Preparation method and application of dual-modified sodium alginate gel beads
The double-modified sodium alginate gel ball prepared by combining biomass carbon and nanomagnesium oxide with sodium alginate has solved the problem of low efficiency in the control of cadmium pollution and environmental damage in the soil, and effectively reduced cadmium in a short period of time and demonstrate good recyclability.
Patent Information
- Application Number
- CN202411275773.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-12
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art is difficult to effectively remove cadmium in soil heavy metal pollution control, and common methods will damage the soil environment and texture, and the treatment efficiency is low, making it difficult to reduce the cadmium content to the safety limit in a short period of time.
The preparation method of bimodified sodium alginate gel spheres is used to form gel spheres by combining biomass charcoal and nanomagnesium oxide with sodium alginate, and cross-link hardening treatment is used to adsorb and remove cadmium in the soil. , use the joint modification effect of biomass charcoal and nanomagnesium oxide to improve cadmium removal efficiency.
During the fallow period from February to March, the cadmium content in moderately and severely contaminated soil can be significantly reduced to the national security limit, and this technology will not damage the soil environment, and has good recyclability and efficient cadmium removal effect.
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Figure CN119114020A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of adsorbent preparation and water pollution treatment, and specifically relates to a preparation method and application of double-modified sodium alginate gel balls. Background Art
[0002] Cadmium is a non-essential element for living things. When the accumulated concentration of cadmium is too high, it will affect the quality of soil and agricultural products, thus posing a health risk to humans. According to the 2014 National Soil Pollution Survey Report released by the Ministry of Environmental Protection and the Ministry of Land and Resources, 19.4% of the soil pollution points in my country's total cultivated land exceeded the standard, and the rate of inorganic pollutants exceeding the standard was higher than that of organic pollutants, of which the rate of inorganic cadmium exceeding the standard was 7.0%.
[0003] Heavy metal pollution control technologies commonly used in industrial land, such as chemical leaching, electrokinetic repair, solidification and stabilization, often have a great impact on soil texture, and the soil after treatment has lost the function of arable land. The foliar barrier control technology, soil conditioner technology, pH adjustment technology, water conditioning technology, etc., which are mainly used in arable land treatment, are based on the basic principle of passivating heavy metals and reducing the transfer of heavy metals from soil to rice, and cannot really remove heavy metals from the soil. Plant extraction technology is a method that uses plant roots to absorb toxic and harmful pollutants from contaminated sites (soil, sediment, water), migrate to the aboveground parts of plants and accumulate continuously, and then take away pollutants by harvesting the aboveground parts of plants. It has the effect of absorbing and removing heavy metals from the soil, but because the biomass of hyperaccumulators is small and the growth is slow, the treatment time is as long as several years and there is no economic benefit, it is difficult to be accepted by farmers. Therefore, it is urgent to develop a heavy metal removal technology that will not damage the geochemical properties and texture of arable land and is friendly to the soil environment.
[0004] There are also reports on the use of agricultural waste to remove water and soil pollutants, but eucalyptus residue and sugarcane bagasse have not been used in soil treatment, and they are widely available and low cost. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide a method for preparing double-modified sodium alginate gel balls in view of the deficiencies of the above-mentioned prior art, and use the double-modified sodium alginate gel balls for removing soil cadmium. The present invention uses eucalyptus residue and sugarcane bagasse to prepare biochar, and uses the biochar and nano-magnesium oxide to modify sodium alginate, and develops a technology that does not damage the soil environment and has high cadmium pollution removal efficiency, which can achieve the purpose of reducing the cadmium content of moderately and severely polluted farmland to the national safety limit during the fallow period of February to March.
[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:
[0007] A method for preparing double-modified sodium alginate gel spheres, characterized in that it comprises the following steps:
[0008] S1. Add biochar (BC), nano magnesium oxide (MgO) and sodium alginate (SA) into deionized water, stir evenly to obtain a mixed solution;
[0009] S2, dropping the mixed solution obtained in S1 into a calcium chloride (CaCl2) solution, stirring the solution at a constant speed while dropping, to form gel balls;
[0010] S3. The gel spheres obtained in S2 are cross-linked and hardened, and then washed and dried to obtain magnesium oxide / biochar@sodium alginate gel spheres (MgO / BC@SA).
[0011] Preferably, the preparation method of biochar described in S1 is: after washing and removing impurities from bagasse and eucalyptus residue, dry them at 80°C for 24 hours respectively, cool them to room temperature, grind them with a grinder, pass them through an 18-mesh sieve, and obtain bagasse powder and eucalyptus residue powder; then pyrolyze the bagasse powder and eucalyptus residue powder at a temperature of 550°C for 2 hours under nitrogen protection at a dry weight ratio of 1:1 to obtain biochar.
[0012] Preferably, in the mixed solution of S1, the mass fraction of biochar is 0.075%, the mass fraction of nano magnesium oxide is 0.025%, and the mass fraction of sodium alginate is 6%.
[0013] Preferably, the stirring time in S1 is 2 to 4 hours and the temperature is 25°C.
[0014] Preferably, the mass fraction of the CaCl2 solution in S2 is 3.5%, and the volume ratio of the mixed solution to the CaCl2 solution is 1:3.
[0015] Preferably, the uniform stirring speed in S2 is 500 r / min.
[0016] Preferably, the diameter of the gel ball in S2 is 2 to 5 mm.
[0017] Preferably, the cross-linking and hardening temperature in S3 is 4° C. and the time is 12 to 18 hours; the drying temperature is 40° C. and the drying time is 24 to 48 hours.
[0018] The present invention also provides an application of the double-modified sodium alginate gel ball, and the double-modified sodium alginate gel ball is used for removing cadmium from soil.
[0019] The method of removing soil cadmium using double-modified sodium alginate gel balls is:
[0020] Step 1: Preparation: Put the double-modified sodium alginate gel balls into a plastic mesh bag, with a weight of 10kg / bag;
[0021] Step 2: Adsorption: apply the net bag filled with double-modified sodium alginate gel balls into the soil at a rate of 6000-8000 kg / mu, irrigate the soil and net bag with water, and let it stand for more than 12 hours;
[0022] Step 3: Desorption: Take out the mesh bag and soak it in a 0.1 mol / L HCl solution for 30 min to elute the heavy metal ions adsorbed on the surface of the gel ball;
[0023] Step 4: Cleaning: Take out the net bag and soak it in clean water for 30 minutes to wash away the H adsorbed on the surface. + ;
[0024] Step 5: Repeat the "adsorption-desorption-cleaning" process described in steps 2 to 4 20 to 30 times, depending on the heavy metal level in the soil, until the cadmium content in the soil drops to within the safety limit.
[0025] The present invention has significant technical effects due to the adoption of the above technical solution:
[0026] 1. The present invention provides a method for preparing double-modified sodium alginate gel balls. The method uses eucalyptus residue and bagasse to prepare biochar, and then uses sodium alginate as a hydrogel polymer matrix to wrap the biochar and nano-magnesium oxide in the matrix to prepare double-modified sodium alginate gel balls. The method has the advantages of simple operation, low cost and easy promotion.
[0027] 2. The double-modified sodium alginate gel balls of the present invention can be used to remove soil cadmium, and have the advantages of good effect, short time, and no pollution. They also have good recyclability. The regenerated gel ball material still has a good adsorption capacity for cadmium. It is a new technology that does not damage the soil environment and has a high cadmium removal efficiency. It can achieve the purpose of reducing the cadmium content of medium and heavily polluted cultivated land to the national safety limit during the fallow period of February to March, and can effectively solve the problem that plant restoration and chemical-physical treatment methods are difficult to implement.
[0028] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 This is a process flow chart of the preparation of the double-modified sodium alginate gel spheres of the present invention;
[0030] Figure 2 This is a morphology picture of magnesium oxide / biomass charcoal@sodium alginate gel sphere (MgO / BC@SA) prepared in Example 1;
[0031] Figure 3 This is a graph showing the adsorption performance of the double-modified sodium alginate gel spheres of Example 4 to cadmium. DETAILED DESCRIPTION
[0032] Example 1
[0033] A method for preparing double-modified sodium alginate gel spheres comprises the following steps:
[0034] S1. Add biochar (BC), nano magnesium oxide (MgO) and sodium alginate (SA) into deionized water, stir at 25°C for 3 hours to obtain a mixed solution; the mass fraction of biochar in the mixed solution is 0.075%, the mass fraction of nano magnesium oxide is 0.025%, and the mass fraction of sodium alginate is 6%.
[0035] Among them, the preparation method of biochar is as follows: after washing and removing impurities from bagasse and eucalyptus residue, they are placed in an oven at 80°C for 24 hours, cooled to room temperature, crushed with a grinder, and passed through an 18-mesh sieve to obtain bagasse powder and eucalyptus residue powder; then, the bagasse powder and eucalyptus residue powder are added to a box-type atmosphere furnace at a dry weight ratio of 1:1, nitrogen is introduced for 30 minutes to maintain an anaerobic environment, and then pyrolyzed at 550°C for 2 hours to obtain biochar.
[0036] S2. Drop the mixed solution obtained in S1 into a CaCl2 solution with a mass fraction of 3.5% to form gel balls. The volume ratio of the mixed solution to the CaCl2 solution is 1:3. Stir the solution at a speed of 500 r / min while dropping until completely hardened gel balls with a diameter of about 3 mm are formed.
[0037] S3. Put the gel balls obtained in S2 into a refrigerator and cross-link and harden them at 4°C for 12 hours, then wash them with water three times and dry them at 40°C for 24 hours to obtain magnesium oxide / biochar@sodium alginate gel balls (MgO / BC@SA).
[0038] Figure 1 The present invention is a flow chart of the preparation process of the double-modified sodium alginate gel spheres.
[0039] Figure 2 This is a morphology picture of magnesium oxide / biochar@sodium alginate gel sphere (MgO / BC@SA) prepared in this example.
[0040] Example 2
[0041] A method for preparing double-modified sodium alginate gel spheres comprises the following steps:
[0042] S1. Add biochar, nano-magnesium oxide and sodium alginate into deionized water, stir at 25° C. for 2 h to obtain a mixed solution; the mass fraction of biochar in the mixed solution is 0.075%, the mass fraction of nano-magnesium oxide is 0.025%, and the mass fraction of sodium alginate is 6%, wherein the preparation method of biochar is the same as that of Example 1.
[0043] S2. Drop the mixed solution obtained in S1 into a CaCl2 solution with a mass fraction of 3.5% to form gel balls. The volume ratio of the mixed solution to the CaCl2 solution is 1:3. Stir the solution at a speed of 500 r / min while dropping until completely hardened gel balls with a diameter of about 4 mm are formed.
[0044] S3. Put the gel balls obtained in S2 into a refrigerator and cross-link and harden them at 4°C for 16 hours, then wash them with water twice and dry them at 40°C for 36 hours to obtain magnesium oxide / biochar@sodium alginate gel balls (MgO / BC@SA).
[0045] Example 3
[0046] The double-modified sodium alginate gel balls prepared by the present invention are used to remove soil cadmium, and the method comprises the following steps:
[0047] Step 1: Preparation: Put the double-modified sodium alginate gel balls into a plastic mesh bag, with a weight of 10kg / bag;
[0048] Step 2: Adsorption: apply the net bag filled with double-modified sodium alginate gel balls into the soil at a rate of 6000-8000 kg / mu, irrigate the soil and net bag with water, and let it stand for more than 12 hours;
[0049] Step 3: Desorption: Take out the mesh bag and put it into a pool of water containing 0.1 mol / L HCl solution for 30 minutes to elute the heavy metal ions adsorbed on the surface of the gel ball;
[0050] Step 4: Cleaning: Take out the net bag and move it into another clean water pool to soak for 30 minutes to wash away the H adsorbed on the surface. + ;
[0051] Step 5. Repeat the "adsorption-desorption-cleaning" process 20 to 30 times according to the heavy metal level in the soil until the cadmium content in the soil drops to the safe limit.
[0052] Example 4
[0053] This example is a study on the adsorption performance of double-modified sodium alginate gel spheres on cadmium.
[0054] Weigh 20 mg of the double-modified sodium alginate gel sphere (MgO / BC@SA) prepared in Example 1 into a 50 mL centrifuge tube, add 20 mL of 50 mg / L Cd solution, and culture at 25 ° C and 200 r / min under constant temperature shaking. Samples were taken at 0, 1, 2, 4, 8, 16, 24, 36, 48, and 72 h, respectively, and centrifuged at 4000 r / min for 10 min. The supernatant was filtered with a 0.45 μm water filter membrane, and the Cd concentration was determined by ICP-OES. The same amount of biochar (BC) and sodium alginate single-modified biochar (BC@SA) were used as comparisons.
[0055] The results are as follows Figure 3 As shown, the vertical coordinate Q e Represents the amount of cadmium adsorbed. After BC@SA and MgO / BC@SA were added to the solution, the amount of cadmium adsorbed by MgO / BC@SA increased significantly in the first 8 hours, and then the adsorption gradually reached saturation, and basically reached adsorption equilibrium after 12 hours. The BC material basically reached adsorption equilibrium 4 hours after being added to the solution. In terms of adsorption amount, MgO / BC@SA had the best adsorption effect, with an adsorption rate of 42%.
[0056] Example 5
[0057] The topsoil of 0-20cm in the area with mild cadmium pollution was collected, and the basic physical and chemical properties of the soil are shown in Table 1. 100g of soil was placed in an experimental container, water was added, and the water-soil ratio was 1:2. The double-modified sodium alginate gel balls (MgO / BC@SA) prepared in Example 1 were put into a nylon mesh bag and placed in the water layer of the soil at a ratio of 2% and 4% of the mass of the tillage layer soil. Three treatments were set up in the experiment, namely: T1 (only deionized water was added), T2 (deionized water was added, 2% MgO / BC@SA was added), and T3 (deionized water was added, 4% MgO / BC@SA was added). MgO / BC@SA was taken out every 24h, and the taken out gel balls were placed in 200mL0.1mol / L HCl solution and shaken for 2h, so that Cd in MgO / BC@SA was desorbed into the solution; after the desorbed MgO / BC@SA was rinsed with deionized water several times, MgO / BC@SA was put back into the soil solution, and repeated 20 times.
[0058] Table 1 Basic physical and chemical properties of soil
[0059]
[0060] The experimental results are shown in Table 2. After 20 repeated experiments, the cadmium concentration in the soil treated with T3 dropped to 0.341 mg / kg, a decrease of 41.21%.
[0061] Table 2 Adsorption results
[0062] Experimental treatment T1 T2 T3 Soil cadmium concentration (mg / kg) 0.566 0.422 0.341
[0063] Example 6
[0064] The topsoil of 0-20cm in the area with severe cadmium pollution was collected, and the basic physical and chemical properties of the soil are shown in Table 3. 100g of soil was placed in an experimental container, water was added, and the water-soil ratio was 1:2. The double-modified sodium alginate gel balls (MgO / BC@SA) prepared in Example 1 were put into a nylon mesh bag and placed in the water layer of the soil at a ratio of 2% and 4% of the mass of the tillage layer soil; three treatments were set up in the experiment, namely: T1 (only deionized water was added), T2 (deionized water was added, 2% MgO / BC@SA was added), and T3 (deionized water was added, 4% MgO / BC@SA was added). MgO / BC@SA was taken out every 24h, and the taken out gel balls were placed in 200mL0.1mol / L HCl solution and shaken for 2h to desorb Cd in MgO / BC@SA into the solution; the desorbed MgO / BC@SA was rinsed with deionized water for many times, and then MgO / BC@SA was put back into the soil solution, and repeated 20 times.
[0065] Table 3 Basic physical and chemical properties of soil
[0066]
[0067] The experimental results are shown in Table 4. After 20 repeated experiments, the cadmium concentration in the soil treated with T3 dropped to 1.853 mg / kg, a decrease of 40.99%.
[0068] Table 4 Adsorption results
[0069] Experimental treatment T1 T2 T3 Soil cadmium concentration (mg / kg) 3.127 2.412 1.853
[0070] Example 7
[0071] This example is a study on the regeneration performance of adsorption saturated double-modified sodium alginate gel spheres.
[0072] The adsorption saturated double-modified sodium alginate gel spheres (MgO / BC@SA) were rinsed with deionized water for 3 to 5 times, placed in a 50 mL centrifuge tube, added with 20 mL of 0.1 mol / L HCl solution, cultured at 25 °C and 180 r / min for 120 min, centrifuged at 4000 r / min for 10 min, and the supernatant was filtered with a 0.45 μm water filter membrane. The Cd concentration of the supernatant was determined by ICP-OES and its desorption rate was calculated. The results are shown in Table 5.
[0073] Table 5 Desorption rate of MgO / BC@SA in 0.1 mol / L HCl solution
[0074] frequency first Second time The third time Fourth Fifth Sixth Desorption rate (%) 98.1129 97.9668 98.8804 97.5429 98.9525 97.6681
[0075] The experimental results show that when the MgO / BC@SA saturated with cadmium adsorption is placed in a 0.1 mol / L HCl solution for desorption, the desorption rate can reach more than 97%.
[0076] The double-modified sodium alginate gel ball material of the present invention not only has a good cleaning effect on soil cadmium, but also has good recyclability. After regeneration, the gel ball material still has a good adsorption capacity for cadmium.
[0077] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.
Claims
1. A method for preparing double-modified sodium alginate gel spheres, It is characterized in that The following steps are involved: S1. Add biochar, nano magnesium oxide and sodium alginate into deionized water and stir evenly to obtain a mixed solution; S2, dropping the mixed solution obtained in S1 into the calcium chloride solution, stirring the solution at a constant speed while dropping, to form gel balls; S3, cross-linking and hardening the gel spheres obtained in S2, and then washing and drying them to obtain magnesium oxide / biomass charcoal@sodium alginate gel spheres.
2. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that S1 The preparation method of biomass charcoal is as follows: after washing and removing impurities from bagasse and eucalyptus residue, they are placed at 80°C for drying for 24 hours respectively, cooled to room temperature, crushed with a grinder, and passed through an 18-mesh sieve to obtain bagasse powder and eucalyptus residue powder; then, the bagasse powder and eucalyptus residue powder are pyrolyzed at a temperature of 550°C for 2 hours under nitrogen protection at a dry weight ratio of 1:1 to obtain biomass charcoal.
3. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that In the mixed solution S1, the mass fraction of biochar is 0.075%, the mass fraction of nano magnesium oxide is 0.025%, and the mass fraction of sodium alginate is 6%.
4. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that The stirring time in S1 is 2 to 4 hours, and the temperature is 25°C.
5. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that The mass fraction of the calcium chloride solution in S2 is 3.5%, and the volume ratio of the mixed solution to the calcium chloride solution is 1:
3.
6. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that The uniform stirring speed of S2 is 500r / min.
7. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that The diameter of the gel ball S2 is 2 to 5 mm.
8. A method for preparing double-modified sodium alginate gel spheres according to claim 1, It is characterized in that The cross-linking and hardening temperature in S3 is 4°C and the time is 12 to 18 hours; the drying temperature is 40°C and the drying time is 24 to 48 hours.
9. An application of the double-modified sodium alginate gel sphere according to claim 1, It is characterized in that The double-modified sodium alginate gel spheres are used for removing soil cadmium.
10. The use according to claim 9, It is characterized in that The method for removing soil cadmium by using double-modified sodium alginate gel balls is as follows: Step 1: Preparation: Put the double-modified sodium alginate gel balls into a plastic mesh bag, with a weight of 10kg / bag; Step 2: Adsorption: apply the net bag filled with double-modified sodium alginate gel balls into the soil at a rate of 6000-8000 kg / mu, irrigate the soil and net bag with water, and let it stand for more than 12 hours; Step 3: Desorption: Take out the mesh bag and soak it in a 0.1 mol / L HCl solution for 30 min to elute the heavy metal ions adsorbed on the surface of the gel ball; Step 4: Cleaning: Take out the net bag and soak it in clean water for 30 minutes to wash away the H adsorbed on the surface. + ; Step 5: Repeat the "adsorption-desorption-cleaning" process described in steps 2 to 4 20 to 30 times, depending on the heavy metal level in the soil, until the cadmium content in the soil drops to within the safety limit.