Inorganic modified sodium-based stripped montmorillonite for adsorbing and removing heavy metal arsenic in mining area wastewater and preparation method of inorganic modified sodium-based stripped montmorillonite

Abstract

The invention discloses inorganic modified sodium-based stripped montmorillonite for adsorbing and removing arsenic in mining area wastewater and a preparation method of the inorganic modified sodium-based stripped montmorillonite, and belongs to the technical field of environmental functional materials and wastewater treatment. Aiming at the characteristics of high acidity and complex components of arsenic-containing wastewater in the Guangxi mining area, the method comprises the following steps: firstly, efficiently stripping natural sodium bentonite (BT) by utilizing a microwave hydrothermal-ultrasonic synergistic method, and remarkably increasing the specific surface area and active sites of the natural sodium bentonite to obtain stripped bentonite (BTex); then, BTex and cellulose nanofibers (CNF-C) with the surfaces rich in carboxyl are compounded under the microwave condition, and the CNF-C / BTex composite material is prepared. The material combines the good adsorption performance of BTex on heavy metals and the three-dimensional network skeleton advantages of CNF-C, and has the advantages of large adsorption capacity, fast dynamics, wide pH adaptation range (3-7) and the like on arsenic pollutants. The preparation process is simple, efficient, low in cost and environmentally friendly, and an efficient and practical new technical scheme is provided for treatment of arsenic pollution in Guangxi mining areas.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials technology, specifically to a highly efficient adsorption material for treating heavy metal polluted wastewater, particularly an inorganic modified sodium-based exfoliated montmorillonite adsorption material designed and developed for acidic arsenic-containing wastewater from mining areas in Guangxi, and its preparation method. Background Technology

[0002] Guangxi mining areas are an important non-ferrous metal production base in my country, and long-term mining activities have generated a large amount of acidic mine wastewater. This type of wastewater has a low pH value and contains high concentrations of heavy metal ions such as arsenic (As), lead (Pb), and cadmium (Cd), forming complex compound pollution. Among them, arsenic mainly exists in the form of arsenate and arsenite anions, which are extremely toxic and carcinogenic, posing a significant challenge to environmental remediation. Therefore, developing efficient and economical arsenic pollution remediation technologies is of urgent practical significance.

[0003] Adsorption is considered an effective method for treating low-concentration arsenic-containing wastewater due to its simple operation and relatively low cost. Montmorillonite, with its layered structure, strong cation exchange capacity, abundant reserves, and low cost, has been widely studied for heavy metal adsorption. However, natural montmorillonite has strong interlayer forces and a limited specific surface area, resulting in insufficient adsorption capacity and selectivity for arsenic ions. Exfoliation treatment to increase interlayer spacing and specific surface area is key to improving its adsorption performance. Traditional exfoliation methods, such as single ultrasonic methods, are time-consuming and energy-intensive, and their efficiency needs improvement. Currently, a microwave hydrothermal-ultrasound synergistic method can efficiently exfoliate montmorillonite.

[0004] Carboxylated cellulose nanofibers (CNF-C), derived from natural cellulose, possess advantages such as biodegradability, environmental friendliness, large specific surface area, and rich surface carboxyl groups (-COOH), making them excellent composite matrix materials. Combining CNF-C with exfoliated montmorillonite is expected to utilize the three-dimensional network structure of CNF-C to disperse and stabilize montmorillonite nanosheets, while simultaneously enhancing the adsorption performance for arsenic through the potential interaction between CNF-C surface carboxyl groups and arsenate groups.

[0005] Therefore, if a material can be designed that retains the high adsorption activity of montmorillonite for arsenic while utilizing the porous network structure of CNF-C to achieve uniform dispersion of active components and integral material molding, and endows the material with good water permeability and easy recyclability, it is expected to develop a new type of high-efficiency and easy-to-operate adsorption material suitable for the treatment of arsenic-containing wastewater in mining areas. This would have significant theoretical value and application prospects for promoting the advancement of arsenic-containing heavy metal wastewater treatment technology. Currently, there are no reports on the use of CNF-C combined with inorganically modified sodium-based exfoliated montmorillonite for the specific adsorption of arsenic. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing montmorillonite-based adsorbent materials, such as limited arsenic adsorption performance, poor recyclability, and insufficient stability under acidic conditions. It provides a carboxylated cellulose nanofiber / sodium-based exfoliated montmorillonite composite adsorbent material (CNF-C / BTex) with excellent adsorption performance, stable structure, reusability, and suitability for acidic environments, as well as its preparation method. This material is particularly effective against arsenic pollution in acidic mine wastewater, combining the advantages of high-efficiency adsorption and convenient operation.

[0007] Sodium-based montmorillonite possesses certain adsorption properties for heavy metals. After exfoliation, its interlayer spacing and specific surface area increase, further enhancing its adsorption performance for heavy metals. Furthermore, carboxylated cellulose nanofibers (CNF-C) are rich in carboxyl groups on their surface, exhibiting excellent mechanical properties. They can serve as a three-dimensional framework material for composite materials, combining with BTex to form a carboxylated cellulose nanofiber / sodium-based exfoliated montmorillonite (CNF-C / BTex) composite material. This invention demonstrates excellent adsorption performance for arsenic, a heavy metal found in Guangxi mining areas. It is a novel, specific adsorbent with a short reaction time, simple and efficient process, no need for high-temperature calcination, and convenient post-processing, making it suitable for industrialization.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater includes the following steps:

[0010] (1) Sodium-based montmorillonite (BT) was added to a mixed solvent of ultrapure water and anhydrous ethanol and stirred to form a homogeneous suspension. The suspension was then subjected to hydrothermal treatment in a microwave solid-liquid phase extraction synthesizer. The rapid bulk heating of the microwave and the intercalation effect of ethanol were used to weaken the interlayer forces of montmorillonite. Subsequently, the microwave-treated mixture was ultrasonically dispersed to further exfoliate the montmorillonite layers. Finally, the exfoliated slurry was dried and ground in a vacuum drying oven to obtain sodium-based exfoliated montmorillonite (BTex) with a high specific surface area.

[0011] (2) The BTex obtained in step (1) and CNF-C are mixed in ultrapure water. After the mixture is homogeneous, the mixed solution is placed in a microwave solid-liquid phase extraction synthesizer for hydrothermal treatment. CNF-C and BTex are tightly bound together through physical entanglement, hydrogen bonding and other forces. After the reaction is completed, the final product CNF-C / BTex composite adsorbent material is obtained by solid-liquid separation, drying in a vacuum drying oven and grinding.

[0012] To further achieve the purpose of this invention, as a preferred technical solution, in step (1), the volume ratio of ultrapure water to anhydrous ethanol is 1:1 to 1:3; the microwave solid-liquid phase extraction synthesizer is set with the following parameters: power 300 to 700W, temperature 30 to 80℃, and reaction time 0.5 to 4h.

[0013] As a preferred technical solution, in step 1), the ultrasonic intensity of the ultrasonic disperser is set to 50-100%, and the ultrasonic time is 0.5-4h; the vacuum drying temperature is 40-90℃, and the drying time is 2-24h.

[0014] As a preferred technical solution, in step 2), the mass ratio of sodium-based exfoliated montmorillonite (BTex) to carboxylated cellulose nanofibers (CNF-C) is 1:1 to 1:3.

[0015] As a preferred technical solution, in step 2), the settings of the microwave solid-liquid phase extraction synthesizer are as follows: power 300-700W, temperature 30-80℃, reaction time 0.5-4h; temperature of the vacuum drying oven 40-90℃, drying time 0.5-12h.

[0016] An inorganic modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater is prepared by the above method. The composite adsorbent material has strong adsorption performance, good stability, and can be recycled multiple times.

[0017] The inorganic modified sodium-based exfoliated montmorillonite is used for the adsorption and removal of arsenic pollutants in water, especially in acidic arsenic-containing wastewater from mining areas in Guangxi.

[0018] Compared with the prior art, the present invention has the following significant advantages and beneficial effects:

[0019] 1. Simple and efficient preparation process: The "microwave-hydrothermal-ultrasound synergistic" exfoliation technology is adopted. Microwaves are first used to promote ethanol intercalation and thermal expansion, and then ultrasonic cavitation is used for complete exfoliation. This process is highly efficient, energy-saving, and significantly increases the specific surface area of ​​montmorillonite. Subsequent microwave-assisted compounding is carried out, which is fast and uniform, avoiding the disadvantages of traditional long-term stirring.

[0020] 2. Synergistic enhancement of adsorption performance: BTex provides the main adsorption sites and ion exchange capacity. The three-dimensional network structure of CNF-C prevents the aggregation of BTex sheets, increases the contact area with pollutants, and the carboxyl groups on its surface may also coordinate with arsenate, producing a synergistic adsorption effect of "1+1>2".

[0021] 3. Strong environmental adaptability: The composite material maintains a high removal rate of arsenic (adsorption performance higher than 90%) within a wide pH range (1-5), making it particularly suitable for treating acidic wastewater from mining areas in Guangxi, and it has a wide range of applications.

[0022] 4. Good structural stability and recyclability: The material has strong acid resistance and oxidation resistance. After multiple adsorption-desorption cycles, its adsorption performance decay rate is low (the adsorption rate remains above 85% after 5 cycles), which enables multiple cycles and reduces operating costs.

[0023] 5. Green economy and easy to promote: The main raw materials, montmorillonite and cellulose, are widely available, inexpensive, and environmentally friendly. The preparation process is simple, requiring no complex equipment or harsh conditions, conforming to the concepts of green chemistry and sustainable development, and has good prospects for industrialization. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation process of the CNF-C / BTex adsorbent material obtained in Example 3 of the present invention.

[0025] Figure 2 This is the X-ray diffraction pattern of the CNF-C / BTex adsorbent material prepared in Example 3 of the present invention.

[0026] Figure 3 The Fourier transform infrared spectrum of the CNF-C / BTex adsorbent material prepared in Example 3 of this invention is shown.

[0027] Figure 4 This is an electron microscope image of the CNF-C / BTex adsorbent material prepared in Example 3 of this invention.

[0028] Figure 5 This is a graph showing the adsorption performance of the CNF-C / BTex adsorbent material prepared in Example 3 of this invention for heavy metal arsenic under different pH conditions.

[0029] Figure 6 These are images showing the adsorption-desorption cycle performance of the CNF-C / BTex adsorbent material prepared in Example 3 of this invention for the heavy metal arsenic. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Example 1:

[0032] (1) Measure approximately 250 mL of ultrapure water and 250 mL of anhydrous ethanol (volume ratio 1:1) and mix them in a beaker. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 300 W, the temperature to 30 °C, and react for 0.5 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser, sonicating it at 50% intensity for 1 h. Dry the ultrasonicated slurry in a vacuum drying oven at 40 °C for 6 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0033] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 1.0g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 300W, the temperature to 30℃, and react for 0.5h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 40℃ for 0.5h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0034] Example 2

[0035] (1) Measure approximately 250 mL of ultrapure water and 375 mL of anhydrous ethanol (volume ratio 1:1.5) into a beaker and mix. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 450 W, the temperature to 45 °C, and react for 0.8 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser, sonicating it at 60% intensity for 1 h. Dry the ultrasonicated slurry in a vacuum drying oven at 50 °C for 9 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0036] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 1.5g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 450W, the temperature to 45℃, and react for 1h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 50℃ for 1.5h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0037] Example 3

[0038] (1) Measure approximately 250 mL of ultrapure water and 500 mL of anhydrous ethanol (volume ratio 1:2) into a beaker and mix. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 600 W, the temperature to 60 °C, and react for 1.0 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser, sonicating it at 70% intensity for 1.5 h. Dry the ultrasonicated slurry in a vacuum drying oven at 60 °C for 12 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0039] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 2.0g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 600W, the temperature to 60℃, and react for 2h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 60℃ for 2h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0040] Example 4

[0041] (1) Measure approximately 250 mL of ultrapure water and 600 mL of anhydrous ethanol (volume ratio 1:2.2) into a beaker and mix. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 600 W, the temperature to 65 °C, and react for 2.0 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser for ultrasonic treatment at 80% intensity for 2 h. Dry the ultrasonicated slurry in a vacuum drying oven at 70 °C for 15 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0042] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 2.3g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 600W, the temperature to 65℃, and react for 2.5h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 70℃ for 6h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0043] Example 5

[0044] (1) Measure approximately 250 mL of ultrapure water and 650 mL of anhydrous ethanol (volume ratio 1:2.6) into a beaker and mix. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 650 W, the temperature to 70 °C, and react for 3.0 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser, sonicating it at 90% intensity for 3 h. Dry the ultrasonicated slurry in a vacuum drying oven at 80 °C for 20 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0045] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 2.5g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 650W, the temperature to 70℃, and react for 3h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 80℃ for 10h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0046] Example 6

[0047] (1) Measure approximately 250 mL of ultrapure water and 750 mL of anhydrous ethanol (volume ratio 1:3) into a beaker and mix. Add 8 g of sodium bentonite (BT) and stir with a glass rod for 30 min to initially disperse it. Transfer the suspension to a three-necked flask in a microwave reactor, set the power to 700 W, the temperature to 80 °C, and react for 4.0 h. After the reaction is complete, pour the mixture into a beaker and place it in an ultrasonic disperser for ultrasonic treatment at 100% intensity for 4 h. Dry the ultrasonicated slurry in a vacuum drying oven at 90 °C for 24 h, grind it, and pass it through a 200-mesh sieve to obtain exfoliated bentonite (BTex).

[0048] (2) Weigh 1.0g of the BTex powder prepared in step (1) and place it in a three-necked flask. Weigh 3.0g of dried CNF-C powder, add it to the flask, add 50mL of ultrapure water, and stir until homogeneous. Transfer the mixture to a microwave synthesizer, set the power to 700W, the temperature to 80℃, and react for 4h. After the reaction is complete, centrifuge to separate the solid, dry the solid product in a vacuum drying oven at 90℃ for 12h, grind it through a 200-mesh sieve, and obtain the CNF-C / BTex composite adsorbent material.

[0049] The BTex / CNF-C composite adsorbent material synthesized in Example 3 above, which can be used to adsorb and remove heavy metal arsenic from mining wastewater, was characterized and its performance was tested. The results are as follows:

[0050] Figure 2 The image shows the X-ray diffraction pattern of the CNF-C / BTex prepared in Example 3. Figure 1 As shown, microwave-ultrasound synergistic exfoliation successfully shifted the (001) plane diffraction peak of sodium bentonite (BTex) from 8.0° (d = 1.26 nm) to 6.5° (d = 1.61 nm), significantly expanding the interlayer spacing and creating a channel for trivalent arsenic (As(III)) molecules to enter the interlayer domain. The exfoliated BTex still retained the characteristic diffraction peaks of montmorillonite and quartz, located at 22.1° and 61.8° (2θ), respectively, with the quartz characteristic diffraction peak being more pronounced, indicating that BT had undergone delamination after exfoliation. The diffraction pattern of carboxylated cellulose nanofibers (CNF-C) showed typical broadened cellulose diffraction peaks at 22.6° and 34.7°, corresponding to the (002) and (004) crystal planes of CNF-C, respectively, confirming its nano-sized and low-crystallinity characteristics and exposing abundant surface carboxyl active sites. The XRD pattern of the CNF-C / BTex composite material shows that the intensity of the (001) peak of BTex is significantly weakened and broadened, while the characteristic peak of CNF-C is also present but with reduced intensity. This indicates that CNF-C is effectively intercalated between the exfoliated layers of BTex, forming a more loosely structured and disordered three-dimensional composite network. This structural evolution synergistically increases the specific surface area and accessibility of the material. Combined with the interlayer active sites of BTex and the surface carboxyl groups of CNF-C, they together constitute a multi-scale spatial and multi-functional system for highly efficient adsorption of As(III).

[0051] Figure 3 The image shows the Fourier transform infrared (FTIR) spectrum of the CNF-C / BTex adsorbent material prepared in Example 3. FTIR analysis indicates that the exfoliated sodium bentonite (BTex) exhibits high spectral density at 3620 cm⁻¹. -1 The characteristic peak of Al-OH stretching vibration of montmorillonite structure appears at 1040 cm⁻¹. -1 The peak at 501 cm⁻¹ is the vibrational peak of the Si-O-Si framework. -1 The peak at 1735 cm⁻¹ represents the stretching vibration of Al-O-Si (octahedral aluminum). The broadening of this peak after exfoliation indicates a decrease in the orderliness of the silicon-oxygen tetrahedra. Carboxylated cellulose nanofibers (CNF-C) show a peak at 1735 cm⁻¹. -1 and 1605cm -1 A significant C=O stretching vibration peak appears at this point (corresponding to protonated -COOH and deprotonated -COO, respectively). - (Form), its 3340cm -1 The OH vibration peak is significantly broadened. In the spectrum of the CNF-C / BTex composite material, the Si-O-Si peak of BTex (1040 cm⁻¹) is significantly broadened. -1 ) shifted to a lower wavenumber to 1032cm -1 Furthermore, the peak width is broadened, and the C=O peak of the carboxyl group in CNF-C is (1735 / 1605 cm⁻¹). -1 Redshift and peak shape changes occur, and at 3340cm-1 The OH vibration peaks were significantly enhanced and broadened. These changes confirm that CNF-C successfully constructed a stable composite structure through hydrogen bonding and electrostatic interactions with the silanol and aluminol groups on the BTex sheet surface via carboxyl groups. This structure not only retains the coordination adsorption sites of BTex for As(III), but also introduces a large number of surface carboxyl groups (COOH / -COO) through CNF-C. - It provides additional hydrogen bonding and weak coordination ability, which synergistically enhance the capture and fixation effect of heavy metal As molecules in the composite material over a wide pH range.

[0052] Figure 4 The images show electron microscopy (SEM) images of the CNF-C / BTex adsorbent material prepared in Example 3. The exfoliated BTex exhibits a distinctly loose and fluffy morphology, with significantly reduced sheet thickness and curling and separation, revealing a large specific surface area. The carboxylated cellulose nanofibers (CNF-C) exhibit a highly interwoven three-dimensional nanofiber network structure with fiber diameters ranging from 10 to 100 μm, forming a rich porous framework. SEM images of the CNF-C / BTex composite material clearly show that the exfoliated BTex sheets are successfully encapsulated and anchored within the three-dimensional CNF-C fiber network, with the two interwoven to form a stable "sheet-fiber" composite architecture. This structure effectively prevents the recombination of BTex sheets; the CNF-C network framework provides macroscopic support and creates interconnected hierarchical pores, while the uniformly dispersed BTex nanosheets provide a dense adsorption active interface. This unique composite morphology synergistically increases the material's contact area with trivalent arsenic, optimizes the mass transfer channels, and enhances the efficient capture and fixation of neutral trivalent arsenic through a combination of physical retention by the CNF-C network and surface chemisorption by the BTex sheets.

[0053] Adsorption performance studies of trivalent arsenic under different pH conditions showed that the CNF-C / BTex composite material exhibited pH-dependent and overall excellent adsorption properties. Figure 5 The material exhibits optimal adsorption of trivalent arsenic in a strongly acidic environment (pH 2–3). This is attributed to the fact that under these conditions, arsenic primarily exists as electrically neutral arsenic trioxide molecules (H₃AsO₃), effectively avoiding interaction with the large amounts of H₂O in the solution. +The adsorption of H3AsO3 is competitive, and the protonated hydroxyl groups on the BTex surface and the partially protonated carboxyl groups (-COOH) on CNF-C in the composite material can be strongly bound to H3AsO3 through hydrogen bonds and intermolecular forces. When the pH value rises to the near-neutral and weakly acidic range of 4-7, the adsorption capacity decreases slightly compared to pH=2 but still remains at a high level, indicating that the composite material has effective adsorption capacity over a wide pH range. Under alkaline conditions (pH>7), the adsorption performance decreases significantly, mainly due to the electrostatic repulsion caused by the enhanced negative charge on the BTex surface and the complete deprotonation of the CNF-C carboxyl groups (-COOH). - This reduces the number of hydrogen bond sites. It is worth emphasizing that, across the entire pH range, the adsorption performance of CNF-C / BTex is significantly superior to that of BTex or CNF-C alone, demonstrating the synergistic adsorption effect and pH buffering capacity brought about by the composite structure. Therefore, this material is particularly suitable for treating acidic arsenic-containing wastewater commonly found in mining areas of Guangxi, achieving maximum adsorption efficiency at pH 2.

[0054] A study on the adsorption-desorption cycle performance of trivalent arsenic (As(III)) by a carboxylated cellulose nanofiber / exfoliated sodium bentonite (CNF-C / BTex) composite material showed that the material maintained excellent structural stability and adsorption efficiency even after five consecutive "adsorption-desorption-regeneration" cycles. Figure 6 In each cycle, using a 0.1 mol / L NaOH solution as a desorbent effectively eluted over 90% of the adsorbed arsenic. The material could be regenerated after washing with ultrapure water and drying. After 5 cycles, the composite material retained over 85% of its adsorption capacity for As(III), indicating excellent reusability.

[0055] Furthermore, the adsorption performance of CNF-C / BTex adsorbents prepared in Examples 1-6 for the heavy metal arsenic was compared. As shown in Table 1, the CNF-C / BTex adsorbent prepared in Example 3 exhibited the best adsorption performance for trivalent arsenic. This result is attributed to the optimized combination of preparation parameters in Example 3, which ensured the formation of a structurally stable, large-specific-surface-area three-dimensional porous network system for the CNF-C / BTex adsorbent, enabling the most efficient adsorption of heavy metal arsenic. Therefore, Example 3 was determined to be the optimal construction scheme for this CNF-C / BTex adsorbent.

[0056] The inorganic modified sodium-based montmorillonite (CNF-C / BTex) of this invention is applied to the treatment of high-viscosity crude oil wastewater.

[0057] Table 1. Effects of different adsorbents on heavy metal arsenic (initial concentration 10 mg·L⁻¹) -1 Comparison of adsorption performance

[0058]

Claims

1. A method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater, characterized in that, Includes the following steps: (1) Disperse natural sodium montmorillonite in a mixed solution of pure water / anhydrous ethanol, stir it evenly and then place it in a microwave solid-liquid phase extraction synthesizer to react, so that ethanol molecules can be fully inserted into the interlayer of natural sodium montmorillonite; after the reaction is completed, place the mixed solution of natural sodium montmorillonite in an ultrasonic disperser for ultrasonic dispersion, and then place it in a vacuum drying oven to dry, so as to obtain natural sodium exfoliated montmorillonite (BTex). (2) The natural sodium-based exfoliated montmorillonite (BTex) prepared in step (1) is mixed with carboxylated cellulose nanofibers (CNF-C) in pure water, stirred evenly, and then placed in a microwave solid-liquid phase extraction synthesizer for reaction; after the reaction is completed, it is placed in a vacuum drying oven to dry, and inorganic modified sodium-based exfoliated montmorillonite adsorbent material (CNF-C / BTex) can be obtained.

2. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 1, characterized in that, In step (1), the volume ratio of pure water to anhydrous ethanol is 1:1 to 1:

3. The microwave solid-liquid phase extraction synthesizer is set with the following parameters: power: 300-700W, temperature: 30-80℃, and reaction time: 0.5-4h.

3. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 1, characterized in that, In step (1), the ultrasonic intensity of the ultrasonic disperser is 50-100%, and the ultrasonic time is 0.5-4 hours. The temperature of the vacuum drying oven is 40-90℃, and the drying time is 2-24 hours.

4. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 1, characterized in that, In step (2), the mass ratio of natural sodium-based exfoliated montmorillonite (BTex) to carboxylated cellulose nanofibers (CNF-C) is 1:1 to 1:

3. The microwave solid-liquid phase extraction synthesizer is set with the following parameters: power 300–700 W, temperature 30–80 °C, and reaction time 0.5–4 h. The vacuum drying oven is set with a temperature of 40–90 °C and a drying time of 0.5–12 h.

5. An inorganically modified sodium-based exfoliated montmorillonite prepared by the preparation method according to any one of claims 2 to 4.

6. An application of inorganically modified sodium-based exfoliated montmorillonite as described in claim 5 in the adsorption and removal of arsenic pollutants in water, particularly suitable for treating arsenic-containing wastewater generated in mining areas of Guangxi and similar geological backgrounds.

7. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 5, characterized in that: The pH value of the solution containing the heavy metal ions is 1.0 to 5.

0.

8. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 5, characterized in that: Adsorption equilibrium can be reached in 0.5 to 3 hours.

9. The method for preparing inorganically modified sodium-based exfoliated montmorillonite for adsorbing and removing heavy metal arsenic from mining wastewater according to claim 5, characterized in that: The inorganic modified sodium-based exfoliated montmorillonite can be recycled 5 to 15 times.

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