Preparation method of a blocky inorganic arsenic adsorbent

Abstract

The present invention relates to a preparation method of a bulk inorganic arsenic adsorbent, belonging to the technical field of inorganic arsenic adsorption. A preparation method of a bulk inorganic arsenic adsorbent is as follows: the bamboo slices are processed to obtain a bulk inorganic arsenic adsorbent. Step 1: Take the bamboo slices and completely immerse them into a potassium permanganate solution for the first time. After taking them out, wash them with ultrapure water to obtain an oxidized bamboo slice matrix. Step 2: Immerse the bamboo slice matrix in the potassium permanganate solution for the second time and stir at room temperature. During the stirring process, simultaneously add a ferrous sulfate solution and a strong base solution. Among them, the molar ratio of iron and manganese ions is 1:1; the strong base solution is a sodium hydroxide solution, and the addition amount is 2:1 to 6:1 of the volume ratio with the potassium permanganate solution. After the reaction, age at room temperature, take out the reacted bamboo slice matrix, wash it with ultrapure water and dry it to obtain a high-performance bulk inorganic arsenic adsorbent Fe-Mn-O / MB material.

Description

Technical Field

[0001] The present invention relates to a preparation method of a bulk inorganic arsenic adsorbent, belonging to the technical field of inorganic arsenic adsorption technology. Background Art

[0002] Arsenic pollutants mainly exist in the form of toxic inorganic arsenic. Since the human body cannot metabolize arsenic benignly, it can cause skin, blood vessel, and nervous system diseases as well as cancer. Among many arsenic removal technologies, the adsorption method is generally considered to be one of the most promising methods due to its advantages such as strong scalability, high efficiency, simple operation, low cost, and sustainability. The adsorbent material is the core of the adsorption arsenic removal technology. Iron-manganese bimetallic oxide nanocomposites are considered to be effective adsorbents for removing arsenic due to their good selectivity and synergistic effect. In particular, manganese dioxide has a high oxidation ability and oxidizes As(III) to As(V) in an environmentally friendly way, thereby improving the removal efficiency of As(III).

[0003] However, iron-manganese bimetallic oxide nanoparticles have problems of easy aggregation and difficulty in separating from water during actual application. At the same time, there is a risk that nanoparticle adsorbents may release nanoparticles into the treated water body, which may not only cause potential damage to the ecosystem and human health but also increase the water treatment cost. Therefore, using a porous support material to load nanoparticles to prepare a composite adsorbent is a feasible strategy to solve the problems of nanoparticle aggregation and fixation at the same time. However, the existing support materials still have some disadvantages, such as high cost, high synthetic energy consumption, and use of hazardous chemicals. Therefore, it is crucial to construct an effective adsorbent with excellent performance, high cost-effectiveness, low energy consumption, significant environmental protection advantages, and easy separation. Summary of the Invention

[0004] In order to solve the problems of nanoparticle aggregation and fixation, a preparation method of a bulk inorganic arsenic adsorbent is provided. Nanoscale iron-manganese bimetallic oxides can be in-situ deposited on the surface of waste bamboo slices, which can not only adsorb inorganic arsenic in water through surface active nanoparticles but also recycle the adsorbent through simple filtration for reuse.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] A preparation method of a bulk inorganic arsenic adsorbent is characterized in that the bamboo slices are processed as follows to obtain the bulk inorganic arsenic adsorbent, and the specific steps are as follows:

[0007] Step 1: Take bamboo slices with a thickness of 1.8 - 2.5 mm, completely immerse them in a potassium permanganate solution with a concentration of 0.01 - 0.05 mol / L for 10 - 15 h for the first time, take them out and wash them with ultrapure water to obtain an oxidized bamboo slice matrix;

[0008] Step 2: Immerse the bamboo substrate in a potassium permanganate solution with a concentration of 0.005 - 0.02 mol / L for the second time, stir at room temperature, with a stirring speed of 200 - 550 rpm. During the stirring process, add ferrous sulfate solution and strong base solution simultaneously; among them, the molar ratio of iron to manganese ions is 1:1; the strong base solution is a sodium hydroxide solution with a concentration of 0.4 - 0.6 mol / L, and the addition amount is 2:1 - 6:1 in volume ratio to the potassium permanganate solution; after the reaction, age at room temperature for 1 - 6 h, take out the reacted bamboo substrate, wash it with ultrapure water and dry it to obtain the high-performance bulk inorganic arsenic adsorbent Fe-Mn-O / MB material.

[0009] In Step 1, the oxidation degree of the bamboo surface is controlled by controlling the concentration of the first immersion of potassium permanganate. When the concentration is low, the oxidation ability is insufficient to make the surface of the bamboo substrate rough; when the concentration is high, a large amount of generated manganese dioxide particles will adhere to the surface of the bamboo substrate, hindering the subsequent deposition of iron-manganese bimetallic oxide nanoparticles, thus affecting the performance of adsorbing inorganic arsenic.

[0010] In Step 2, the aggregation thickness of nanoparticles is controlled by controlling the concentration of the second immersion of potassium permanganate (fixing the ratio of manganese ions to iron ions at 1:1 and adjusting the concentration of ferrous sulfate simultaneously); when the concentration is too low, too few particles are generated, which is not enough to completely cover the surface of the bamboo substrate; when the concentration is too high, it will cause thicker nanoparticles to aggregate on the bamboo surface, and the outer layer particles are not firmly combined, and need to be completely washed away in the rinsing step to avoid leakage into the water during the adsorption process, resulting in secondary pollution of the water body. Therefore, increasing the concentration will not improve the adsorption performance and will cause waste of drugs.

[0011] In Step 2, the uniformity of nanoparticle loading on the substrate surface is controlled by controlling the stirring speed: if the stirring speed is too slow, the stirring will be insufficient, resulting in uneven loading of nanoparticles on the substrate surface; if the stirring speed is too fast, the particles on the substrate surface will not adhere sufficiently, and the thickness of the tightly adhered layer will decrease, resulting in a decrease in the amount of active substance adhered and a decrease in the adsorption capacity.

[0012] In Step 2, the occurrence of the precipitation reaction is controlled by controlling the concentration / volume ratio of the strong base solution. The acidity of the solution directly affects the coprecipitation process. If the solution acidity is too strong, the precipitation reaction cannot occur; if the solution alkalinity is too strong, the deposited particles will be too large to form nanoparticles.

[0013] The loading amount is controlled by controlling the aging time: if the time is too short, the loading amount is too small; after the loading sites are saturated, extending the aging time will not increase the loading amount.

[0014] The advantages of the above technical solution are as follows: In step 1, the bamboo is pretreated, and the bamboo is oxidized with a potassium permanganate solution to obtain blocky bamboo slices with a rough surface, changing the smooth fiber wall on the surface of the bamboo slices, and then regulating the growth orientation and distribution degree of the iron-manganese bimetallic oxide on the bamboo slices, thereby improving the adsorption activity of the adsorbent; In step 2, iron-manganese bimetallic oxide nanoparticles are in-situ deposited on the oxidized bamboo slices by the coprecipitation method to obtain a blocky inorganic arsenic adsorbent with high adsorption activity.

[0015] On the basis of the above technical solution, the following improvements are made:

[0016] Further, in step 1, the solid-liquid ratio of the potassium permanganate solution to the bamboo slices is 1:5.

[0017] Further, in step 2, the solid-liquid ratio of the potassium permanganate solution to the bamboo slices is 1:10.

[0018] Further, in step 2, the concentration of the ferrous sulfate solution is 0.005 - 0.02 mol / L.

[0019] Further, in step 2, the volume ratio of the ferrous sulfate solution to the potassium permanganate solution is 1:1, and the volume ratio to the sodium hydroxide solution is 2:1 - 6:1.

[0020] Further, the dropping rate of the ferrous sulfate is 0.10 mL / s, and the dropping rate of the sodium hydroxide is 0.025 mL / s.

[0021] The present invention has the following beneficial effects:

[0022] 1. The preparation method of the present invention has a simple process, low cost, and is environmentally friendly. It can use waste bamboo and iron and manganese metal raw materials with rich reserves to obtain a blocky inorganic arsenic adsorbent with high activity. This blocky inorganic arsenic adsorbent has a macroscopic blocky structure, can be filtered and recovered after adsorption saturation, has high selectivity for inorganic arsenic in a complex hydrochemical environment, and can be recycled and reused to achieve circular utilization.

[0023] 2. The preparation method of the present invention through pre-oxidation treatment, oxidatively etches the smooth fiber surface of the bamboo slices to make it rough, with more attachment sites.

[0024] 3. The preparation method of the present invention tightly combines the bamboo matrix with natural three-dimensional pore structure with iron-manganese bimetallic oxide nanoparticles, effectively improving the phenomenon of aggregation of active nanoparticles, increasing the utilization rate of adsorption active sites, and promoting the full exposure of active components.

[0025] 4. The preparation method of the present invention deposits high-valent manganese ions on the surface of the bamboo matrix through the coprecipitation method, increasing the oxidation performance of the adsorbent and achieving the rapid oxidation of arsenite ions to arsenate ions, thereby improving the removal efficiency of arsenite ions.

[0026] 5. The preparation method of the present invention anchors iron-manganese bimetallic oxide nanoparticles on the surface of massive bamboo biomass through the coprecipitation method, avoiding the leakage of iron ions and manganese ions into the water body during the adsorption process, resulting in secondary pollution, and improving the stability of the adsorbent.

[0027] 6. The present invention can obtain a high-performance massive inorganic arsenic adsorbent material Fe-Mn-O / MB and apply it to the adsorption and removal of inorganic arsenic pollutants in water. This adsorbent has excellent adsorption activity, and the adsorption capacity for arsenite ions and arsenate ions pollutants in water reaches 30 - 50 mg / g. When only considering the adsorption active substances, its adsorption capacity reaches 150 - 200 mg / g; this adsorbent has high selectivity, and the adsorption efficiency for inorganic arsenic in the co-existing anion (Cl - , SiO3 2- , SO4 2- , NO3 - , HCO3 - ) environment is 80 - 100%. When there is HPO4 3- in the water environment, the adsorption efficiency for inorganic arsenic is 60 - 85%; after 5 cycles of regeneration, the adsorption efficiency for inorganic arsenic still remains 80 - 90%. Description of the Drawings

[0028] Figure 1 SEM image of the Fe-Mn-O / MB adsorbent prepared in Example 1;

[0029] Figure 2 Optical picture of the Fe-Mn-O / MB adsorbent prepared in Example 1;

[0030] Figure 3 SEM image of the Fe-Mn-O / MB adsorbent prepared in Comparative Example 1;

[0031] Figure 4 SEM image of Fe-Mn-O prepared in Comparative Example 2;

[0032] Figure 5 SEM image of the MB bamboo slices prepared in Comparative Example 3;

[0033] Figure 6 X-ray diffraction pattern of the Fe-Mn-O / MB adsorbent prepared in Example 1;

[0034] Figure 7Adsorption capacity diagrams of the Fe-Mn-O / MB adsorbents prepared in Example 1 and Comparative Example 1 and the MB bamboo slices prepared in Comparative Example 3 for arsenite ions;

[0035] Figure 8 Adsorption isotherms of the Fe-Mn-O / MB adsorbents prepared in Examples 1, 2, and 3 for arsenite ions;

[0036] Figure 9 Adsorption efficiency diagram of the Fe-Mn-O / MB adsorbent prepared in Example 1 for inorganic arsenic in five recycling and regeneration cycles. Detailed implementation manners

[0037] The following examples in conjunction with the accompanying drawings are only to illustrate the technical solutions recorded in the claims and are not intended to limit the scope of protection of the claims. Example 1

[0038] A preparation method of a blocky inorganic arsenic adsorbent. The blocky inorganic arsenic adsorbent is obtained after the bamboo slices are processed as follows. The specific steps are as follows:

[0039] Step (1): Wash the waste bamboo with deionized water, dry the surface moisture, remove the surface impurities, cut it into bamboo slices with a thickness of 2 mm, take 10 slices (about 2.5 g) and completely immerse them in 12 mL of a potassium permanganate solution with a concentration of 0.01 mol / L for 12 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices, that is, the bamboo slice matrix, and set it aside;

[0040] Step (2): Prepare solutions A, B, and C. Solution A (c(Mn 7+ ) = 0.01 mol / L): Weigh 0.0395 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions; Solution B (c(Fe 2+ ) = 0.01 mol / L): Weigh 0.0695 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min; Solution (c(OH - ) = 0.5 mol / L): Weigh 0.125 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions;

[0041] Step (3): Immerse the 10 bamboo slice matrices obtained after being processed in step (1) in solution A, transfer them to a beaker, and magnetically stir at a speed of 350 rpm. Under the stirring conditions, simultaneously add solution B and solution C. Solution B is added at a dropping rate of 0.10 mL / s, and solution C is added at a dropping rate of 0.025 mL / s. After all the dropping is completed, stop stirring;

[0042] Step (4): Cover the beaker in step (3) with a watch glass and let it stand and age for 3 h. Then take out the bamboo slices and wash them repeatedly with deionized water until the solution does not change color;

[0043] Step (5): The bamboo slices treated in step (4) are freeze-dried at -60°C for 24 h to obtain the bulk Fe-Mn-O / MB adsorbent material. Freeze-drying can maintain the original three-dimensional structure of bamboo (without shrinking due to dehydration), ensuring a large matrix area for nanoparticle attachment; at the same time, it ensures that the interior of the bulk material is porous, facilitating the entry of contaminated water into the interior of the adsorbent. Example 2

[0044] A preparation method of a bulk inorganic arsenic adsorbent, which is obtained by treating bamboo slices as follows. The specific steps are as follows:

[0045] Step (1): Wash the waste bamboo clean, cut it into bamboo slices with a thickness of 1.8 mm, take 12 slices and immerse them completely in 10 mL of a potassium permanganate solution with a concentration of 0.05 mol / L for 10 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices, that is, the bamboo slice matrix, for standby.

[0046] Step (2): Prepare solutions A, B, and C. Solution A (c(Mn 7+ ) = 0.005 mol / L): Weigh 0.0198 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions; Solution B (c(Fe 2+ ) = 0.005 mol / L): Weigh 0.0348 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min; Solution C (c(OH - ) = 0.4 mol / L): Weigh 0.125 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions.

[0047] Step (3): Immerse the 12 bamboo slices treated in step (1) in solution A, transfer them to a beaker, and magnetically stir at a speed of 200 rpm. Under stirring conditions, simultaneously add B at a dropping rate of 0.08 mL / s and add C at a dropping rate of 0.02 mL / s. After all the dropping is completed, stop stirring.

[0048] Step (4): Cover the beaker in step (3) with a watch glass and let it stand for aging for 1 h. Then take out the bamboo slices and wash them repeatedly with deionized water until the solution does not change color.

[0049] Step (5): The bamboo slices treated in step (4) are freeze-dried at -60°C for 20 h to obtain the bulk Fe-Mn-O / MB adsorbent material. Example 3

[0050] A preparation method of a bulk inorganic arsenic adsorbent, which is obtained by treating bamboo slices as follows. The specific steps are as follows:

[0051] Step (1): Clean the waste bamboo, cut it into bamboo slices with a thickness of 2.5 mm, take 8 slices and immerse them completely in 15 mL of potassium permanganate solution with a concentration of 0.03 mol / L for 15 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices for standby.

[0052] Step (2): Prepare solutions A, B, and C. Solution A (c(Mn 7+ ) = 0.02 mol / L): Weigh 0.0593 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions. Solution B (c(Fe 2+ ) = 0.02 mol / L): Weigh 0.1043 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min. Solution C (c(OH - ) = 0.6 mol / L): Weigh 0.125 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions.

[0053] Step (3): Immerse the 8 bamboo slices treated in step (1) in solution A, transfer them to a beaker, and stir magnetically at a speed of 550 rpm. Under the stirring condition, simultaneously add solution B at a dropping rate of 0.12 mL / s and add solution C at a dropping rate of 0.03 mL / s. After all the dropping is completed, stop stirring.

[0054] Step (4): Cover the beaker in step (3) with a watch glass and let it stand for aging for 5 h. Then take out the bamboo slices and wash them repeatedly with deionized water until the solution does not change color.

[0055] Step (5): Freeze-dry the bamboo slices treated in step (4) at -60 °C for 36 h to obtain the bulk Fe-Mn-O / MB adsorbent material. Example 4

[0056] A preparation method of a bulk inorganic arsenic adsorbent. The bamboo slices are processed as follows to obtain the bulk inorganic arsenic adsorbent. The specific steps are as follows:

[0057] Step (1): Clean the waste bamboo, cut it into bamboo slices with a thickness of 2 mm, take 10 slices (about 2.5 g) and immerse them completely in 10 mL of potassium permanganate solution with a concentration of 0.01 mol / L for 13 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices for standby.

[0058] Step (2): Prepare solutions A, B, and C. Solution A (c(Mn 7+ ) = 0.01 mol / L): Weigh 0.0395 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions. Solution B (c(Fe 2+ ) = 0.01 mol / L): Weigh 0.0695 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min. Solution C (c(OH- ) = 0.5 mol / L): Weigh 0.125 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions.

[0059] In step (3), the 10 bamboo slices treated in step (1) are immersed in solution A, transferred to a beaker, and magnetically stirred at a speed of 300 rpm. While stirring, solution B is added at a dropping rate of 0.09 mL / s and solution C is added at a dropping rate of 0.025 mL / s. After all the dropping is completed, stop stirring.

[0060] In step (4), cover the beaker in step (3) with a watch glass and let it stand for aging for 6 h. Then take out the bamboo slices and wash them repeatedly with deionized water until the solution does not change color.

[0061] In step (5), the bamboo slices treated in step (4) are freeze-dried at -60 °C for 24 h to obtain the bulk Fe-Mn-O / MB adsorbent material. Example 5

[0062] A preparation method of a bulk inorganic arsenic adsorbent. The bulk inorganic arsenic adsorbent is obtained after the following treatment of bamboo slices. The specific steps are as follows:

[0063] In step (1), wash the waste bamboo clean, cut it into bamboo slices with a thickness of 2.5 mm, take 8 slices and immerse them completely in 15 mL of a potassium permanganate solution with a concentration of 0.02 mol / L for 14 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices for standby.

[0064] In step (2), prepare solutions A, B, and C. Solution A (c(Mn 7+ ) = 0.02 mol / L): Weigh 0.0593 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions. Solution B (c(Fe 2+ ) = 0.02 mol / L): Weigh 0.1043 g of ferrous sulfate heptahydrate, dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min. Solution C (c(OH - ) = 0.6 mol / L): Weigh 0.125 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions.

[0065] In step (3), the 8 bamboo slices treated in step (1) are immersed in solution A, transferred to a beaker, and magnetically stirred at a speed of 400 rpm. While stirring, solution B is added at a dropping rate of 0.011 mL / s and solution C is added at a dropping rate of 0.025 mL / s. After all the dropping is completed, stop stirring.

[0066] In step (4), cover the beaker in step (3) with a watch glass and let it stand for aging for 4 h. Then take out the bamboo slices and wash them repeatedly with deionized water until the solution does not change color.

[0067] Step (5): The bamboo slices treated in step (4) are freeze-dried at -60°C for 48 h to obtain the bulk Fe-Mn-O / MB adsorbent material.

[0068] The inorganic arsenic adsorption performance test of the obtained Fe-Mn-O / MB composite material is carried out through the following steps:

[0069] (1) Fill the prepared composite adsorbent material into a fixed-bed column, and pass a certain concentration of arsenite solution or arsenate solution through the column and reflux in a bottom-up manner. Adjust the flow rate of the inorganic arsenic solution through the column by a peristaltic pump.

[0070] (2) Sample 8 - 15 times at intervals of 0 - 350 min, each time sampling 1 - 3 mL. Measure the arsenic concentration in the water sample using an atomic fluorescence spectrometer and fit it with a second-order kinetic adsorption model to evaluate the adsorption kinetics.

[0071] (3) In the range of initial inorganic arsenic concentration of 1 - 20 mg / L, after refluxing through the adsorption column for 350 min, sample 1 - 3 mL. Measure the arsenic concentration in the water sample using an atomic fluorescence spectrometer and fit it with the Langmuir isotherm model to evaluate its isothermal adsorption curve and calculate the adsorption capacity.

[0072] (4) Add co-existing anions to the initial inorganic arsenic solution. After refluxing through the adsorption column for 350 min, sample 1 - 3 mL. Measure the arsenic concentration in the water sample using an atomic fluorescence spectrometer to evaluate its selective adsorption performance.

[0073] (5) Collect the Fe-Mn-O / MB composite material saturated with adsorbed inorganic arsenic, then elute it with a regeneration eluent (0.5 mol / L NaOH solution, 100 mL) for 8 h, followed by rinsing with deionized water and freeze-drying, and then use it for the next cycle.

[0074] Comparative Example 1

[0075] Prepare a comparative adsorbent material through the following steps:

[0076] Step (1): Wash the waste bamboo clean, cut it into bamboo slices with a thickness of 2 mm, and wash it three times with ultrapure water to obtain the bamboo slices for standby.

[0077] Step (2): Prepare solutions A, B, and C. Solution A: Weigh 0.0395 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions. Solution B: Weigh 0.0695 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min. Solution C: Weigh 0.15 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions.

[0078] Step (3): The 10 bamboo slices processed in step (1) are immersed in solution A, transferred to a beaker, and magnetically stirred at a speed of 200 rpm. While stirring, B is added at a dropping rate of 0.10 mL / s, and C is added at a dropping rate of 0.025 mL / s. After all the dropping is completed, the stirring is stopped;

[0079] Step (4): After covering the beaker in step (3) with a watch glass and allowing it to stand and age for 3 h, the bamboo slices are taken out and repeatedly washed with deionized water until the solution does not change color;

[0080] Step (5): The bamboo slices processed in step (4) are freeze-dried at -60 °C for 24 h to obtain the bulk Fe-Mn-O / MB adsorbent material.

[0081] Comparative Example 2

[0082] The comparative adsorbent material is prepared through the following steps:

[0083] Step (1): Prepare solutions A, B, and C. Solution A: Weigh 0.0395 g of potassium permanganate and dissolve it in 25 mL of deionized water under stirring conditions; Solution B: Weigh 0.0695 g of ferrous sulfate heptahydrate and dissolve it in 25 mL of deionized water, and ultrasonicate for 5 min; Solution C: Weigh 0.15 g of sodium hydroxide and dissolve it in 6.25 mL of deionized water under stirring conditions;

[0084] Step (2): Transfer solution A to a beaker and magnetically stir at a speed of 350 rpm. While stirring, B is added at a dropping rate of 0.10 mL / s, and C is added at a dropping rate of 0.025 mL / s. After all the dropping is completed, the stirring is stopped;

[0085] Step (3): After covering the beaker in step (2) with a watch glass and allowing it to stand and age for 3 h, centrifuge to obtain a precipitate, and wash it three times with deionized water;

[0086] Step (4): Freeze-dry the precipitate obtained in step (3) at -60 °C for 24 h to obtain the powdered Fe-Mn-O adsorbent material.

[0087] Comparative Example 3

[0088] Step (1): Wash the waste bamboo clean, cut it into bamboo slices with a thickness of 2 mm, take 10 slices (about 2.5 g) and completely immerse them in 12 mL of a potassium permanganate solution with a concentration of 0.01 mol / L for 12 h. After taking them out, wash them three times with ultrapure water to obtain the oxidized bamboo slices;

[0089] Step (2): Repeatedly wash the bamboo slices in step (1) with deionized water until the solution does not change color;

[0090] Step (3), freeze-drying the bamboo slices treated in step (2) at -60°C for 24 hours to obtain a bulk Fe-Mn-O / MB adsorbent material.

[0091] The obtained microscopic and macroscopic structure diagrams of Example 1 are shown in the attached Figure 1 and Figure 2 As shown in the figure, it can be seen that the microstructure of the adsorbent obtained in Example 1 maintains the three-dimensional network pore structure of the bamboo matrix and the iron-manganese bimetallic oxide nanoparticles are tightly attached to the surface of the bamboo matrix, while maintaining the macroscopic block shape. Figure 3 As shown in the figure, compared with Example 1, the substrate surface attachments are significantly reduced and loosely attached. Figure 4 , 5 As shown, the size of the surface nanoparticles is less than 100 nm, and the surface of the substrate of Comparative Example 3 is obviously roughened. The results show that the adsorbent material with macroscopic bulk and microscopic three-dimensional structure loaded with nanoparticles is successfully prepared by pre-oxidation combined with co-precipitation.

[0092] Attached Figure 6 (The horizontal axis 2θ is the diffraction angle (degree), and the vertical axis Intensity is the intensity (au)) is the X-ray diffraction spectrum of Example 1. There are three broad diffraction peaks in the spectrum, which are located at about 21°, 36° and 56°, respectively, corresponding to the semi-crystalline diffraction polymers of MnO2 (JCPDS: 43-1455) and FeOOH (JCPDS: 18-0639). The broad peaks in the range of 12° to 35° in Example 1 correspond to the diffraction peaks of the bamboo matrix, which supplements that the nanoparticles are uniformly dispersed on the surface of the bamboo frame. The crystal structure characterization results show that the Fe-Mn-O / MB composite material has been successfully prepared.

[0093] Attached Figure 7 (The horizontal axis is the adsorption time (min), and the vertical axis is the residual arsenic concentration (mg / L)) are the test results of the adsorption performance of arsenite ions in Example 1 and Comparative Examples 1 and 3. Comparative Example 3 has almost no arsenic adsorption characteristics, while Example 1 and Comparative Example 1 have the same arsenic removal trend, indicating that Fe-Mn-O nanoparticles are the key to the adsorption and removal of inorganic arsenic in aqueous solution. The equilibrium concentration of Example 1 is 5.33 mg / L, which is lower than that of Comparative Example 1 (9.3 mg / L), indicating that the pre-oxidation technology can improve the arsenic adsorption capacity of the adsorbent.

[0094] Attached Figure 8 (The horizontal axis is the initial inorganic arsenic solution concentration (mg / L), and the vertical axis is the adsorption capacity (mg / g)) reveals the performance of the bulk Fe-Mn-O / MB adsorbent material in adsorbing inorganic arsenic. 2The values are all greater than 0.97, indicating that the adsorption process is chemisorption. The R values obtained by fitting the Langmuir model for Examples 1-3 2 are all greater than 0.96, further verifying their chemisorption characteristics, and the maximum adsorption capacities obtained from the fitting results are 36.41 mg / g, 25.52 mg / g, and 21.48 mg / g, respectively.

[0095] adsorption Figure 9 (The abscissa is the regeneration cycle, and the ordinate is the adsorption removal efficiency) reveals the stability and recyclability of the bulk Fe-Mn-O / MB adsorbent materials prepared in Examples 1-3 for arsenic removal. After five adsorption and regeneration cycles, the adsorption capacities of the examples showed a similar downward trend, maintaining 87.33%, 85.30%, and 83.28%, respectively, indicating their good cycle stability. In addition, the Fe-Mn-O nanoparticles are firmly attached to the bamboo framework to minimize iron and manganese leakage after adsorption to meet the drinking water requirements, ensuring high reusability and preventing secondary water pollution.

[0096] The results of the examples show that the present invention uses a pre-oxidation combined with a co-precipitation method to prepare a high-performance bulk inorganic arsenic adsorbent material Fe-Mn-O / MB, which has excellent properties such as high adsorption capacity, easy recovery, strong cycle stability, and no secondary water pollution.

[0097] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a bulk inorganic arsenic adsorbent, characterized in that, The bamboo slices are processed as follows to obtain a block inorganic arsenic adsorbent, and the specific steps are as follows: Step 1: Take bamboo slices with a thickness of 1.8 - 2.5 mm, completely immerse them in a potassium permanganate solution with a concentration of 0.01 - 0.05 mol / L for 10 - 15 h for the first time, take them out and wash with ultrapure water to obtain an oxidized bamboo slice matrix; Step 2: Immerse the bamboo slice matrix in a potassium permanganate solution with a concentration of 0.005 - 0.02 mol / L for the second time, stir at room temperature, and the stirring speed is 200 - 550 rpm. During the stirring process, add a ferrous sulfate solution and a strong base solution at the same time; among them, the molar ratio of iron to manganese ions is 1:1; the strong base solution is a sodium hydroxide solution with a concentration of 0.4 - 0.6 mol / L, and the addition amount is 2:1 - 6:1 of the volume ratio to the potassium permanganate solution; after the reaction, age at room temperature for 1 - 6 h, take out the reacted bamboo slice matrix, wash with ultrapure water and dry to obtain a high-performance block inorganic arsenic adsorbent Fe-Mn-O / MB material.

2. The preparation method of the bulk inorganic arsenic adsorbent according to claim 1, characterized in that, In the above Step 1, the solid-liquid ratio of the potassium permanganate solution to the bamboo slices is 1:

5.

3. The preparation method of the bulk inorganic arsenic adsorbent according to claim 1, characterized in that, In the above Step 2, the solid-liquid ratio of the potassium permanganate solution to the bamboo slices is 1:

10.

4. The preparation method of the bulk inorganic arsenic adsorbent according to claim 2 or 3, characterized in that, In the above Step 2, the concentration of the ferrous sulfate solution is 0.005 - 0.02 mol / L.

5. The preparation method of the bulk inorganic arsenic adsorbent according to claim 1, characterized in that, In the above Step 2, the volume ratio of the ferrous sulfate solution to the potassium permanganate solution is 1:1, and the volume ratio to the sodium hydroxide solution is 2:1 - 6:

1.

6. The preparation method of the bulk inorganic arsenic adsorbent according to claim 1, characterized in that, The dropping rate of the ferrous sulfate is 0.10 mL / s, and the dropping rate of the sodium hydroxide is 0.025 mL / s.

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