A method for preparing composite materials based on high-speed shearing method and application thereof

Abstract

The application provides a preparation method and application of a novel composite material based on a high-speed shearing method. The composite material is prepared by compounding mercapto cellulose and mercapto bentonite, the mercapto cellulose is rapidly intercalated into the sheet structure of the mercapto bentonite by the high-speed shearing method, and the mass ratio of the cellulose, the bentonite and the mercapto in the composite material is 1:1:2. The application also provides application of the mercapto cellulose / bentonite nanocomposite material in cadmium pollution treatment. The preparation method of the mercapto cellulose / bentonite nanocomposite material has the advantages of short preparation time, fast surface modification speed, enlarged interlamellar spacing of the bentonite, high adsorption, rich selective sites for complexation of metal cadmium, high remediation efficiency, small influence on soil physical and chemical properties, and the ability to improve soil enzyme activity. The material is used for cadmium pollution treatment, and has the advantages of simple use method and small influence on the environment.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal cadmium pollution control and composite material technology, specifically relating to a method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing and its application. Background Technology

[0002] Cadmium is one of the main pollutants in soil and water environments. The 2014 National Soil Pollution Survey Bulletin showed that cadmium (Cd) pollution was the most prominent pollutant in my country's farmland soil, with an exceedance rate of 7.0%. As a major surface source of drinking water, the main heavy metal pollutants in my country's rivers, lakes, and reservoirs, in descending order of severity, are mercury, cadmium, chromium, and lead. Cadmium pollution in water bodies generally originates from: industrial wastewater, the use of pyrite ore, the smelting of non-ferrous metals, the incineration of plastic products, and the use of pigments and surfactants. Cadmium pollution in soil generally originates from: the accumulation of cadmium-containing waste residue, the excessive application of phosphate fertilizers, and the discharge of cadmium-containing waste near factories. The heavy metal cadmium affects crop growth and can also accumulate in crops, harming human health. Cd has strong toxic effects on the human body, especially on the liver, placenta, kidneys, lungs, brain, and bones. Long-term exposure to Cd and its compounds leads to Cd accumulation in the kidneys. If the organ concentration exceeds a critical threshold, renal tubular cells are damaged, and kidney function is affected.

[0003] Existing methods for remediating heavy metal-contaminated soil are generally classified into three types: physical, chemical, and biological methods. Chemical methods include chemical leaching and chemical passivation. Chemical passivation involves adding passivating materials to the soil to alter and regulate its physicochemical properties, causing heavy metal ions to undergo adsorption, complexation, or redox reactions, thereby reducing the impact of heavy metals on the soil environment. Compared to traditional soil remediation methods, chemical passivation is simpler to operate, lower in cost, and produces less secondary pollution, making it more feasible in the actual remediation of heavy metal-contaminated soil. Existing methods for removing heavy metals from water bodies mainly include ion exchange, chemical precipitation, adsorption, and electrolysis. However, some of these methods are complex and costly, some generate significant secondary pollution, and some are difficult to implement. In comparison, adsorption is simple to operate, has good treatment effects, and is the most practical method for treating heavy metal pollution in water. Therefore, there is a need to develop an adsorbent material that is easy to operate and has good selective adsorption properties for cadmium to address cadmium pollution.

[0004] Bentonite is a material with high specific surface area and strong ion exchange capacity, but it has low loading capacity and low metal selectivity. Cellulose has a three-dimensional network structure and a large number of oxygen-containing active functional groups, but its polydispersity and structural heterogeneity lead to poor adsorption capacity and adsorption effect. Therefore, intercalation is chosen to allow cellulose to enter the interlayer gaps of bentonite, thereby improving the adsorption capacity of the composite material for heavy metals. According to the principle of hard and soft acid-base theory, -SH (thiol group) is a soft base and Cd(II) is a soft acid. Therefore, -SH easily combines with Cd(II), and soft-soft combination is more stable. To improve the selectivity and adsorption stability of the composite material for cadmium, surface grafting is considered to introduce thiol groups to modify the surface of bentonite and cellulose. The existing organic solvent heating reflux grafting method is inefficient, energy-intensive, and time-consuming. High-speed shearing method is simple and efficient, can quickly complete surface modification, and effectively avoids the oxidation of thiol groups. Therefore, the purpose of this invention is to provide a method for rapidly preparing thiolized cellulose / bentonite nanocomposites using high-speed shearing and its application in cadmium pollution control. Summary of the Invention

[0005] The purpose of this invention is to provide a thiolized cellulose / bentonite nanocomposite material with high adsorption and high selectivity for cadmium.

[0006] Another objective of this invention is to provide a method for preparing the above-mentioned thiolated cellulose / bentonite nanocomposite material.

[0007] Another objective of this invention is to provide an application of the above-mentioned thiolated cellulose / bentonite nanocomposite material in cadmium pollution control.

[0008] To achieve the above objectives, the present invention provides a thiolated cellulose / bentonite nanocomposite material, which is composed of thiolated cellulose and thiolated bentonite.

[0009] The mass ratio of cellulose, bentonite and thiol is 1:1:2.

[0010] The thiol cellulose is rapidly intercalated into the thiolized bentonite sheet structure via a high-speed shearing method.

[0011] This invention also provides a method for preparing the above-mentioned thiolated cellulose / bentonite nanocomposite material. This thiolated cellulose / bentonite nanocomposite material is obtained by rapidly intercalating thiolated cellulose into thiolated bentonite using a high-speed shearing method. The specific preparation method includes the following steps:

[0012] a. Mix 2.5g of cellulose with 47.5ml of distilled water and shear at 13500rpm for 5min to obtain a cellulose suspension.

[0013] b. Mix 2.5g of bentonite with 47.5ml of distilled water, and shear at high speed for 5min at 13500rpm to obtain a bentonite suspension.

[0014] c. Mix the above cellulose suspension and bentonite suspension, add 5g of 3-mercaptopropyltrimethoxysilane to the mixture, and shear at high speed for 15min at 13500rpm to obtain a thiolized cellulose / bentonite suspension.

[0015] d. Place the above thiolated cellulose / bentonite suspension in a high-speed centrifuge at 4000 r / min for 5 min, then discard the supernatant to obtain a composite material solid containing impurities.

[0016] e. Wash the composite material containing impurities with distilled water and dichloromethane, centrifuge at 4000 r / min for 5 min, and repeat the washing process at least three times.

[0017] f. The washed solid was vacuum dried at 60°C for 12 h to obtain a thiolized cellulose / bentonite nanocomposite material.

[0018] This invention also provides the application of the above-mentioned thiolated cellulose / bentonite nanocomposite material in the treatment of cadmium-contaminated wastewater.

[0019] The method for preparing the thiolized cellulose / bentonite nanocomposite material of the present invention uses cellulose and bentonite, which are widely found in nature, as raw materials. Cellulose and bentonite are dispersed separately in water. After the suspensions of the two are mixed, 3-mercaptopropyltrimethoxysilane is used to intercalate and modify the bentonite and cellulose. At the same time, the thiol-modified cellulose is intercalated into the sheet-like structure of thiolized bentonite by a high-speed shearing method, and finally the thiolized cellulose / bentonite nanocomposite material is obtained.

[0020] The preparation method provided by this invention inserts polymers into nanoscale clay minerals, which enhances the adsorption capacity of the minerals and improves the passivation efficiency for heavy metals.

[0021] The preparation method provided by this invention uses thiol groups to intercalate and modify bentonite and cellulose. The introduction of thiol groups provides abundant selective adsorption sites for Cd(II) complexation, thereby improving the material's selective adsorption capacity for cadmium.

[0022] The high-speed shearing method used in the preparation method provided by this invention accelerates the peeling of bentonite sheets, expands the interlayer spacing, increases the thiol grafting sites, improves efficiency, and shortens the preparation time, thereby avoiding the oxidation of thiol groups due to prolonged exposure to air.

[0023] The thiolized cellulose / bentonite nanocomposite material prepared in this invention has a larger interlamellar spacing and high pore volume and pore size compared to bentonite, which is beneficial for the adsorption of heavy metals.

[0024] The preparation method of thiolated cellulose / bentonite nanocomposite material provided by this invention has simple operation steps, short preparation cycle, and requires readily available and economical materials and instruments. It is also environmentally friendly and has great practical and social benefits.

[0025] The thiolated cellulose / bentonite nanocomposite material of the present invention can efficiently adsorb cadmium metal while increasing soil organic matter content and enzyme activity, and belongs to the passivation material with good environmental benefits.

[0026] The thiolated cellulose / bentonite nanocomposite material of the present invention is used for the treatment of heavy metal cadmium. The treatment process is simple, has little impact on the environment, and has high adsorption efficiency for cadmium. Attached Figure Description

[0027] Figure 1 XRD patterns of BE-LCS-SH, BE-SH, and BE

[0028] Figure 2 The effects of adding five materials on wastewater The effect of adsorption efficiency

[0029] Figure 3 The dosage of BE-LCS-SH in wastewater The effect of adsorption efficiency

[0030] Figure 4 For BE-LCS-SH at different concentrations Adsorption capacity in solution

[0031] Figure 5 Five materials at different concentrations Adsorption capacity in solution

[0032] Figure 6 pH value of BE-LCS-SH adsorption wastewater Effect of adsorption efficiency

[0033] Figure 7 The effect of temperature on BE-LCS-SH adsorption wastewater Effect of adsorption efficiency

[0034] Figure 8 The adsorption time of BE-LCS-SH adsorption wastewater Effect of adsorption efficiency

[0035] Figure 9The passivation efficiency of BE-LCS-SH in soil remediation of heavy metal cadmium

[0036] Figure 10 The passivation efficiency of BE-LCS-SH, BE-SH, and BE for cadmium in soil.

[0037] Figure 11 Effects of BE-LCS-SH on catalase activity in soil

[0038] Figure 12 Effects of BE-LCS-SH on urease activity in soil

[0039] Figure 13 Effects of BE-LCS-SH on dehydrogenase activity in soil Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Unless otherwise specified, the consumables, instruments, and pharmaceuticals mentioned below are all common commercially available products well-known in the art. Steps and methods not described in detail below can be performed normally according to conventional experimental steps and methods described in the literature of this art.

[0041] Example 1: This example provides a method for preparing thiolated cellulose / bentonite nanocomposite materials, wherein the specific steps of the method are as follows:

[0042] 1. Preparation of thiolated cellulose / bentonite nanocomposites

[0043] Preparation of cellulose and bentonite suspension

[0044] Mix 2.5g of cellulose with 47.5ml of distilled water and shear at 13500rpm for 5min to obtain a cellulose suspension; mix 2.5g of bentonite with 47.5ml of distilled water and shear at 13500rpm for 5min to obtain a bentonite suspension.

[0045] (2) Preparation of thiolated cellulose / bentonite nanocomposites

[0046] a. Mix the above cellulose suspension and bentonite suspension evenly, add 5g of 3-mercaptopropyltrimethoxysilane to the mixture, and shear at high speed of 13500rpm for 15min to obtain the composite material suspension.

[0047] b. Place the obtained suspension in a centrifuge and centrifuge at 4000 r / min for 5 min. Discard the supernatant and wash the obtained solid with distilled water and dichloromethane. After washing, centrifuge at 4000 r / min for 5 min using a high-speed centrifuge. Discard the supernatant and keep the solid. Repeat the washing process at least three times to obtain a water-containing thiolated cellulose / bentonite nanocomposite material.

[0048] c. The water-containing thiolated cellulose / bentonite nanocomposite material prepared above was vacuum dried at 60°C for 12 h to obtain thiolated cellulose / bentonite nanocomposite material (BE-LCS-SH).

[0049] (3) The high-speed shearing method provided above can also be used to prepare thiolated cellulose and thiolated bentonite. The specific steps for preparing thiolated cellulose are as follows:

[0050] a. Mix 2.5g of cellulose with 47.5ml of distilled water and shear at 13500rpm for 5min to obtain a cellulose suspension.

[0051] b. Add 5g of 3-mercaptopropyltrimethoxysilane to the cellulose suspension obtained above, and shear at high speed of 13500rpm for 15min to obtain a thiolized cellulose suspension.

[0052] c. Place the obtained thiolated cellulose suspension in a centrifuge and centrifuge at 4000 r / min for 5 min. Discard the supernatant and wash the obtained solid with distilled water and dichloromethane. Centrifuge at 4000 r / min for 5 min and discard the supernatant. Repeat the washing process at least three times to obtain the thiolated cellulose material containing water.

[0053] d. The water-containing thiolated cellulose material prepared above is vacuum dried at 60°C for 12 hours to obtain thiolated cellulose material (LCS-SH).

[0054] Thioyl bentonite (BE-SH) is prepared in the same way as thioyl cellulose; simply replace the cellulose in the above steps with an equal amount of bentonite.

[0055] 2. Characterization of thiolated cellulose / bentonite nanocomposites

[0056] 2.1 Determination of β-LCS-SH thiol content by indirect iodometric titration

[0057] The content of thiolized cellulose / bentonite nanocomposites prepared above was analyzed by indirect iodometric titration, and the thiol content in the cellulose and bentonite used was analyzed. The thiol content of each nanocomposite is shown in Table 1.

[0058] Table 1: Thiol content in BE-LCS-SH

[0059]

[0060] As shown in Table 1, the thiol content in the composite material is 4.02%, the thiol content in cellulose is 0.24%, and the thiol content in bentonite is 1.47%. The thiol content in BE-LCS-SH is 2.55% higher than that in bentonite. The significantly higher thiol content in the prepared BE-LCS-SH compared to the cellulose and bentonite used indicates that the high-speed shearing method successfully introduced thiol groups into BE-LCS-SH.

[0061] 2.2 Crystal structure of thiolated cellulose / bentonite nanocomposites

[0062] The XRD patterns of BE-LCS-SH, BE-SH, and BE are as follows: Figure 1 .Depend on Figure 1 It can be seen that, compared with bentonite, no new diffraction peaks appeared throughout the diffraction range of thiolized bentonite, indicating that thiolized bentonite well maintained the crystal structure of bentonite, and the introduction of thiol groups did not change the basic structure of bentonite. The interlayer spacing d of the thiolized cellulose / bentonite nanocomposite was larger than that of bentonite, indicating that the high-speed shearing method successfully destroyed the lamellar structure, thus expanding the interlayer spacing and interlayer voids of the composite material.

[0063] Application Example 1: This application example provides the application of the thiolated cellulose / bentonite nanocomposite material prepared in the examples in the treatment of cadmium-contaminated wastewater. The application includes the following steps:

[0064] 1. Contains Wastewater preparation

[0065] Prepare 200 mL solutions of cadmium nitrate hexahydrate containing... aqueous solution, The concentrations were 150 mg / L, 225 mg / L, 300 mg / L, 450 mg / L, 530 mg / L, and 600 mg / L, respectively, and the prepared... Reserve the aqueous solution for later use.

[0066] 2. The effect of thiolated cellulose / bentonite nanocomposite materials on the content of thiolated cellulose in wastewater processing

[0067] Using thiolated cellulose / bentonite nanocomposite materials as adsorbents, treatment was carried out on substances containing... The specific procedures for treating the wastewater are as follows: Accurately weigh three portions of BE-LCS-SH, each weighing 0.1000g. Place the weighed composite material into three 100mL polypropylene centrifuge tubes, and take one set as a parallel sample. Add 50mL of the above-prepared 450mg / L concentration of [a specific compound / concentration] to each centrifuge tube. Wastewater was collected, and then centrifuge tubes were placed in a constant temperature water bath shaker at 40℃ and 120 rpm for 4 hours. After shaking, the centrifuge tubes were removed, cooled to room temperature, and then transferred to a high-speed centrifuge for 3 minutes at 4000 rpm. The centrifuged sample was filtered, and the concentration of the impurities in the resulting solution was measured using an atomic absorption spectrophotometer. The concentration. Repeat the above experimental procedure, according to... The above experiment was conducted with solution concentrations of 150 mg / L, 225 mg / L, 300 mg / L, 530 mg / L, and 600 mg / L, and the experimental data were recorded.

[0068] Based on the experimental data obtained above, BE-LCS-SH will be applied to wastewater... The adsorption capacity and BE-LCS-SH for wastewater The adsorption efficiency of the thiolated cellulose / bentonite nanocomposite was calculated. The adsorption capacity and the effect of thiolized cellulose / bentonite nanocomposites on The formula for calculating the adsorption efficiency is as follows:

[0069]

[0070] Adsorption efficiency (%) =

[0071] in: express Initial concentration (mg / L); Represents time t Concentration (mg / L); The adsorption amount (mg / g) of the adsorbent at time t is represented; V represents the volume of the solution; and m represents the mass (g) of Cd adsorbed.

[0072] 3. BE-LCS-SH treatment of cadmium-contaminated wastewater

[0073] 3.1 Dosage in wastewater Effect of adsorption efficiency

[0074] The effects of adding five materials on wastewater The effect of adsorption efficiency Figure 2 As shown. The specific experimental conditions are: The initial concentration was 450 mg / L, the temperature was 40℃, the time was 4 h, and the material dosage gradient was: 0.05 g, 0.08 g, 0.10 g, 0.15 g, 0.20 g.

[0075] from Figure 2 The adsorption efficiencies of several materials for cadmium can be observed. Under different dosages, BE-LCS-SH showed superior adsorption performance compared to the other four materials. At a dosage of 0.10g, the adsorption efficiencies of BE-LCS-SH were 75.03%, BE-SH was 63.86%, and LCS-SH was 49.16%. The adsorption efficiencies of BE-LCS-SH were 11.17% and 25.87% higher than those of BE-SH and LCS-SH, respectively.

[0076] The dosage of BE-LCS-SH in wastewater The effect of adsorption efficiency, such as Figure 3 As shown, from Figure 3 It can be seen that when the dosage of BE-LCS-SH is less than 0.10g, the effect of BE-LCS-SH on wastewater decreases with increasing dosage. The adsorption efficiency increases sharply, but the upward trend begins to slow down after the dosage exceeds 0.10g. At lower dosages, there are fewer adsorption sites, and as the dosage increases, more active sites appear, leading to higher adsorption efficiency. Furthermore, at a dosage of 0.10g, the adsorption efficiency is 75.03%, and further increases in adsorbent dosage do not result in a significant increase, indicating that 0.10g is the optimal dosage of adsorbent.

[0077] 3.2 Five materials at different concentrations Performance of adsorption capacity in solution

[0078] Thiol-modified cellulose / bentonite nanocomposites at different concentrations The adsorption capacity in solution is expressed as follows Figure 4 As shown. Five materials at different concentrations The adsorption capacity in solution is expressed as follows Figure 5 As shown.

[0079] Depend on Figure 4 The results show that the thiolized cellulose / bentonite nanocomposite material is effective against different concentrations. Aqueous solutions all exhibit good adsorption capacity. When the concentration of the solution is below 450 mg / L, as... The adsorption capacity showed an increasing trend with increasing concentration, indicating that... When the solution concentration is below 450 mg / L, the adsorption sites on the surface of the composite material are not saturated, and the adsorbent has excess adsorption capacity, i.e., BE-LCS-SH has insufficient adsorption capacity. It exhibits good treatment performance for wastewater with concentrations below 450 mg / L. The adsorption capacity of BE-LCS-SH reached its peak at a solution concentration of 450 mg / L, with an adsorption capacity of 121.8575 mg / g. When the solution concentrations are 530 mg / L and 600 mg / L, the adsorption capacities of the adsorbent are 122.4431 mg / g and 122.3250 mg / g, respectively. When the solution concentration exceeds 450 mg / L, the adsorption capacity of the adsorbent no longer shows a significant increase, and the curve approaches a straight line, indicating that the adsorption capacity of the adsorbent is limited. The solution reached saturation at a concentration of 450 mg / L, indicating that all active sites on the thiolated cellulose / bentonite nanocomposite were saturated. Occupied. Explanation. The treatment effect is optimal when the solution concentration is 450 mg / L, and there is no problem of excessive adsorbent capacity.

[0080] Depend on Figure 5 The results show that, under the same conditions, the adsorption capacity curve of BE-LCS-SH is consistently above that of the other four materials. When the solution concentration was 450 mg / L, the adsorption capacities of BE-LCS-SH were 124.85 mg / g, BE-SH was 112.69 mg / g, and LCS-SH was 95.43 mg / g; the adsorption capacities of BE were 103.88 mg / g and LCS-SH was 74.44 mg / g. This indicates that BE-LCS-SH, compared to the other four materials, showed better adsorption capacity for substances containing […]. Wastewater exhibits a higher adsorption capacity, and BE-LCS-SH has a richer number of active adsorption sites than bentonite, thiolated bentonite, cellulose, and thiolated cellulose.

[0081] 3.3 The effect of pH value on BE-LCS-SH adsorption wastewater Effect of adsorption efficiency

[0082] pH value affects the pH value of BE-LCS-SH adsorption wastewater The effect of adsorption efficiency is as follows Figure 6 As shown, the specific experimental conditions were: BE-LCS-SH dosage was 0.08g. The initial concentration was 450 mg / L, the temperature was 40℃, and the time was 4 hours. Figure 6The results show that as the pH value increased from 3 to 7, the adsorption efficiency rose from 45.62% to 65.1%. When the pH value increased from 3 to 6, the adsorption efficiency rose from 45.62% to 54.16%, showing a relatively stable upward trend. However, when the pH value increased from 6 to 7, the adsorption efficiency increased rapidly due to the higher pH. The conversion to cadmium precipitate causes a sudden change in adsorption efficiency. Therefore, pH 6 is the optimal pH for adsorption.

[0083] 3.4 Effect of temperature on BE-LCS-SH adsorption wastewater Effect of adsorption efficiency

[0084] The effect of temperature on BE-LCS-SH adsorption wastewater The effect of adsorption efficiency is as follows Figure 7 As shown, the specific experimental conditions were: BE-LCS-SH dosage was 0.10g. The initial concentration was 450 mg / L, the pH was 6, and the time was 4 hours. Figure 7 The results show that as the temperature rises, BE-LCS-SH has an effect on wastewater... The adsorption efficiency showed an increasing trend, rising from 33.87% to 54.16% between 30℃ and 40℃. The increasing trend slowed down after 40℃, possibly due to the wastewater... As the concentration decreases, the upward trend in adsorption efficiency is reduced. Therefore, 40℃ was selected as the optimal adsorption temperature.

[0085] 3.5 Effect of adsorption time on BE-LCS-SH adsorption of wastewater Effect of adsorption efficiency

[0086] Adsorption time for BE-LCS-SH adsorption of wastewater The effect of adsorption efficiency is as follows Figure 8 As shown. By Figure 8 The results show that the adsorption efficiency rapidly increases before 120 minutes, reaching near its peak at 120 minutes (54.16%). The increase in adsorption efficiency then slows down after 120 minutes, reaching 56.87% at 180 minutes. After 180 minutes, the adsorption efficiency begins to decline, reaching 56.41% at 480 minutes. Throughout the adsorption cycle, the adsorption efficiency first increases and then decreases, indicating that increasing the time is detrimental to the adsorption of wastewater by BE-LCS-SH. Therefore, the optimal adsorption time was chosen to be 120 min.

[0087] Application Example 2: This application example provides the application of the thiolated cellulose / bentonite nanocomposite material prepared in the examples in the treatment of cadmium-contaminated soil. The application includes the following steps:

[0088] 1. Preparation of Cd(II)-containing soil

[0089] Use CdNO3 to prepare An aqueous solution containing An aqueous solution was added to an uncontaminated soil sample, mixed thoroughly, and a soil sample with a cadmium content of 11 mg / kg was prepared. The prepared soil was then dried for later use.

[0090] 2. Treatment of Cadmium in Soil Using Thioyl Cellulose / Bentonite Nanocomposites

[0091] Take 250g of the prepared cadmium-containing soil into a beaker, and add BE-LCS-SH at a mass ratio of 1%, mixing thoroughly. Add distilled water to the mixed beaker to maintain the soil moisture content at 25%. The treated soil sample is stored at room temperature for remediation over a period of 20 days. Samples are taken on days 2, 5, 10, 15, and 20 of the remediation process. The soil samples are subjected to TCLP extraction of cadmium. The extract is filtered through a 0.2 μm filter membrane, and the concentration of cadmium in the extract is measured using an atomic absorption spectrophotometer. The concentration was determined and the data recorded. A control experiment was conducted following the same steps as the experimental group, except that no adsorbent was added to the soil sample; all other experimental procedures and conditions were identical.

[0092] Based on the experimental data obtained above, the adsorption efficiency of thiolated cellulose / bentonite nanocomposite materials for cadmium in soil was calculated. The formula for calculating the passivation efficiency is as follows:

[0093] Passivation efficiency = (1- )×100%

[0094] Where: M represents the content of the heavy metal cadmium in the soil after passivation. The value represents the cadmium content in the control group.

[0095] 3. Thiol-modified cellulose / bentonite nanocomposite materials for remediation of cadmium heavy metal in soil

[0096] 3.1 Passivation effect of thiolated cellulose / bentonite nanocomposite material on remediation of heavy metal cadmium in soil

[0097] The passivation efficiency of thiolated cellulose / bentonite nanocomposites in soil remediation is as follows: Figure 9 As shown, the passivation efficiencies of BE-LCS-SH, BE-SH, and BE for cadmium in soil are as follows: Figure 10 As shown.

[0098] Figure 9The data shows the change in the remediation efficiency of thiolated cellulose / bentonite nanocomposite for cadmium in soil within a passivation cycle. It can be seen that the remediation efficiency shows an upward trend within one cycle, indicating that BE-LCS-SH can continuously immobilize cadmium in the soil during the 20-day treatment cycle. On day 2, the remediation efficiency rapidly increased from 0 to 45.97%, possibly due to the high cadmium concentration in the soil at the initial stage of adsorption, resulting in abundant adsorption sites on the adsorbent material and thus a rapid increase in adsorption efficiency. From day 2 onwards, as cadmium in the soil is immobilized, the increase in adsorption efficiency slows down, but still maintains a high upward trend. By day 10, the passivation efficiency reached 68.23%, indicating that most of the cadmium in the soil was fixed. From day 10 onwards, the passivation efficiency of BE-LCS-SH for cadmium in the soil increased slowly, increasing from 68.23% to 71.64% within 10 days. This suggests that as the concentration of cadmium in the soil decreases and the adsorption sites on BE-LCS-SH are bound, the increase in adsorption efficiency is no longer significant. Considering both time cost and remediation efficiency, the remediation effect of 71.64% at 20 days is considered optimal. Within one passivation cycle, the thiolated cellulose / bentonite nanocomposite material has a good remediation effect on cadmium in the soil, effectively fixing 71.64% of the heavy metal cadmium in the soil.

[0099] Depend on Figure 10 It can be seen that the passivation efficiency of several materials for cadmium approaches its peak on day 10, and the passivation efficiency no longer increases significantly after 10 days. At 10 days, the passivation efficiency of BE-LCS-SH is 68.23%; that of BE-SH is 62.86%; and that of BE is 26.53%. The passivation efficiency of thiolized bentonite and the composite material is significantly higher than that of bentonite alone. Furthermore, throughout the entire passivation period, the passivation efficiency of BE-LCS-SH for cadmium in soil is consistently higher than that of BE-SH. These results indicate that BE-LCS-SH performs superiorly in the remediation of heavy metal cadmium in soil.

[0100] 3.2 Effects of thiolated cellulose / bentonite nanocomposites on enzyme activity in soil

[0101] The effects of BE-LCS-SH on catalase activity in soil, such as Figure 11 As shown, the effect of BE-LCS-SH on urease activity in soil is as follows: Figure 12 As shown, the effect of BE-LCS-SH on dehydrogenase activity in soil is as follows: Figure 13As shown in the figure above, the results indicate that BE-LCS-SH exhibits a good promoting effect on the activities of catalase, urease, and dehydrogenase in the soil within one passivation cycle. This is because the lignocellulose in BE-LCS-SH has a loose and porous structure that can improve soil aeration and water conductivity, and its organic matter and organic carbon content can promote enzyme metabolism, thereby enhancing enzyme activity.

[0102] 3.3 Effects of thiolated cellulose / bentonite nanocomposites on soil physicochemical properties

[0103] The effects of BE-LCS-SH on soil physicochemical properties are shown in Table 2.

[0104] Table 2: Effects of BE-LCS-SH on soil physicochemical properties

[0105]

[0106] As shown in Table 2, due to the strong buffering capacity of soil, BE-LCS-SH had no significant effect on soil pH and cation exchange capacity. Furthermore, compared to the control group, BE-LCS-SH slowed the loss of organic phosphorus from the soil and did not cause serious damage to the soil environment. After BE-LCS-SH remediation, the cadmium content in the soil decreased from 11 mg / kg to 3.11 mg / kg, indicating effective cadmium fixation. The organic matter content of the soil increased from 10.16 g / kg to 15.23 g / kg, effectively increasing soil nutrient availability.

[0107] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing thiolated cellulose / bentonite nanocomposites by high-speed shearing, wherein the composite material is composed of thiolated cellulose and bentonite; The thiol-modified cellulose is rapidly intercalated into the thiol-modified bentonite sheet structure via a high-speed shearing method; the mass ratio of 3-mercaptopropyltrimethoxysilane to the mass of cellulose and bentonite is 2:1:1, with the mass unit being g; The specific preparation method includes the following steps: a. Mix cellulose with distilled water and shear at high speed to obtain a cellulose suspension; b. Mix bentonite and distilled water, and shear at high speed to obtain a bentonite suspension; c. Mix the above cellulose suspension and bentonite suspension, add 3-mercaptopropyltrimethoxysilane to the mixture, shear at high speed, centrifuge, wash the obtained solid with distilled water and dichloromethane at least three times, and dry to obtain thiolized cellulose / bentonite nanocomposite material.

2. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the mass ratio of cellulose to distilled water in step a is 1:38, with mass units in g and volume units in mL.

3. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the high-speed shearing speed in steps a and b is 13500 rpm and the shearing time is 5 min.

4. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the mass ratio of bentonite to distilled water in step b is 1:38, with mass units in g and volume units in mL.

5. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the high-speed shearing rotation speed in step c is 13500 rpm and the shearing time is 15 min.

6. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the centrifugation speed in step c is 4000 r / min and the time is 5 min.

7. The method for preparing thiolized cellulose / bentonite nanocomposite materials by high-speed shearing as described in claim 1, wherein the drying in step c is vacuum drying, the drying temperature is 60°C, and the drying time is 12 h.

8. The application of the material prepared by the high-speed shearing method for preparing thiolized cellulose / bentonite nanocomposites as described in claim 1 in the treatment of cadmium pollution.

Images