CN113620407B

CN113620407B - Method for treating sewage by catalytic ozonation with monoatomic catalyst

Info

Publication number: CN113620407B
Application number: CN202110861392.0A
Authority: CN
Inventors: 赵超; 王晶; 黄红锋; 吴宇波
Original assignee: Liankehua Technology Co ltd
Current assignee: Liankehua Technology Co ltd
Priority date: 2021-07-29
Filing date: 2021-07-29
Publication date: 2023-05-02
Anticipated expiration: 2041-07-29
Also published as: CN113620407A

Abstract

The invention discloses a method for treating sewage by ozone oxidation catalyzed by a single-atom catalyst, which comprises the steps of loading transition metal on a carrier in a single-atom form, preparing the single-atom catalyst, coating the single-atom catalyst on a silicon carbide honeycomb ceramic plate, and applying the coated silicon carbide honeycomb ceramic plate to ozone oxidation sewage treatment equipment to treat sewage; the monoatomic catalyst has a large number of metal monoatomic active sites, the electronic unsaturated effect of the monoatomic catalyst can efficiently catalyze ozone to decompose into a higher oxidant, namely hydroxyl free radical, and the oxidation selectivity of the hydroxyl free radical is smaller than that of ozone, so that more pollutants can be degraded, and the ozone oxidation capability is greatly improved; the transition metal is one or more of silver, copper, iron and manganese; the carrier is modified porous active nano carbon. The invention is based on the novel monoatomic technology, has the advantages of simple operation, difficult inactivation of the catalyst, strong catalytic capability and the like, and has good effect on the aspect of sewage treatment.

Description

Method for treating sewage by catalytic ozonation with monoatomic catalyst

Technical Field

The invention belongs to the technical field of sewage treatment, and particularly relates to a method for treating sewage by ozone oxidation catalyzed by a monoatomic catalyst.

Background

Along with the rapid development of the economy in China, people pay more and more attention to the quality of life, and the quality of water body plays an important role in the life of people, so that the treatment of sewage becomes serious. Ozone advanced oxidation is an emerging effective way for treating sewage, and has good effects in the aspects of sewage deodorization, disinfection, decolorization, organic matter removal, COD removal and the like. The ozone advanced oxidation degradation organic matter is fast, the reaction condition is mild, no secondary pollution is generated, and the method has wide application in water treatment. The advanced ozone oxidation sewage treatment technology is developed, which is favorable for the treatment and protection of water environment.

At present, a plurality of ozone catalyst products are also produced on the market, but most products have the following problems: (1) The catalytic activity is low, and the capability of catalyzing ozone to decompose organic matters is limited; (2) The service life is low, the repeated utilization rate of a plurality of ozone catalysts is low, and the ozone catalysts can be continuously catalyzed to decompose organic matters even after the ozone catalysts are used for a few days; (3) The catalyst is easy to separate, the existing method for preparing the catalyst mainly uses porous active nano carbon as a carrier to be loaded on the surface of the carrier by an impregnation method in metal salt, and the catalyst has low adsorption capacity and is easy to separate, so that the catalyst does not have catalytic action after long service time.

Therefore, how to prepare an ozone catalyst with high catalytic activity, long service life and strong adsorption performance is the development direction of a plurality of scientific researchers.

Compared with the nano-scale, the single-atom technology enables the metal to be dispersed in an atomic level, the characteristics of each metal atom can be fully reflected, the utilization rate of the metal atoms reaches 100%, and the complete atomic economy is realized. The single-atom technology has great potential in realizing the breakthrough of the characteristics of functional metal materials, the reasonable utilization of metal resources and the realization of atom economy. The monoatomic catalyst is being widely focused on because of the characteristics of easy preparation, high catalytic activity, no consumption, environmental friendliness and the like.

Disclosure of Invention

The invention aims to provide a method for treating sewage by catalyzing ozone oxidation by using a single-atom catalyst, which has the advantages of simple operation, difficult inactivation of the catalyst, strong catalytic capability and the like, and has good effect on sewage treatment.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for catalytic ozonation treatment of sewage by using a single-atom catalyst comprises the steps of loading transition metal on a carrier in a single-atom form, preparing the single-atom catalyst, coating the single-atom catalyst on a silicon carbide honeycomb ceramic plate, and applying the coated silicon carbide honeycomb ceramic plate to ozonation sewage treatment equipment to treat sewage; the transition metal is one or more of silver, copper, iron and manganese; the carrier is modified porous active nano carbon.

Preferably, the molar ratio of the transition metal to the carrier is 1:50-1:200.

Preferably, the modification method of the modified porous activated nano carbon comprises the following steps: adding the porous active nano carbon into sulfuric acid solution, stirring and refluxing, then washing to be neutral, and drying to obtain the modified porous active nano carbon.

Preferably, the stirring reflux temperature is 80-90 ℃.

Preferably, the stirring reflux time is 3-5 h.

Preferably, the drying method comprises the following steps: drying in an oven at 75-85 ℃ for 2-3 h.

Preferably, the preparation method of the single-atom catalyst comprises the following steps:

(1) Dissolving metal salt in a solvent to obtain a solution;

(2) Adding modified porous active nano carbon into the solution, heating and stirring for 20-40 min; adding sodium carbonate aqueous solution, continuously stirring for 10-14 h under coprecipitation to obtain mixed solution, and removing most of solvent in the mixed solution to obtain a crude product;

(3) Washing the crude product to be neutral, drying, then carrying out sectional calcination under the protection of argon, cooling to room temperature after the calcination is finished, and grinding to obtain the monoatomic catalyst.

Preferably, in the step (1), the metal salt is any one of chloride salt, nitrate salt and sulfate salt.

Preferably, in the step (1), the solvent is water or an ethanol solution formed by mixing water and ethanol according to a volume ratio of 1:1.

Preferably, in the step (2), the temperature is raised to 60-85 ℃, and the stirring is performed under magnetic stirring, wherein the stirring speed is 100-300 rpm.

Preferably, in the step (2), the concentration of the sodium carbonate aqueous solution is 0.3mol/L.

Preferably, in step (3), the modified porous activated carbon is added to the dissolution liquid at a rate of 5 g/spoon for 1 min.

Preferably, in the step (3), the drying method is as follows: drying in an oven at 80-100 ℃ for 2-3 h.

Preferably, in step (3), the step of calcining is performed as follows: firstly, heating to 200-400 ℃ at 3-5 ℃/min, and keeping for 1-3 h; then heating to 400-800 ℃ at 3-5 ℃/min, and keeping for 3-5 h.

The beneficial effects of the invention are as follows:

1. the monoatomic catalyst prepared by the invention has a large number of metal monoatomic active sites, the electronic unsaturated effect can efficiently catalyze ozone to decompose into a higher oxidant, namely a hydroxyl radical, and the hydroxyl radical has smaller oxidation selectivity than ozone, can degrade more pollutants, greatly improves the degradation rate of COD and ammonia nitrogen in sewage, improves the bacterial killing rate and the algae removal rate in sewage, and further improves the sewage treatment effect.

2. The preparation method is based on a novel monoatomic technology, and transition metal materials are subjected to special treatment in a monoatomic form and can be attached to a carrier, so that the transition metal materials can be directly used for catalytic ozone oxidation; the carrier of the invention is modified porous active nano carbon, which has certain adsorption property and can cooperate with transition metal to improve sewage treatment effect.

3. The single-atom catalyst adopts a novel single-atom technology, the transition metal is attached to the carrier in a single-atom form, other auxiliary conditions are not needed, the utilization rate of metal atoms reaches 100%, and the complete 'atom economy' is realized; compared with the traditional catalyst, the method has the advantages that under the condition of ensuring the same effect, the ozone consumption is reduced by more than 50%, meanwhile, the sewage can be efficiently treated, the catalyst consumption is saved, and the cost is greatly reduced.

Drawings

FIG. 1 shows the degradation rate of COD in sewage under different treatments;

FIG. 2 shows the degradation rate of ammonia nitrogen in sewage under different treatments;

FIG. 3 shows the bacterial kill rate in the wastewater under different treatments.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Example 1

A method for treating sewage by catalytic ozonation with a monoatomic catalyst, which comprises the following steps:

(1) Weighing 50g of powdery porous active nano carbon, putting into a volumetric flask, then adding 200mL of 65% sulfuric acid, installing a reflux device, heating to 85 ℃, and continuously stirring for 4 hours at 200 rpm; taking out the acid-washed porous activated carbon after cooling, repeatedly washing with deionized water until the pH value is neutral, putting into a baking oven, baking at 80 ℃ for 3 hours, and drying to remove residual moisture to obtain the modified porous activated carbon;

(2) Weighing 250mL of deionized water and 250mL of absolute ethyl alcohol, mixing, weighing 0.71g of silver nitrate and 4.72g of manganese chloride, putting into a mixed solution of water and ethanol, adding magnetons, and stirring at 200rpm for 1h to completely and uniformly dissolve metal salts to obtain a solution;

(3) Adding the modified porous active nano carbon prepared in the step (1) into the solution at the speed of 5 g/spoon within 1min, heating to 70 ℃, continuously stirring at 200rpm for 20min, dropwise adding 50mL of sodium carbonate aqueous solution with the concentration of 0.3mol/L at the speed of 10 mu L/sec, and continuously stirring for 12h under coprecipitation; sealing the bottle mouth by using a sealing film to prevent the solvent from volatilizing, so as to obtain a mixed solution; evaporating water-ethanol completely by using a rotary evaporator at the rotation speed of 80rpm and the temperature of 80 ℃, and collecting solid powder to obtain a monoatomic catalyst crude product;

(4) Washing the monoatomic catalyst crude product prepared in the step (3) to be neutral by deionized water, putting the product into an oven at 80 ℃ for baking for 3 hours until the product is dried, then putting the product into a tube furnace, introducing 99.999% of argon for protection, heating to 250 ℃ at 3 ℃/min, and keeping the temperature for 2 hours; then heating to 400 ℃ at 5 ℃/h, and keeping for 5h; then cooling to room temperature, and grinding to 500nm by a planetary ball mill (zirconium oxide ball milling tank) to obtain the required single-atom catalyst;

(5) Then adding a dispersing auxiliary, a binder and a leveling agent into the monoatomic catalyst to prepare mixed emulsion, coating the mixed emulsion on a silicon carbide honeycomb ceramic plate, and applying the coated silicon carbide honeycomb ceramic plate to swimming pool water purifying equipment with the patent publication number of CN213171894U for sewage treatment.

Example 2

(1) Weighing 50g of powdery porous active nano carbon, putting into a volumetric flask, then adding 200mL of 65% sulfuric acid, installing a reflux device, heating to 80 ℃, and continuously stirring for 4 hours at 200 rpm; taking out the acid-washed porous activated carbon after cooling, repeatedly washing with deionized water until the pH value is neutral, putting into a baking oven, baking at 75 ℃ for 3 hours, and drying to remove residual moisture to obtain the modified porous activated carbon;

(2) 7.10g of copper chloride dihydrate and 5.26g of manganese chloride are weighed and dissolved in 450mL of water, and ultrasonic treatment is carried out for 30min at 100kHz to completely and uniformly dissolve the copper chloride dihydrate and the manganese chloride to obtain a dissolution solution;

(3) Adding the modified porous active nano carbon prepared in the step (1) into the solution at the speed of 5 g/spoon within 1min, heating to 60 ℃, stirring at 300rpm for 30min, dropwise adding 50mL of sodium carbonate aqueous solution with the concentration of 0.3mol/L at the speed of 10 mu L/sec, and continuously stirring for 10h under coprecipitation, wherein a sealing film is used for sealing the bottle mouth to prevent the solvent from volatilizing; stirring the mixture to obtain a mixed solution; filtering out most of water in the mixed solution, and collecting solid powder to obtain a coarse product of the single-atom catalyst;

(4) Washing the monoatomic catalyst crude product prepared in the step (3) to be neutral by deionized water, then putting the product into a baking oven, raising the temperature to the boiling point of water, baking for 2 hours, drying off the residual water, putting the product into a tubular furnace, introducing 99.999% of argon for protection, raising the temperature to 200 ℃ at 3 ℃/min, and keeping the temperature for 1 hour; then heating to 700 ℃ at 4 ℃/min, and keeping for 3 hours; then cooling to room temperature, and grinding to 500nm by using a planetary ball mill (zirconia ball mill tank) to obtain the required single-atom catalyst;

(5) Mixing a monoatomic catalyst with a dispersing auxiliary, a binder and a leveling agent to prepare mixed emulsion, coating the mixed emulsion on a silicon carbide honeycomb ceramic plate, and applying the coated silicon carbide honeycomb ceramic plate to swimming pool water purifying equipment with a patent publication number of CN213171894U for sewage treatment.

Example 3

The sewage is treated by adopting the monoatomic catalyst prepared by the following preparation method:

(1) Weighing 50g of powdery porous active nano carbon, putting into a volumetric flask, then adding 200mL of sulfuric acid, installing a reflux device, heating to 90 ℃, and continuously stirring for 3 hours at 300 rpm; taking out the acid-washed porous activated nano carbon after cooling, repeatedly washing with deionized water until the pH value is neutral, putting into a baking oven, baking at 85 ℃ for 2 hours, and baking off residual moisture to obtain the modified porous activated nano carbon;

(2) 1.33g of manganese chloride and 2.86g of ferrous sulfate heptahydrate are weighed and dissolved in 450mL of water, magnetons are added, and stirring is carried out at 200rpm until metal salts are completely dissolved, so as to obtain a solution;

(3) Adding the modified porous active nano carbon prepared in the step (1) into the solution at the speed of 5 g/spoon within 1min, heating to 85 ℃, continuously stirring at 200rpm for 40min, dropwise adding 50mL of sodium carbonate water solution with the concentration of 0.3mol/L at the speed of 10 mu L/sec, and continuously stirring for 12h under coprecipitation to obtain a mixed solution; filtering out most of water in the mixed solution, and collecting solid powder to obtain a coarse product of the monoatomic catalyst;

(4) Washing the monoatomic catalyst crude product prepared in the step (3) to be neutral by deionized water, putting the product into an oven for drying at 85 ℃ for 2 hours, finally putting the product into a tubular furnace, introducing 99.999% of argon for protection, heating to 300 ℃ at a heating rate of 3 ℃/min, and keeping for 3 hours; then heating to 600 ℃ at 3 ℃/min, and keeping for 5 hours; then cooling to room temperature, and grinding to 500nm by a planetary ball mill (zirconia ball milling tank) to obtain the required single-atom catalyst;

Example 4

(1) Weighing 50g of powdery porous active nano carbon, putting into a volumetric flask, then adding 200mL of 65% sulfuric acid, installing a reflux device, heating to 85 ℃, and continuously stirring for 5 hours at 100 rpm; taking out the acid-washed porous activated carbon after cooling, repeatedly washing with deionized water until the pH value is neutral, putting into a baking oven, baking at 80 ℃ for 3 hours, and drying to remove residual moisture to obtain the modified porous activated carbon;

(2) Weighing 5.25g of manganese chloride, dissolving in 450mL of water, adding magnetons, and stirring at 400rpm until the manganese chloride is completely dissolved to obtain a manganese chloride aqueous solution;

(3) Adding the modified porous activated nano carbon prepared in the step (1) into a manganese chloride aqueous solution at a speed of 5 g/spoon within 1min, heating to 80 ℃, stirring at 150rpm for 30min, dropwise adding 50mL of a sodium carbonate aqueous solution of 0.3mol/L at a speed of 10 mu L/sec, and continuing stirring for 12h under coprecipitation to obtain a mixed solution; filtering out most of water in the mixed solution, and collecting solid powder to obtain a monoatomic catalyst crude product;

(4) Washing the monoatomic catalyst crude product prepared in the step (3) to be neutral by deionized water, then putting the product into an oven to be dried at 80 ℃ for 3 hours until the water is dried, finally putting the product into a tubular furnace, introducing 99.999% of argon for protection, heating to 400 ℃ at 4 ℃/min, and keeping for 1 hour; then heating to 800 ℃ at 5 ℃/min, and keeping for 3 hours; then cooling to room temperature, and grinding to 500nm by a planetary ball mill (zirconia ball milling tank) to obtain the required single-atom catalyst;

Comparative example 1

Ozone catalyst purchased from Duckweed city Lihua filler limited company is mixed with a dispersing auxiliary agent, a binder and a leveling agent to prepare mixed emulsion, the mixed emulsion is coated on a silicon carbide honeycomb ceramic plate, and the coated silicon carbide honeycomb ceramic plate is applied to swimming pool water purifying equipment with a patent publication number of CN213171894U for sewage treatment.

Comparative example 2

The modified porous activated nano carbon prepared in the example 1 is mixed with a dispersing auxiliary, a binder and a leveling agent to prepare mixed emulsion, the mixed emulsion is coated on a silicon carbide honeycomb ceramic plate, and the coated silicon carbide honeycomb ceramic plate is applied to swimming pool water purifying equipment with a patent publication number of CN213171894U for sewage treatment.

Comparative example 3

The silicon carbide honeycomb ceramic plate without any catalyst was applied to swimming pool water purifying apparatus of patent publication No. CN213171894U for sewage treatment.

Performance testing

1. COD degradation experiment

1. The sewage is treated by the methods of examples 1-4 and comparative examples 1-3 respectively, an ozone catalytic performance test experiment is carried out, the ozone aeration time is 20-60 min, and a water sample is taken after the aeration time is reached to carry out COD concentration test.

2. COD concentration was determined as follows:

(1) taking 10.0mL of water sample, putting the water sample into an conical flask, sequentially adding 5.00mL of mercuric sulfate solution, potassium dichromate standard solution and a plurality of anti-explosion boiling glass beads, and shaking uniformly;

connecting the conical flask to the lower end of a condensing pipe of the reflux device, slowly adding 15mL of silver sulfate-sulfuric acid solution from the upper end of the condensing pipe to prevent the escape of low-boiling-point organic matters, and continuously rotating the conical flask to uniformly mix the low-boiling-point organic matters; keeping micro-boiling reflux for 2h after the solution begins to boil; in the case of a water cooling device, the condensed water should be introduced before the silver sulfate-sulfuric acid solution is added.

(2) After refluxing and cooling, 45mL of water was added from the upper end of the condenser to rinse the condenser, and the flask was removed.

(3) After the solution is cooled to room temperature, adding 3 drops of a ferrous sulfate indicator solution, and titrating with a ferrous sulfate ammonium standard solution, wherein the final point is that the color of the solution is changed from yellow to reddish brown from blue-green; record the consumption volume V of the ferrous ammonium sulfate standard solution ₁ 。

(4) Blank experiment: the experimental method is the same as the steps (1) to (4), 10mL of experimental water is used for replacing the sample to carry out a blank experiment, and the consumption volume V of the standard solution of ferrous ammonium sulfate at the time of blank drop is recorded ₀ 。

(5) COD concentration was calculated according to the following formula:

mass concentration p (mg/L) of chemical oxygen demand:

wherein:

c, the concentration of the standard solution of ferrous ammonium sulfate, mol/L;

V ₀ -volume of ferrous ammonium sulphate standard solution consumed in blank test, mL;

V ₁ -water sample determination of volume of ferrous ammonium sulphate standard solution consumed, mL;

V ₂ -volume of water sample taken during heating reflux, mL;

f-dilution of sample;

8000-quarter O ₂ Converted values in mg/L of the molar mass.

3. The experimental results of advanced oxidative degradation of COD by ozone under each treatment are shown in Table 1 and FIG. 1.

TABLE 1 results of advanced oxidative degradation of COD by ozone under different treatments

As can be seen from Table 1, the monoatomic catalysts prepared in examples 1 to 4 of the present invention have remarkable effect of catalyzing ozone oxidation and degrading COD, and the monoatomic catalyst of the present invention has high degradation rate in sewage treatment and can greatly shorten the time required for sewage treatment.

As can be seen from FIG. 1, the single-atom catalysts prepared in examples 1-4 of the present invention are used for catalyzing ozone, the degradation rate is higher than that of comparative example 1, and comparative example 3 does not use any catalyst for direct ozone aeration treatment; wherein, the mol ratio of the silver to the manganese to the modified porous active nano carbon of the silver-manganese-porous active nano carbon single-atom catalyst in the embodiment 1 is 0.1:0.9:100, and the highest COD degradation rate reaches 83.4 percent, which is 2 times that of the comparative example 3; the catalytic effect of the iron-manganese-porous activated nano carbon single-atom catalyst of example 3 increases with time, the catalytic efficiency increases, and the COD degradation rate gradually increases; in comparative example 2, experiments were performed using the modified porous activated carbon, and the degradation rate was also superior to that of ozone alone, indicating that the porous activated carbon itself also had a certain effect of adsorbing organic matters.

2. Experiment for degrading ammonia nitrogen

1. The sewage was treated by the methods of examples 1 to 4 and comparative examples 1 to 3, respectively, and ammonia nitrogen degradation experiments were performed.

2. The ammonia nitrogen concentration is measured before and after treatment according to the following method:

(1) 50mL of boric acid absorbent was transferred into the receiving flask, ensuring that the condenser outlet was below the level of the boric acid solution. Taking 250mL of water sample (such as high ammonia nitrogen content, adding water to 250mL, adding 2 drops of bromothymol blue indicator), adjusting pH to 6.0 (indicator is yellow) to 7.4 (indicator is blue) with sodium hydroxide solution or sulfuric acid solution if necessary, adding 0.25g of light magnesium oxide and a plurality of glass beads, adding an antifoaming agent if necessary, immediately connecting nitrogen balls and a condenser tube, heating and distilling to ensure that the distillate rate is about 10 mL/min, and stopping distilling when the distillate reaches 200 mL.

(2) Transferring all distillate into conical flask, adding 2 drops of mixing indicator (4.12), and titrating with hydrochloric acid standard titration solution (4.14) until the distillate changes from green to light purplePoint and record volume V of hydrochloric acid standard titration solution consumed _a 。

(3) Blank control: deionized water is used to replace a water sample, the measurement method is consistent with the measurement method, and the volume V of the consumed hydrochloric acid standard titration solution is recorded _b 。

(4) And (3) calculating results:

the concentration of ammonia nitrogen in the water sample is calculated according to the following formula:

wherein:

ρ _N the concentration of ammonia nitrogen (calculated by N) in the water sample, mg/L;

v-volume of sample, mL;

V _a -volume of hydrochloric acid standard titration solution consumed by titration of the sample, mL;

V _b -volume of hydrochloric acid standard titration solution consumed by titration blank, mL;

c-concentration of hydrochloric acid standard solution for titration, mol/L;

14.01-atomic weight of nitrogen, g/moL.

2. The results of the experiments under each treatment are shown in FIG. 2.

As can be seen from FIG. 2, the single-atom catalyst prepared in examples 1-4 of the invention is used for catalyzing ozone to treat sewage, and the ammonia nitrogen removal rate reaches 80% in 20 min; when 30min, the ammonia nitrogen removal rate of the embodiment 1-4 reaches 95%, and the ammonia nitrogen value reaches the emission standard; while the use of comparative example 3 does not use any catalyst, the degradation rate of ammonia nitrogen is only 20%; comparative example 1 catalyzed ozonation with a commercial catalyst, the effect was only 53%; comparative example 2 using porous activated nanocarbon has little impact on ammonia nitrogen removal; experimental results show that the monoatomic catalyst can treat sewage more efficiently and remove ammonia nitrogen in water rapidly.

3. Sterilization test experiment

1. The methods of examples 1 to 4 and comparative examples 1 to 3 were used to treat sewage, respectively, and a test for sterilization was performed.

2. The total number of colonies of the water sample before and after the treatment is measured, and the steps are as follows:

sucking 1mL of water sample by using a sterile suction pipe, adding the water sample into a flat plate (two flat plates are made for each water sample in parallel), uniformly smearing the water sample by using a sterile coater, labeling the side surface of a culture dish clearly, placing the culture dish in a 37 ℃ incubator for culturing for 24-48 hours, and counting the total number of bacterial colonies.

3. The results of the experiments under each treatment are shown in FIG. 3.

As can be seen from FIG. 3, the single-atom catalyst prepared in examples 1-4 of the invention is used for catalyzing ozone oxidation to treat sewage, and the sterilization efficiency reaches 99.9% in 20 min; while in comparative example 3, sewage is directly treated by ozone aeration, the sterilization efficiency is only 63%; comparative example 1 treated sewage with ozone catalyzed by a commercially available catalyst, the sterilization efficiency was 78%. The single-atom catalyst of the invention can treat sewage more efficiently and kill bacteria in the water.

4. Algae killing test experiment

1. The sewage was treated by the methods of examples 1 to 4 and comparative examples 1 to 3, respectively, and algae killing test experiments were performed.

2. The total algae count of the water samples before and after treatment is measured, and the method comprises the following steps:

(1) Taking about 29mL of 500mL of water sample, and filtering the residual water sample by a suction filtration device. Taking out the filter membrane after water filtration, putting the filter membrane into a beaker containing 29mL of water sample, and putting the beaker into an ultrasonic oscillator to oscillate for about 15min until the natural color of the filter membrane is reproduced and no other impurities exist;

(2) Removing the oscillated filter membrane, fixing the volume of the concentrated water sample to 30mL, and adding 2-3 drops of Lu Ge iodine solution;

(3) The concentrated and fixed-volume sample is sufficiently and uniformly shaken, a bottle stopper is immediately opened, 0.1mL of the sample is sucked out of the central part by a 0.1mL suction pipe, the sample is injected into a counting frame, a slide is carefully covered, the sample is uniformly distributed, no bubble is ensured in the counting frame, then the sample is counted under a 10 multiplied by 40 micro-mirror, and the counted visual field is uniformly distributed in the counting frame;

calculating the number of algae in the water according to a formula:

wherein: n—number of phytoplankton per liter of water (ten thousand/L);

cs-number of phytoplankton per liter of water (mm) ² )；

Fs-area of each field counting frame (mm) ² )；

Fn—number of fields after each count;

pn—the number of individual algae or cells per sheet counted by counting the actual number;

V-1L of water after concentration;

u-the volume of the counting frame.

3. The results of the experiment for algae removal in the wastewater under each treatment are shown in Table 2.

TABLE 2 algae removal results in wastewater under different treatments

As can be seen from Table 2, the single-atom catalyst prepared in examples 1 to 4 of the present invention was used to catalyze the oxidation treatment of sewage with ozone, and the removal rate of algae reached 88% in 60 min; in the comparative example 3, no catalyst is adopted, sewage is directly treated by ozone aeration, and the algae removal rate is only 38%; comparative example 1 treated sewage by catalytic ozonation using a commercially available catalyst, the algae removal rate was 57%. The single-atom catalyst can treat sewage more efficiently and remove algae in water efficiently; the modified porous activated nano carbon adopted in comparative example 2 has little influence on ammonia nitrogen removal.

Claims

1. A method for treating sewage by catalytic ozonation with a monoatomic catalyst is characterized in that: loading transition metal on a carrier in a single-atom form to prepare a single-atom catalyst, coating the single-atom catalyst on a silicon carbide honeycomb ceramic plate, and applying the coated silicon carbide honeycomb ceramic plate on ozone oxidation sewage treatment equipment to treat sewage; the transition metal is one or more of silver, copper, iron and manganese; the carrier is modified porous active nano carbon;

the mol ratio of the transition metal to the carrier is 1:50-1:200;

the modification method of the modified porous active nano carbon comprises the following steps: adding the porous active nano carbon into sulfuric acid solution, stirring and refluxing, then washing to be neutral, and drying to obtain modified porous active nano carbon;

the preparation method of the monoatomic catalyst comprises the following steps:

(1) Dissolving metal salt in a solvent to obtain a solution;

2. The method for treating sewage by catalytic ozonation with a single-atom catalyst according to claim 1, wherein: the temperature of stirring reflux is 80-90 ℃.

3. The method for treating sewage by catalytic ozonation with a single-atom catalyst according to claim 1, wherein: the stirring reflux time is 3-5 h.

4. The method for treating sewage by catalytic ozonation with a single-atom catalyst according to claim 1, wherein: in the step (1), the metal salt is any one of chloride, nitrate and sulfate.

5. The method for treating sewage by catalytic ozonation with a single-atom catalyst according to claim 1, wherein: in the step (1), the solvent is water or an ethanol solution prepared by mixing water and ethanol according to a volume ratio of 1:1.

6. The method for treating sewage by catalytic ozonation with a single-atom catalyst according to claim 1, wherein: in the step (2), the temperature is raised to 60-85 ℃ and the stirring speed is 100-300 rpm.

7. The method for catalytic ozonation of wastewater treatment with a single-atom catalyst according to claim 1, wherein in the step (3), the staged calcination is: firstly, heating to 200-400 ℃ at 3-5 ℃/min, and keeping for 1-3 h; then heating to 400-800 ℃ at 3-5 ℃/min, and keeping for 3-5 h.