Method for preparing nitrogen-sulfur doped biochar material from canna flower and use of biochar material in dye wastewater adsorption

Abstract

Preparation of nitrogen-sulfur co-doped canna flower-based biochar and a use thereof in the removal of malachite green in wastewater. The method comprises: washing, drying, and pulverizing a collected canna flower, mixing same with a certain amount of phosphoric acid in a beaker, adding an appropriate amount of deionized water, stirring same, loading a feed liquid into a hydrothermal kettle, and then placing same in an oven for hydrothermal treatment to obtain a canna flower-based hydrothermal carbon; uniformly mixing hydrothermal carbon powder with a certain mass ratio of thiourea and molten salt, placing the mixture in a muffle furnace for firing in air, cooling same with the furnace after firing is completed, finally taking out a sample, separating the molten salt, performing acid washing on the biochar, washing same with alcohol, washing same with water, and then drying same to obtain the nitrogen-sulfur co-doped canna flower-based biochar; and using the nitrogen-sulfur co-doped canna flower-based biochar to remove malachite green in wastewater. Compared with conventional carbon materials, the nitrogen-sulfur co-doped carbon material prepared by the method has greatly improved removal efficiency for malachite green in a water body. In addition, the preparation method provides a way to treat a biomass waste, saves costs, and realizes resource utilization of biomass wastes.

Description

Method for preparing nitrogen and sulfur doped biochar material from canna indica flowers and application thereof in dye wastewater adsorption TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and particularly relates to preparation of nitrogen and sulfur doped canna indica flower based biochar and application thereof in removal of malachite green in water. BACKGROUND

[0002] In recent years, with the great improvement of China's industrial manufacturing strength, the rapid development of printing, coating, textile, leather, cosmetics and papermaking industries, a large amount of industrial wastewater containing organic dyes is discharged. At present, dye wastewater is one of the main water pollution sources in China, and effective removal of dyes in water environment is one of the hot issues to be solved in the current environmental field. Malachite green is a toxic and carcinogenic triphenylmethane substance and is easily soluble in water, and is often used as a dye and a disinfectant in aquaculture. Therefore, if the wastewater containing malachite green is not properly treated, it will pose a great threat to the natural ecological environment and human health. The unmodified biochar material has a low adsorption capacity for malachite green, and the adsorption capacity of the modified biochar material is still not high enough.

[0003] At present, the common treatment methods for dye wastewater are chemical oxidation method, biological degradation method, photolysis method, membrane treatment method and adsorption method. The adsorption method is concerned due to its low cost, simple operation, reusability and high removal efficiency. Biochar material has the advantages of rich and low raw material, large specific surface area, developed pore structure, stable properties in solution and reusability, and thus becomes a research hotspot of adsorption materials in recent years. However, the original biochar material has limited active sites, and thus it is often necessary to modify the biochar to improve its adsorption performance. According to the literature, the introduction of heteroatoms (B, P, N or S) in carbon materials can change the surface electronic properties, enrich the surface active functional groups of carbon matrix, improve the pore structure and increase the specific surface area, so as to optimize the affinity to water and significantly improve the adsorption performance of pollutants. In addition, due to the synergistic effect, the double-doped biochar has better adsorption performance than the single-doped biochar.

[0004] There are two strategies for preparing heteroatom doped biochar: direct doping method and post-doping method. The direct doping method is to burn biomass, activator and dopant together at high temperature to directly dope heteroatoms in the carbonization process. The post-treatment method is to form initial carbon by pre-burning the biomass source, then blend with the dopant and activator, and prepare the carbon material containing heteroatoms by high-temperature carbonization. However, this method has complicated steps, low biochar yield and low heteroatom doping amount. Both methods need to be burned at high temperature under the protection of nitrogen or other inert gases to prepare biochar, and a large amount of activator is used to make pores, so the preparation of doped biochar has the problems of high cost and secondary pollution.

[0005] Plants are the most abundant renewable resources in nature. Canna is an ornamental plant widely cultivated in China. Canna has a strong adaptability and low environmental requirements, so it has a long history of cultivation in China. It is also known as red canna in ancient times. The flower of canna is large, with a maximum diameter of 20 cm, bright color, and long flowering period, which can open from early summer to late autumn. It can bloom all year round in tropical regions and has the reputation of "flower bed queen". At present, the most studied in China is the extraction of natural pigment from canna and its medicinal value. There is no research report on the transformation of canna flower into adsorbent material and its application in wastewater treatment. If canna flower can be effectively transformed into biochar material and applied in the treatment of dye wastewater in water environment, it will open up a new path for the resource utilization of canna flower.

[0006] However, such research,

[0007] SUMMARY

[0008] In order to overcome the shortcomings of the prior art, obtain a biochar material with low cost, simple preparation process and high adsorption efficiency, the application provides a preparation method of nitrogen and sulfur co-doped canna flower-based biochar material and application of the biochar material in adsorbing malachite green.

[0009] The technical scheme of the application is as follows: a preparation method of nitrogen and sulfur co-doped canna flower-based biochar material, comprising the following steps:

[0010] Step one, after the collected canna flowers are washed, dried and crushed, a certain amount of phosphoric acid is mixed in a beaker, a proper amount of deionized water is added, the mixture is stirred and then loaded into a hydrothermal kettle, and then placed in an oven for hydrothermal treatment to obtain canna flower hydrothermal carbon;

[0011] Step two, the hydrothermal carbon powder obtained above is uniformly mixed with a certain mass ratio of thiourea and molten salt, placed in a crucible, sealed with a small amount of molten salt, then covered with a crucible cover and placed in a muffle furnace, burned at a certain temperature in air, cooled in the furnace after burning, and finally taken out;

[0012] Step three, the biochar prepared in step two is scraped out with a medicine spoon and a small amount of water, and the remaining mixed salt in the crucible is purified and recovered by recrystallization;

[0013] Step four, the biochar powder obtained in step three is pickled, alcohol-washed, then water-washed to neutral, dried and finely ground, and packed for storage. The product is nitrogen and sulfur co-doped canna flower-based biochar.

[0014] Further, the concentration of phosphoric acid in step one is 30-50 %; the solid-liquid ratio of the canna indica pollen and phosphoric acid is 1:4-1:6; the mixture of the canna indica pollen and phosphoric acid is stirred in a magnetic stirrer, the stirring speed is 500 r / min, the stirring time is 12 h, after the stirring is completed, the mixture is loaded into a hydrothermal kettle, then the hydrothermal kettle is placed in an oven and hydrothermal treatment is carried out at 200 DEG C for 6 h, after the hydrothermal treatment is completed, the canna indica flower hydrothermal carbon in the hydrothermal kettle is filtered and washed, and finally the canna indica flower hydrothermal carbon is placed in an oven and dried at 100 DEG C for 10 h.

[0015] Further, the mass ratio of the hydrothermal carbon powder and thiourea in step two is 1:3-1:5; the molten salt used in step two is a mixed salt of sodium chloride and potassium chloride with an equimolar ratio, and the mass of the mixed salt added is 3-5 times the mass of the mixture of the hydrothermal carbon and thiourea.

[0016] Further, the calcination in step two is carried out in a muffle furnace, the heating rate is 5 DEG C / min, the temperature is raised to 600-800 DEG C, after the temperature is reached, the temperature is maintained for 1-3 h, and then the temperature is naturally cooled to room temperature.

[0017] Further, the mixed salt in the crucible in step three is dissolved in a certain amount of distilled water, then filtered, the filtrate is heated to 100 DEG C and boiled for 10 min, and then recrystallized at room temperature.

[0018] Further, the acid washing in step four is carried out using hydrochloric acid with a concentration of 1-2 mol / L. -1 , in a magnetic stirrer, the stirring speed is 500 r / min, the stirring time is 4 h, then filtered, washed with ultrapure water until the pH value is close to neutral, washed with alcohol several times, and dried at 100 DEG C for 12 h, to obtain the nitrogen and sulfur co-doped canna indica flower-based biochar.

[0019] A nitrogen and sulfur co-doped canna indica flower-based biochar material prepared by the above preparation method.

[0020] The application of the above-mentioned nitrogen and sulfur co-doped canna indica flower-based biochar material in adsorbing malachite green.

[0021] The advantages and beneficial effects of the present application are as follows:

[0022] (1) The canna indica flower used as the raw material of the biochar belongs to agricultural waste, which is abundant in resources, renewable, and has no production cost, and the resource recycling of the canna indica flower is realized.

[0023] (2) The preparation conditions and process are simple and easy to control, the raw material sources are wide, the preparation process temperature is low, the energy consumption is low, and the cost is low, which is conducive to large-scale production; in order to avoid the introduction of inert gas and realize green and low-cost preparation, the nitrogen and sulfur co-doped canna indica flower-based biochar is prepared by the molten salt method.

[0024] (3) The present application relates to a method for effectively preparing a biomass carbon material, the carbon material prepared by biomass molten salt mixing under the protection of no inert gas has a high specific surface area, and the characteristics of microporous, mesoporous and macroporous pore size structures, so that the carbon material has very high adsorption performance, and the molten salt can be recycled and reused.

[0025] (4) The prepared nitrogen-doped sulfur biomass carbon material has good adsorption performance on malachite green, and the adsorption performance is 3 times that of commercial activated carbon malachite green; BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a nitrogen adsorption / desorption graph of the canna flower-based biomass carbon material prepared in Example 1.

[0027] Table 1 is a pore size analysis of the canna flower-based biomass carbon material prepared in Example 1.

[0028] Figure 2 is a pore size distribution graph of the canna flower-based biomass carbon material prepared in Example 1.

[0029] Figure 3 is a SEM graph of the canna flower-based biomass carbon material prepared in Examples 1-4 (a is 0.5NS-BC, b is 1NS-BC, c is 1.5NS-BC, and d is 2NS-BC).

[0030] Figure 4 is a face scanning graph and energy spectrum graph of the canna flower-based biomass carbon material prepared in Example 1.

[0031] Figure 5 is an xps graph of the nitrogen-sulfur co-doped carbon material prepared in Example 1.

[0032] Figure 6(a) is a mixed sample of molten salt and biomass carbon in a crucible prepared in Example 1 of the present application, and Figure 6(b) is the molten salt obtained by recrystallization.

[0033] Figure 7 is a malachite green removal effect graph of the canna flower-based biomass carbon material prepared in Examples 1-4 and the control example. DETAILED DESCRIPTION

[0034] The present application will be further described below in conjunction with specific examples, but the scope of protection of the present application is not limited thereto.

[0035] Example 1 A nitrogen-sulfur co-doped canna flower-based biomass carbon material is prepared, and the steps are as follows:

[0036] 1) First, get the canna indica flower from the canna indica tree, wash the canna indica flower, dry it after washing, crush it with a crusher, pass it through a 100 mesh screen, wash the screened canna indica flower powder again, and then put it into an oven to dry the moisture to obtain canna indica flower raw powder. Put 50g of canna indica flower powder in a beaker and add 200ml of 50% phosphoric acid, stir for 6h at 500rpm, after stirring, pour the liquid into an autoclave, then put it into an oven at 200°C for 6h, after hydrothermal treatment, filter and wash the canna indica hydrothermal carbon in the autoclave, and finally put it into an oven at 100°C for 10h, take it out after drying and grind it into powder in an agate mortar for subsequent steps.

[0037] 2) Put 2.5g of canna indica hydrothermal carbon powder obtained in step 1) and 3.75g of thiourea into a mortar and grind for 5min, then add 7.5g of mixed salt of sodium chloride and potassium chloride in equimolar ratio, continue to grind in the mortar for 15min, pour the mixture into a crucible, and seal it with a small amount of mixed salt of sodium chloride and potassium chloride, then cover the crucible with a lid and put it into a muffle furnace, and calcine it at 800°C in air for 1h, cool it in the furnace after calcination, and finally take it out.

[0038] 3) Use a medicine spoon and a small amount of water to scrape out the biochar prepared in step 2), and use recrystallization method to purify and recover the mixed salt remaining in the crucible.

[0039] 4) Put the biochar powder obtained in step 3) into dilute HCl solution and stir for 4h, filter, wash with ultrapure water until the pH value is near neutral, wash several times with alcohol, and dry at 100°C for 12h to obtain nitrogen-doped sulfur canna indica flower-based biochar, marked as 1.5NS-BC.

[0040] Example 2

[0041] The method is the same as example 1, except that 2.5g of canna indica hydrothermal carbon and 1.25g of thiourea are weighed to obtain nitrogen and sulfur co-doped canna indica flower-based biochar material, marked as 0.5NS-BC.

[0042] Example 3

[0043] The method is the same as example 1, except that 2.5g of canna indica hydrothermal carbon and 2.5g of thiourea are weighed to obtain nitrogen and sulfur co-doped canna indica flower-based biochar material, marked as 1NS-BC.

[0044] Example 4

[0045] The method is the same as example 1, except that 2.5g of canna indica hydrothermal carbon and 5g of thiourea are weighed to obtain nitrogen and sulfur co-doped canna indica flower-based biochar material, marked as 2NS-BC.

[0046] Comparative Example 1

[0047] The method is the same as Example 1, except that 2.5 g of water-heat carbon of canna flower, 0 g of thiourea are weighed, and undoped canna flower-based biochar material is obtained, marked as BC.

[0048] Example 5

[0049] The adsorption capacity of the seven kinds of biomass carbon materials obtained in Examples 1-4 and Comparative Example 1 for malachite green is tested, which specifically includes: first, a malachite green solution with a concentration of 300 mg / L is prepared, and 25 ml is transferred to a conical flask. Then 10 mg of biochar material is weighed and added to the conical flask solution. Next, the conical flask is placed in a constant temperature oscillator, and a certain rotation speed (150 r / min) and temperature (25℃) are set, and oscillation is carried out under this condition for 12 h to reach adsorption equilibrium. Finally, 10 ml of the upper liquid is taken with a plastic syringe, filtered with a 0.22 μm organic filter head to obtain a filtrate, and the concentration of malachite green in the filtrate is determined by ultraviolet spectrophotometry at a wavelength of 618 nm.

[0050] The adsorption performance of canna flower biochar is evaluated by adsorption rate R and adsorption capacity q, and the formula is as follows: R = (C0-c) / C0x100% (1-1) q = ((C0-c) x V) / m (1-2)

[0051] Wherein C0, C is the concentration of malachite green solution before and after adsorption (unit: mg / L), V is the volume of malachite green solution (unit: L), and m represents the amount of biochar (unit: g).

[0052] Test Example

[0053] The nitrogen-sulfur co-doped carbon material prepared in the above examples is tested for adsorption performance of malachite green in water, and the carbon material with the best adsorption performance is tested for nitrogen adsorption and desorption, pore size analysis, scanning electron microscopy and energy spectrum characterization, and XRD analysis.

[0054] Figure 7 is a graph showing the effect of the carbon material prepared in Examples 1-4 and the control on the adsorption and removal of malachite green in water. As shown in Figure 7, the nitrogen-sulfur co-doped carbon material prepared in Example 1 (1.5NS-BC) has a maximum adsorption capacity for malachite green in water of 541 mg / g, with an adsorption rate of 72.2%; the nitrogen-sulfur co-doped carbon material prepared in Example 2 (0.5NS-BC) has an adsorption capacity of 373 mg / g, with an adsorption rate of 49.69%; the nitrogen-sulfur co-doped carbon material prepared in Example 3 (1NS-BC) has an adsorption capacity of 391 mg / g, with an adsorption rate of 52.09%; the nitrogen-sulfur co-doped carbon material prepared in Example 4 (2NS-BC) has an adsorption capacity of 387 mg / g, with an adsorption rate of 51.55%; and the carbon material prepared in the control (without nitrogen and sulfur doping) has an adsorption capacity of 268 mg / g, with an adsorption rate of 35.73%. As shown in the graph, the adsorption performance of the carbon material for malachite green is greatly improved when nitrogen and sulfur are doped into the carbon material. The adsorption effect is best when the mass ratio of thiourea to cattail flower hydrochar is 1.5.

[0055] Figure 1 is a nitrogen adsorption / desorption curve of the nitrogen-sulfur co-doped carbon material prepared in Example 1 (1.5NS-BC). Figure 2 and Table 1 are, respectively, a pore size distribution graph and a pore distribution analysis graph of the nitrogen-sulfur co-doped carbon material prepared in Example 1 (1.5NS-BC). As shown in Figure 2 and Table 1, the prepared carbon material has both microporous and mesoporous structures. As shown in Figures 1 and 2, the specific surface area of the nitrogen-sulfur co-doped carbon material prepared in Example 1 (1.5NS-BC) is 656 m 2 / g, the average pore size and the total pore volume are 2.52 nm and 0.413 cm 3 / g, respectively. Figure 3 is a scanning electron microscope (SEM) image of the nitrogen-sulfur co-doped carbon material prepared in Examples 1-4. As shown in Figure 3, the prepared cattail carbon material has an irregular sheet shape, and the number of large pores on the surface of the carbon material gradually increases as the amount of dopant increases. The carbon sheet prepared in Example 1 has the largest number of large pores. Figure 4 is an elemental face scanning image and an energy spectrum image of the nitrogen-sulfur co-doped carbon material prepared in Example 1. As shown in Figure 4, the nitrogen and sulfur elements are uniformly distributed on the carbon material, indicating that the nitrogen-sulfur co-doped carbon material is successfully prepared. Figure 5 is an xps image of the nitrogen-sulfur co-doped carbon material prepared in Example 1. Figure 6(a) is a mixed sample of molten salt and carbon material prepared by the molten salt method in Example 1, and Figure 6(b) is molten salt obtained by the recrystallization method. The recovery rate of the molten salt is as high as 75%.

Claims

1. A method of preparing a nitrogen-sulfur co-doped Canna indica flower-based biochar material, characterized by, It comprises the following steps: Step one, the collected canna flowers are washed, dried, and crushed, and then mixed with a certain amount of phosphoric acid in a beaker, and a proper amount of deionized water is added, and after stirring, the material liquid is loaded into a hydrothermal kettle, and then put into an oven for hydrothermal treatment, and canna flower hydrochar is prepared; Step two, the hydrochar powder obtained above is mixed with a certain mass ratio of thiourea and molten salt, put into a crucible, and sealed with a small amount of molten salt, then cover the crucible cover and put it into a muffle furnace, and burn at a certain temperature in air, and after the burning is completed, the furnace is cooled down, and finally taken out; Step three, the biochar prepared in step two is scraped out with a medicine spoon and a small amount of water, and the remaining mixed salt in the crucible is purified and recovered by recrystallization; Step four, the biochar powder obtained in step three is pickled, alcohol washed, and then water washed to neutral, dried and ground, and packed for storage, which is the nitrogen and sulfur co-doped canna flower based biochar.

2. The method of claim 1, wherein the nitrogen and sulfur co-doped Canna indica flower-based biochar is prepared by the steps of: The concentration of phosphoric acid in step one is 30-50%; the solid-liquid ratio of canna flower powder to phosphoric acid is 1:4-1:6; the mixture of canna flower powder and phosphoric acid is stirred in a magnetic stirrer, the stirring speed is 500 rpm, the stirring time is 12 h, after stirring, the material liquid is loaded into a hydrothermal kettle, and then put into an oven for hydrothermal treatment at 200℃ for 6h, after hydrothermal treatment, the canna flower hydrochar in the hydrothermal kettle is filtered and washed, and finally put into an oven for drying at 100℃ for 10h.

3. The method of claim 1, wherein the nitrogen and sulfur co-doped Canna indica flower-based biochar is prepared by the steps of: The mass ratio of hydrochar powder to thiourea in step two is 1:3-1:5; the molten salt used in step two is a mixed salt of sodium chloride and potassium chloride with equal molar ratio, and the mass of the mixed salt added is 3-5 times the mass of the mixture of hydrochar and thiourea.

4. The method of claim 1, wherein the nitrogen and sulfur co-doped Canna indica flower-based biochar is prepared by the steps of: In step two, the calcination is carried out in a muffle furnace, the heating rate is 5℃ / min, the temperature is raised to 600-800℃, and after reaching the temperature, it is kept for 1-3h, and then naturally cooled to room temperature.

5. The method of claim 1, wherein the nitrogen and sulfur co-doped Canna indica flower-based biochar is prepared by the steps of: In step three, the mixed salt in the crucible is dissolved in a certain amount of distilled water, then filtered, and the filtrate is heated to 100℃ and boiled for 10 minutes, and then recrystallized at room temperature.

6. The method of claim 1, wherein the nitrogen and sulfur co-doped Canna indica flower-based biochar is prepared by the steps of: The acid washing in step four is hydrochloric acid with a concentration of 1-2 mol / L -1 In a magnetic stirrer, the stirring speed is 500 rpm, the stirring time is 4 h, then suction filtration is performed, and the product is washed with ultrapure water until the pH value is close to neutral, then washed with alcohol several times, and dried at 100 DEG C for 12 h to obtain the nitrogen-doped Zantedeschia aethiopica flower-based biochar.

7. A nitrogen and sulfur co-doped canna flower based biochar material prepared by the preparation method of claim 1.

8. The application of the nitrogen and sulfur co-doped canna flower based biochar material of claim 7 in adsorbing malachite green.

Images