Pectin / titanium pillared bentonite composite adsorption material and preparation method thereof

Abstract

The invention discloses a pectin / titanium pillared bentonite composite adsorption material and a preparation method thereof, and belongs to the technical field of wastewater treatment. According to the method, sodium bentonite is used as a matrix, tetrabutyl titanate is used as a titanium source, titanium pillared bentonite is prepared through a sol-gel method, then the titanium pillared bentonite is compounded with a pectin solution, and the pectin / titanium pillared bentonite composite adsorption material is prepared. The problems that natural bentonite swells when encountering water and solid-liquid separation is difficult are solved through titanium pillared modification, and the specific surface area of the bentonite is increased from 21.22 m < 2 > / g to 116.23 m < 2 > / g; the material is endowed with excellent heavy metal complexation and flocculation performance through pectin compounding, the maximum adsorption capacity of the prepared pectin / titanium pillared bentonite composite adsorption material to Hg (II) reaches 31.40 mg / g, the flocculation settling time is shortened by 90% or above compared with natural bentonite, and the material has photocatalytic reduction performance. The invention has the advantages of wide raw material source, simple preparation process, low cost and no secondary pollution, and has wide application prospect in the field of heavy metal wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a pectin / titanium-pillared bentonite composite adsorbent material and its preparation method. Background Technology

[0002] With the rapid development of industry, mercury pollution has become a key and challenging issue in the field of water treatment due to its high toxicity, bioaccumulation, and recalcitrant nature. In particular, the calcium carbide-based PVC production process generates a large amount of mercury-containing wastewater, necessitating the development of efficient, low-cost, and environmentally friendly treatment technologies and materials.

[0003] Bentonite is a hydrous clay mineral with montmorillonite as its main component. my country has the world's largest reserves of bentonite, which is abundant, inexpensive, and has excellent cation exchange and adsorption properties, making it a highly promising adsorption material for water treatment. However, natural bentonite easily swells in water to form slurry, making solid-liquid separation extremely difficult. In addition, its specific surface area is limited and its adsorption capacity is insufficient, which seriously restricts its large-scale application in wastewater treatment.

[0004] Pillaring modification is a core method to improve the performance of bentonite. Among them, titanium-pillared bentonite can open up the bentonite crystal layers through oxide pillars, solving the problem of swelling when exposed to water. At the same time, it can significantly increase the specific surface area of ​​the material and endow the material with excellent photocatalytic activity. Compared with organic pillared bentonite, it has better thermal and chemical stability. However, titanium-pillared bentonite alone still has problems in wastewater treatment, such as insufficient flocculation performance, easy loss of fine particles, and limited targeted adsorption capacity for low concentrations of heavy metals.

[0005] Pectin is a natural linear polysaccharide extracted from biomass such as plant peels and roots. It is widely available, biocompatible, and does not cause secondary pollution. Its molecular chain contains a large number of active groups such as carboxyl and hydroxyl groups, which can complex with heavy metal ions in water and also have good flocculation properties. However, when pectin is used alone as an adsorbent, it has defects such as poor mechanical strength, easy dispersion and loss in water, difficulty in recovery, and poor reusability, so it cannot be used alone for industrial wastewater treatment.

[0006] Currently, there is no existing technology to combine titanium-pillared bentonite with pectin to prepare a composite adsorbent material with multiple functions including adsorption, catalysis, and flocculation. This technology cannot simultaneously solve the problems of difficult solid-liquid separation of bentonite, difficult pectin recovery, and limited adsorption performance of single materials. Therefore, developing a composite adsorbent material with widely available raw materials, a simple preparation process, low cost, no secondary pollution, and excellent removal effect on heavy metals has significant practical significance and application value. Summary of the Invention

[0007] In view of this, the present invention provides a pectin / titanium-pillared bentonite composite adsorbent material and its preparation method. The method first solves the problems of water swelling and solid-liquid separation difficulties of natural bentonite by modifying it with titanium pillars, which significantly improves the specific surface area and adsorption activity of the material. Then, the titanium-pillared bentonite is combined with pectin. By utilizing the rich active functional groups in the pectin molecular chain, the material is endowed with excellent flocculation performance and heavy metal complexation ability. The prepared pectin / titanium-pillared bentonite composite adsorbent material not only adsorbs heavy metals, but also has photocatalytic reduction and flocculation sedimentation effects. It has excellent removal effect on Hg(II) in water, and is environmentally friendly and low in cost, making it suitable for heavy metal wastewater treatment.

[0008] The technical solution provided by this invention is as follows: This invention provides a method for preparing a pectin / titanium-pillared bentonite composite adsorbent material, comprising the following steps: S1. Preparation of sodium-based bentonite suspension Sodium-based bentonite was added to distilled water to prepare a sodium-based bentonite suspension. The suspension was stirred at room temperature for 2-4 hours and aged for 20-28 hours to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, anhydrous ethanol, tetrabutyl titanate and glacial acetic acid are mixed evenly to prepare solution A. Nitric acid solution and anhydrous ethanol are mixed evenly to prepare solution B. Under stirring, solution B is added dropwise to solution A at a uniform rate to react and obtain titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred vigorously at room temperature for 2-4 hours and aged for 10-16 hours. After aging, the supernatant was discarded, and the lower precipitate was washed with distilled water until neutral, dried, and ground to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a muffle furnace and calcined at 450~550 ℃ for 2~4 h, cooled to room temperature, and ground to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:(8~12) to form a suspension. Pectin solution was added, and the mixture was stirred at high speed at room temperature for 2~4 h. After the reaction was completed, the suspension was centrifuged, washed, dried, and ground to obtain the pectin / titanium-pillared bentonite composite adsorbent material.

[0009] Preferably, the mass fraction of the sodium-based bentonite suspension in step S1 is 0.5-1.5%.

[0010] Preferably, in step S2, the volume ratio of anhydrous ethanol, tetrabutyl titanate, and glacial acetic acid is 20:10:2; the concentration of the nitric acid solution is 1 mol / L, and the volume ratio of the nitric acid solution to anhydrous ethanol is 2:5.

[0011] Preferably, the dropping rate of liquid B in step S2 is 1~2 drops / second. If the dropping rate is too fast, the titanium source hydrolysis reaction is too violent, which easily forms titanium hydroxide particles with uneven particle size. It is impossible to form a uniform titanium sol, which leads to uneven interlayer of bentonite in the titanium column during the subsequent columnarization reaction, reducing the specific surface area and adsorption performance of the material.

[0012] Preferably, the stirring speed in step S3 is ≥1200 rpm. If the speed is lower than 1200 rpm, the titanium sol columnarizing agent and the bentonite suspension will not mix sufficiently, the columnarizing agent will not be able to uniformly contact the interlayer cations of bentonite, the intercalation reaction will be incomplete, the bentonite crystal layer will not be well spread, the material specific surface area will increase only slightly, and there will be insufficient adsorption active sites.

[0013] Preferably, the mass fraction of the pectin solution in step S5 is 0.5~3.0%.

[0014] Preferably, the pectin solution has a mass fraction of 0.5%.

[0015] Preferably, the high-speed stirring speed in step S5 is ≥1500 rpm. If the speed is lower than 1500 rpm, the pectin molecules cannot be uniformly loaded on the surface and in the pores of the titanium-pillared bentonite, and local aggregation is likely to occur. Not only will the complexing and flocculation effects of pectin not be fully utilized, but the pores of the titanium-pillared bentonite will also be unevenly blocked, resulting in a decrease in the adsorption and catalytic performance of the material.

[0016] Based on the same inventive concept, the present invention provides a pectin / titanium-pillared bentonite composite adsorbent material, wherein the pectin / titanium-pillared bentonite composite adsorbent material is prepared by any of the preparation methods described above.

[0017] Based on the same inventive concept, this invention provides the application of a pectin / titanium-pillared bentonite composite adsorbent material as described in any of the preceding claims in the adsorption of Hg(II) in water.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces a titanium-based columnarizing agent into the interlayer of bentonite using a sol-gel method. After calcination, stable titanium dioxide oxide columns are formed, effectively expanding the bentonite crystal layers and increasing the interlayer spacing from 1.24 nm to 2.68 nm. This fundamentally solves the problems of water swelling and solid-liquid separation difficulties in natural bentonite, while also increasing the specific surface area of ​​bentonite from 21.22 m². 2 / g increased significantly to 116.23 m 2 / g significantly increased the adsorption active sites and adsorption capacity of the material.

[0019] 2. This invention combines titanium-pillared bentonite with natural biomass pectin. By utilizing the abundant carboxyl and hydroxyl active groups on the pectin molecular chain, the material is further endowed with excellent heavy metal complexing ability and flocculation performance, realizing the integration of adsorption-catalysis-flocculation multifunctionality. This not only increases the adsorption capacity of Hg(II) in water to 31.40 mg / g, but also improves the sedimentation performance of the material in water, significantly reducing the solid-liquid separation cost in the water treatment process.

[0020] 3. The preparation process of this invention is simple and controllable, the reaction conditions are mild, and no complex equipment is required; the core raw material, bentonite, is abundant and inexpensive in my country, and pectin can be extracted from agricultural by-products such as citrus peel and apple peel, realizing the high-value utilization of biomass resources. The overall preparation cost of the material is low, making it suitable for large-scale production and industrial application.

[0021] 4. The pectin / titanium-pillared bentonite composite adsorbent material prepared by this invention has no secondary pollution and has excellent adsorption performance for Hg(II) in water. It can be widely used in the treatment of mercury-containing wastewater from calcium carbide PVC production and various industrial heavy metal wastewater. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the synthesis of the pectin / titanium-pillared bentonite composite adsorbent material prepared according to the present invention.

[0023] Figure 2 Wide-angle X-ray diffraction patterns of titanium dioxide, sodium-based bentonite, and titanium-pillared bentonite.

[0024] Figure 3 X-ray diffraction patterns of sodium-based bentonite and titanium-pillared bentonite.

[0025] Figure 4 This is a comparison chart of the adsorption capacity of different materials for Hg(II). Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0027] Sodium-based bentonite was purchased from Xinjiang Zhongfei Xiazijie Bentonite Co., Ltd.

[0028] Example 1 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 3 h and age for 24 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was vigorously stirred at 1200 rpm for 3 h at room temperature and aged for 12 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 500 °C for 3 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:10 to form a suspension. A pectin solution with a mass fraction of 0.5% was added, and the mixture was stirred at a high speed of 1500 rpm for 3 h at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 65 ℃, and ground to obtain a pectin / titanium-pillared bentonite composite adsorbent material.

[0029] The performance of the pectin / titanium-pillared bentonite composite adsorbent prepared in this embodiment was tested: The specific surface area of ​​titanium-supported bentonite is 116.23 m². 2 / g, the saturated adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent for Hg(II) is 31.40 mg / g; the flocculation performance test shows that the composite adsorbent completely settles within 5 min after addition, the flocculation and settling time is shortened by 90% compared with natural bentonite, and the transmittance of the supernatant is ≥95%; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 26.8%.

[0030] Depend on Figure 1 It can be seen that, using sodium-based bentonite as the matrix, a pectin / titanium-pillared bentonite composite adsorbent material integrating adsorption-catalysis-flocculation was successfully prepared through titanium sol pillaring, calcination, and pectin composite, which has a stable structure and uniform functional group loading.

[0031] Depend on Figure 2 It can be seen that the titanium-pillared bentonite exhibits the characteristic diffraction peaks of anatase TiO2, proving that the TiO2 pillars were successfully intercalated between bentonite layers, and that the crystal structure was intact and the crystallinity was high.

[0032] Depend on Figure 3 It can be seen that after titanium pillar support, the characteristic diffraction peaks of bentonite shift to a smaller angle, and the interlayer spacing increases from 1.24 nm to 2.68 nm, indicating that the crystal layers are effectively expanded, and the specific surface area and adsorption sites are significantly improved.

[0033] Example 2 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 4 h and age for 26 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred vigorously at 1200 rpm for 4 h at room temperature and aged for 16 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 500 °C for 3 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:10 to form a suspension. A pectin solution with a mass fraction of 1.0% was added, and the mixture was stirred at a high speed of 1600 rpm for 3 h at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 65 ℃, and ground to obtain a pectin / titanium-pillared bentonite composite adsorbent material.

[0034] The performance of the pectin / titanium-pillared bentonite composite adsorbent prepared in this embodiment was tested: The specific surface area of ​​titanium-supported bentonite is 108.76 m². 2 / g, the saturated adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent for Hg(II) is 28.35 mg / g; the flocculation performance test shows that the composite adsorbent completely settles within 6 min after addition, and the solid-liquid separation effect is good; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 22%.

[0035] Example 3 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 2 h and age for 20 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred vigorously at 1300 rpm for 2 h at room temperature and aged for 14 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 550 °C for 4 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:10 to form a suspension. A pectin solution with a mass fraction of 2.0% was added, and the mixture was stirred at a high speed of 1500 rpm for 3 hours at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 65°C, and ground to obtain a pectin / titanium-pillared bentonite composite adsorbent material.

[0036] The performance of the pectin / titanium-pillared bentonite composite adsorbent prepared in this embodiment was tested: The specific surface area of ​​the titanium-supported bentonite is 99.42 m². 2 / g, the saturated adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent for Hg(II) is 25.18 mg / g; the flocculation performance test shows that the composite adsorbent completely settles within 7 min after addition; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 20%.

[0037] Example 4 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 3 h and age for 24 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 2 drops / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred vigorously at 1200 rpm for 3 h at room temperature and aged for 16 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 550 °C for 4 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:12 to form a suspension. A pectin solution with a mass fraction of 2.5% was added, and the mixture was stirred at a high speed of 1700 rpm for 3 hours at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 65 °C, and ground to obtain a pectin / titanium-pillared bentonite composite adsorbent material.

[0038] The performance of the pectin / titanium-pillared bentonite composite adsorbent prepared in this embodiment was tested: The specific surface area of ​​the titanium-supported bentonite is 92.35 m². 2 / g, the saturated adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent for Hg(II) is 20.56 mg / g; the flocculation performance test shows that the composite adsorbent completely settles within 8 min after addition, and the transmittance of the supernatant is ≥88%; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 18%.

[0039] Example 5 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 3 h and age for 24 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was vigorously stirred at 1200 rpm for 3 h at room temperature and aged for 12 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 480 ℃ for 3.5 h, cooled to room temperature, ground and passed through a 200 mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:10 to form a suspension. A pectin solution with a mass fraction of 3.0% was added, and the mixture was stirred at a high speed of 1500 rpm for 3.5 h at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 70 ℃, and ground to obtain a pectin / titanium-pillared bentonite composite adsorbent material.

[0040] The performance of the pectin / titanium-pillared bentonite composite adsorbent prepared in this embodiment was tested: The specific surface area of ​​titanium-supported bentonite is 85.68 m². 2 / g, the saturated adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent for Hg(II) is 14.82 mg / g; the flocculation performance test shows that the composite adsorbent completely settles within 9 minutes after addition, and the transmittance of the supernatant is ≥85%; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 15%.

[0041] Comparative Example 1 A method for preparing a titanium-pillared bentonite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium-based bentonite and add it to 1000 mL of distilled water while stirring to prepare a 1% sodium-based bentonite suspension. Stir at room temperature for 3 h and let it age for 24 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was vigorously stirred at 1200 rpm for 3 h at room temperature and aged for 12 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 500 °C for 3 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite.

[0042] Compared with Example 1, no pectin solution was added to this comparative example.

[0043] The performance of the titanium-pillared bentonite prepared in this comparative example was tested: The specific surface area of ​​titanium-supported bentonite is 116.23 m². 2 / g, the saturated adsorption capacity of titanium-pillared bentonite for Hg(II) is 15.32mg / g; the flocculation performance test shows that the composite adsorbent material completely settles within 30min after addition, the solid-liquid separation time is significantly extended, and the transmittance of the supernatant is ≥78%; the catalytic performance test shows that the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation is 26.0%.

[0044] This comparative example only prepared titanium-pillared bentonite without pectin. Although the photocatalytic reduction rate was slightly improved due to the absence of pectin blocking the catalytic sites, the lack of pectin's heavy metal complexing ability and flocculation performance resulted in a significant reduction in the adsorption of Hg(II), and the flocculation and sedimentation time was significantly prolonged. The solid-liquid separation effect was poor, and the overall treatment performance was far inferior to the pectin / titanium-pillared bentonite composite adsorbent material in Example 1.

[0045] Comparative Example 2 A method for preparing a pectin / sodium-based bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 3 h and age for 24 h to allow the bentonite to fully swell. S2. Preparation of pectin / sodium-based bentonite composite materials The sodium-based bentonite suspension obtained in step S1 was directly mixed with distilled water at a solid-liquid ratio of 1:10. A pectin solution with a mass fraction of 0.5% was added, and the mixture was stirred at a high speed of 1500 rpm for 3 h at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 70 ℃, and ground to obtain a pectin / sodium-based bentonite composite material.

[0046] Compared with Example 1, this comparative example did not undergo titanium pillar modification treatment.

[0047] The performance of the pectin / sodium-based bentonite composite material prepared in this comparative example was tested: The material has a specific surface area of ​​23.56 m². 2 / g, with a saturated adsorption capacity of 9.82 mg / g for Hg(II); flocculation performance test showed that it completely settled within 8 min after addition, but the material still showed slight swelling when exposed to water, and fine particles were suspended after solid-liquid separation, with a light transmittance of ≥86% in the supernatant; it had no obvious photocatalytic reduction performance, and the reduction rate of Hg(II) under ultraviolet light irradiation was <1%.

[0048] Comparative Example 3 A method for preparing a pectin / titanium-pillared bentonite composite adsorbent material includes the following steps: S1. Preparation of sodium-based bentonite suspension Weigh 10 g of dried sodium bentonite and add it to 1000 mL of distilled water while stirring to prepare a sodium bentonite suspension with a mass fraction of 1%. Stir at room temperature for 3 h and age for 24 h to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, 20 mL of anhydrous ethanol, 10 mL of tetrabutyl titanate and 2 mL of glacial acetic acid were mixed evenly to prepare solution A; 2 mL of 1 mol / L nitric acid solution and 5 mL of anhydrous ethanol were mixed evenly to prepare solution B. Under vigorous magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop / second using a constant pressure funnel, and the mixture was stirred continuously to obtain a pale yellow transparent titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred at 1000 rpm for 3 h at room temperature and aged for 12 h. After aging, the supernatant was discarded, and the lower white solid precipitate was washed with distilled water until neutral. After drying at 70 ℃, it was ground through a 200-mesh sieve to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a porcelain crucible, placed in a muffle furnace, calcined at 500 °C for 3 h, cooled to room temperature, ground and passed through a 200-mesh sieve to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:10 to form a suspension. A pectin solution with a mass fraction of 0.5% was added, and the mixture was stirred at a high speed of 1500 rpm for 3 h at room temperature. After the reaction was completed, the suspension was centrifuged, washed until neutral, dried at 70 ℃, and ground to obtain a pectin / titanium-pillared bentonite composite material.

[0049] Compared with Example 1, the stirring speed in step S3 of this comparative example is lower than 1200 rpm.

[0050] The performance of the composite material prepared in this comparative example was tested: The specific surface area of ​​titanium-supported bentonite is 52.68 m². 2 / g, with a saturated adsorption capacity of 12.15 mg / g for Hg(II); flocculation performance test showed that it completely settled within 18 min after addition, and the transmittance of the supernatant was ≥75%; the synchronous photocatalytic reduction rate of Hg(II) under ultraviolet light irradiation was 12.3%.

[0051] The stirring speed of the columnar reaction in this comparative example was less than 1200 rpm, which resulted in insufficient mixing of the titanium sol columnar agent and the bentonite suspension. This led to uneven intercalation of the titanium column into the bentonite layers, poor expansion of the bentonite crystal layers, a significant reduction in the specific surface area of ​​the material, and insufficient adsorption and catalytic active sites. At the same time, the uneven structure also resulted in poor flocculation and sedimentation performance. This fully demonstrates that a strong stirring speed ≥1200 rpm in the columnar reaction is a necessary condition for the preparation of high-performance composite adsorbent materials.

[0052] Figure 4 shows the adsorption capacity comparison, indicating that the adsorption capacity of the pectin / titanium-pillared bentonite composite adsorbent material prepared in this invention for Hg(II) is significantly higher than that of titanium dioxide, sodium-based bentonite, titanium-pillared bentonite, and pure pectin. The saturated adsorption capacity of pure pectin for Hg(II) is 6.35 mg / g. The adsorption capacity of the material is highest when the mass fraction of the pectin solution is 0.5%, and the adsorption capacity decreases as the mass fraction of the pectin solution increases. This is because as the pectin concentration increases, the amount of pectin composite on the surface of titanium-pillared bentonite increases. Excessive pectin will block the pores of titanium-pillared bentonite and occupy the adsorption active sites on its surface. At the same time, the carboxyl groups on the surface of pectin and the hydroxyl groups on the surface of bentonite combine through cation bridges, water bridges, and hydrogen bridges, reducing the active groups that can complex with Hg(II), ultimately leading to a decrease in the adsorption capacity of the material for Hg(II).

[0053] Table 1. Performance comparison of materials prepared in each embodiment and comparative example. As shown in Table 1, the specific surface area of ​​sodium-based bentonite is only 21.22 m². 2 The adsorption capacity for Hg(II) was 5.86 mg / g, with a flocculation and sedimentation time of up to 30 min, and almost no photocatalytic activity. The specific surface area of ​​pure pectin was only 3.92 m². 2 The adsorption capacity for Hg(II) was 6.35 mg / g, indicating poor flocculation and photocatalytic performance. After modification with titanium pillars (Comparative Example 1), the specific surface area of ​​bentonite increased to 116.23 m². 2The material exhibits good photocatalytic reduction performance, with an adsorption capacity of 15.32 mg / g for Hg(II), but the flocculation and sedimentation time remains at 30 min, and the solid-liquid separation effect is poor. The material without titanium pillars and only composited with pectin (Comparative Example 2) has a low specific surface area, limited adsorption capacity, and no photocatalytic activity. If the stirring speed of the columnar reaction is lower than 1200 rpm, the specific surface area, adsorption capacity, and photocatalytic performance of the material will significantly decrease, and the flocculation and sedimentation time will be prolonged. The pectin / titanium pillared bentonite composite adsorbent material prepared in this invention has excellent comprehensive performance, with Example 1 showing the best performance, achieving a specific surface area of ​​116.23 m². 2 The adsorption capacity of Hg(II) was 31.40 mg / g, the flocculation and sedimentation time was only 5 min, and the photocatalytic reduction rate was 26.8%. Moreover, as the mass fraction of pectin solution increased, the adsorption capacity, specific surface area and photocatalytic reduction rate of the material gradually decreased, and the flocculation and sedimentation time was correspondingly prolonged. This indicates that the appropriate pectin concentration and process parameters are the key to ensuring the high efficiency of the material.

[0054] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a pectin / titanium-pillared bentonite composite adsorbent, characterized in that, Includes the following steps: S1. Preparation of sodium-based bentonite suspension Sodium-based bentonite was added to distilled water to prepare a sodium-based bentonite suspension. The suspension was stirred at room temperature for 2-4 hours and aged for 20-28 hours to allow the bentonite to fully swell. S2. Preparation of titanium sol columnarizing agent At room temperature, anhydrous ethanol, tetrabutyl titanate and glacial acetic acid are mixed evenly to prepare solution A. Nitric acid solution and anhydrous ethanol are mixed evenly to prepare solution B. Under stirring, solution B is added dropwise to solution A at a uniform rate to react and obtain titanium sol columnarizing agent. S3. Columnarization reaction The titanium sol columnarizing agent obtained in step S2 was added dropwise to the sodium-based bentonite suspension obtained in step S1. The mixture was stirred vigorously at room temperature for 2-4 hours and aged for 10-16 hours. After aging, the supernatant was discarded, and the lower precipitate was washed with distilled water until neutral, dried, and ground to obtain the titanium columnar precursor. S4. Heat Treatment The titanium pillar precursor obtained in step S3 was placed in a muffle furnace and calcined at 450~550 ℃ for 2~4 h, cooled to room temperature, and ground to obtain titanium pillar bentonite. S5. Preparation of pectin / titanium-pillared bentonite The titanium-pillared bentonite obtained in step S4 was mixed with distilled water at a solid-liquid ratio of 1:(8~12) to form a suspension. Pectin solution was added, and the mixture was stirred at high speed at room temperature for 2~4 h. After the reaction was completed, the suspension was centrifuged, washed, dried, and ground to obtain the pectin / titanium-pillared bentonite composite adsorbent material.

2. The preparation method of a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S1, the mass fraction of the sodium-based bentonite suspension is 0.5-1.5%.

3. The preparation method of a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S2, the volume ratio of anhydrous ethanol, tetrabutyl titanate, and glacial acetic acid is 20:10:2; the concentration of the nitric acid solution is 1 mol / L, and the volume ratio of the nitric acid solution to anhydrous ethanol is 2:

5.

4. The preparation method of a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S2, the dropping rate of liquid B is 1~2 drops / second.

5. The method for preparing a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S3, the stirring speed is ≥1200 rpm.

6. The method for preparing a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S5, the pectin solution has a mass fraction of 0.5-3.0%.

7. The preparation method of a pectin / titanium-pillared bentonite composite adsorbent material according to claim 6, characterized in that, The pectin solution has a mass fraction of 0.5%.

8. The method for preparing a pectin / titanium-pillared bentonite composite adsorbent material according to claim 1, characterized in that, In step S5, the speed of the high-speed stirrer is ≥1500 rpm.

9. A pectin / titanium-pillared bentonite composite adsorbent material, characterized in that, The pectin / titanium-pillared bentonite composite adsorbent material is prepared by the preparation method according to any one of claims 1-8.

10. The application of the pectin / titanium-pillared bentonite composite adsorbent material as described in claim 9 in the adsorption of Hg(II) in water.

Images