CN109395701B - Preparation method and application of molybdenum and nitrogen doped lignocellulose composite nano adsorption material - Google Patents

Preparation method and application of molybdenum and nitrogen doped lignocellulose composite nano adsorption material Download PDF

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CN109395701B
CN109395701B CN201811371506.8A CN201811371506A CN109395701B CN 109395701 B CN109395701 B CN 109395701B CN 201811371506 A CN201811371506 A CN 201811371506A CN 109395701 B CN109395701 B CN 109395701B
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CN109395701A (en
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谈晶
张娅
王宏归
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Yangzhou University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
    • B01J20/0218—Compounds of Cr, Mo, W
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/286—Treatment of water, waste water, or sewage by sorption using natural organic sorbents or derivatives thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/4825—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C02F2101/22—Chromium or chromium compounds, e.g. chromates

Abstract

The invention relates to a preparation method and application of a molybdenum and nitrogen doped lignocellulose composite nano adsorption material, which comprises the following steps: (1) calcining lignocellulose in an ammonia atmosphere, naturally cooling, and grinding to obtain nitrogen-doped lignocellulose; (2) dissolving ammonium molybdate in deionized water to prepare a solution I; (3) dissolving thioacetamide in deionized water to prepare a solution II; (4) fully and uniformly mixing the solution I and the solution II to prepare a solution III; (5) adding nitrogen-doped lignocellulose into the solution III, and stirring to obtain a solution IV; (6) transferring the solution IV to a high-pressure reaction kettle, and reacting at a high temperature; (7) and cooling the solution IV subjected to the high-temperature reaction, and then performing centrifugal separation on the reaction product to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material. According to the invention, the molybdenum and nitrogen doped lignocellulose composite has a good adsorption effect on hexavalent chromium, the adsorption performance of the molybdenum and nitrogen doped lignocellulose composite is basically kept unchanged after repeated tests, and the molybdenum and nitrogen doped lignocellulose composite has good stability.

Description

Preparation method and application of molybdenum and nitrogen doped lignocellulose composite nano adsorption material
Technical Field
The invention relates to a preparation method and application of a molybdenum and nitrogen doped lignocellulose composite nano adsorption material, and belongs to the technical field of preparation of molybdenum and nitrogen doped lignocellulose composite nano adsorption materials.
Background
The conventional treatment methods of chromium-containing wastewater are more, and the commonly used treatment methods mainly comprise an adsorption method, an ion exchange method, a chemical precipitation method, a membrane separation method and the like, wherein the adsorption method is known as one of the most effective methods due to simple operation, low investment and good treatment effect. The adsorbent has various types, is commonly used by active carbon, can simultaneously adsorb various heavy metal ions, has large adsorption capacity, but has short service life, needs regeneration and has high operation cost. Therefore, the development and application of the novel adsorbent have very important significance. Magnetic nanoparticles, metal compounds and other nanomaterials are receiving wide attention due to their advantages of large specific surface area, high activity, simple desorption process and the like, and have been successfully applied to the removal process of heavy metal ions such As Hg, Cr, Pb, As and the like.
Molybdenum disulfide is a common sulfide and is also one of the hot adsorbents. Lignocellulose is also a common carbon material. The molybdenum dioxide is compounded with the modified lignocellulose, so that the adsorption capacity of the molybdenum dioxide to hexavalent chromium ions in a water body can be improved. Therefore, the molybdenum disulfide is compounded with the modified lignocellulose, so that a good hexavalent chromium adsorbent can be developed.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide a preparation method and application of a molybdenum and nitrogen doped lignocellulose composite nano adsorption material, in particular to a preparation method and an adsorption technology of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material.
The invention aims to realize the preparation method of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material, which is characterized by comprising the following steps:
(1) calcining lignocellulose in an ammonia atmosphere, naturally cooling, and grinding to obtain nitrogen-doped lignocellulose;
(2) dissolving 0.1-1 mmol of ammonium molybdate in 10-100 mL of deionized water to prepare a solution I;
(3) dissolving 5-10 mmol of thioacetamide in 10-50 mL of deionized water to prepare a solution II;
(4) fully and uniformly mixing the solution I and the solution II to prepare a solution III;
(5) adding nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
(6) transferring the solution IV into a high-pressure reaction kettle for high-temperature reaction;
(7) and (3) after the solution IV subjected to the high-temperature reaction is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing with deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material.
In the step (1), the reaction calcination temperature is 600-800 ℃, the temperature rise speed is 5-15 ℃/min, and the calcination time is 1-3 h.
In the step (5), the mass of the lignocellulose is 10-30 mg.
In the step (6), the volume of the solution IV is 60-100 mL, the reaction temperature is 180-220 ℃, and the reaction time is 16-24 hours.
In the step (7), the centrifugation speed is 2000-6000 r/min, the cleaning times of the ethanol and the water are 3-6 times, and the stable temperature of the oven is 60-80 ℃.
The application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material is characterized by comprising the following steps:
a) putting 4-10 mg of molybdenum and nitrogen doped lignocellulose composite nano adsorption material into a 50mL test tube, adding 20-50 mL potassium dichromate solution, adjusting the pH value of the solution by using hydrochloric acid or sodium hydroxide, and reacting under the condition of magnetic stirring to obtain a reacted solution;
b) taking the reacted solution, filtering, putting 2-5 mL of filtrate into a colorimetric tube, diluting to a marked line, adding sulfuric acid, 1:1 phosphoric acid and a diphenylcarbazide solution in a volume ratio of 1:1, developing for 5min, and measuring the absorbance of the solution at a wavelength of 540nm by using a spectrophotometer;
c) 5 potassium dichromate stock solutions with different concentrations are prepared, and the absorbances of the stock solutions are respectively detected by a spectrophotometer to obtain a standard curve of the relation between the absorbances and the concentrations;
d) calculating the adsorption efficiency or hexavalent chromium removal rate (C)0–Ct)/C0×100％，C0Concentration mg/L, C of hexavalent chromium ions in solution before reactiontAfter the reaction time t, the concentration of hexavalent chromium ions in the solution is mg/L;
e) calculated material adsorption capacity ═ C0-Ct)V/W，C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction is t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, and W is the mass g of the adsorbent participating in the reaction.
In the step a), the pH is 2-9, the concentration of a potassium dichromate solution is 20-60 ppm, and the reaction time is 0-150 min.
In the step b), the volume of the added phosphoric acid is 0.5mL, the volume of the added sulfuric acid is 0.5mL, and the volume of the added diphenylcarbazide solution is 2 mL.
The technical scheme for realizing the aim of the invention is a preparation method and an adsorption technology of a molybdenum and nitrogen doped lignocellulose composite nano adsorption material, which comprises the following steps:
the method comprises the steps of calcining the lignocellulose in an ammonia gas atmosphere, naturally cooling and grinding to obtain the nitrogen-doped lignocellulose;
dissolving 0.1-1 mmol of ammonium molybdate in 10-100 mL of deionized water to prepare a solution I;
thirdly, dissolving 5-10 mmol of thioacetamide in 10-50 mL of deionized water to prepare a solution II;
fully and uniformly mixing the solution I and the solution II to prepare a solution III;
fifthly, adding the nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
sixthly, transferring the solution IV into a high-pressure reaction kettle, and carrying out high-temperature reaction;
after the solution is cooled, performing centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively cleaning the precipitates with deionized water and absolute ethyl alcohol, and placing the cleaned reaction product in an oven for drying overnight to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
putting 4-10 mg of the product of step-night into a 50mL test tube, adding 20-50 mL potassium dichromate solution, adjusting the pH value of the solution by using hydrochloric acid or sodium hydroxide, and reacting under the condition of magnetic stirring;
taking the solution after the self-lifting reaction, filtering, putting 2-5 mL of filtrate into a colorimetric tube, diluting to a marked line, adding sulfuric acid, 1:1 phosphoric acid and a dibenzhydrazine solution in a volume ratio of 1:1, developing for 5min, and measuring the absorbance of the solution at a wavelength of 540nm by using a spectrophotometer;
preparing 5 potassium dichromate stock solutions with different concentrations, and respectively detecting the absorbance of the stock solutions by using a spectrophotometer to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or hexavalent chromium removal rate is calculated as (C)0-Ct)/C0×100％(C0Before the reaction, the concentration of hexavalent chromium ions in the solution is mg/L, and after the Ct reaction time is t, the concentration of hexavalent chromium ions in the solution is mg/L)
Calculating adsorption capacity of material (C)0-Ct)V/W(C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction for t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, and W is the mass g of the adsorbent participating in the reaction).
The reaction calcination temperature in the step (1) is 600-800 ℃, the temperature rise speed is 5-15 ℃/min, and the calcination time is 1-3 h.
The mass of the lignocellulose obtained in the step fifthly is 10-30 mg.
The volume of the solution in the step (6) is 60-100 mL, the reaction temperature is 180-220 ℃, and the reaction time is 16-24 hours.
The centrifugation rate of the step S is 2000-6000 r/min, the cleaning times of the ethanol and the water are 3-6 times, and the stable temperature of an oven is 60-80 ℃.
And the pH value is 2-9, the concentration of the potassium dichromate solution is 20-60 ppm, and the reaction time is 0-150 min.
The volume of the added phosphoric acid is 0.5mL, the volume of the added sulfuric acid is 0.5mL, and the volume of the added diphenylcarbazide solution is 2 mL.
Compared with the prior art, the invention has the following beneficial effects:
firstly, the nitrogen-doped lignocellulose is added into a molybdenum sulfide synthesis system to better regulate and control the structure of molybdenum sulfide, so that a molybdenum sulfide compound has larger specific surface area and better dispersion performance, and the synergistic effect of molybdenum disulfide and nitrogen-doped lignocellulose can ensure that the obtained compound has better adsorption performance.
Secondly, the calcined lignocellulose has better structure, more stable performance, corrosion resistance, aging resistance and high reuse rate.
And thirdly, in step-S, firstly, washing with ethanol to remove unreacted thioacetamide, and then washing with deionized water to remove unreacted inorganic ions, so that the pure molybdenum and nitrogen doped lignocellulose composite nano material can be obtained.
The molybdenum and nitrogen doped lignocellulose composite nano material has excellent adsorption performance, simple synthesis method and lower cost, has high removal rate when being used for chromium-containing wastewater, and has higher potential industrial application value. For wastewater with the initial hexavalent chromium concentration lower than 50ppm, the removal rate of hexavalent chromium can reach more than 80% according to 200mg/L of molybdenum and nitrogen doped lignocellulose.
To sum up, the invention relates to preparation and application of a molybdenum and nitrogen doped lignocellulose composite nano antibacterial material, which comprises the following steps: and uniformly dispersing the calcined nitrogen-doped lignocellulose into a system for synthesizing molybdenum disulfide, reacting in a high-pressure reaction kettle, centrifugally separating precipitates, and drying overnight to obtain the molybdenum and nitrogen-doped lignocellulose composite. Adding a certain amount of the nano composite material into hexavalent chromium solutions with different concentrations, and magnetically stirring for reaction. And (3) taking out a proper amount of solution after different times of reaction, filtering, adding a sulfuric acid solution, a phosphoric acid solution and a diphenylcarbazide solution into the filtrate, detecting the absorbance of the solution by using a spectrophotometer, and calculating the concentration of the reacted hexavalent chromium solution through a standard curve to obtain the removal efficiency. The results prove that: the molybdenum and nitrogen doped lignocellulose composite has good adsorption effect on hexavalent chromium, the adsorption performance of the molybdenum and nitrogen doped lignocellulose composite is basically kept unchanged after repeated tests, and the molybdenum and nitrogen doped lignocellulose composite has good stability.
Drawings
Fig. 1 is an SEM image of a molybdenum and nitrogen doped lignocellulosic composite in example 1 of the present invention.
Fig. 2 is a TEM image of a molybdenum and nitrogen doped lignocellulosic composite of example 1 of the present invention.
FIG. 3 shows the removal rate of hexavalent chromium ions by reacting molybdenum-and nitrogen-doped lignocellulose at different initial concentrations for different times.
FIG. 4 shows the adsorption capacity of the material when the equilibrium of the molybdenum-nitrogen doped lignocellulose is reached under different initial concentration conditions.
Detailed Description
The invention is further described with reference to the accompanying drawings and the description thereof.
Example 1
The preparation and application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material sequentially comprise the following steps:
calcining lignocellulose at 800 ℃ for 2h in an ammonia atmosphere, naturally cooling at the heating rate of 5 ℃/min, and grinding to obtain nitrogen-doped lignocellulose;
dissolving 0.5mmol of ammonium molybdate in 40mL of deionized water to prepare solution I;
dissolving 10mmol of thioacetamide in 40mL of deionized water to prepare a solution II;
mixing the solution I and the solution II sufficiently to prepare a solution III;
adding 30mg of nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
fifthly, transferring 80mL of solution IV into a 100mL high-pressure reaction kettle, and reacting for 20h at 200 ℃;
sixthly, after the solution is cooled, performing centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively cleaning the precipitates for 3 times by using deionized water and absolute ethyl alcohol, and placing the cleaned reaction product in a drying oven for drying overnight at 60 ℃ to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material, wherein the morphology of the adsorption material is shown in figures 1 and 2;
putting 6mg of the product of stephans into a 50mL test tube, adding 30mL of potassium dichromate solution with the concentration of 20ppm, adjusting the pH of the solution to 2 by using hydrochloric acid or sodium hydroxide, and reacting for 5, 10, 20 and 30min under the condition of magnetic stirring;
taking the reacted solution, filtering, putting 2mL of filtrate into a colorimetric tube, diluting to a marked line, respectively adding 1:1 sulfuric acid, 1:1 phosphoric acid, 0.5mL and 2mL of diphenylcarbazide solution, developing for 5min, and measuring the absorbance at the wavelength of 540nm by using a spectrophotometer;
preparing five potassium dichromate stock solutions with different concentrations of 20ppm, 30ppm, 40ppm, 50ppm and 60ppm from the self-skin, and detecting the absorbance of the stock solutions by using a spectrophotometer respectively to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or the hexavalent chromium removal rate is calculated as (C)0-Ct)/C0×100％(C0Before the reaction, the concentration of hexavalent chromium ions in the solution is mg/L, and after the Ct reaction time is t, the concentration of hexavalent chromium ions in the solution is mg/L)
Calculated material adsorption capacity ═ C0-Ct)V/W(C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction for t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, W is the mass g of the adsorbent participating in the reaction)
Hexavalent chromium removal efficiency (C)0-C1)/C0×100％＝100％
Example 2
The preparation and application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material sequentially comprise the following steps:
calcining lignocellulose at 800 ℃ for 2h in an ammonia gas atmosphere, naturally cooling at the heating rate of 5 ℃/min, and grinding to obtain nitrogen-doped lignocellulose;
dissolving 0.5mmol of ammonium molybdate in 40mL of deionized water to prepare a solution I;
dissolving 10mmol of thioacetamide in 40mL of deionized water to prepare a solution II;
fully and uniformly mixing the solution I and the solution II to prepare a solution III;
fifthly, adding 30mg of nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
sixthly, transferring 80mL of the solution IV into a 100mL high-pressure reaction kettle, and reacting for 20h at 200 ℃;
after the solution is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing the precipitates for 3 times by using deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight at 60 ℃ to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
putting 6mg of the product of step-night into a 50mL test tube, adding 30mL of potassium dichromate solution with the concentration of 30ppm, adjusting the pH of the solution to 2 by using hydrochloric acid or sodium hydroxide, and reacting for 5, 10, 20 and 30min under the condition of magnetic stirring;
taking the solution after the self-lifting reaction, filtering, taking 2mL of filtrate in a colorimetric tube, diluting to a marked line, respectively adding 1:1 sulfuric acid, 1:1 phosphoric acid 0.5mL and 2mL of diphenylcarbazide solution, developing for 5min, and measuring the absorbance at the wavelength of 540nm by using a spectrophotometer;
preparing five potassium dichromate stock solutions with different concentrations of 20ppm, 30ppm, 40ppm, 50ppm and 60ppm respectively, and detecting the absorbance of the five potassium dichromate stock solutions by using a spectrophotometer respectively to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or hexavalent chromium removal rate is calculated as (C)0-Ct)/C0×100％(C0Before the reaction, the concentration of hexavalent chromium ions in the solution is mg/L, and after the Ct reaction time is t, the concentration of hexavalent chromium ions in the solution is mg/L)
Calculating adsorption capacity of material (C)0-Ct)V/W(C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction for t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, W is the mass g of the adsorbent participating in the reaction)
Hexavalent chromium removal efficiency (C)0-C1)/C0×100％＝100％
Example 3
The preparation and application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material sequentially comprise the following steps:
calcining lignocellulose at 800 ℃ for 2h in an ammonia gas atmosphere, naturally cooling at the heating rate of 5 ℃/min, and grinding to obtain nitrogen-doped lignocellulose;
dissolving 0.5mmol of ammonium molybdate in 40mL of deionized water to prepare a solution I;
dissolving 10mmol of thioacetamide in 40mL of deionized water to prepare a solution II;
fully and uniformly mixing the solution I and the solution II to prepare a solution III;
fifthly, adding 30mg of nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
sixthly, transferring 80mL of the solution IV into a 100mL high-pressure reaction kettle, and reacting for 20h at 200 ℃;
after the solution is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing the precipitates for 3 times by using deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight at 60 ℃ to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
putting 6mg of the product of step-night into a 50mL test tube, adding 30mL of potassium dichromate solution with the concentration of 40ppm, adjusting the pH of the solution to 2 by using hydrochloric acid or sodium hydroxide, and reacting for 5, 10, 20 and 30min under the condition of magnetic stirring;
taking the solution after the self-lifting reaction, filtering, taking 2mL of filtrate in a colorimetric tube, diluting to a marked line, respectively adding 1:1 sulfuric acid, 1:1 phosphoric acid 0.5mL and 2mL of diphenylcarbazide solution, developing for 5min, and measuring the absorbance at the wavelength of 540nm by using a spectrophotometer;
preparing five potassium dichromate stock solutions with different concentrations of 20ppm, 30ppm, 40ppm, 50ppm and 60ppm respectively, and detecting the absorbance of the five potassium dichromate stock solutions by using a spectrophotometer respectively to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or hexavalent chromium removal rate is calculated as (C)0-Ct)/C0×100％(C0Before the reaction, the concentration of hexavalent chromium ions in the solution is mg/L, and after the Ct reaction time is t, the concentration of hexavalent chromium ions in the solution is mg/L)
Calculating adsorption capacity of material (C)0-Ct)V/W(C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction for t time is mg/L, and V is the concentration participating in the reactionVolume L of potassium dichromate solution, W is mass g of adsorbent participating in reaction
Hexavalent chromium removal efficiency (C)0-C1)/C0×100％＝94.0％
Example 4
The preparation and application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material sequentially comprise the following steps:
calcining lignocellulose at 800 ℃ for 2h in an ammonia gas atmosphere, naturally cooling at the heating rate of 5 ℃/min, and grinding to obtain nitrogen-doped lignocellulose;
dissolving 0.5mmol of ammonium molybdate in 40mL of deionized water to prepare a solution I;
dissolving 10mmol of thioacetamide in 40mL of deionized water to prepare a solution II;
fully and uniformly mixing the solution I and the solution II to prepare a solution III;
fifthly, adding 30mg of nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
sixthly, transferring 80mL of the solution IV into a 100mL high-pressure reaction kettle, and reacting for 20h at 200 ℃;
after the solution is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing the precipitates for 3 times by using deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight at 60 ℃ to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
putting 6mg of the product of step-night into a 50mL test tube, adding 30mL of potassium dichromate solution with the concentration of 50ppm, adjusting the pH of the solution to 2 by using hydrochloric acid or sodium hydroxide, and reacting for 5, 10, 20 and 30min under the condition of magnetic stirring;
taking the solution after the self-lifting reaction, filtering, taking 2mL of filtrate in a colorimetric tube, diluting to a marked line, respectively adding 1:1 sulfuric acid, 1:1 phosphoric acid 0.5mL and 2mL of diphenylcarbazide solution, developing for 5min, and measuring the absorbance at the wavelength of 540nm by using a spectrophotometer;
preparing five potassium dichromate stock solutions with different concentrations of 20ppm, 30ppm, 40ppm, 50ppm and 60ppm respectively, and detecting the absorbance of the five potassium dichromate stock solutions by using a spectrophotometer respectively to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or hexavalent chromium removal rate is calculated as (C)0-Ct)/C0X 100% (concentration mg/L of hexavalent chromium ion in the solution before C0 reaction, concentration mg/L of hexavalent chromium ion in the solution after Ct reaction time t)
Calculating adsorption capacity of material (C)0-Ct)V/W(C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction for t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, W is the mass g of the adsorbent participating in the reaction)
Hexavalent chromium removal efficiency (C)0-C1)/C0×100％＝80.4％
Example 5
The preparation and application of the molybdenum and nitrogen doped lignocellulose composite nano adsorption material sequentially comprise the following steps:
calcining lignocellulose at 800 ℃ for 2h in an ammonia gas atmosphere, naturally cooling at the heating rate of 5 ℃/min, and grinding to obtain nitrogen-doped lignocellulose;
dissolving 0.5mmol of ammonium molybdate in 40mL of deionized water to prepare a solution I;
dissolving 10mmol of thioacetamide in 40mL of deionized water to prepare a solution II;
fully and uniformly mixing the solution I and the solution II to prepare a solution III;
fifthly, adding 30mg of nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
sixthly, transferring 80mL of the solution IV into a 100mL high-pressure reaction kettle, and reacting for 20h at 200 ℃;
after the solution is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing the precipitates for 3 times by using deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight at 60 ℃ to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
putting 6mg of the product of step-night into a 50mL test tube, adding 30mL of potassium dichromate solution with the concentration of 60ppm, adjusting the pH of the solution to 2 by using hydrochloric acid or sodium hydroxide, and reacting for 5, 10, 20 and 30min under the condition of magnetic stirring;
taking the solution after the self-lifting reaction, filtering, taking 2mL of filtrate in a colorimetric tube, diluting to a marked line, respectively adding 1:1 sulfuric acid, 1:1 phosphoric acid 0.5mL and 2mL of diphenylcarbazide solution, developing for 5min, and measuring the absorbance at the wavelength of 540nm by using a spectrophotometer;
preparing five potassium dichromate stock solutions with different concentrations of 20ppm, 30ppm, 40ppm, 50ppm and 60ppm respectively, and detecting the absorbance of the five potassium dichromate stock solutions by using a spectrophotometer respectively to obtain a standard curve of the relationship between the absorbance and the concentration;
the adsorption efficiency or hexavalent chromium removal rate is calculated as (C)0-Ct)/C0×100％(C0Before the reaction, the concentration of hexavalent chromium ions in the solution is mg/L, and after the Ct reaction time is t, the concentration of hexavalent chromium ions in the solution is mg/L)
Calculating adsorption capacity of material (C)0-Ct) V/W (concentration mg/L of hexavalent chromium ions in the solution before the reaction C0, concentration mg/L of hexavalent chromium ions in the solution after the time t of the Ct reaction, V is the volume L of the potassium dichromate solution involved in the reaction, W is the mass g of the adsorbent involved in the reaction)
Hexavalent chromium removal efficiency (C)0-C1)/C0×100％＝68.6％
The data of examples 1 to 5 were calculated, and the removal efficiency was calculated from the data of examples 1 to 5 and plotted as FIG. 3, and the adsorption capacity at the adsorption equilibrium was calculated from the data of examples 1 to 5 and plotted as FIG. 4.
As can be seen from FIG. 3, at a material concentration of 200mg/L, the removal efficiency can reach 100% for a hexavalent chromium solution having a concentration of less than 30ppm, and at a hexavalent chromium concentration of less than 50ppm, the removal efficiency is greater than 80%, and a balance is reached within 150min, and as the initial concentration of hexavalent chromium increases, the adsorption capacity continuously increases, but at a hexavalent chromium ion concentration of 60ppm, the adsorption capacity reaches a maximum and is maintained at 266 mg/g.
The absorbance detection is carried out by a Spectrum ultraviolet-visible spectrophotometer.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention. In addition to the above examples, the present invention may have other embodiments, for example, the mass and volume of each component may be scaled up several times. All the technical solutions formed by using equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention. Technical features of the present invention which are not described may be implemented by or using the prior art, and will not be described herein.

Claims (7)

1. A preparation method of a molybdenum and nitrogen doped lignocellulose composite nano adsorption material is characterized by comprising the following steps:
(1) calcining lignocellulose in an ammonia atmosphere, naturally cooling, and grinding to obtain nitrogen-doped lignocellulose;
(2) dissolving 0.1-1 mmol of ammonium molybdate in 10-100 mL of deionized water to prepare a solution I;
(3) dissolving 5-10 mmol of thioacetamide in 10-50 mL of deionized water to prepare a solution II;
(4) fully and uniformly mixing the solution I and the solution II to prepare a solution III;
(5) adding nitrogen-doped lignocellulose into the solution III, and uniformly stirring to obtain a solution IV;
(6) transferring the solution IV into a high-pressure reaction kettle for high-temperature reaction;
(7) after the solution IV of the high-temperature reaction is cooled, carrying out centrifugal separation on the reaction product obtained in the step (6), collecting precipitates, respectively washing the precipitates with deionized water and absolute ethyl alcohol, and placing the washed reaction product in an oven for drying overnight to obtain the molybdenum and nitrogen doped lignocellulose composite nano adsorption material;
when in application, the method comprises the following steps:
a) putting 4-10 mg of molybdenum and nitrogen doped lignocellulose composite nano adsorption material into a 50mL test tube, adding 20-50 mL potassium dichromate solution, adjusting the pH value of the solution by using hydrochloric acid or sodium hydroxide, and reacting under the condition of magnetic stirring to obtain a reacted solution;
b) taking the reacted solution, filtering, putting 2-5 mL of filtrate into a colorimetric tube, diluting to a marked line, adding sulfuric acid, 1:1 phosphoric acid and a diphenylcarbazide solution in a volume ratio of 1:1, developing for 5min, and measuring the absorbance of the solution at a wavelength of 540nm by using a spectrophotometer;
c) 5 potassium dichromate stock solutions with different concentrations are prepared, and the absorbances of the stock solutions are respectively detected by a spectrophotometer to obtain a standard curve of the relation between the absorbances and the concentrations;
d) calculating the adsorption efficiency or hexavalent chromium removal rate = (C)0–Ct)/C0× 100% ，C0Concentration mg/L, C of hexavalent chromium ions in solution before reactiontAfter the reaction time t, the concentration of hexavalent chromium ions in the solution is mg/L;
e) calculated material adsorption capacity = (C)0-Ct)V/W，C0The concentration of hexavalent chromium ions in the solution before the reaction is mg/L, the concentration of hexavalent chromium ions in the solution after the Ct reaction is t time is mg/L, V is the volume L of the potassium dichromate solution participating in the reaction, and W is the mass g of the adsorbent participating in the reaction.
2. The preparation method of the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material as claimed in claim 1, wherein in the step (1), the reaction calcination temperature is 600-800 ℃, the temperature rise speed is 5-15 ℃/min, and the calcination time is 1-3 h.
3. The preparation method of the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material as claimed in claim 1, wherein in the step (5), the mass of the lignocellulose is 10-30 mg.
4. The preparation method of the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material as claimed in claim 1, wherein in the step (6), the volume of the solution IV is 60-100 mL, the reaction temperature is 180-220 ℃, and the reaction time is 16-24 hours.
5. The preparation method of the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material according to claim 1, wherein in the step (7), the centrifugation rate is 2000-6000 r/min, the cleaning times of ethanol and water are 3-6 times, and the stable temperature of an oven is 60-80 ℃.
6. The preparation method of the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material as claimed in claim 1, wherein in the step a), the pH is 2-9, the concentration of the potassium dichromate solution is 20-60 ppm, and the reaction time is 0-150 min.
7. The method for preparing the molybdenum and nitrogen doped lignocellulose composite nano-adsorption material as recited in claim 1, wherein in the step b), the volume of the added phosphoric acid is 0.5mL, the volume of the added sulfuric acid is 0.5mL, and the volume of the added diphenylcarbazide solution is 2 mL.
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