CN115722251A - Preparation method and application of hetero-atom-doped algae-based biochar loaded nano zero-valent metal catalyst - Google Patents

Abstract

The invention discloses a preparation method of a heteroatom-doped algae-based biochar loaded nano zero-valent metal catalyst, which comprises the steps of pretreatment of algae organisms, preparation of heteroatom-doped algae-based biochar, preparation of phosphorus and heteroatom co-doped algae-based biochar, loading of nano zero-valent metal and the like to obtain the heteroatom-doped algae-based biochar loaded nano zero-valent metal catalyst, and application of the catalyst in treatment of heavy metal-organic matter composite polluted wastewater.

Description

Preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst and applications

technical field

The invention belongs to the technical field of non-ferrous metal industrial wastewater treatment; in particular, it relates to a preparation method of a highly active composite catalyst of heteroatom-doped algae-based biochar loaded with nano-zero-valent metals for efficient treatment of non-ferrous metal industrial wastewater, and the use of the composite catalyst material The activated oxidant is used in the treatment of heavy metal-organic compound polluted wastewater in nonferrous metal industrial wastewater.

Background technique

The pollution caused by non-ferrous metal industrial wastewater is mainly organic oxygen-consuming substances pollution, inorganic solid suspended matter pollution, heavy metal pollution, petroleum pollution, alcohol pollution, acid-base pollution and heat pollution. If the wastewater produced by the non-ferrous metal industry is directly discharged into the environment, it will not only cause serious pollution to the water body or other environmental factors, affect the ecological environment, but also cause a waste of resources. Therefore, how to efficiently and stably treat colored industrial wastewater and recover valuable elements from colored industrial wastewater has become an urgent problem to be solved in the current treatment of colored industrial wastewater.

The SO ₄ ^- produced by activated persulfate has a higher standard reduction potential (2.5-3.1eV) and a longer active time (30-40μs) than the hydroxyl radical (OH) produced by the traditional Fenton technology ) and wider pH reactivity and stability, which makes the advanced oxidation technology based on sulfate radicals widely used in the field of wastewater treatment. Nano-zero-valent metal materials represented by nano-zero-valent iron and nickel have the advantages of environmental friendliness, low price, high catalytic activity, and strong reducibility, and are widely used in environmental remediation fields such as sewage treatment, especially as sulfate-based Efficient heterogeneous catalysts in radical advanced oxidation technology for enhanced degradation of pollutants in wastewater. However, due to their small particle size and high chemical activity, nano-zero-valent metals are prone to oxidation, agglomeration, and loss during water treatment. In addition, when interacting with target pollutants, most of the electrons generated by nano-zero-valent metals cannot be effectively transferred to reactive groups, but to hydrogen ions or dissolved oxygen in the water phase, resulting in a decrease in the effective electron utilization. This affects the reactivity and pollutant removal efficiency of nano-zero-valent metals in water containing pollutants.

Contents of the invention

Aiming at the problem that nanometer zero-valent metals are easily oxidized and agglomerated in the process of wastewater treatment, the present invention provides a heteroatom-doped algae-based organism that can stably exist in wastewater solution with high reactivity, low economic cost, and environmental friendliness. Preparation method of carbon-supported nanometer zero-valent metal catalyst.

The preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst of the present invention is as follows:

(1) Collect the algae, clean them, dry them, crush them, and sieve them, then add a glutaraldehyde solution with a volume concentration of 2.5% to 5%, mix and stir them for 10 to 15 hours, and wash the solids with ultrapure water for 4 to 6 hours after solid-liquid separation. After three times, the algal organisms were soaked in ethanol solutions with a volume concentration of 70%, 90%, and 100% in sequence, soaked for 0.5 h each, separated from solid and liquid, and dried to obtain pretreated algal organisms;

The algal organisms are one or more of chlorella, cyanobacteria, diatoms, green algae, golden algae, and dinoflagellates;

Crush and sieve to obtain a powder with a particle size below 0.4mm;

(2) Place the pretreated algae in the extract solution, and disperse it ultrasonically at 50-70°C for 0.5-1.0 h. After solid-liquid separation, the solid is washed with ultrapure water until the pH is 9.5-10, and the washed product is placed in Solvothermal reaction is carried out in the heteroatom precursor solution. After the reaction, the solid and liquid are separated, and the solid is alternately washed with ultrapure water and absolute ethanol solution until the pH is neutral, and vacuum dried to constant weight to obtain heteroatom doping Algae-based biochar;

The extract is prepared by mixing a sodium dodecyl sulfate solution with a mass volume concentration of 3-5% and a sodium hydroxide solution with a mass concentration of 2-4% in a volume ratio of 1:1-3; the heteroatom precursor It is one of nitrogen source, boron source and sulfur source, the concentration of heteroatom precursor solution is 0.3-0.9 mol/L, and the nitrogen source is ammonium chloride, ammonium persulfate, melamine, urea, ammonium bicarbonate One or more; the boron source is one or more of boric acid, ammonium borate, dimethylamine borane; the sulfur source is thioacetic acid, thiourea, thiosemicarbazide, thioacetamide, L- One or more of cysteine and L-methionine; the hydrothermal reaction temperature is 180-210°C, and the reaction time is 3-8 h;

(3) Under an inert atmosphere, mix heteroatom-doped algae-based biochar and hypophosphite and then place it in a tube furnace for pyrolysis and carbonization to obtain phosphorus and heteroatom-doped algae-based biochar;

Heteroatom-doped algae-based biochar and hypophosphite are mixed at a mass ratio (2-4): 1, heated to 250-350°C at a rate of 1-5°C/min, and kept for 0.5-1 h to promote The solid hypophosphite gradually decomposes to generate phosphine gas and continuously fumigates the algae-based biochar. Under this atmospheric condition, the phosphine gas selectively corrodes the heteroatom-doped algae-based biochar, and the phosphine gas enters the cell wall of the biochar. Occupy vacancies in the middle; then raise the temperature to 500-800°C at a rate of 6-12°C/min, and pyrolyze for 1.5-5 hours, and the generated phosphine gas provides an additional source of phosphorus. With the increase of pyrolysis temperature, the Phosphorus is also uniformly doped into heteroatom-doped algae-based biochar during the process of mesopores appearing on the surface of atom-doped algae-based biochar; hypophosphites are sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, hypophosphorous One or several kinds of magnesium;

(4) Under a nitrogen atmosphere, place phosphorus and heteroatom co-doped algae-based biochar in a 0.025-0.1g/mL metal salt solution, stir for 0.5h, then slowly add the reducing agent solution dropwise, after the dropwise addition is completed Continue to stir for 0.5h to separate the solid from the liquid. The solid is then cleaned by vacuum filtration with ultrapure water and absolute ethanol solution for 3 to 6 times each, and vacuum dried to obtain phosphorus and heteroatom co-doped algae-based biochar-loaded nano Zero-valent metal catalysts;

Described metal salt is one or both in iron salt, molybdenum salt, cobalt salt, nickel salt, cerium salt, zinc salt, copper salt; When metal salt is two kinds, the mass ratio of double metal salt is 1: 5 to 5:1; the reducing agent is one of potassium borohydride, sodium borohydride, lithium borohydride, ascorbic acid, and tea polyphenols, and the molar ratio of metal salt to reducing agent is 1:5 to 1:15.

Another object of the present invention is to apply the heteroatom-doped algae-based biochar-loaded nano-zero-valent metal catalyst prepared by the above method in the treatment of heavy metal-organic compound polluted wastewater, and the heteroatom-doped algae-based biochar-loaded nano-zero-valent metal Catalyst and one or more of persulfate (PS), peroxide (hydrogen peroxide H ₂ O ₂ /calcium peroxide CP), peracetic acid (PAA), potassium permanganate (KMnO ₄ ) use.

The method of the invention not only reduces the preparation cost and simplifies the operation procedure, but also effectively prevents the oxidation and agglomeration of nano-zero-valent metal particles in the wastewater treatment process on the basis of no secondary pollution to the environment, and effectively improves the concentration of nano-zero-valent metal particles. The surface activity and stability of the particles; the invention also opens up a new way for the resource utilization of waste algae biomass and the development of low-cost, high-activity and green catalysts.

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

(1) The present invention proposes for the first time the use of algae to prepare heteroatom-doped mesoporous biochar materials with high reactivity and low economic cost. The algae used in the present invention have a wide range of sources, and the harmful algae can be prepared by a simple preparation method. High-value environmental functional materials can be used to remove harmful algae while utilizing the resource value of algae. This method is environmentally friendly and easy to promote in large-scale production;

(2) The present invention prepares heteroatom-doped mesoporous biochar materials by means of heteroatom doping and morphology control, and obtains algae-based biochar rich in functional groups by adjusting the hydrothermal reaction conditions;

(3) In the present invention, on the basis that solid hypophosphite is easily decomposed under heated conditions to produce phosphine, it is cleverly introduced into heteroatom-doped algae-based biochar, and the heteroatom-doped algae The phosphine gas produced in this process will conduct controllable corrosion on the heteroatom-doped algae-based biochar under closed conditions, and then obtain phosphorus and heteroatom co-doping after further carbonization at a medium temperature. Mesoporous algae-based biochar composite material; the innovative use of medium-temperature fumigation of phosphine vapor not only endows the biochar material with a highly mesoporous structure, but also achieves a double-difference in the process of phosphorus being uniformly doped into heteroatom-doped biochar. The co-doping of atoms can greatly improve the efficiency of biochar materials in electron transport and mass transfer. In addition, the co-doping of diatoms in biochar materials enhances the chemical adsorption of pollutants and the activation efficiency of highly active oxidants, lowers the catalytic activation barrier, and the synergistic adjustment of defects and diatomic doping improves the reaction kinetics;

(4) By regulating the structure of algae-based biochar, nano-zero-valent metals were subsequently introduced into heteroatom-doped mesoporous algae-based biochar by liquid phase reduction precipitation method to form heteroatom-doped mesoporous algae-based biochar loaded with nano-zero-valent metals The highly active composite reaction material greatly shortens the mass transfer distance between the active center species (nano-zero-valent metal core, free radicals) and the target pollutants, and promotes fast diffusion kinetics to ensure effective contact between the active center species and the target pollutants , which enhances the overall effect of the reaction system, and at the same time solves the shortcomings of poor electron selectivity and easy agglomeration of nano-zero-valent metals, and the shortcomings of free radical self-quenching or ineffective oxidation reactions (such as reactions with water molecules);

(4) In the present invention, heteroatom-doped mesoporous algae-based biochar is obtained in a novel, green and sustainable way. Due to the presence of magnetic metal elements such as nanometer zero-valent iron, nickel, and cobalt in the algae-based biochar material, it can be The simple recycling of the composite material can be realized, and the loss of the composite material can be avoided, which has a good prospect of large-scale application.

Description of drawings

Figure 1 is a scanning electron microscope (SEM) image of nanometer zero-valent iron in Comparative Example 1;

Fig. 2 is a scanning electron microscope (SEM) image of nitrogen and phosphorus co-doped algae-based biochar-supported nano-zero-valent iron catalyst in Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments. It should be understood that the protection scope of the present invention is not limited to the content shown.

Example 1

(1) After collecting the chlorella and washing it, crush and sieve to obtain a powder with a particle size of ≤0.4 mm, add glutaraldehyde solution with a volume concentration of 2.5% to the chlorella powder, stir for 10 hours, filter, and rinse the filter residue with ultrapure water After 5 times, soak in ethanol solutions with a volume concentration of 70%, 90%, and 100% in sequence, soak for 0.5 hours each, filter with suction, and dry the solid at 80°C to obtain pretreated chlorella powder;

(2) Put 3 g of pretreated chlorella powder in the extract solution (sodium lauryl sulfate solution with a mass volume concentration of 3% and a sodium hydroxide solution with a mass concentration of 2.9% are prepared by mixing the volume ratio of 1:1 ), ultrasonically (320W) at 60°C for 0.5h, suction filtered, and the solid was washed with ultrapure water until the pH was 9.5-10, and the washed product was placed in a 0.3mol/L melamine solution and solvothermally heated at 180°C React for 6 hours. After the reaction is completed, filter, wash the solid with ultrapure water and absolute ethanol alternately until the pH is neutral, and dry it in vacuum at 80°C to constant weight to obtain nitrogen-doped chlorella-based biochar;

(3) In a nitrogen atmosphere, nitrogen-doped chlorella-based biochar and sodium hypophosphite were mixed at a mass ratio of 2:1, placed in a tube furnace, and heated to 250°C at a rate of 2°C/min , after keeping for 1h, the temperature was raised to 600°C at a rate of 7°C/min, and pyrolyzed for 5h to obtain nitrogen and phosphorus co-doped algae-based biochar;

(4) Under a nitrogen atmosphere, place nitrogen and phosphorus co-doped chlorella biochar in 0.025 g/mL ferric chloride solution, stir for 0.5 h, then slowly add tea polyphenol solution (ferric chloride and tea The molar ratio of polyphenols is 1:15), after the dropwise addition, continue to stir for 0.5 h, then filter with suction, and filter the filter residue with ultrapure water and absolute ethanol solution in order to vacuum filter, wash each 4 times, and vacuum dry at 60°C for 8 h The nitrogen-phosphorus co-doped chlorella biochar-supported nano zero-valent iron catalyst was obtained (Figure 2).

Comparative example 1: In 0.025g/mL ferric chloride solution, slowly add tea polyphenol solution dropwise (the molar ratio of ferric chloride to tea polyphenol is 1:15), continue to stir for 0.5h after the dropwise addition, and pump After filtering, the filter residue was cleaned by vacuum filtration with ultrapure water and absolute ethanol solution in turn, each washed 4 times, and vacuum-dried at 60°C for 8 hours to obtain the nano-zero-valent iron catalyst (Figure 1). It can be seen from the figure that the nano-zero-valent iron The iron particles are in the state of chain aggregates, and the agglomeration is very serious.

Example 2

(1) Collect cyanobacteria, wash them, crush and sieve to obtain a powder with a particle size of ≤0.4mm, add glutaraldehyde solution with a volume concentration of 3.5% to the cyanobacteria powder, stir for 12 hours, filter, and rinse the filter residue with ultrapure water for 5 times. Soak in ethanol solutions with a volume concentration of 70%, 90%, and 100% in sequence, soak for 0.5 hours each, filter with suction, and dry the solid at 70°C to obtain pretreated cyanobacteria powder;

(2) Put 5 g of pretreated cyanobacteria powder in the extract solution (made by mixing sodium lauryl sulfate solution with a mass volume concentration of 4% and a sodium hydroxide solution with a mass concentration of 3.0% at a volume ratio of 1:1) , disperse by ultrasonic (320W) at 50°C for 1h, filter with suction, wash the solid with ultrapure water until the pH is 9.5-10, put the washed product in 0.9 mol/L L-methionine solution, and react with solvent heat at 190°C for 5h , after the reaction is finished, filter, wash the solid alternately with ultrapure water and absolute ethanol solution until the pH is neutral, and vacuum-dry at 85°C to constant weight to obtain sulfur-doped cyanobacteria-based biochar;

(3) In a nitrogen atmosphere, mix sulfur-doped cyanobacteria-based biochar and potassium hypophosphite in a mass ratio of 3:1 and place it in a tube furnace, heat up to 300 °C at a rate of 3 °C/min, and keep After 0.8h, the temperature was raised to 700°C at a rate of 8°C/min, and pyrolyzed for 4h to obtain sulfur and phosphorus doped algae-based biochar;

(4) Under a nitrogen atmosphere, place sulfur and phosphorus co-doped cyanobacterial biochar in 0.05 g/mL nickel phosphate solution, stir for 0.5 h, then slowly add sodium borohydride solution dropwise (the moles of nickel phosphate and sodium borohydride ratio of 1:6), continue to stir for 0.5h after the dropwise addition, and filter with suction. The filter residue is cleaned by vacuum filtration with ultrapure water and absolute ethanol solution successively, each washed 5 times, and vacuum-dried at 60°C for 8 hours to obtain sulfur phosphorus Co-doped cyanobacterial biochar supported nanometer zero-valent nickel catalyst.

Comparative example 2: Slowly add sodium borohydride solution dropwise into 0.05g/mL nickel phosphate solution (the molar ratio of nickel phosphate to sodium borohydride is 1:6), continue to stir for 0.5h after the dropwise addition, and filter with suction. The filter residue was vacuum-filtered and washed with ultrapure water and absolute ethanol solution successively, each washed 5 times, and vacuum-dried at 60°C for 8 h to obtain the nanometer zero-valent nickel catalyst.

Example 3

(1) Collect the diatoms, wash them, crush and sieve to obtain a powder with a particle size of ≤0.4mm, add glutaraldehyde solution with a volume concentration of 4.0% to the diatom powder, stir for 14 hours, filter, and rinse the filter residue with ultrapure water for 5 times Afterwards, soak in ethanol solutions with a volume concentration of 70%, 90%, and 100% in turn, soak for 0.5 hours each, filter with suction, and dry the solid at 75°C to obtain pretreated diatom powder;

(2) Put 5g of pretreated diatom powder in the extract (prepared by mixing sodium lauryl sulfate solution with a mass volume concentration of 4% and sodium hydroxide solution with a mass concentration of 3.5% at a volume ratio of 1:2) disperse by ultrasonic (320W) at 70°C for 0.5h, filter with suction, wash the solid with ultrapure water until the pH is 9.5-10, put the washed product in 0.6 mol/L boric acid solution, and react with solvent heat at 200°C 3h, after the reaction is completed, filter, wash the solid alternately with ultrapure water and absolute ethanol solution until the pH is neutral, and dry it in vacuum at 85°C to constant weight to obtain boron-doped diatom-based biochar;

(3) In a nitrogen atmosphere, boron-doped diatom-based biochar and ammonium hypophosphite were mixed at a mass ratio of 4:1, placed in a tube furnace, and heated to 350 °C at a rate of 4 °C/min. After keeping for 0.5h, the temperature was raised to 750°C at a rate of 9°C/min, and pyrolyzed for 2h to obtain boron and phosphorus co-doped diatom biochar;

(4) Under a nitrogen atmosphere, place boron and phosphorus co-doped algae-based biochar in 0.08g/mL copper chloride solution, stir for 0.5h, and slowly add potassium borohydride solution (nickel phosphate and potassium borohydride The molar ratio is 1:10), after the dropwise addition, continue to stir for 0.5h, filter with suction, and wash the filter residue with ultrapure water and absolute ethanol solution in vacuum, wash each 5 times, and dry in vacuum at 60°C for 8 hours to obtain Boron and phosphorus co-doped diatom biochar supported nano-zero valent copper catalyst;

Comparative example 3: In 0.08g/mL copper chloride solution, slowly dropwise add potassium borohydride solution (the molar ratio of nickel phosphate to potassium borohydride is 1:10), continue stirring for 0.5 h after the dropwise addition, and filter with suction , the filter residue was cleaned by vacuum filtration with ultrapure water and absolute ethanol solution successively, each washed 5 times, and vacuum-dried at 60°C for 8 hours to obtain the nano-zero-valent copper catalyst.

Example 4

(1) Collect the chlorella, wash it, crush and sieve it to obtain a powder with a particle size of ≤0.4mm, add glutaraldehyde solution with a volume concentration of 3% to the chlorella powder, stir for 15 hours, filter, and rinse the filter residue with ultrapure water After 4 times, soak in ethanol solutions with a volume concentration of 70%, 90%, and 100% in sequence, soak for 0.5 h each, filter with suction, and dry the solid at 80°C to obtain pretreated chlorella powder;

(2) Put 5 g of pretreated chlorella powder in the extract solution (sodium lauryl sulfate solution with a mass volume concentration of 4% and a sodium hydroxide solution with a mass concentration of 4% are mixed in a ratio of 1:3 by volume) ), disperse by ultrasonic (320W) at 55°C for 1h, filter with suction, wash the solid with ultrapure water until the pH is 9.5-10, place the washed product in 0.6 mol/L ammonium chloride solution and dissolve it at 200°C Heat reaction for 4 hours, after the reaction, filter, wash the solid alternately with ultrapure water and absolute ethanol solution until the pH is neutral, and vacuum-dry at 85°C to constant weight to obtain nitrogen-doped chlorella-based biochar;

(3) In a nitrogen atmosphere, nitrogen-doped chlorella-based biochar and magnesium hypophosphite were mixed at a mass ratio of 3:1, placed in a tube furnace, and heated to 350°C at a rate of 5°C/min , after keeping for 0.5 h, the temperature was raised to 800 °C at a rate of 10 °C/min, and pyrolyzed for 1.5 h to obtain nitrogen and phosphorus co-doped chlorella biochar;

(4) Under a nitrogen atmosphere, place nitrogen and phosphorus co-doped chlorella biochar in 0.1 g/mL iron phosphate-nickel phosphate (mass ratio 1:5) solution, stir for 0.5 h, and slowly add boron dropwise Potassium hydride solution (the molar ratio of phosphate to potassium borohydride is 1:15), continue to stir for 0.5 h after the dropwise addition, and then filter with suction. The nitrogen-phosphorous co-doped chlorella biochar-supported nano-zero-valent iron-nickel catalyst was obtained by vacuum drying at 60°C for 8 h.

Comparative example 4: Slowly add potassium borohydride solution (the molar ratio of phosphate to potassium borohydride is 1:12) into the solution of 0.1g/mL iron phosphate-nickel phosphate (mass ratio 1:5), after the addition is completed Stirring was continued for 0.5 h, suction filtered, and the filter residue was cleaned by vacuum filtration with ultrapure water and absolute ethanol solution successively, each washed 5 times, and vacuum-dried at 60°C for 8 h to obtain a nanometer zero-valent iron-nickel catalyst.

Example 5

(1) Collect cyanobacteria, wash them, crush and sieve to obtain a powder with a particle size of ≤0.4mm, add a glutaraldehyde solution with a volume concentration of 3.0% to the cyanobacteria powder, stir for 14 hours, filter, and rinse the filter residue with ultrapure water for 6 times, followed by Soak in ethanol solutions with a volume concentration of 70%, 90%, and 100%, soak for 0.5 hours each, filter with suction, and dry the solid at 80°C to obtain pretreated cyanobacteria powder;

(2) Put 5g of pretreated cyanobacteria powder in the extract solution (made by mixing sodium lauryl sulfate solution with a mass volume concentration of 3% and a sodium hydroxide solution with a mass concentration of 3% at a volume ratio of 1:2) , disperse by ultrasonic (320W) at 60°C for 0.5h, filter with suction, wash the solid with ultra-pure water until the pH is 9.5-10, put the washed product in 0.5mol/L ammonium borate solution, and conduct solvothermal reaction at 185°C After 7 hours of reaction, filter, wash the solid with ultrapure water and absolute ethanol solution alternately until the pH is neutral, and dry it in vacuum at 85°C to constant weight to obtain boron-doped cyanobacteria biochar;

(3) In a nitrogen atmosphere, mix boron-doped cyanobacterial biochar and ammonium hypophosphite at a mass ratio of 3:1 and place it in a tube furnace, raise the temperature to 300°C at a rate of 1°C/min, and keep at 0.6 After 1 h, the temperature was raised to 700 °C at a rate of 7 °C/min, and pyrolyzed for 3 h to obtain boron and phosphorus co-doped cyanobacterial biochar;

(4) Under nitrogen atmosphere, place boron and phosphorus co-doped cyanobacteria biochar in 0.08g/mL ferric nitrate-cerium nitrate (mass ratio 1:2) solution, stir for 0.5h, then slowly add sodium borohydride dropwise solution (the molar ratio of nitrate to sodium borohydride is 1:12), continue to stir for 0.5h after the dropwise addition is completed, and then filter with suction. The filter residue is cleaned with ultrapure water and absolute ethanol solution by vacuum filtration, each cleaning 5 times, Boron and phosphorus co-doped cyanobacterial biochar supported nano-zero-valent iron-cerium catalysts were obtained by vacuum drying at 60°C for 8 h.

Comparative example 5: In 0.08g/mL ferric nitrate-cerium nitrate (mass ratio 1:2) solution, slowly dropwise add sodium borohydride solution (the molar ratio of nitrate to sodium borohydride is 1:12), dropwise After completion, continue to stir for 0.5h, filter with suction, and wash the filter residue with ultrapure water and absolute ethanol solution successively, each cleaning 5 times, and vacuum-dry at 60°C for 8 hours to obtain phosphorus-doped algae-based biochar-loaded nano-zero valence Iron cerium catalyst.

Example 6: The catalyst prepared in the above examples was used for the treatment of smelting wastewater in a non-ferrous metal smelting workshop, and 1000 mL of wastewater from the workshop was collected. The pH of the water sample was 6.5±0.5, and the initial dose of pollutants is shown in Table 1;

Take by weighing 0.27g sodium persulfate, put into the 250mL conical flask that fills 50mL water sample, adjust water sample pH subsequently to be 3.5 ± 0.2, the catalyst 0.5g prepared in embodiment 1-5 and comparative example 1-5 , placed in the above-mentioned 250mL Erlenmeyer flasks respectively, placed the Erlenmeyer flasks in a constant temperature water bath shaker at 25°C for 1h, then took the supernatant and filtered, and measured the concentration of heavy metal ions with an inductively coupled plasma spectrometer (ICP-OES). The COD value was measured by spectrophotometry, and the removal amount was calculated according to the difference between the concentration of heavy metal ions before and after the reaction, and the dosage unit was mg/L. The test results are shown in Table 1.

Table 1

。

.

Example 7: The catalyst prepared in the above examples was used for the treatment of smelting wastewater in a non-ferrous metal smelting workshop, and 1000 mL of wastewater from the workshop was collected. The pH of the water sample was 6.5±0.5, and the initial dose of pollutants is shown in Table 2;

0.54g peracetic acid is put into the 250mL Erlenmeyer flask that fills 50mL water sample, adjust water sample pH to be 3.5 ± 0.2, take by weighing respectively the catalyst prepared in 0.5g embodiment 1-5 and comparative example 1-5, Put them into the above-mentioned 250mL Erlenmeyer flasks respectively, place the Erlenmeyer flasks in a constant temperature water bath shaker at 25°C for 1h, take the supernatant and filter them, and measure the concentration of heavy metal ions with an inductively coupled plasma spectrometer (ICP-OES). The COD value was measured by spectrophotometry, and the removal amount was calculated according to the difference in the concentration of heavy metal ions before and after the reaction, and the dosage unit was mg/L. The test results are shown in Table 2.

Table 2

As can be seen from Table 1 and Table 2, the heteroatom-doped algae-based biochar-loaded nano-zero-valent metal catalyst prepared by the method of the present invention has achieved a better treatment effect on smelting wastewater; the concentration of heavy metal ions contained in the treated wastewater, The COD values all meet the discharge requirements of the "Lead and Zinc Industrial Pollutant Discharge Standards" (GB 25466-2010), while the heavy metal ions and COD values contained in the waste water treated by the comparative catalyst do not meet the "Lead and Zinc Industrial Pollutant Discharge Standards" "(GB 25466-2010) emission requirements.

In summary, the method of the present invention prepares harmful algae into a heteroatom-doped mesoporous algae-based biochar material with high reactivity and low economic cost, and utilizes the resource value of algae while removing harmful algae. By adjusting the structural properties of heteroatom-doped mesoporous algae-based biochar, nano-zero-valent metals were introduced into heteroatom-doped mesoporous algae-based biochar by liquid phase reduction method to form heteroatom-doped mesoporous algae-based biochar loaded with nano-zero-valent metals The high-activity composite catalyst greatly shortens the mass transfer distance between active center species (nano-valent zero-valent metals, free radicals) and target pollutants, ensures effective contact between active center species and target pollutants, and enhances the overall catalytic reaction system effect, thereby simultaneously solving the shortcomings of passivation and agglomeration of nano-zero-valent metals and the shortcomings of free radical self-quenching or ineffective oxidation reactions (such as reactions with water molecules), and due to the nano-zero-valent iron, nickel, The existence of magnetic metal elements such as cerium can realize the simple recycling of composite materials and avoid the loss of composite materials, which proves its good prospect of large-scale application.

Claims (10)

1. A preparation method of heteroatom-doped algae-based biochar loaded nanometer zero-valent metal catalyst, characterized in that, the steps are as follows: (1) Collect the algae, clean them, dry them, crush them, and sieve them, then add a glutaraldehyde solution with a volume concentration of 2.5% to 5%, mix and stir them for 10 to 15 hours, and wash the solids with ultrapure water for 4 to 6 hours after solid-liquid separation. After three times, the algal organisms were soaked in ethanol solutions with a volume concentration of 70%, 90%, and 100% in sequence, soaked for 0.5 h each, separated from solid and liquid, and dried to obtain pretreated algal organisms; (2) Put the pretreated algae into the extract solution, ultrasonically disperse at 50-70°C for 0.5-1.0 h, after solid-liquid separation, wash the solid with ultrapure water until the pH is 9.5-10, and place the washed product in Solvothermal reaction is carried out in the heteroatom precursor solution. After the reaction, the solid and liquid are separated, and the solid is alternately washed with ultrapure water and absolute ethanol solution until the pH is neutral, and vacuum dried to constant weight to obtain heteroatom doping Algae-based biochar; (3) Under an inert atmosphere, mix heteroatom-doped algae-based biochar and hypophosphite and then place it in a tube furnace for pyrolysis and carbonization to obtain phosphorus and heteroatom-doped algae-based biochar; (4) Under a nitrogen atmosphere, place phosphorus and heteroatom co-doped algae-based biochar in a 0.025-0.1g/mL metal salt solution, stir for 0.5h, then slowly add the reducing agent solution dropwise, after the dropwise addition is completed Continue to stir for 0.5 h, separate the solid from the liquid, wash the solid with ultrapure water and absolute ethanol solution in vacuum filtration, each wash 3 to 6 times, and vacuum dry to obtain heteroatom co-doped algae-based biochar-loaded nano-zero-valent metals catalyst. 2. The preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to claim 1, characterized in that: the algae in step (1) are biologically pulverized and sieved to obtain a powder with a particle size of ≤0.4mm . 3. The preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to claim 1, characterized in that: the heteroatom precursor in step (2) is nitrogen source, boron source, sulfur source One of them, the concentration of the heteroatom precursor solution is 0.3-0.9mol/L; the nitrogen source is one or more of ammonium chloride, ammonium persulfate, melamine, urea, and ammonium bicarbonate; the boron source is One or more of boric acid, ammonium borate, dimethylamine borane; sulfur source is thioacetic acid, thiourea, thiosemicarbazide, thioacetamide, L-cysteine, L-methionine one or more. 4. The preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to claim 1, characterized in that: the extract in step (2) is dodecane with a mass volume concentration of 3-5% It is prepared by mixing sodium sulfate solution and sodium hydroxide solution with a mass concentration of 2 to 4% in a volume ratio of 1:1 to 3. 5. The method for preparing heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to claim 1, characterized in that: the hydrothermal reaction temperature is 180-210° C., and the reaction time is 3-8 hours. 6. The method for preparing heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalysts according to claim 1, characterized in that: in step (3), heteroatom-doped algae-based biochar and hypophosphite by mass Ratio (2~4): 1 mixed, heat up to 250~350°C at a speed of 1~5°C/min, keep it for 0.5~1h, then raise the temperature to 500~800°C at a speed of 6~12°C/min, Pyrolysis 1.5 ~ 5h. 7. the preparation method of heteroatom-doped algae-based biochar-supported nanometer zero-valent metal catalyst according to claim 5, is characterized in that: hypophosphite is sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite, magnesium hypophosphite one or more of them. 8. The preparation method of heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to claim 1, wherein the metal salt is iron salt, molybdenum salt, cobalt salt, nickel salt, cerium salt, zinc One or two of salt and copper salt; when there are two metal salts, the mass ratio of the bimetallic salt is 1:5-5:1. 9. The preparation method of heteroatom-doped algae-based biochar-supported nanometer zero-valent metal catalyst according to claim 1, characterized in that: the reducing agent is potassium borohydride, sodium borohydride, lithium borohydride, ascorbic acid, tea poly A kind of phenol, the molar ratio of metal salt to reducing agent is 1:5～1:15. 10. The heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst prepared by the preparation method of the heteroatom-doped algae-based biochar-supported nano-zero-valent metal catalyst according to any one of claims 1-9 is processing heavy metals -Application in organic compound polluted wastewater, characterized in that: heteroatom-doped algae-based biochar loaded nanometer zero-valent metal catalyst and one or more of persulfate, peroxide, peracetic acid, potassium permanganate used simultaneously.

Images