Attapulgite adsorbent material, preparation method and application thereof

Abstract

The application discloses a palygorskite adsorption material and a preparation method and application thereof, and belongs to the technical field of heavy metal contaminated wastewater treatment. The palygorskite adsorption material is obtained by crushing and ball milling of palygorskite raw ore. The method improves the physicochemical properties of the palygorskite by controlling the ball milling conditions, so that the adsorption capacity of the palygorskite for heavy metal ions is improved. The removal rates of the obtained palygorskite adsorption material for Pd 2+ and Cd 2+ in an aqueous solution are nearly 6 times and 4.5 times higher than those of the palygorskite raw ore respectively.

Description

Technical Field

[0001] This invention relates to an adsorption material, particularly an attapulgite adsorption material, and also to the application of an attapulgite adsorption material in the adsorption of heavy metal ions, belonging to the field of heavy metal water pollution treatment technology. Background Technology

[0002] Global water pollution has reached a critical level, and with limited water resources, usable freshwater is dwindling, making water pollution control an urgent priority. Among various water pollutants, heavy metal ions often pose the greatest threat. Therefore, to improve and maintain water quality, excessive levels of heavy metals in water bodies must be effectively treated. Currently, various processes exist for treating water pollutants, such as chemical precipitation, electrochemical degradation, membrane osmosis, coagulation, and biodegradation. Among these, adsorption methods have broad development prospects due to their simplicity, low cost, and high efficiency.

[0003] Attapulgite, also known as palygorskite, is a 2:1 chain-like magnesium aluminum silicate mineral. Attapulgite possesses characteristics such as large specific surface area, numerous pores, abundant surface hydroxyl groups, high catalytic site activity, and non-toxicity, making it widely used in adsorption, catalysis, pharmaceuticals, and food applications. However, natural attapulgite ore suffers from defects such as the presence of many associated minerals, agglomerated rod-shaped crystals, and large grain size, resulting in relatively low overall adsorption performance.

[0004] Currently, there are many methods for modifying attapulgite to improve its adsorption performance for heavy metal ions. For example, Chinese patent (publication number: CN117482930 A) specifically discloses a method of refining and modifying attapulgite to obtain refined modified attapulgite; calcining the refined modified attapulgite in air to obtain an attapulgite adsorbent that rapidly adsorbs and removes heavy metal ions. This method, by modifying attapulgite, can improve its adsorption rate and selectivity for heavy metals. However, this method of modifying attapulgite requires a high-temperature calcination process, resulting in high energy consumption and high cost. Chinese patent (publication number: CN104528863B) discloses a method for modifying attapulgite by reacting it with cationic gemini and other surfactants, 0.5-2 mol / L hydrochloric acid and deionized water at a temperature of 50-65℃ and a rotation speed of 100-250 rpm for 2.5-5 hours. The modified attapulgite improves the removal efficiency of heavy metals from landfill leachate by 30% compared with the unmodified attapulgite. However, this method does not significantly improve the adsorption performance of attapulgite. Summary of the Invention

[0005] To address the limitations of existing methods for modifying attapulgite, such as limited ability to improve the adsorption performance of raw attapulgite ore, high cost, and long processing time, the first objective of this invention is to provide a method for modifying Pd in ​​aqueous solutions. 2+ Cd 2+Attapulgite adsorbents exhibit high adsorption activity for heavy metal ions, compared to raw attapulgite ore, particularly for Pd. 2+ Cd 2+ The adsorption effect was increased by about 6 times and 4.5 times respectively.

[0006] The second objective of this invention is to provide a method for preparing attapulgite adsorbent materials with high heavy metal ion adsorption activity using attapulgite ore. This method can reduce the particle size of attapulgite and activate the adsorption channels by a simple one-step ball milling activation, which greatly improves the adsorption activity of attapulgite for heavy metal ions. This method is simple to operate, has low energy consumption, and is conducive to industrial production.

[0007] The third objective of this invention is to provide an application of attapulgite adsorbent material for the adsorption of heavy metal ions in aqueous solutions. It has the characteristics of large adsorption capacity and fast adsorption rate, and its adsorption activity for heavy metal ions is significantly improved compared with raw attapulgite ore.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing attapulgite adsorbent material. The method involves crushing and ball milling attapulgite ore to obtain the attapulgite adsorbent material. The ball milling conditions are as follows: the ball milling speed is 600-700 rad / min, and the ball milling time is 10-60 min. During the ball milling process, three types of grinding beads with particle sizes of 4-6 mm, 9-11 mm, and 14-16 mm are used, and the mass ratio of the three types of grinding beads is 3-5: 3-5:1.

[0009] This invention activates attapulgite ore using ball milling. By controlling the milling speed and time, and selecting matching grinding beads, the particle size of the attapulgite is reduced, its specific surface area is increased, and its adsorption channels are activated, thereby significantly improving the adsorption activity of attapulgite for heavy metal ions. More specifically, ball milling activation mainly alters the original physicochemical properties of attapulgite through mechanical force, resulting in superior physicochemical performance. Under mechanical force, the grinding media and attapulgite undergo disordered collisions. The forces generated by these collisions exceed the mechanical load that the attapulgite can withstand. Macroscopically, this manifests as a reduction in attapulgite particle size and a significant increase in specific surface area; microscopically, it manifests as the generation of lattice defects, exposure of adsorption active sites, and changes in surface potential. The milling speed and time, as well as the matching of the milling media with the particle size of the attapulgite ore, have a significant impact on the activation of attapulgite. Different grinding beads of different sizes have varying effects on attapulgite. For example, large-sized grinding beads primarily act on large attapulgite particles, while having less effect on small-sized attapulgite particles. Combining grinding beads of different sizes to activate attapulgite can result in more uniform activation. The ball milling speed and time are also crucial operating parameters. Under appropriate ball milling parameters, the adsorption active sites of attapulgite can be maximized, particle size reduced, and specific surface area increased. However, excessive ball milling activation can lead to the aggregation of attapulgite particles, a decrease in specific surface area, and consequently, a weakening of their adsorption activity.

[0010] As a preferred option, the ball milling time is 40-60 min or 20-40 min. Given a fixed ball milling speed and the selected grinding beads, the attapulgite adsorbent material exhibits the best adsorption effect for cadmium ions when the ball milling time is 40-60 min, while the attapulgite adsorbent material exhibits the best adsorption effect for lead ions when the ball milling time is 20-40 min.

[0011] As a preferred embodiment, the grinding beads are spherical and / or cylindrical in shape. A cylindrical shape is further preferred. The contact methods between spherical and cylindrical grinding beads and attapulgite differ; spherical beads primarily engage in point contact, while cylindrical beads engage in point, line, and surface contact. Therefore, using cylindrical grinding beads to ball-mill and activate attapulgite provides three more contact methods compared to using spherical media: point-to-line contact, line-to-line contact, and surface-to-surface contact. However, the point contact area of ​​spherical grinding beads is relatively small, resulting in the greatest force, which may lead to uneven grinding of the attapulgite particles and the phenomenon of excessively fine grinding and damage to the rod crystals. The line and surface contact of cylindrical media can effectively alleviate the problem of the large force between spherical grinding beads and attapulgite, which damages the microstructure of the attapulgite. The contact between cylindrical grinding beads and attapulgite includes point-to-point contact, line-to-line contact, and surface-to-surface contact, offering greater variety in both contact area and impact force compared to spherical grinding beads. Therefore, cylindrical grinding beads can effectively crush and activate attapulgite mineral particles of all sizes, including large, medium, and small particles. Spherical grinding beads, on the other hand, are too monotonous, primarily acting on large particles, while medium and small particles may experience insufficient grinding and activation due to lower contact probability. Therefore, cylindrical grinding beads are the preferred choice.

[0012] As a preferred embodiment, the filling amount of the grinding beads in the ball mill jar is 0.9~1.0 kg / L.

[0013] As a preferred embodiment, the ball milling is a wet ball milling process.

[0014] As a preferred embodiment, the wet ball milling uses water as the ball milling solvent.

[0015] As a preferred embodiment, the ball milling solvent is mixed with the attapulgite ore at a solid-liquid ratio of 0.1–0.2 g / mL.

[0016] As a preferred embodiment, a dispersant with a mass concentration of 4% to 5% is added during the ball milling process. A specific example of a dispersant is sodium hexametaphosphate.

[0017] As a preferred embodiment, the ball milling process further preferably uses three types of grinding beads with particle sizes of 5mm, 10mm, and 15mm. The mass ratio of the three types of grinding beads (from smallest to largest) during the ball milling process is further preferably 3-4:4-5:1. The grinding beads are made of zirconium oxide.

[0018] The attapulgite ore of the present invention is crushed to a particle size of less than 2 mm.

[0019] The ball milled material of the present invention is dried at a temperature of 60°C.

[0020] The present invention also provides an attapulgite adsorbent material, which is obtained by the preparation method described above.

[0021] This invention also provides an application of attapulgite adsorbent material for adsorbing heavy metal ions in aqueous solutions.

[0022] As a preferred embodiment, the heavy metal ions include Pd. 2+ and / or Cd 2+ .

[0023] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0024] (1) The present invention uses mechanical activation to effectively improve the adsorption performance of attapulgite ore. Compared with attapulgite ore, the attapulgite adsorbent material prepared by mechanical activation has a higher adsorption performance for Pd. 2+ Cd 2+ The removal rates increased by nearly 6 times and 4.5 times, respectively.

[0025] (2) The method for preparing attapulgite adsorbent material in this invention is simple and convenient, which greatly reduces costs and simplifies operation procedures. Attached Figure Description

[0026] Figure 1 This is a particle size distribution diagram of the attapulgite ore ground for 10-60 min in Example 1.

[0027] Figure 2 The effects of different grinding times on Pd from attapulgite ore in Example 1 2+ A graph showing the relationship between the rate of increase in removal rate.

[0028] Figure 3 This is a particle size distribution diagram of the attapulgite ore ground for 10-60 min in Example 2.

[0029] Figure 4 The effects of different grinding times on Cd in attapulgite ore in Example 2 2+ A graph showing the relationship between the rate of increase in removal rate.

[0030] Figure 5 To illustrate the effects of different shaped grinding balls on Pd in ​​Comparative Example 2, the raw attapulgite ore was subjected to different grinding balls. 2+ and Cd 2+ A graph showing the relationship between the rate of increase in removal rate.

[0031] Figure 6 To compare the effects of attapulgite ore on Pd under different particle size grinding bead ratios in Example 3 2+ and Cd 2+ A graph showing the relationship between the rate of increase in removal rate. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments, but the following specific embodiments do not limit the scope of protection of the claims of the present invention.

[0033] Example 1

[0034] (1) Crushing the raw ore: The raw attapulgite ore of this invention comes from Xuyi, Jiangsu. The lumpy attapulgite clay is simply picked to remove the obvious impurities, and the remaining ore is mechanically crushed to less than 2 mm.

[0035] (2) Grinding attapulgite: The grinding test was conducted in a zirconia jar with an internal volume of 100 mL. The grinding media were all made of zirconia, and the grinding media were cylindrical in shape with three sizes: 15 mm, 10 mm, and 5 mm. The amount of grinding media filled in the test was 100 g. The grinding method was wet grinding, the solid-liquid ratio was 1:5 (5 g of attapulgite ore corresponds to 25 mL of ultrapure water), the amount of dispersant was 4% (0.2 g of sodium hexametaphosphate), the speed of the planetary ball mill was 700 rad / min, and the grinding media size ratio (large:medium:small = 1:5:3) and grinding time were 10, 20, 30, 40, 50, and 60 min, respectively. The particle size distribution of attapulgite minerals under different ball milling times is shown in the figure. Figure 1 As shown, the attapulgite adsorbent materials obtained under different ball milling times are denoted as attapulgite A-10, attapulgite A-20, attapulgite A-30, attapulgite A-40, attapulgite A-50 and attapulgite A-60, respectively.

[0036] (3) Drying the attapulgite: The ground slurry is dried in air at 60°C until the moisture evaporates.

[0037] (4) Adsorption of Pd 2+ Measure 50 mL of 20 mg / L Pd 2+ The solution was placed in conical flasks, with six aliquots serving as controls. 50 mg of attapulgite A-10, attapulgite A-20, attapulgite A-30, attapulgite A-40, attapulgite A-50, and attapulgite A-60 were added to each flask, respectively. The solutions were incubated at 25°C and 200 rpm for 4 h. After the adsorption reaction was complete, the supernatant was collected, filtered, and analyzed to calculate Pd. 2+ The removal rate of Pd was [not specified]. The results showed that after treatment with attapulgite-30, [the removal rate of Pd was not specified]. 2+ It exhibits excellent adsorption properties, with a removal rate nearly six times higher than the previous year. Specific data is as follows: Figure 2 As shown.

[0038] Example 2

[0039] (1) Crushing raw ore: See Example 1.

[0040] (2) Grinding attapulgite: The grinding test was conducted in a zirconia jar with an internal volume of 100 mL. The grinding media were made of zirconia, and the grinding media were round with three sizes: 15 mm, 10 mm, and 5 mm. The filling amount of grinding media in the test was 100 g. The grinding method was wet grinding, the solid-liquid ratio was 1:5 (5 g of attapulgite ore corresponds to 25 mL of ultrapure water), the amount of dispersant was 4% (0.2 g of sodium hexametaphosphate), and the rotation speed of the planetary ball mill was 700 rad / min. The grinding media size ratio (large:medium:small = 1:3:5) and grinding time were 10, 20, 30, 40, 50, and 60 min, respectively. The particle size distribution of attapulgite minerals under different ball milling times is shown in the figure. Figure 3 As shown, the attapulgite adsorbent materials obtained under different ball milling times are denoted as attapulgite B-10, attapulgite B-20, attapulgite B-30, attapulgite B-40, attapulgite B-50 and attapulgite B-60, respectively.

[0041] (3) Drying the attapulgite: The ground slurry is dried in air at 60°C until the moisture evaporates.

[0042] (4) Adsorption of Cd 2+ Measure 50 mL of 20 mg / L Cd 2+ The solution was placed in conical flasks, with six aliquots serving as controls. 50 mg of attapulgite B-10, attapulgite B-20, attapulgite B-30, attapulgite B-40, attapulgite B-50, and attapulgite B-60 were added to each flask, respectively. The solutions were incubated at 25°C and 200 rpm for 4 h. After the adsorption reaction was complete, the supernatant was collected, filtered, and analyzed to calculate Cd. 2+ The removal rate of Cd was [not specified]. The results showed that attapulgite B-60 significantly reduced the removal rate of Cd. 2+ It exhibits excellent adsorption properties, with a removal rate nearly 4.5 times higher than the previous year. Specific data is as follows: Figure 4 As shown.

[0043] Other aspects are the same as in Example 1.

[0044] Comparative Example 1

[0045] Take 50 mg of attapulgite ore and add 50 mL of 20 mg / L Pd. 2+ and Cd 2+ In solution, the system was run at 25℃ and 200 rpm for 4 h. After the adsorption reaction was complete, the supernatant was collected for filtration and analysis, and Pd was calculated. 2+ and Cd 2+ The removal rate of Pd was [not specified]. The results showed that attapulgite ore significantly reduced the removal rate of Pd. 2+ and Cd 2+ Its adsorption capacity is very poor, and the removal rate is only about 10%.

[0046] Example 3

[0047] (1) Crushing raw ore: See Example 1.

[0048] (2) Grinding of attapulgite: The grinding test was conducted in a zirconia container with an internal volume of 100 mL. The grinding media were all made of zirconia, and the shapes of the grinding media were cylindrical and spherical. As a control, the grinding media had three sizes: 15 mm, 10 mm, and 5 mm. The amount of grinding media filled in the test was 100 g. The grinding method was wet grinding, the solid-liquid ratio was 1:5 (5 g of attapulgite ore corresponds to 25 mL of ultrapure water), the amount of dispersant was 4% (0.2 g of sodium hexametaphosphate), and the speed of the planetary ball mill was 700 rad / min. The grinding media size ratio (large:medium:small = 1:5:3) and the grinding time was 30 min. The resulting attapulgite adsorbent materials were denoted as attapulgite C1-30 and attapulgite C2-30, respectively.

[0049] (3) Drying the attapulgite: The ground slurry is dried in air at 60°C until the moisture evaporates.

[0050] (4) Adsorption of Pd 2+ and Cd 2+ Measure 50 mL of 20 mg / L Pd. 2+ and Cd 2+ The solution was placed in an Erlenmeyer flask, and 50 mg of attapulgite C1-30 and attapulgite C2-30 were added separately. The solution system was run at 25℃ and 200 rpm for 4 h. After the adsorption reaction was completed, the supernatant was collected, filtered, and analyzed to calculate Pd. 2+ and Cd 2+ The removal rate of Pd was [not specified]. The results showed that the attapulgite C1-30 obtained after activation treatment with cylindrical media significantly improved the removal efficiency of Pd. 2+ and Cd 2+ It exhibits good adsorption properties, and its effect is superior to that of attapulgite C2-30. Specific data are as follows: Figure 4 As shown.

[0051] Example 4

[0052] (1) Crushing raw ore: See Example 1.

[0053] (2) Grinding of attapulgite: The grinding test was conducted in a zirconia container with an internal volume of 100 mL. The grinding media were made of zirconia and were cylindrical in shape, with three sizes: 15 mm, 10 mm, and 5 mm. The amount of grinding media filled in the test was 100 g. The grinding method was wet grinding, with a solid-liquid ratio of 1:5 (5 g of attapulgite ore corresponds to 25 mL of ultrapure water), and the amount of dispersant was 4% (0.2 g of sodium hexametaphosphate). The speed of the planetary ball mill was 700 rad / min. Three groups of grinding media size ratios were used as controls: large: medium: small = 1:5:3, 1:4:4, and 1:3:5, with a grinding time of 30 min. The resulting attapulgite adsorbent materials were designated as attapulgite D-153, attapulgite D-144, and attapulgite D-135, respectively.

[0054] (3) Drying the attapulgite: The ground slurry is dried in air at 60°C until the moisture evaporates.

[0055] (4) Adsorption of Pd 2+ and Cd 2+ Measure 50 mL of 20 mg / L Pd. 2+ and Cd 2+ The solution was placed in an Erlenmeyer flask, and 50 mg of attapulgite D-153, attapulgite D-144, and attapulgite D-135 were added respectively. The solution system was run at 25℃ and 200 rpm for 4 h. After the adsorption reaction was completed, the supernatant was collected, filtered, and analyzed to calculate Pd. 2+ and Cd 2+ The removal rate of Pd was [not specified]. The results showed that attapulgite D-153 and attapulgite D-135 [were effective against Pd]. 2+ and Cd 2+ It exhibits the best adsorption properties, while attapulgite D-144 shows the best adsorption properties for Pd. 2+ and Cd 2+ All exhibited moderate adsorption performance. This is mainly because lead ions have a larger hydrated ionic radius, making them more prone to adsorption on the attapulgite surface. The hydroxyl and silanol groups on the attapulgite surface can bind to lead ions. D-153 contains fewer small-particle grinding media, which avoids damage to the adsorption groups on the attapulgite surface. Therefore, with the increase of small-particle grinding media, the damage to the adsorption groups on the attapulgite surface becomes more significant, leading to a decrease in lead ion removal rate. Cadmium ions have a smaller hydrated ionic radius and are mainly adsorbed within the attapulgite pores. Small-sized grinding media can grind the attapulgite more finely, optimizing the pore size and pore volume. Therefore, D-135 performs better than D-153 and D-144 in removing cadmium ions. Specific data are as follows... Figure 6 As shown.

Claims

1. Use of attapulgite adsorbent material, characterized in that: For adsorbing heavy metal ions in aqueous solutions; the heavy metal ions include Pd 2+ and / or Cd 2+ ; The attapulgite adsorption material is prepared by the following method: crushing and ball milling of attapulgite raw ore to obtain the attapulgite adsorption material. The ball milling speed is 600-700 rad / min, and the ball milling time is 10-60 min. Three kinds of grinding beads with particle sizes of 4-6 mm, 9-11 mm and 14-16 mm are used in the ball milling process, and the mass ratio of the three kinds of grinding beads is 3-5:3-5:

1. The shape of the grinding beads is cylindrical.

2. Use of attapulgite adsorbent material according to claim 1, characterized in that: The filling amount of the grinding beads in the ball milling tank is 0.9-1.0 kg / L.

3. Use of attapulgite adsorbent material according to claim 1, characterized in that: The ball milling is wet ball milling. Water is used as the ball milling solvent in the wet ball milling. The ball milling solvent and the attapulgite raw ore are mixed according to a solid-liquid ratio of 0.1-0.2 g / mL.

4. Use of attapulgite adsorbent material according to claim 3, characterized in that: A dispersant with a mass concentration of 4%-5% is added in the ball milling process.

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