Efficient modified plant-based water nitrate bio-adsorbent and preparation method thereof

Abstract

The invention provides an efficient modified plant-based water nitrate bio-adsorbent and a preparation method thereof. Compared with a traditional activated carbon adsorbent, the prepared efficient modified plant-based water body nitrate bio-adsorbent has the advantages that the specific surface area is larger, nitrate in a water body can be effectively removed, the continuous and efficient adsorption effect on the nitrate is achieved within the adsorption time of 15-180 min, the cost of albizia hardtii seed raw materials is extremely low, and the environment-friendly effect is achieved. The raw materials are stable in source and easy to obtain, and good economic and social benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a highly efficient modified plant-based water nitrate biosorbent and a preparation method thereof. Background Art

[0002] Nitrate pollution has serious negative impacts on the environment and human health. It may cause methemoglobinemia in infants (blue baby syndrome) and gastric cancer, and cause eutrophication of water bodies. The main methods for removing nitrates are ion exchange, phytoremediation, chemical / catalytic reduction, electrodialysis and adsorption. The adsorption process has the advantages of economy, energy saving, design, and flexible operation. The most significant advantage is that the adsorbent can be reused many times and has been proven to have high economic benefits.

[0003] At present, the common adsorbents are mainly organic adsorbents represented by activated carbon. This type of adsorbent is widely used due to its extremely high adsorption efficiency. Although activated carbon has a high adsorption capacity for nitrate ions and other pollutants, it has major disadvantages in cost and regeneration capacity, which puts it at a disadvantage in treating nitrate ions in wastewater. Therefore, it is necessary to further study more cost-effective and efficient nitrate adsorbents. Biosorption has become an effective method to eliminate pollutants such as heavy metals and organic matter from aqueous solutions. Albizia albizia has been widely used in the research of adsorbents due to its ability to adsorb organic matter, dyes, anionic compounds and heavy metals in water, and has good economic benefits and promotion potential. Summary of the invention

[0004] In view of the defects of the prior art, the object of the present invention is to provide a highly efficient modified plant-based water nitrate biosorbent and a preparation method thereof.

[0005] To achieve the above purpose, the solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a highly efficient modified plant-based water nitrate biosorbent, comprising the following steps:

[0007] Step (1), repeatedly washing the plant branches and leaves or plant epidermis with deionized water and placing them in a dry place to air dry naturally;

[0008] Step (2), placing the plant branches and leaves or plant epidermis obtained in step (1) into a grinding device for grinding, then washing the ground product with deionized water, and then drying and sieving;

[0009] Step (3), adding ferric chloride into deionized water, and then adding the product obtained in step (2), and continuously stirring to modify the plant-based powder;

[0010] Step (4), slowly adding sodium hydroxide solution to adjust the pH value of the solution to 12, and then aging;

[0011] Step (5), after aging, filtering the suspension with a suction pump, washing it again with deionized water to remove residual chloride ions, and then drying it to obtain the highly efficient modified plant-based water nitrite biosorbent. Preferably, the plant branches and leaves or plant epidermis are selected from one or more of neem leaves, guava leaves, orange peels and mango leaves.

[0012] Preferably, the plant branches and leaves or plant epidermis are from the species Albizia julibrissin.

[0013] According to the preparation method of the present invention, the present invention preferentially selects Albizia julibrissin seeds as the raw material of the plant-based water nitrate biosorbent. The material has higher selectivity and lower price than traditional activated carbon adsorbents, and has good economic benefits and promotion potential.

[0014] Preferably, in step (1), the plant is rinsed repeatedly with deionized water for three times, and the natural air-drying time is 3-7 days to ensure that the water in the plant branches and leaves or plant epidermis is completely evaporated.

[0015] Preferably, in step (2): the grinding speed of the grinding device is 2500-3500 rpm, and the particle size of the plant-based powder after grinding is 0.05-1.0 mm; the drying temperature is 25-35°C, and the drying time is 1.5-2.5 h; the mesh size of the sieve is 40 mesh.

[0016] Preferably, in step (3), the concentration of ferric chloride is 0.6-0.8 g / ml, and the mass ratio of ferric chloride to plant-based powder is (0.1-5):1, preferably (0.1-3):1, and more preferably (0.5-2):1; the stirring speed is continuously 100-150 rpm, and the stirring time is 30-45 min to ensure sufficient contact and reaction between ferric chloride and plant-based powder.

[0017] According to the preparation method of the present invention, in this step, the ground plant-based powder is modified with a ferric chloride solution, which can not only destroy the crystallinity of the fibrous tissue of the plant-based powder, but also destroy the cutin and wax layers of the fibrous tissue, so that the adsorbent is exposed to the outside, increasing the specific surface area of ​​the plant-based powder, thereby increasing the contact area with the adsorbed substance and improving the adsorption performance. Moreover, in the preparation method of the present invention, the plant branches and leaves or the plant epidermis are first crushed, and then the crushed plant-based powder is modified with a ferric chloride solution, so that the surface of the crushed powder is modified, and the modification effect is more thorough.

[0018] Preferably, in step (4), the aging temperature is 50-70°C.

[0019] Preferably, in step (5), the drying temperature is 100-110° C. and the drying time is 5-7 h.

[0020] In a second aspect, the present invention also provides a highly efficient modified plant-based water nitrate biosorbent obtained by the preparation method as described above.

[0021] Preferably, the particle size of the highly efficient modified plant-based water nitrate biosorbent is 0.05-1.0 mm, and the specific surface area is 1730-1980 m 2 / g.

[0022] Preferably, the removal effect of nitrate by the highly efficient modified plant-based water nitrate biosorbent is analyzed by ultraviolet spectrophotometer, and the results show that the highly efficient modified plant-based water nitrate biosorbent has an adsorption capacity of nitrate exceeding 25 mg / g within the adsorption time of 15-180 min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The high-efficiency modified plant-based water nitrate biosorbent prepared by the present invention has a larger specific surface area than traditional activated carbon adsorbents, can effectively remove nitrate from water, and has a continuous and efficient adsorption effect on nitrate within the adsorption time of 15-180 minutes. The raw material cost of Albizzia julibrissin seeds is extremely low, the source of raw materials is stable and easy to obtain, and has good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the highly efficient modified plant-based water nitrate biosorbent of the present invention.

[0026] Figure 2 The figure is a graph showing the variation of the nitrate adsorption amount of the high-efficiency modified plant-based water nitrate biosorbent according to the present invention with the reaction time.

[0027] Figure 3 The figure is a graph showing the variation of the nitrate adsorption amount of the high-efficiency modified plant-based water nitrate biosorbent according to the present invention with the pH value.

[0028] Figure 4 The figure is a graph showing the variation of the nitrate adsorption amount of the high-efficiency modified plant-based water nitrate biosorbent according to the present invention with the initial nitrate concentration. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with examples, the purpose of which is to better understand the content of the present invention and reflect the essential characteristics of the present invention, so the examples cited should not be regarded as limiting the scope of protection of the present invention. It is also particularly pointed out here that the specific experimental methods and equipment involved in the examples are conventional methods or implemented under the conditions recommended by the manufacturer's instructions unless otherwise specified, and the reagents involved are commercially available unless otherwise specified.

[0030] Example 1

[0031] This embodiment provides a highly efficient modified plant-based water nitrate biosorbent, the preparation method of which comprises the following steps:

[0032] Step S1: The Albizzia julibrissin seed pods are repeatedly rinsed with deionized water for 3 times, and placed in a dry place to air dry for 5 to 7 days until all the water is completely evaporated;

[0033] Step S2: Grinding the dried Albizzia julibrissin seed pods into powder with a diameter of 0.6 mm using a plant tissue grinder at a grinding speed of 3000 rpm, and then rinsing with deionized water, and baking in an oven at a temperature of 30° C. for 2 h;

[0034] Step S3: filtering the dried product through a 40-mesh sieve to obtain a plant-based water nitrate biosorbent;

[0035] Step S4: adding 60 g of ferric chloride to 100 ml of deionized water, and adding 50 g of the plant-based water nitrate biosorbent prepared in S3 while continuously stirring at a stirring speed of 150 rpm for 30 min;

[0036] Step S5: slowly add 200 ml of 2.5 M sodium hydroxide solution, adjust the pH value of the solution to 12, and place in an oven for aging for 24 hours;

[0037] Step S6: After the aging process, the suspension was filtered with a suction pump and rinsed again with deionized water to remove residual chloride ions, and then the resulting material was dried in an oven at a temperature of 105°C for 6 hours to complete the modification of the biosorbent, and a batch adsorption test was carried out to verify the removal effect of the modified biosorbent on nitrate.

[0038] Example 2

[0039] This embodiment provides a highly efficient modified plant-based water nitrate biosorbent, the preparation method of which comprises the following steps:

[0040] Step S1: The Albizzia julibrissin seed pods are repeatedly rinsed with deionized water for 3 times, and placed in a dry place to air dry for 5 to 7 days until all the water is completely evaporated;

[0041] Step S2: Grinding the dried Albizzia julibrissin seed pods into powder with a diameter of 0.6 mm using a plant tissue grinder at a grinding speed of 3000 rpm, and then rinsing with deionized water, and baking in an oven at a temperature of 30° C. for 2 h;

[0042] Step S3: filtering the dried product through a 40-mesh sieve to obtain a plant-based water nitrate biosorbent;

[0043] Step S4: adding 70 g of ferric chloride to 100 ml of deionized water, and adding 60 g of the plant-based water nitrate biosorbent prepared in S3 while continuously stirring at a stirring speed of 150 rpm for 35 min;

[0044] Step S5: slowly add 200 ml of 2.5 M sodium hydroxide solution, adjust the pH value of the solution to 12, and place in an oven for aging for 24 hours;

[0045] Step S6: After the aging process, the suspension was filtered with a suction pump and rinsed again with deionized water to remove residual chloride ions, and then the resulting material was dried in an oven at a temperature of 105°C for 6 hours to complete the modification of the biosorbent, and a batch adsorption test was carried out to verify the removal effect of the modified biosorbent on nitrate.

[0046] Example 3

[0047] This embodiment provides a highly efficient modified plant-based water nitrate biosorbent, the preparation method of which comprises the following steps:

[0048] Step S1: The Albizzia julibrissin seed pods are repeatedly rinsed with deionized water for 3 times, and placed in a dry place to air dry for 5 to 7 days until all the water is completely evaporated;

[0049] Step S2: Grinding the dried Albizzia julibrissin seed pods into powder with a diameter of 0.6 mm using a plant tissue grinder at a grinding speed of 3000 rpm, and then rinsing with deionized water, and baking in an oven at a temperature of 30° C. for 2 h;

[0050] Step S3: filtering the dried product through a 40-mesh sieve to obtain a plant-based water nitrate biosorbent;

[0051] Step S4: adding 80 g of ferric chloride to 100 ml of deionized water, and adding 70 g of the plant-based water nitrate biosorbent prepared in S3 while continuously stirring at a stirring speed of 150 rpm for 45 min;

[0052] Step S5: slowly add 200 ml of 2.5 M sodium hydroxide solution, adjust the pH value of the solution to 12, and place in an oven for aging for 24 hours;

[0053] Step S6: After the aging process, the suspension was filtered with a suction pump and rinsed again with deionized water to remove residual chloride ions, and then the resulting material was dried in an oven at a temperature of 105°C for 6 hours to complete the modification of the biosorbent, and a batch adsorption test was carried out to verify the removal effect of the modified biosorbent on nitrate.

[0054] Detection of the adsorption and removal effect of nitrate by the biosorbent prepared in Examples 1-3:

[0055] The detection steps include:

[0056] S1, adding the high-efficiency modified plant-based water nitrate biosorbent prepared in Examples 1-3 into a 50 ml reagent tube containing the diluted nitrate stock solution, and adjusting the pH value of the solution using 0.1 M sodium hydroxide and hydrochloric acid solutions;

[0057] S2, the reagent tube was placed in a constant temperature shaker, stirred at 180 rpm for 2 h, and then filtered. The filtrate was then concentrated in a water bath, and the nitric acid removal effect was analyzed using an ultraviolet spectrophotometer at 410 nm.

[0058] The variation of nitrate adsorption amount of the highly efficient modified plant-based water nitrate biosorbent prepared in Examples 1-3 with reaction time is as follows: Figure 2 shown.

[0059] from Figure 2 It can be seen that the high-efficiency modified plant-based water nitrate biosorbent prepared by the present invention has an adsorption capacity of nitrate that continuously exceeds 25 mg / g within the adsorption time of 15-180 min.

[0060] The nitrate adsorption capacity of the highly efficient modified plant-based water nitrate biosorbent prepared in Examples 1-3 changes with the pH value of the solution as shown in Figure 3 shown.

[0061] from Figure 3 It can be seen that the adsorption amount of nitrate by the high-efficiency modified plant-based water nitrate biosorbent prepared by the present invention fluctuates greatly in an acidic environment (pH<8).

[0062] The variation of the nitrate adsorption amount of the highly efficient modified plant-based water nitrate biosorbent prepared in Examples 1-3 with the initial nitrate concentration is as follows: Figure 4 shown.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a highly efficient modified plant-based water nitrate biosorbent, characterized in that: The steps include: Step (1), repeatedly washing the plant branches and leaves or plant epidermis with deionized water and placing them in a dry place to air dry naturally; Step (2), placing the plant branches and leaves or plant epidermis obtained in step (1) into a grinding device for grinding, then washing the ground product with deionized water, and then drying and sieving; Step (3), adding ferric chloride into deionized water, and then adding the product obtained in step (2), and continuously stirring to modify the plant-based powder; Step (4), slowly adding sodium hydroxide solution to adjust the pH value of the solution to 12, and then aging; Step (5), after aging, filtering the suspension with a suction pump, washing it again with deionized water to remove residual chloride ions, and then drying it to obtain the highly efficient modified plant-based water nitrite biosorbent.

2. The preparation method according to claim 1, characterized in that: The plant branches and leaves or plant epidermis are from the species Albizia julibrissin.

3. The preparation method according to claim 1, characterized in that: In step (1), the plant is rinsed repeatedly with deionized water for 3 times and air-dried for 3-7 days to ensure that the water in the plant branches and leaves or plant epidermis is completely evaporated.

4. The preparation method according to claim 1, characterized in that: In step (2), the grinding speed of the grinding device is 2500-3500 rpm, and the particle size of the plant-based powder after grinding is 0.05-1.0 mm; the drying temperature is 25-35° C., and the drying time is 1.5-2.5 h; and the mesh size of the sieve is 40 mesh.

5. The preparation method according to claim 1, characterized in that: In step (3), the concentration of ferric chloride is 0.6-0.8 g / ml, and the mass ratio of ferric chloride to plant-based powder is (0.1-5):1, preferably (0.1-3):1, and more preferably (0.5-2):1; the stirring speed is continuously 100-150 rpm, and the stirring time is 30-45 min to ensure sufficient contact and reaction between ferric chloride and plant-based powder.

6. The preparation method according to claim 1, characterized in that: In step (4), the aging temperature is 50-70°C.

7. The preparation method according to claim 1, characterized in that: In step (5), the drying temperature is 100-110° C. and the drying time is 5-7 h.

8. A highly efficient modified plant-based water nitrate biosorbent obtained by the preparation method according to any one of claims 1 to 7.

9. The high-efficiency modified plant-based water nitrate biosorbent according to claim 8, characterized in that: The particle size of the highly efficient modified plant-based water nitrate biosorbent is 0.05-1.0 mm, and the specific surface area is 1730-1980 m 2 / g.

10. The high-efficiency modified plant-based water nitrate biosorbent according to claim 8, characterized in that: The results of ultraviolet spectrophotometer analysis of the nitrate removal effect of the high-efficiency modified plant-based water nitrate biosorbent show that the high-efficiency modified plant-based water nitrate biosorbent has a continuous adsorption capacity of more than 25 mg / g of nitrate within the adsorption time of 15-180 minutes.

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