lead ion removal rate. As can be seen from Figure 5It can be seen that when the added amount reaches 0.2 g, the removal rate reaches the maximum value of 90%. When the content of the sample increases to 0.25 g, the removal rate still remains at 90%. This is mainly because when the concentration of the lead ion solution is extremely low, the ion diffusion rate is slow and it is difficult to be adsorbed, so the change in the removal rate is small.

[0113] 4. Test of lead ion removal rate

[0114] Take 9 sample bottles, and use lead nitrate and deionized water in the sample bottles to prepare 100 mL of an aqueous solution with a Pb 2+ concentration of 10 mg / L, adjust the pH value to 7. Add 0.2 g of the lead ion adsorbent prepared in Examples 1-7 and Comparative Examples 1-2 to the 9 sample bottles respectively, then place the sample bottles in a constant temperature shaker and shake at 180 rpm and 23 ± 2 °C for 5 h until the adsorption and desorption reach equilibrium. Then, test the concentration of Pb 2+ according to the atomic absorption spectrophotometry in GB / T7475-1987, and calculate the lead ion removal rate. The calculation formula for the removal rate is: (concentration of lead ions in the solution before adsorption - concentration of lead ions after adsorption) / concentration of lead ions before adsorption. The results are shown in Table 3.

[0115] 5. Test of cycling performance

[0116] Weigh 0.2 g of the lead ion adsorbent and add it to a sample bottle containing 100 mL of 10 mg / L Pb 2+ nitrate aqueous solution, then place the sample bottle in a constant temperature shaker and shake at 180 rpm and 23 ± 2 °C for 5 h. After the adsorption process is completed, filter and collect the adsorbent after adsorbing lead ions, and then regenerate it for the next round of lead ion adsorption determination. The regeneration is carried out by washing the adsorbent 3 times with a sulfuric acid solution with pH = 2. The above adsorption and elution cycle experiments are carried out 15 times to determine the cycling and regeneration performance of the adsorbent material and observe the rupture situation of the adsorbent after 15 cycles. The results are shown in Table 3.

[0117] Table 3 Test results of the adsorption performance of the adsorbents prepared in Examples 1-7 and Comparative Examples 1-2 for lead ions

[0118]

[0119] As can be seen from Table 3, the adsorbent samples prepared in Applications 1-7 of the present application can be recycled and reused more than 15 times. After being recycled and reused more than 15 times, the adsorbent does not rupture or produce debris, and still has a relatively high removal rate for Pb 2+ . In Comparative Examples 1-2, due to the too small particle size, it cannot be separated from the system and cannot be recycled. Further, the adsorbent samples prepared in Examples 1-3 and Example 7 of the present application have a relatively high removal rate for Pb 2+The removal rate is above 87%, which is comparable to the Pb removal rate of the adsorbent samples prepared in Comparative Examples 1-2. However, the adsorbent samples prepared in Examples 1-3 and Example 7 have better strength and can be made into blocks or granules, which is convenient for recycling. After 15 cycles of recycling, the removal rate of Pb by the adsorbent samples prepared in Examples 1-3 and Example 7 hardly decreases. Therefore, the lead ion adsorbent prepared in this application has high adsorption performance and stable structure, can be easily separated and recovered from the system, and realizes recycling. It has broad application prospects in the field of Pb-containing sewage treatment. 2+ The removal rate is comparable, but the adsorbent samples prepared in Examples 1-3 and Example 7 have better strength and can be made into blocks or granules, which is convenient for recycling. After 15 cycles of recycling, the removal rate of Pb by the adsorbent samples prepared in Examples 1-3 and Example 7 hardly decreases. 2+ Therefore, the lead ion adsorbent prepared in this application has high adsorption performance and stable structure, can be easily separated and recovered from the system, and realizes recycling. 2+ It has broad application prospects in the field of sewage treatment containing Pb.

[0120] The above are only the preferred embodiments of the implementation of the present invention, and do not impose any formal restrictions on the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An adsorbent for adsorbing lead ions, characterized in that: The adsorbent is prepared by a method comprising the steps of mixing raw materials, hot pressing and calcining. The raw materials include the following components by weight: 30-60% polymer, 20-50% diatomaceous earth and 12-30% glass powder.

2. The adsorbent according to claim 1, characterized in that The raw materials include the following components by weight: 50-60% polymer, 25-30% diatomaceous earth and 12-25% glass powder.

3. The adsorbent according to claim 1 or 2, characterized in that The sum of the weight percentages of the diatomaceous earth and the glass powder is 40-70%, preferably 40-50%; and / or, The weight ratio of the diatomaceous earth to the glass powder is 0.5-2.5:1; preferably 1-2.5:1, and more preferably 1-1.5:

1.

4. The adsorbent according to any one of claims 1 to 3, characterized in that The polymer comprises linear low-density polyethylene and / or ethylene-vinyl acetate copolymer, and preferably the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 30-50wt%; Preferably, the polymer comprises linear low-density polyethylene and ethylene-vinyl acetate copolymer, preferably the weight percentage content of the linear low-density polyethylene is 5-15%, the weight percentage content of the ethylene-vinyl acetate copolymer is 20-50%, and more preferably the mass ratio of the linear low-density polyethylene to the ethylene-vinyl acetate copolymer is 1:3-5; and / or, The glass powder is a low melting point glass powder with a melting point ranging from 350 to 550° C. and a preferred particle size ranging from 1000 to 2500 meshes.

5. The adsorbent according to any one of claims 1 to 4, characterized in that The mixing temperature is 150-180°C, preferably 140-160°C; and / or, The temperature of the hot pressing molding is 160-180°C, preferably the unit pressure of the hot pressing molding is 10-20MPa, and more preferably the hot pressing time is 2-4min; and / or, The calcination temperature is 700-900° C., and the preferred calcination time is 1-4 hours.

6. The adsorbent according to any one of claims 1 to 5, characterized in that The adsorbent is in the shape of blocks or particles. Preferably, when the adsorbent is in the shape of particles, the average diameter thereof is 0.1-0.3 mm.

7. The method for preparing an adsorbent for adsorbing lead ions according to any one of claims 1 to 6, comprising the steps of: (1) Mix the raw materials, wherein: The raw materials include polymer, diatomaceous earth and glass powder; (2) hot pressing the mixed raw materials into a mold; (3) calcining the semi-finished product formed in step (2) to obtain the adsorbent for adsorbing lead ions.

8. The preparation method according to claim 7, characterized in that: The mixing temperature in step (1) is 150-180° C., preferably 140-160° C., and the mixing time is more preferably 8-10 min; and / or, The temperature of the hot pressing molding in step (2) is 160-180° C., preferably the hot pressing unit pressure is 10-20 MPa, and more preferably the hot pressing time is 2-4 min; and / or, The calcination temperature in step (3) is 700-900° C., and the preferred calcination time is 1-4 hours.

9. The preparation method according to claim 8 or 9, characterized in that: Step (3) also includes a crushing step after calcination.

10. A method for adsorbing lead ions from an aqueous solution, characterized in that: The method comprises the step of adding the adsorbent described in any one of claims 1 to 6 or the adsorbent prepared by the preparation method described in any one of claims 7 to 9 into an aqueous solution for adsorption.

11. The method according to claim 10, characterized in that The pH of the aqueous solution is 7-11, and / or, based on the volume of the aqueous solution, the amount of the adsorbent added is 0.2 g / 100 mL or more, preferably 0.2-0.25 g / 100 mL.

12. The method according to claim 10 or 11, characterized in that: The adsorption time is more than 5 hours, preferably 5-6 hours.

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