A recyclable sewage treatment agent and preparation method thereof

Abstract

The present invention discloses a recyclable sewage treatment agent and a preparation method thereof, and belongs to the technical field of urban sewage treatment. The method comprises the following steps: crushing and screening plant fibers and then carbonizing them at high temperature to obtain plant fiber charcoal; oxidizing the plant fiber charcoal by hydrogen vapor in an ultraviolet environment to obtain oxidized plant fiber charcoal; ultrasonically dispersing the oxidized plant fiber charcoal, mixing and adsorbing with a copper-containing inorganic compound and polyacrylamide; and then precipitating with an inorganic sulfiding agent to obtain a sewage treatment agent. The present invention utilizes the physical adsorption, metal coordination and electrostatic adsorption of hydrogen bonds formed between oxygen-containing groups, polyacrylamine and copper-containing inorganic compounds on the oxidized plant fiber charcoal to fix polyacrylamide and copper ions on the surface of the oxidized plant fiber charcoal, and then through the sulfidation precipitation of the sulfiding agent, copper sulfide with a photothermal effect is attached and fixed on the surface of the oxidized plant fiber charcoal, thereby obtaining a recyclable sewage treatment agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of urban sewage treatment, and particularly relates to a recyclable sewage treatment agent and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, the generation of sewage has increased sharply, and the treatment and discharge of sewage have become one of the major environmental problems faced globally. Sewage not only affects the water quality of water bodies, but also poses a serious threat to the ecological environment and human health. Therefore, establishing an efficient sewage treatment system is a necessary measure to protect water resources and maintain ecological balance. Sewage treatment is not only a requirement for environmental protection, but also an important part of sustainable development. Sewage mainly comes from industrial production, life and agricultural activities. According to different sources, sewage can be divided into domestic sewage, industrial wastewater and agricultural sewage. Domestic sewage mainly refers to the sewage generated by households and public places, usually containing a large amount of organic matter, nitrogen, phosphorus and other pollutants. Industrial wastewater refers to the sewage generated during industrial production, and its composition is complex, and may contain heavy metals, organic solvents, acids and bases and other harmful substances. Agricultural sewage mainly comes from farmland irrigation and agricultural activities, usually containing chemical substances such as pesticides and fertilizers. The composition of sewage is complex and diverse, mainly including the following categories: (1) Organic matter: mainly from domestic and industrial wastewater, often existing in the form of suspended solids and dissolved state; (2) Nitrogen and phosphorus: nitrogen mainly comes from urea and ammonia water, and phosphorus is mainly introduced by phosphates in fertilizers and detergents; (3) Heavy metals: such as lead, cadmium, mercury, etc., mainly from industrial production and waste discharge; (4) Pathogenic microorganisms: such as bacteria, viruses and parasites, mainly from domestic sewage and agricultural sewage; (5) Other pollutants: including emerging pollutants such as drug residues and plastic particles.

[0003] Wastewater treatment technologies have evolved from simple physical treatment to modern biological and chemical treatment. The following are the main development stages of wastewater treatment technologies: (1) Primary treatment: mainly removes large particulate suspensions in wastewater through physical methods. Common technologies include sedimentation, screening, and filtration. The treatment efficiency at this stage is relatively low, usually only removing about 30% of pollutants; (2) Secondary treatment: mainly biological treatment, using the metabolic action of microorganisms to degrade organic matter in wastewater. Common secondary treatment processes include the activated sludge process, biofilm process, oxidation ditch process, etc. The treatment efficiency at this stage is significantly improved, capable of removing 70% - 90% of organic matter and nutrients such as nitrogen and phosphorus; (3) Tertiary treatment: based on secondary treatment, chemical treatment and advanced treatment processes are added to remove residual pollutants and microorganisms. Common tertiary treatment technologies include coagulation sedimentation, membrane separation, depth filtration, etc. The treatment at this stage can make the effluent quality meet higher standards and is suitable for reclamation; (4) Advanced oxidation treatment: uses strong oxidants (such as ozone, hydrogen peroxide, etc.) and photocatalysis to treat refractory organic pollutants. This technology can effectively remove drug residues and other emerging pollutants in water.

[0004] Patent CN118420080A discloses a wastewater treatment agent containing o-tert-butylcyclohexyl acetate and its preparation method. In this invention, o-tert-butylcyclohexyl acetate, quaternized β-cyclodextrin, ferric trichloride, and polyacrylamide are added to a stirrer and stirred to obtain a wastewater treatment agent containing o-tert-butylcyclohexyl acetate; cyclodextrin has a unique cavity structure. For heavy metal ions in wastewater, cyclodextrin can adsorb heavy metal ions through the hydrophobic interaction inside its cavity and the coordination of hydroxyl functional groups on the outside; the siloxane therein effectively removes heavy metal ions through chemical adsorption; the quaternary ammonium salt therein removes heavy metal ions in wastewater through complexation; the amide bond formed through amidation reaction, the carbonyl and nitrogen atoms in its structure coordinate with heavy metal ions to form a stable complex, thereby achieving the purification treatment of wastewater.

[0005] Patent CN118324231A discloses a method for treating urban sewage. First, the diatomite is pretreated to improve the surface activity of the diatomite and enhance its dispersion performance. Then, it is mixed with carbon black and deionized water. The carbon black can form a network structure with a large specific surface area with metal ions in the diatomite. After high-temperature calcination, the C molecules in the carbon black molecules escape from the diatomite, thereby increasing the specific surface area and adsorption performance of the diatomite. Then, the pretreated diatomite is modified twice. While improving the dispersion and wetting performance of the diatomite, the surface of the diatomite is rich in carboxyl groups. In the secondary modification step, the carboxyl groups on the surface of the diatomite can undergo an amidation reaction with the amino groups of chitosan, forming a strong connection between the diatomite and chitosan and improving its binding force. Finally, the prepared modified diatomite has a uniform internal structure, a large specific surface area, good adsorption performance, good stability, and a good treatment effect on urban sewage. Then, functional carbon fibers are prepared by a specific method. The carbon fibers are light in weight, have good corrosion resistance, good stability, and good adsorption performance. They combine the components of the flocculant polyacrylamide and the coagulant aid ferrous sulfate. The hydroxyl groups on the surface of the carbon fibers can form hydrogen bonds with the amide groups on the surface of polyacrylamide and modified diatomite, causing the modified diatomite, functional carbon fibers, and polyacrylamide molecules to entangle with each other, forming a network structure, increasing the chain-chain contact points between the molecular chains, having strong binding performance, enhancing the dispersion performance of the sewage treatment agent in the sewage, improving the acid and alkali resistance and stability, and the molecular chains of polyacrylamide are in an unfolded state, increasing the contact area with the sewage, promoting the combination of impurities such as particulate suspensions in the sewage with the sewage treatment agent, thereby enhancing the sewage treatment effect and improving the treatment efficiency.

[0006] Patent CN118145742A discloses a method for treating overflow sewage with a magnetic polymer-clay material. The magnetic polymer-clay material of this invention can aggregate the dissolved organic matter in the overflow sewage through physical adsorption. At the same time, polyaluminum chloride can promptly undergo an electro-neutralization reaction with the aggregated dissolved organic matter, thereby achieving the effect of efficient and rapid flocculation at a low cost, and at the same time can avoid the defect of only precipitating particulate pollutants by counterweight when using a single magnetic polymer-clay material, a single magnetic powder, or a combination of a magnetic polymer-clay material and a magnetic powder.

[0007] Although the above-mentioned sewage treatment agent has good application in water treatment, since the adsorbed sewage treatment agent is difficult to be reused again after binding with suspended particles, when the sewage treatment agent is reused, the effect of removing suspended particles cannot be achieved, which in turn makes it difficult for the sewage treatment agent to be recycled, and new sewage treatment agents need to be repeatedly added for sewage purification treatment.

[0008] Therefore, the development of a sewage treatment agent that can be recycled is of great significance for improving the utilization efficiency of sewage treatment agents. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the present invention uses plant fibers derived from plants as raw materials, and sequentially performs high-temperature treatment and oxidation treatment on them to obtain oxidized plant fiber carbon. Then, through the hydrogen bond physical adsorption, metal coordination, and electrostatic adsorption effects formed between the oxygen-containing groups on the oxidized plant fiber carbon, polyacrylamide, and copper-containing inorganic compounds, polyacrylamide and copper ions are fixed on the surface of the oxidized plant fiber carbon. Furthermore, through the sulfide precipitation effect of a sulfiding agent, copper sulfide with a photothermal effect is attached and fixed on the surface of the oxidized plant fiber carbon, thereby obtaining a sewage treatment agent that can be recycled. Specifically, the technical solution of the present invention includes the following steps:

[0010] A preparation method of a recyclable sewage treatment agent, the preparation method including the following steps:

[0011] The plant fibers are crushed and sieved to obtain plant fiber particles, and the plant fiber particles are carbonized at high temperature to obtain plant fiber carbon;

[0012] The plant fiber carbon is oxidized by hydrogen peroxide vapor in an ultraviolet environment to obtain oxidized plant fiber carbon;

[0013] After the oxidized plant fiber carbon is ultrasonically dispersed in deionized water, it is mixed and stirred with a copper-containing inorganic compound and polyacrylamide for adsorption;

[0014] After the stirring and adsorption are completed, the sewage treatment agent is obtained by precipitation with an inorganic sulfiding agent.

[0015] Furthermore, the plant fibers include straw, rice straw, and wheat straw.

[0016] Furthermore, the conditions for the high-temperature carbonization include a temperature of 200°C to 300°C and a carbonization time of 2h to 4h.

[0017] Furthermore, the ultraviolet environment includes an ultraviolet light wavelength of 320nm to 370nm and an ultraviolet light power of 10W to 20W.

[0018] Furthermore, the conditions for the hydrogen peroxide vapor oxidation include a hydrogen peroxide vapor mass concentration of 4% to 10%, a hydrogen peroxide vapor flow rate of 200 mL / min to 300 mL / min, and an oxidation time of 50 min to 100 min.

[0019] Furthermore, the amount of the plant fiber carbon oxidized by hydrogen peroxide vapor in the ultraviolet environment is 50g to 100g.

[0020] Further, the copper-containing inorganic compound is anhydrous copper chloride or anhydrous copper sulfate.

[0021] Further, the polyacrylamide is an anionic polyacrylamide.

[0022] Further, the inorganic sulfurizing agent includes sodium sulfide or ammonium sulfide.

[0023] Further, the mass ratio of the oxidized plant fiber carbon: deionized water: copper-containing inorganic compound: polyacrylamide: inorganic sulfurizing agent is 1: 80-100: 0.1-0.4: 0.2-0.3: 1-2.

[0024] Further, the conditions for the stirring adsorption include a stirring speed of 100 r / min to 200 r / min and an adsorption time of 12 h to 20 h.

[0025] Further, the conditions for the precipitation of the inorganic sulfurizing agent include a precipitation temperature of 80 °C to 90 °C and a precipitation time of 30 min to 50 min.

[0026] A sewage treatment agent prepared by the preparation method of a recyclable sewage treatment agent.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the present invention, plant fibers from plants are used as raw materials, and plant fiber carbon with adsorption activity is obtained through high-temperature carbonization. Then, through the dual oxidation of ultraviolet combined with hydrogen peroxide vapor, the surface of the plant fiber carbon is oxidized and modified to obtain oxidized plant fiber carbon with oxygen-containing functional groups such as hydroxyl and carboxyl groups. Then, the oxidized plant fiber is dispersed in deionized water, and then mixed and adsorbed with a copper-containing inorganic compound and polyacrylamide. The oxygen-containing groups on the oxidized plant fiber carbon can respectively generate hydrogen bond adsorption with the amino group on the polyacrylamine and the copper ions in the copper-containing inorganic compound, and metal coordination. Moreover, the polyacrylamide can generate a coordination effect with the copper ions through the amide bond and form an electrostatic bond with the copper ions through the anions on the polyacrylamide, further fixing the copper ions on the oxidized plant fiber carbon. Finally, a sulfurizing agent is used to deposit the copper ions on the oxidized plant fiber carbon in the solid structure of nano copper sulfide through chemical precipitation. The prepared sewage treatment agent can not only increase the effect of sewage purification treatment under the synergy of the oxidized plant fiber carbon with adsorption activity and polyacrylamide with adsorption activity, but also, due to the nano copper sulfide with a photothermal effect carried by the sewage treatment agent after adsorption, the sewage treatment agent after sewage treatment can generate a high-temperature effect under the treatment of infrared light, promoting the decomposition of the suspended particles carried by the sewage treatment agent and playing a role in high-temperature sterilization. It not only realizes the recycling of the sewage treatment agent of the present invention, but also reduces the pollution of pathogens and the like in the adsorbed suspended particles.

[0029] (2) The raw material used in the sewage treatment agent prepared by the present invention is plant fiber carbon. Compared with activated carbon, since the high-temperature carbonization temperature is much lower than that for the preparation of activated carbon, it is easily degraded. And after the adsorbed suspended particles are simply irradiated with infrared light, the photothermal phenomenon generated by copper sulfide nanoparticles can be used to kill some pathogenic microorganisms, so that the suspended particles and the sewage treatment agent are expected to be used as fertilizers to improve the soil conditions, further expanding the application fields of the sewage treatment agent of the present invention. Specific Embodiments

[0030] The technical solutions of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0031] Unless otherwise specified, the raw materials and reagents used in the present invention below are all commercially available products or can be prepared by known methods.

[0032] Anionic polyacrylamide was purchased from Suzhou Shunhuachangli Environmental Protection New Materials Co., Ltd.;

[0033] Activated carbon was purchased from Jiangsu Enkai Activated Carbon Co., Ltd.

[0034] Example 1:

[0035] A preparation method of a recyclable sewage treatment agent specifically includes the following processes:

[0036] After washing the surface impurities of straw, rice straw and wheat straw with tap water, they were placed in an oven at 60 °C to dry and remove the surface moisture. After complete drying, the plant fibers were crushed with a pulverizer and passed through a 20-mesh sieve to obtain plant fiber particles. At this time, the plant fiber particles were placed in a crucible and heated to 200 °C at a heating rate of 20 °C / min, and carbonized for 2 h in this temperature environment. After the carbonization was completed, it was cooled to room temperature and taken out to obtain plant fiber carbon;

[0037] 50 g of plant fiber carbon was fixed in a U-shaped quartz tube reactor, and then under the irradiation of ultraviolet light with a wavelength of 320 nm and a power of 10 W, hydrogen peroxide vapor with a mass concentration of 4% was introduced into the U-shaped quartz tube reactor at a flow rate of 200 mL / min for a 50-min oxidation reaction on the plant fiber carbon. After the oxidation was completed, the ultraviolet light was turned off and the introduction of hydrogen peroxide vapor was stopped, and the U-shaped quartz reactor was purged with nitrogen, and then taken out to obtain oxidized plant fiber carbon;

[0038] Disperse 10 g of oxidized plant fiber carbon in 800 g of deionized water with an ultrasonic power of 50 W, then add 1 g of anhydrous copper chloride and 2 g of anionic polyacrylamide and mix. Adsorb for 12 h at a stirring speed of 100 r / min. After the adsorption is completed, add 10 g of sodium sulfide and stir until completely dissolved, then heat to 80 °C and time the reaction for 30 min. After the reaction is completed, cool to room temperature, filter to obtain solid particles, rinse repeatedly with acetone 3 times, then rinse repeatedly with deionized water 3 times, and finally dry in an oven to obtain the sewage treatment agent.

[0039] Example 2:

[0040] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0041] Wash the straw, rice straw and wheat straw with tap water to remove surface impurities, and then dry them in an oven at 60 °C to remove surface moisture. After complete drying, crush the plant fibers with a crusher and pass through a 20-mesh sieve to obtain plant fiber particles. At this time, place the plant fiber particles in a crucible and heat them to 220 °C at a heating rate of 20 °C / min, and time the carbonization for 2.5 h in this temperature environment. After the carbonization is completed, cool to room temperature and take out to obtain plant fiber carbon;

[0042] Fix 60 g of plant fiber carbon in a U-shaped quartz tube reactor, and then under ultraviolet light irradiation with a wavelength of 330 nm and a power of 10 W, introduce hydrogen peroxide vapor with a mass concentration of 6% into the U-shaped quartz tube reactor at a flow rate of 200 mL / min for a 60-min oxidation reaction of the plant fiber carbon. After the oxidation is completed, turn off the ultraviolet light and stop the introduction of hydrogen peroxide vapor, and purge the U-shaped quartz reactor with nitrogen, and then take out to obtain oxidized plant fiber carbon;

[0043] Disperse 10 g of oxidized plant fiber carbon in 850 g of deionized water with an ultrasonic power of 60 W, then add 2 g of anhydrous copper chloride and 2 g of anionic polyacrylamide and mix. Adsorb for 14 h at a stirring speed of 100 r / min. After the adsorption is completed, add 10 g of sodium sulfide and stir until completely dissolved, then heat to 80 °C and time the reaction for 35 min. After the reaction is completed, cool to room temperature, filter to obtain solid particles, rinse repeatedly with acetone 3 times, then rinse repeatedly with deionized water 3 times, and finally dry in an oven to obtain the sewage treatment agent.

[0044] Example 3:

[0045] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0046] After washing the straw, rice straw and wheat straw with tap water to remove surface impurities, they were placed in an oven at 60 °C to dry and remove surface moisture. After complete drying, the plant fibers were pulverized with a pulverizer and passed through a 20-mesh sieve to obtain plant fiber particles. At this time, the plant fiber particles were placed in a crucible and heated to 240 °C at a heating rate of 20 °C / min, and carbonized for 3 h in this temperature environment. After carbonization, it was cooled to room temperature and taken out to obtain plant fiber carbon;

[0047] 70 g of plant fiber carbon was fixed in a U-shaped quartz tube reactor, and then under ultraviolet light irradiation with a wavelength of 340 nm and a power of 15 W, hydrogen peroxide vapor with a mass concentration of 6% was introduced into the U-shaped quartz tube reactor at a flow rate of 250 mL / min for a 70-min oxidation reaction on the plant fiber carbon. After the oxidation was completed, the ultraviolet light was turned off and the introduction of hydrogen peroxide vapor was stopped, and the U-shaped quartz reactor was purged with nitrogen, and then taken out to obtain oxidized plant fiber carbon;

[0048] 10 g of oxidized plant fiber carbon was dispersed in 900 g of deionized water with an ultrasonic power of 70 W, and then 2 g of anhydrous copper chloride and 2.5 g of anionic polyacrylamide were added and mixed, and adsorbed for 16 h at a stirring speed of 150 r / min. After the adsorption was completed, 15 g of sodium sulfide was added and stirred until completely dissolved, and then heated to 85 °C and reacted for 40 min. After the reaction was completed, it was cooled to room temperature, filtered to obtain solid particles, rinsed repeatedly with acetone 3 times, and then rinsed repeatedly with deionized water 3 times, and finally dried in an oven to obtain a sewage treatment agent.

[0049] Example 4:

[0050] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0051] After washing the straw, rice straw and wheat straw with tap water to remove surface impurities, they were placed in an oven at 60 °C to dry and remove surface moisture. After complete drying, the plant fibers were pulverized with a pulverizer and passed through a 20-mesh sieve to obtain plant fiber particles. At this time, the plant fiber particles were placed in a crucible and heated to 260 °C at a heating rate of 20 °C / min, and carbonized for 3.5 h in this temperature environment. After carbonization, it was cooled to room temperature and taken out to obtain plant fiber carbon;

[0052] 80 g of plant fiber carbon was fixed in a U-shaped quartz tube reactor, and then under ultraviolet light irradiation with a wavelength of 350 nm and a power of 15 W, hydrogen peroxide vapor with a mass concentration of 8% was introduced into the U-shaped quartz tube reactor at a flow rate of 250 mL / min for an 80-min oxidation reaction on the plant fiber carbon. After the oxidation was completed, the ultraviolet light was turned off and the introduction of hydrogen peroxide vapor was stopped, and the U-shaped quartz reactor was purged with nitrogen, and then taken out to obtain oxidized plant fiber carbon;

[0053] Disperse 10 g of oxidized plant fiber carbon in 950 g of deionized water with an ultrasonic power of 80 W, then add 3 g of anhydrous copper sulfate and 2.5 g of anionic polyacrylamide and mix. Adsorb for 18 h at a stirring speed of 150 r / min. After the adsorption is completed, add 15 g of ammonium sulfide and stir until completely dissolved, then heat to 85 °C and time the reaction for 40 min. After the reaction is completed, cool to room temperature, filter to obtain solid particles, rinse repeatedly with acetone 3 times, then rinse repeatedly with deionized water 3 times, and finally dry in an oven to obtain the sewage treatment agent.

[0054] Example 5:

[0055] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0056] Wash the surface impurities of straw, rice straw and wheat straw with tap water, and then dry in an oven at 60 °C to remove the surface moisture. After complete drying, crush the plant fibers with a pulverizer and pass through a 20-mesh sieve to obtain plant fiber particles. At this time, place the plant fiber particles in a crucible and heat them to 280 °C at a heating rate of 20 °C / min, and time the carbonization for 4 h in this temperature environment. After the carbonization is completed, cool to room temperature and take out to obtain plant fiber carbon;

[0057] Fix 90 g of plant fiber carbon in a U-shaped quartz tube reactor, and then under ultraviolet light irradiation with a wavelength of 360 nm and a power of 20 W, introduce hydrogen peroxide vapor with a mass concentration of 8% into the U-shaped quartz tube reactor at a flow rate of 300 mL / min to carry out an oxidation reaction on the plant fiber carbon for 90 min. After the oxidation is completed, turn off the ultraviolet light and stop the introduction of hydrogen peroxide vapor, and purge the U-shaped quartz reactor with nitrogen, and then take out to obtain oxidized plant fiber carbon;

[0058] Disperse 10 g of oxidized plant fiber carbon in 1000 g of deionized water with an ultrasonic power of 90 W, then add 4 g of anhydrous copper sulfate and 3 g of anionic polyacrylamide and mix. Adsorb for 20 h at a stirring speed of 200 r / min. After the adsorption is completed, add 20 g of ammonium sulfide and stir until completely dissolved, then heat to 90 °C and time the reaction for 50 min. After the reaction is completed, cool to room temperature, filter to obtain solid particles, rinse repeatedly with acetone 3 times, then rinse repeatedly with deionized water 3 times, and finally dry in an oven to obtain the sewage treatment agent.

[0059] Example 6:

[0060] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0061] After washing the straw, rice straw, and wheat straw with tap water to remove surface impurities, they were placed in an oven at 60 °C to dry and remove surface moisture. After complete drying, the plant fibers were pulverized with a pulverizer and passed through a 20-mesh sieve to obtain plant fiber particles. At this time, the plant fiber particles were placed in a crucible and heated to 300 °C at a heating rate of 20 °C / min, and carbonized for 4 h while timing in this temperature environment. After carbonization, it was cooled to room temperature and taken out to obtain plant fiber charcoal;

[0062] 100 g of plant fiber charcoal was fixed in a U-shaped quartz tube reactor, and then under ultraviolet light irradiation with a wavelength of 370 nm and a power of 20 W, hydrogen peroxide vapor with a mass concentration of 10% was introduced into the U-shaped quartz tube reactor at a flow rate of 300 mL / min for a 100-min oxidation reaction on the plant fiber charcoal. After oxidation, the ultraviolet light was turned off and the introduction of hydrogen peroxide vapor was stopped, and the U-shaped quartz reactor was purged with nitrogen, and then taken out to obtain oxidized plant fiber charcoal;

[0063] 10 g of oxidized plant fiber charcoal was dispersed in 1000 g of deionized water with an ultrasonic power of 100 W, and then 4 g of anhydrous copper sulfate and 3 g of anionic polyacrylamide were added and mixed, and adsorbed for 20 h at a stirring speed of 200 r / min. After adsorption, 20 g of ammonium sulfide was added and stirred until completely dissolved, and then heated to 90 °C and timed for reaction for 50 min. After the reaction, it was cooled to room temperature, filtered to obtain solid particles, rinsed repeatedly with acetone 3 times, and then rinsed repeatedly with deionized water 3 times, and finally dried in an oven to obtain a sewage treatment agent.

[0064] Comparative Example 1:

[0065] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0066] After washing the straw, rice straw, and wheat straw with tap water to remove surface impurities, they were placed in an oven at 60 °C to dry and remove surface moisture. After complete drying, the plant fibers were pulverized with a pulverizer and passed through a 20-mesh sieve to obtain plant fiber particles. At this time, the plant fiber particles were placed in a crucible and heated to 300 °C at a heating rate of 20 °C / min, and carbonized for 4 h while timing in this temperature environment. After carbonization, it was cooled to room temperature and taken out to obtain plant fiber charcoal;

[0067] 100 g of plant fiber charcoal was mixed and stirred with a nitric acid solution with a concentration of 2 mol / L according to a mass ratio of 1:10, and then heated to 100 °C and maintained for 3 h. After treatment, it was cooled to room temperature and rinsed with deionized water until the washing solution was neutral, and then dried to obtain oxidized plant fiber charcoal;

[0068] Disperse 10 g of oxidized plant fiber carbon in 1000 g of deionized water with an ultrasonic power of 100 W, then add 4 g of anhydrous copper sulfate and 3 g of anionic polyacrylamide and mix. Adsorb for 20 h at a stirring speed of 200 r / min. After the adsorption, add 20 g of ammonium sulfide and stir until completely dissolved, then heat to 90 °C and time the reaction for 50 min. After the reaction, cool to room temperature, filter to obtain solid particles, rinse repeatedly with acetone 3 times, then rinse repeatedly with deionized water 3 times, and finally dry in an oven to obtain the sewage treatment agent.

[0069] Comparative Example 2:

[0070] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0071] Replace the plant fiber carbon in Example 6 with activated carbon, and keep the remaining steps the same as in Example 6.

[0072] Comparative Example 3:

[0073] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0074] Remove and do not add anhydrous copper sulfate in Example 6, and keep the remaining conditions the same as in Example 6.

[0075] Comparative Example 4:

[0076] A preparation method of a recyclable sewage treatment agent specifically includes the following process:

[0077] Increase the ultraviolet light irradiation power in Example 6 to 30 W, increase the mass concentration of hydrogen peroxide vapor to 20%, and extend the oxidation time to 2 h, while keeping the remaining conditions the same as in Example 6.

[0078] Take 0.25 g of oxidized plant fiber carbon and oxidized activated carbon obtained from Examples 1 - 6 and Comparative Examples 1 - 4 respectively, and add them to 50 mL of a NaOH solution with a concentration of 0.1 mol / L and impregnate for more than 24 h. The acidic oxygen-containing groups on the surface of the activated carbon are neutralized by NaOH, and then titrate the remaining NaOH with a 0.1 mol / L standard hydrochloric acid solution. Calculate the content of acidic oxygen-containing groups on the surface of the activated carbon according to the consumption of NaOH. The results are shown in Table 1 below:

[0079] Table 1

[0080]

[0081] As can be seen from the data in Table 1 above:

[0082] (1)Under the preparation conditions of the present invention, the oxidized plant fiber carbon obtained has more acidic oxygen-containing groups, which is beneficial to the subsequent loading of copper ions and anionic polyacrylamide through hydrogen bond adsorption, metal coordination, and electrostatic adsorption.

[0083] (2)It can be found from Comparative Example 1 that since nitric acid has strong corrosiveness, although the plant fiber carbon obtained by high-temperature carbonization of the present invention also has oxidizing properties, its strong corrosiveness easily causes the degradation of the plant fiber carbon, resulting in a low number of acidic oxygen-containing groups, which is not conducive to the loading of copper ions and anionic polyacrylamide.

[0084] (3)It can be found from Comparative Example 2 that since the carbonization temperature of activated carbon is extremely high, it is difficult to achieve the oxidation modification of activated carbon under the oxidation conditions of the present invention, and the number of acidic oxygen-containing groups is low, which is not conducive to the loading of copper ions and anionic polyacrylamide.

[0085] (4)It can be found from Comparative Example 4 that further increasing the oxidation intensity of the plant fiber carbon may cause the degradation of the plant fiber carbon, resulting in a low number of acidic oxygen-containing groups, which is not conducive to the loading of copper ions and anionic polyacrylamide.

[0086] Adsorption test:

[0087] The wastewater from the water treatment plant was separately filled into 10 beakers (the filling volume was 1 L). According to the addition amount of 10 mg / L, the sewage treatment agents obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were respectively added to the above beakers filled with the wastewater from the water treatment plant. A separate beaker of wastewater was taken as a blank control. Then, it was stirred at a speed of 250 r / min for 2 min, then stirred at a speed of 150 r / min for 2 min, and finally stirred at a speed of 50 r / min for 5 min. After the stirring was completed, it was left standing for 20 min, and then the water sample at 2 cm below the water surface was taken for the detection of turbidity and chemical oxygen demand COD. The results are shown in Table 2 below:

[0088] Table 2

[0089]

[0090] After the sewage treatment agent that adsorbed suspended particles after the above stirring was filtered and separated, it was treated with NIR laser with a wavelength of 1200 nm at an irradiation power of 0.8 W / cm 2 for 20 min, the water temperature was recorded, and then the sewage treatment agent was recovered. Then, the above adsorption test process was repeated 5 times for the cyclic adsorption test. The water used in each cyclic adsorption experiment was fresh wastewater from the water treatment plant with a unified source. The turbidity and chemical oxygen demand COD values were recorded for the last time. The results are shown in Table 3 below:

[0091] Table 3

[0092]

[0093] It can be seen from the data in Table 2 and Table 3 above that:

[0094] (1) The sewage treatment agent obtained under the preparation conditions of the present invention has good water purification effect, and after being recycled multiple times, the water purification effect is still relatively good.

[0095] (2) It can be known from Comparative Example 1 that due to the relatively low temperature of high-temperature carbonization, the structure of the plant fiber carbon is relatively loose. When using conventional high-temperature oxidation with nitric acid, nitric acid is prone to have a strong corrosive effect on the plant fiber carbon, causing the plant fiber carbon to degrade, resulting in difficulty in loading copper ions and anionic polyacrylamide in the subsequent prepared sewage treatment agent. Only relying on the adsorption of the oxidized plant fiber carbon, the water purification effect is poor. And due to the small amount of copper ions loaded, the amount of nano copper sulfide obtained by sulfidation is small, resulting in a poor photothermal effect of the nano copper sulfide and being unable to exert the sterilization function relying on the photothermal effect.

[0096] (3) It can be known from Comparative Example 2 that due to the extremely high carbonization temperature of the activated carbon, the internal structure is tight. Through the double oxidation of ultraviolet irradiation combined with hydrogen peroxide vapor of the present invention, it is difficult to effectively oxidize and modify the activated carbon, and the number of loaded oxygen-containing groups is small, resulting in a low loading of copper sulfide and anionic polyacrylamide in the subsequent prepared sewage treatment agent. Only relying on the adsorption of the activated carbon, the water purification effect is poor. And due to the small amount of copper ions loaded, the amount of nano copper sulfide obtained by sulfidation is small, resulting in a poor photothermal effect of the nano copper sulfide and being unable to exert the sterilization function relying on the photothermal effect.

[0097] (4) It can be known from Comparative Example 3 that due to the absence of the participation of metal copper ions, after the sewage treatment agent adsorbs suspended particles in water, it is difficult to separate the suspended particles by simply irradiating with infrared light, resulting in poor recycling performance of the sewage treatment agent. And the microorganisms with pathogenic components in the suspended particles are difficult to be effectively removed. If directly filled into the soil as fertilizer, it may have a certain impact on the environment.

[0098] (5) It can be known from Comparative Example 4 that due to the relatively loose structure of the plant fiber carbon, the increase in the oxidation intensity causes partial degradation of the plant fiber carbon, making it difficult to load copper ions and anionic polyacrylamide. Thus, the water purification function of the prepared sewage treatment agent is poor. And due to the small amount of copper ions loaded, the amount of nano copper sulfide obtained by sulfidation is small, resulting in a poor photothermal effect of the nano copper sulfide and being unable to exert the sterilization function relying on the photothermal effect.

[0099] The above-described embodiments have elaborated in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for preparing a recyclable sewage treatment agent, characterized in that: The preparation method comprises the following steps: The plant fibers are crushed and sieved to obtain plant fiber particles, and the plant fiber particles are carbonized at high temperature to obtain plant fiber charcoal; The plant fiber charcoal is oxidized by hydrogen peroxide vapor in an ultraviolet environment to obtain oxidized plant fiber charcoal; The oxidized plant fiber carbon is dispersed in deionized water by ultrasonic method, and then mixed with the copper-containing inorganic compound and polyacrylamide for adsorption by stirring; After the stirring and adsorption is completed, the sewage treatment agent is obtained by precipitation with an inorganic sulfiding agent; The high temperature carbonization conditions include a temperature of 200°C to 300°C and a carbonization time of 2h to 4h; The ultraviolet environment includes an ultraviolet light wavelength of 320nm~370nm and an ultraviolet light power of 10W~20W; The conditions for the hydrogen peroxide steam oxidation include a hydrogen peroxide steam mass concentration of 4% to 10%, a hydrogen peroxide steam flow rate of 200 mL / min to 300 mL / min, and an oxidation time of 50 min to 100 min.

2. The method for preparing a recyclable sewage treatment agent according to claim 1, characterized in that: The copper-containing inorganic compound is anhydrous copper chloride or anhydrous copper sulfate.

3. The method for preparing a recyclable sewage treatment agent according to claim 1, characterized in that: The polyacrylamide is anionic polyacrylamide.

4. The method for preparing a recyclable sewage treatment agent according to claim 1, characterized in that: The inorganic sulfiding agent includes sodium sulfide or ammonium sulfide.

5. The method for preparing a recyclable sewage treatment agent according to claim 1, characterized in that: The mass ratio of the oxidized plant fiber carbon: deionized water: copper-containing inorganic compound: polyacrylamide: inorganic vulcanizing agent is 1:80-100:0.1-0.4:0.2-0.3:1-2.

6. A sewage treatment agent prepared by the method for preparing a recyclable sewage treatment agent according to any one of claims 1 to 5.

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