A method for treating phosphorus-containing sewage based on locally controllable release of iron ions

Abstract

The present invention discloses a method for treating phosphorus-containing sewage based on locally controllable release of iron ions. The process is as follows: using a conductive bacterial cellulose composite material immobilized with iron atoms as the anode; adding the anode and the cathode to the phosphorus-containing sewage and applying an electric current to cause the anode to release iron ions; the phosphoric phosphorus in the phosphorus-containing sewage reacts with the iron ions on the anode surface to form a precipitate that is enriched and in-situ deposited on the anode. The present invention selects conductive bacterial cellulose as the fixed carrier of iron atoms, realizes the efficient dispersion of iron, enables its controllable conversion into iron ions, and under the local supersaturated state, makes the phosphorus in the sewage deposit in the three-dimensional network structure of bacterial cellulose in the form of iron phosphate, avoiding the formation of chemical sludge, without the need for subsequent treatment of the sewage, and achieving the purpose of synchronous phosphorus removal and phosphorus resource utilization. During the treatment process of the present invention, no chemical agents need to be added and no chemical sludge is generated, fundamentally solving the problems of secondary pollution and difficult treatment of the generated sludge.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial and agricultural wastewater treatment; specifically, it relates to a method for treating phosphorus-containing sewage based on locally controllable release of iron ions. Background Art

[0002] Research shows that phosphorus is the main pollution factor causing eutrophication pollution of water bodies. When the total phosphorus content in water bodies reaches 0.015 mg / L, it can trigger eutrophication of water bodies. While emphasizing the urgent need to control phosphorus pollutants in water bodies, it should also be noted that phosphorus is an important resource necessary for the development of industry, agriculture, and even life activities. However, phosphorus belongs to the sedimentary cycle in the geochemical cycle and is a non-renewable and depleted resource. Therefore, researching and developing new technologies that take into account the treatment of phosphorus-containing wastewater and its resource recovery and utilization is an urgent problem in this field.

[0003] Currently, urban sewage treatment plants generally use biological phosphorus removal technology to treat phosphorus-containing aquaculture sewage and domestic sewage. It absorbs dissolved phosphates in water bodies in excess through microorganisms and is treated in the form of excess sludge. This process takes a long time, not only resulting in waste of phosphorus resources, but also being prone to secondary pollution when flowing into surface water and groundwater, and exacerbating the eutrophication of water bodies. More importantly, biological phosphorus removal technology is generally only applicable to low-concentration phosphorus-containing sewage. With the gradual improvement of sewage discharge standards, a single biological phosphorus removal process is difficult to meet the corresponding requirements of the standards.

[0004] Chemical phosphorus removal is another method for treating phosphorus-containing sewage besides biological phosphorus removal. It adds chemical agents to sewage to react with phosphates in the water body and form precipitates to achieve the purpose of phosphorus removal, which can be regarded as an artificial enhancement of natural phosphate precipitation. However, there are still some difficult problems to be solved in chemical phosphorus removal technology: First, in the process of chemical treatment, it is difficult to accurately control the dosage of chemical agents. To achieve an ideal phosphorus removal effect, it is generally required to add an excessive amount of metal salt agents, which will inevitably lead to new water pollution problems and increase the overall treatment cost due to unnecessary waste of agents. Second, the chemical phosphorus removal process will form a large amount of chemical sludge, and its subsequent treatment is more difficult. In addition, the traditional chemical method still fails to overcome the drawback that phosphorus resources are difficult to recycle. Separating and recycling it from sewage requires a lot of manpower and material resources. Summary of the Invention

[0005] The object of the present invention is to provide a novel phosphorus-containing sewage treatment method and a conductive bacterial cellulose composite material loaded with iron atoms for use therein, aiming at the problems of a large amount of excess sludge formed by existing biological phosphorus removal technologies, low treatment efficiency, being only applicable to low-concentration sewage, while chemical phosphorus removal technologies requiring artificial addition of chemical agents, high treatment costs, and great difficulty in subsequent treatment of chemical sludge. At the same time, both technologies are prone to cause secondary pollution and it is difficult to realize the resource utilization of phosphorus elements. The present invention can efficiently remove phosphorus in sewage and realize its resource utilization. During the process, no chemical agents need to be added and no chemical sludge is generated, fundamentally solving the problems of secondary pollution easily caused by conventional biological and chemical technologies, great difficulty in treating the generated sludge, and difficulty in recovering phosphorus resources in phosphorus-containing sewage. The present invention selects conductive bacterial cellulose as the fixing carrier of iron atoms, realizes the efficient dispersion of iron, controllably converts it into iron ions, and makes phosphorus in sewage deposit in situ in the three-dimensional network structure of bacterial cellulose in the form of iron phosphate under the local supersaturated state, avoiding the formation of chemical sludge and eliminating the need for subsequent treatment of sewage, achieving the purpose of synchronous phosphorus removal and realizing the resource utilization of phosphorus.

[0006] In the first aspect, the present invention provides a phosphorus-containing sewage treatment method based on the local controllable release of iron ions. The treatment process is as follows: using a conductive bacterial cellulose composite material loaded with iron atoms as the anode; adding the anode and the cathode into the phosphorus-containing sewage and applying an electric current, so that the anode releases iron ions and a locally supersaturated state of iron ions is formed around the anode; phosphate ions in the phosphorus-containing sewage react with iron ions on the surface of the anode to form a precipitate that accumulates and deposits in situ on the anode.

[0007] The conductive bacterial cellulose composite material loaded with iron atoms is obtained by preparing a bacterial cellulose culture medium, inoculating a film-forming bacterium for cultivation, adding a pyrrole solution to the culture medium after producing bacterial cellulose, and continuing the cultivation, and then successively immersing the obtained product in a potassium persulfate solution, a ferrous chloride solution, and a sodium borohydride solution for reaction.

[0008] Preferably, the voltage applied to the anode and the cathode is 0.1 V to 0.8 V.

[0009] Preferably, the cathode is made of stainless steel, such as a 304 or 316 stainless steel sheet.

[0010] Preferably, the conductivity of the conductive bacterial cellulose composite material loaded with iron atoms is 20 S / m to 1600 S / m, and the mass fraction of iron atoms in the composite material is 0.40 wt% to 3.50 wt%.

[0011] Preferably, the initial phosphate phosphorus value (PO4 3- -P) of the phosphorus-containing sewage is 50 mg / L to 1000 mg / L.

[0012] Preferably, after the phosphorus-containing sewage treatment is completed or the amount of iron phosphate precipitate attached to the conductive bacterial cellulose composite material reaches a preset amount, the conductive bacterial cellulose composite material carrying iron atoms as the anode is taken out, and the iron phosphate precipitate on the anode is recovered.

[0013] Preferably, the iron phosphate recovered from the anode is used as a precursor for preparing lithium iron phosphate, the cathode material of a lithium-ion battery.

[0014] In a second aspect, the present invention provides a method for preparing a conductive bacterial cellulose composite material carrying iron atoms, which includes the following steps:

[0015] Step 1: Prepare a bacterial cellulose culture medium and inoculate a film-forming bacterium for cultivation.

[0016] Step 2: Add a pyrrole solution to the bacterial cellulose culture medium and continue cultivation.

[0017] Step 3: Take out the product obtained in Step 2, immerse it in a potassium persulfate solution, and react.

[0018] Step 4: Take out the product obtained in Step 3, wash it, and then immerse it in a ferrous chloride solution, and carry out ultrasonic treatment for 0.5 h to 5 h.

[0019] Step 5: Immerse the product obtained in Step 4 in a sodium borohydride solution and react. After the reaction is completed, take out the solid product and wash it to obtain a conductive bacterial cellulose composite material carrying iron atoms.

[0020] Preferably, in Step 1, the bacterial cellulose culture medium is a mixed solution of glucose, peptone, yeast extract, disodium hydrogen phosphate, and ethanol. Among them, the mass concentrations of glucose, peptone, yeast extract, disodium hydrogen phosphate, and ethanol in the mixed solution are 4% to 10%, 0.4% to 1.2%, 0.4% to 1.2%, 0.02% to 0.1%, and 0.02% to 0.1%, respectively; the film-forming bacterium is Acetobacter xylinum; the cultivation conditions are: cultivation temperature 25 °C to 35 °C, cultivation time 3 d.

[0021] Preferably, in Step 2, the pyrrole solution is a solution obtained by dissolving pyrrole and nonylphenol polyoxyethylene ether in deionized water; in the pyrrole solution, the mass fraction of pyrrole is 0.2 wt% to 2 wt%, and the mass ratio of pyrrole to nonylphenol polyoxyethylene ether is 5:1 to 1:1.2; the cultivation conditions are: cultivation temperature 25 °C to 35 °C, cultivation time 4 d to 8 d.

[0022] Preferably, in step three, the concentration of the potassium persulfate solution is 2 g / L to 20 g / L; the reaction conditions are: reaction temperature 0 °C to 4 °C, reaction time 4 h to 16 h.

[0023] Preferably, in step four, the cleaning process is: sequentially cleaning with a 0.02 mol / L hydrochloric acid solution, a 0.02 mol / L sodium hydroxide solution, an ethanol aqueous solution with a mass concentration of 75%, and deionized water; the concentration of the ferrous chloride solution is 0.05 mol / L to 0.5 mol / L.

[0024] Preferably, in step five, the concentration of the sodium borohydride solution is 0.10 mol / L to 0.50 mol / L; the reaction conditions are: reaction temperature 20 °C to 80 °C, reaction time 2 h to 12 h.

[0025] In a third aspect, the present invention provides a conductive bacterial cellulose composite material immobilized with iron atoms, which is prepared by the aforementioned preparation method;

[0026] Preferably, the conductivity of the conductive bacterial cellulose composite material immobilized with iron atoms is 20 S / m to 1600 S / m, and the mass fraction of iron atoms in the composite material is 0.40 wt% to 3.50 wt%.

[0027] Compared with the prior art, the present invention has the following beneficial effects.

[0028] 1. The present invention uses a conductive bacterial cellulose composite material immobilized with iron atoms to treat phosphorus-containing sewage in the industrial and agricultural fields. This composite material can in-situ generate iron ions, and in a locally supersaturated state, the generated iron ions react chemically with the phosphate diffused and adsorbed to the composite material to form iron phosphate and deposit in-situ on the composite material, thereby achieving the purpose of treating phosphorus-containing sewage and recycling phosphorus resources. The whole process does not require the addition of chemical agents and does not produce chemical sludge, fundamentally solving the problems such as secondary pollution easily caused by conventional biological and chemical technologies, difficult treatment of the generated sludge, and difficult recovery of phosphorus resources in phosphorus-containing sewage.

[0029] 2. The present invention selects conductive bacterial cellulose as the fixed carrier of iron atoms, realizes the efficient dispersion of iron, enables its controllable conversion into iron ions, and can freely regulate the occurrence and termination of the reaction.

[0030] 3. The present invention makes full use of the specific three-dimensional network structure and high affinity of bacterial cellulose. Phosphate in the sewage can be easily diffused and adsorbed to the composite material, and iron ions and phosphate generate iron phosphate and deposit in-situ on the composite material due to the locally supersaturated state, avoiding the formation of chemical sludge and the subsequent difficult treatment problem.

[0031] 4. After the resource treatment of phosphorus-containing sewage, the obtained iron phosphate can be used as the precursor of lithium iron phosphate, the cathode material of lithium-ion batteries, and can also be widely used as adsorbents, catalysts, rust-proof pigments, and additives. Meanwhile, the hydrogen gas generated during the treatment of phosphorus-containing sewage can also be used as fuel, reducing agent, and chemical raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the change curve of the value of phosphate phosphorus (PO43--P) in sewage with the reaction time.

[0033] Figure 2 It is the mass change of the anode and cathode before and after the reaction.

[0034] Figure 3 It is the field emission scanning electron microscope image of the conductive bacterial cellulose composite material supporting iron atoms before the reaction.

[0035] Figure 4 It is the comparison chart of the phosphate phosphorus removal effects corresponding to Example 1 and Comparative Examples 1-3 of the present invention.

[0036] Figure 5 It is the influence of the circuit connection situation on the treatment result during the treatment of phosphorus-containing sewage with the conductive bacterial cellulose composite material supporting iron atoms.

[0037] Figure 6 It is the test result of the cyclic treatment of phosphorus-containing sewage with the conductive bacterial cellulose composite material supporting iron atoms. DETAILED DESCRIPTION OF THE INVENTION

[0038] The technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Example 1

[0040] A method for treating phosphorus-containing sewage, the process is as follows: using a conductive bacterial cellulose composite material supporting iron atoms as the anode and stainless steel as the cathode, and applying electricity to the phosphorus-containing sewage. During the electrolysis process, the composite material as the anode releases iron ions, forming a state of local supersaturation of iron ions, so that the phosphate ions in the water body combine with the iron ions on the anode surface to form iron phosphate precipitate deposited in situ on the anode; meanwhile, the state of local supersaturation of iron ions promotes the formation of iron phosphate precipitate.

[0041] In this embodiment, the sizes of the anode and cathode are both 1 cm by 1 cm to 5 cm by 5 cm; the anode and cathode are arranged opposite to each other with a spacing of 1 cm to 10 cm; and the voltage applied between the anode and cathode is 0.1 V to 0.8 V.

[0042] The iron phosphate on the anode can be recycled as a precursor of lithium iron phosphate, a positive electrode material for lithium-ion batteries, and can also be widely used as an adsorbent, catalyst, anti-rust pigment and additive. The iron phosphate precipitate on the composite material can be recycled by gently scraping it off.

[0043] The preparation method of the conductive bacterial cellulose composite material with fixed iron atoms comprises the following steps:

[0044] (1) Weigh 15.00 g glucose, 1.20 g peptone, 1.20 g yeast extract, 0.075 g disodium hydrogen phosphate and 0.075 g ethanol respectively and dissolve them in 150 mL deionized water to prepare bacterial cellulose culture medium. Inoculate Acetobacter xylinum into the culture medium and culture it at 30 °C for 3 days to produce bacterial cellulose film.

[0045] (2) Weigh 0.10 g of pyrrole and 0.050 g of nonylphenol polyoxyethylene ether respectively, dissolve in 10 mL of deionized water to prepare a pyrrole solution. Add the obtained pyrrole solution to the culture medium containing bacterial cellulose membrane obtained in step (1), and continue to culture at 30°C for 5 days to allow the bacterial cellulose membrane to continue to grow and introduce pyrrole into the bacterial cellulose membrane.

[0046] (3) Take out the product obtained in step (2), immerse it in a potassium persulfate solution with a concentration of 10 g / L, and react at 0°C for 8 h.

[0047] (4) Take out the product obtained in step (3), wash it with 0.02 mol / L hydrochloric acid solution, 0.02 mol / L sodium hydroxide solution, 75% ethanol aqueous solution and deionized water in sequence, and then immerse it in 0.10 mol / L ferrous chloride solution and ultrasonicate it for 2 h.

[0048] (5) The product obtained in step (4) is immersed in a sodium borohydride solution with a concentration of 0.20 mol / L and reacted at 60°C for 4 hours. After the reaction is completed, the solid is taken out and washed with deionized water to obtain a conductive bacterial cellulose composite material with iron atoms immobilized thereon. The composite material comprises bacterial cellulose, polypyrrole loaded on the bacterial cellulose, and iron atoms loaded on the polypyrrole.

[0049] According to the test, the conductivity of the conductive bacterial cellulose composite material with immobilized iron atoms obtained in this example is 800 S / m, and the mass fraction of iron atoms in the composite material is 2.50 wt%.

[0050] The conductive bacterial cellulose composite material with immobilized iron atoms obtained in this example can be used for the resource utilization of phosphorus-containing sewage. To prove the effect of the composite material prepared in this example in treating phosphorus-containing sewage, the following experiment was carried out:

[0051] Experimental group: 1000 mL of sewage from the supernatant of the primary sedimentation tank of a rural breeding farm was taken. Its phosphate phosphorus (PO4 3- -P, the phosphate phosphorus value specifically represents the concentration in which all inorganic phosphorus is calculated as phosphate radical.) value was 120 mg / L. This sewage was used as the phosphorus-containing sewage to be treated. 3 cm × 3 cm of a conductive bacterial cellulose composite material with immobilized iron atoms obtained in this example and 3 cm × 3 cm of a stainless steel sheet were taken respectively; then the two were used as the anode and cathode respectively, connected to the positive and negative poles of a DC regulated power supply respectively, and the two poles were arranged facing each other with a distance of 4 cm between them, and the reaction temperature was controlled at 30 °C. Electricity was supplied, and the voltage was controlled at 0.4 V. During the reaction process, the change of the phosphate phosphorus (PO4 3- -P) value of the sewage with the reaction time was as Figure 1 shown. After 4 h of reaction, the phosphate phosphorus (PO4 3- -P) value of the sewage decreased by 95.26%. Before and after the experiment, the mass change of the anode and cathode (after cleaning and drying) was as Figure 2 shown. The mass increase of the anode was 0.4722 g, while the mass of the cathode basically did not change.

[0052] From Figure 3 it can be seen that the fiber size in the conductive bacterial cellulose composite material with immobilized iron atoms before the test was about dozens of nanometers, and the pores formed by the stacking between the fibers were clearly visible.

[0053] To determine the change of iron atoms in the anode, the anode after 1 h of power supply was taken out, placed in deionized water and shaken vigorously for 1 h. Dilute sulfuric acid was added dropwise to the solution obtained after shaking, the pH was adjusted to 2, and then acidic potassium permanganate solution was added dropwise. The purple-red color did not fade, indicating that there was no ferrous ion in the solution; potassium thiocyanate solution was added dropwise to the solution obtained after shaking, and the solution turned red, indicating that there was ferric ion in the solution. By calculating the decrease value of phosphate phosphorus (PO4 3- -P) before and after the phosphorus-containing sewage treatment and the mass increase value of the anode, and combining this color reaction, it was confirmed that the formation and in-situ deposition of FePO4×2H2O occurred at the anode.

[0054] At the same time, bubbles could be observed at the cathode. Methylene blue-platinum reagent was dropped into the cathode solution, and the blue color gradually faded. From this, it can be known that the gas generated at the cathode is reducing hydrogen.

[0055] Based on the above experimental results, it is inferred that during the reaction process, the following reactions occur at the anode and cathode respectively:

[0056] Anode:

[0057] Cathode:

[0058] Comparative Example 1

[0059] A method for treating phosphorus-containing sewage. The difference between this comparative example and Example 1 is that the anodes used are different; the difference between the preparation process of the anode used in this example and the conductive bacterial cellulose composite material with immobilized iron atoms used in Example 1 is that pyrrole is not added in step (2), and the finally obtained composite material does not contain polypyrrole and is not conductive.

[0060] In this comparative example, an experiment on treating phosphorus-containing sewage was carried out. As control group 1, other experimental conditions except the anode were the same as those in the experimental group of Example 1. After 4 h of action, the value of phosphoric phosphorus (PO4 3- -P) in the sewage decreased by 6.36% (see Figure 4 ), and the mass of the composite material basically did not change before and after the experiment.

[0061] Comparative Example 2

[0062] A method for treating phosphorus-containing sewage. The difference between this comparative example and Comparative Example 1 is that no voltage is applied during the treatment process.

[0063] In this comparative example, an experiment on treating phosphorus-containing sewage was carried out. As control group 2, other experimental conditions except no voltage application were the same as those in control group 1 of Comparative Example 1. After 4 h of action, the value of phosphoric phosphorus (PO4 3- -P) in the sewage decreased by 6.22% (see Figure 4 ), and the mass of the composite material basically did not change before and after the experiment. From Comparative Example 1 and Comparative Example 2, it can be seen that the non-conductive bacterial cellulose composite material with immobilized iron atoms only has a certain adsorption effect on phosphorus-containing sewage, and the reduction of the value of phosphoric phosphorus (PO4 3- -P) has nothing to do with the electrochemical reaction.

[0064] Comparative Example 3

[0065] A method for treating phosphorus-containing sewage. The difference between this comparative example and Example 1 is that the anodes used are different; the difference between the preparation process of the anode used in this example and the conductive bacterial cellulose composite material with immobilized iron atoms used in Example 1 is that ferrous chloride solution is not used in steps (2) and (4), and the finally obtained composite material does not contain iron.

[0066] This comparative example conducts an experiment on phosphorus-containing sewage treatment and serves as control group 3; other experimental conditions except for the anode are the same as those of the experimental group in Example 1. After 4 hours of action, the value of phosphoric phosphorus (PO4 3- -P) in the sewage decreases by 5.94% (see Figure 4 ), and the mass of the composite material remains basically unchanged before and after the experiment.

[0067] Example 2

[0068] A method for treating phosphorus-containing sewage. The difference between this comparative example and Example 1 lies in that the dosages of some substances and reaction conditions in the preparation method of the conductive bacterial cellulose composite material carrying iron atoms as the anode are different.

[0069] The preparation method of the conductive bacterial cellulose composite material carrying iron atoms in this example includes the following steps:

[0070] (1) Weigh 15.00 g of glucose, 1.20 g of peptone, 1.20 g of yeast extract, 0.075 g of disodium hydrogen phosphate, and 0.075 g of ethanol respectively, dissolve them in 150 mL of deionized water, and prepare a bacterial cellulose medium. Inoculate Acetobacter xylinum into the medium and culture it at 30 °C for 3 days to generate a bacterial cellulose membrane.

[0071] (2) Weigh 0.25 g of pyrrole and 0.050 g of nonylphenol polyoxyethylene ether respectively, dissolve them in 10 mL of deionized water, and prepare a pyrrole solution. Add the obtained pyrrole solution to the mixed solution containing the bacterial cellulose membrane obtained in step (1), and continue to culture at 30 °C for 5 days to allow the bacterial cellulose membrane to continue to grow and introduce pyrrole into the bacterial cellulose membrane.

[0072] (3) Take out the product obtained in step (2), immerse it in a potassium persulfate solution with a concentration of 10 g / L, and react at 0 °C for 8 hours.

[0073] (4) Take out the product obtained in step (3), wash it successively with 0.02 mol / L hydrochloric acid solution, 0.02 mol / L sodium hydroxide solution, 75% ethanol aqueous solution by mass concentration, and deionized water, then immerse it in a ferrous chloride solution with a concentration of 0.10 mol / L, and carry out ultrasonic treatment for 2 hours.

[0074] (5) Immerse the product obtained in step (4) in a sodium borohydride solution with a concentration of 0.20 mol / L and react at 60 °C for 4 hours. After the reaction ends, take out the solid and wash it with deionized water to obtain a conductive bacterial cellulose composite material carrying iron atoms. The conductivity of the obtained conductive bacterial cellulose composite material carrying iron atoms is 1400 S / m, and the mass fraction of iron atoms in the composite material is 2.28 wt%.

[0075] A conductive bacterial cellulose composite material immobilized with iron atoms obtained in this example is used for the resource utilization of phosphorus-containing sewage, and the experimental conditions are the same as those of the experimental group in Example 1. After 4 h of reaction, the value of phosphate phosphorus (PO4 3- -P) in the sewage decreased by 97.27%, and 0.4826 g of FePO4×2H2O was collected at the anode, showing excellent phosphorus-containing sewage removal and resource utilization effects.

[0076] To confirm that the present invention has unique controllability in treating phosphorus-containing sewage, the power was cut off after the reaction proceeded for a certain time, and the change of the phosphate phosphorus (PO4 3- -P) value in the sewage during the process was monitored (see Figure 5 ). As can be seen from Figure 5 , when the circuit is connected, the value of phosphate phosphorus (PO4 3- -P) in the phosphorus-containing sewage decreases significantly as the reaction proceeds; after the power is cut off, the value of phosphate phosphorus (PO4 3- -P) in the sewage remains basically unchanged; after the power is reconnected, the value of phosphate phosphorus (PO4 3- -P) starts to decrease again; after the power is cut off again, the value of phosphate phosphorus (PO4 3- -P) no longer changes. This result shows that the phosphorus-containing sewage treatment technology used in the present invention can freely control the occurrence and termination of the reaction. In the actual treatment process, when it is monitored that the value of phosphate phosphorus (PO4 3- -P) in the sewage reaches the target value, the reaction can be terminated by a simple power-off operation, fundamentally solving the defects of chemical phosphorus removal technology that chemical agents are difficult to accurately control and easily cause many subsequent problems.

[0077] Example 3

[0078] A method for treating phosphorus-containing sewage, the difference between this comparative example and Example 1 is that the dosages of some substances and the reaction conditions are different in the preparation method of the conductive bacterial cellulose composite material immobilized with iron atoms as the anode.

[0079] The preparation method of the conductive bacterial cellulose composite material immobilized with iron atoms in this example includes the following steps:

[0080] (1) Weigh 15.00 g of glucose, 1.20 g of peptone, 1.20 g of yeast extract, 0.075 g of disodium hydrogen phosphate and 0.075 g of ethanol respectively, dissolve them in 150 mL of deionized water, and prepare a bacterial cellulose medium. Acetobacter xylinum is inoculated into the medium and cultured at 30 °C for 3 d to generate a bacterial cellulose membrane.

[0081] (2) Weigh 0.10 g of pyrrole and 0.050 g of nonylphenol polyoxyethylene ether separately, dissolve them in 10 mL of deionized water to prepare a pyrrole solution. Add the obtained pyrrole solution to the mixed solution containing bacterial cellulose membrane obtained in step (1), and continue to culture at 30 °C for 5 d to allow the bacterial cellulose membrane to continue growing and introduce pyrrole into the bacterial cellulose membrane.

[0082] (3) Take out the product obtained in step (2), immerse it in a potassium persulfate solution with a concentration of 10 g / L, and react at 0 °C for 8 h.

[0083] (4) Take out the product obtained in step (3), wash it successively with 0.02 mol / L hydrochloric acid solution, 0.02 mol / L sodium hydroxide solution, 75% ethanol aqueous solution by mass concentration and deionized water, and then immerse it in a ferrous chloride solution with a concentration of 0.30 mol / L, and carry out ultrasonic treatment for 2 h.

[0084] (5) Immerse the product obtained in step (4) in a sodium borohydride solution with a concentration of 0.20 mol / L and react at 60 °C for 4 h. After the reaction is completed, take out the solid and wash it with deionized water to obtain a conductive bacterial cellulose composite material loaded with iron atoms. The conductivity of the obtained conductive bacterial cellulose composite material loaded with iron atoms is 920 S / m, and the mass fraction of iron atoms in the composite material is 3.50 wt%.

[0085] The conductive bacterial cellulose composite material loaded with iron atoms obtained in this example is used for the resource utilization of phosphorus-containing sewage, and the experimental conditions are the same as those of the experimental group in Example 1. After 4 h of reaction, the value of phosphate phosphorus (PO4 3- -P) in the sewage decreased by 98.62%, and at the same time, 0.4877 g of FePO4×2H2O was collected at the anode, showing excellent phosphorus-containing sewage removal and resource utilization effects.

[0086] In order to investigate the recycling treatment ability of the obtained conductive bacterial cellulose composite material loaded with iron atoms for phosphorus-containing sewage, take out the above-mentioned used conductive bacterial cellulose composite material loaded with iron atoms from the reaction solution, wash it with deionized water and then use it again for phosphorus-containing sewage treatment, and keep the experimental conditions unchanged. As Figure 6 shown, after 5 cycles of use, the conductive bacterial cellulose composite material loaded with iron atoms can still reduce the value of phosphate phosphorus (PO4 3- -P) in the phosphorus-containing sewage by 96.79%, indicating that the obtained conductive bacterial cellulose composite material loaded with iron atoms has excellent recycling treatment ability for phosphorus-containing sewage.

[0087] Example 4

[0088] A method for treating phosphorus-containing sewage. The difference between this comparative example and Example 1 lies in that the dosages of some substances and reaction conditions are different in the preparation method of the conductive bacterial cellulose composite material carrying iron atoms as the anode.

[0089] In the preparation method of the conductive bacterial cellulose composite material carrying iron atoms in this example, the following steps are included:

[0090] (1) Weigh 15.00 g of glucose, 1.20 g of peptone, 1.20 g of yeast extract, 0.075 g of disodium hydrogen phosphate and 0.075 g of ethanol respectively, dissolve them in 150 mL of deionized water, and prepare a bacterial cellulose medium. Inoculate Acetobacter xylinum into the medium and culture it at 30 °C for 3 days to generate a bacterial cellulose membrane.

[0091] (2) Weigh 0.20 g of pyrrole and 0.050 g of nonylphenol polyoxyethylene ether respectively, dissolve them in 10 mL of deionized water, and prepare a pyrrole solution. Add the obtained pyrrole solution to the mixed solution containing the bacterial cellulose membrane obtained in step (1), and continue to culture it at 30 °C for 5 days to make the bacterial cellulose membrane continue to grow and introduce pyrrole into the bacterial cellulose membrane.

[0092] (3) Take out the product obtained in step (2), immerse it in a potassium persulfate solution with a concentration of 10 g / L, and react at 0 °C for 8 h.

[0093] (4) Take out the product obtained in step (3), wash it successively with a 0.02 mol / L hydrochloric acid solution, a 0.02 mol / L sodium hydroxide solution, an ethanol aqueous solution with a mass concentration of 75% and deionized water, and then immerse it in a 0.20 mol / L ferrous chloride solution and perform ultrasonic treatment for 2 h.

[0094] (5) Immerse the product obtained in step (4) in a 0.20 mol / L sodium borohydride solution and react at 60 °C for 4 h. After the reaction is completed, take out the solid and wash it with deionized water to obtain a conductive bacterial cellulose composite material carrying iron atoms. The conductivity of the obtained conductive bacterial cellulose composite material carrying iron atoms is 920 S / m, and the mass fraction of iron atoms in the composite material is 2.96 wt%.

[0095] Place the conductive bacterial cellulose composite material carrying iron atoms obtained in this example in 10 L of phosphorus-containing sewage with an initial phosphate phosphorus (PO4 3- -P) value of 1000 mg / L, and conduct an electrolytic reaction until the phosphate phosphorus (PO4 3-When the (P) value no longer changed, it indicated that the iron atoms in the composite material had been depleted. The composite material was taken out of the reaction solution, washed with deionized water, and then immersed in a ferrous chloride solution with a concentration of 0.10 mol / L for 2 h under ultrasonic treatment. The obtained product was then immersed in a sodium borohydride solution with a concentration of 0.20 mol / L and reacted at 60 °C for 4 h. After the reaction, the solid was taken out and washed with deionized water to obtain a conductive bacterial cellulose composite material with immobilized iron atoms again. The conductivity of the obtained conductive bacterial cellulose composite material with immobilized iron atoms was 770 S / m, and the mass fraction of iron atoms in the composite material was 2.58 wt%.

[0096] The conductive bacterial cellulose composite material with re-immobilized iron atoms was used for the resource utilization of phosphorus-containing sewage, and the experimental conditions were the same as those in the experimental group of Example 1. After 4 h of reaction, the value of phosphoric phosphorus (PO4 3- -P) in the sewage decreased by 96.88%, and 0.4791 g of FePO4×2H2O was collected at the anode. The above experimental results showed that the conductive bacterial cellulose composite material with immobilized iron atoms obtained in the present invention had excellent regeneration performance.

[0097] Example 5

[0098] A method for treating phosphorus-containing sewage. The difference between this comparative example and Example 1 was that the amounts of some substances and the reaction conditions in the preparation method of the conductive bacterial cellulose composite material used as the anode were different.

[0099] The preparation method of the conductive bacterial cellulose composite material with immobilized iron atoms in this example included the following steps:

[0100] (1) Weigh 15.00 g of glucose, 1.20 g of peptone, 1.20 g of yeast extract, 0.075 g of disodium hydrogen phosphate, and 0.075 g of ethanol respectively, dissolve them in 150 mL of deionized water, and prepare a bacterial cellulose medium. Acetobacter xylinum was inoculated into the medium and cultured at 30 °C for 3 d to generate a bacterial cellulose membrane.

[0101] (2) Weigh 0.15 g of pyrrole and 0.10 g of nonylphenol polyoxyethylene ether respectively, dissolve them in 10 mL of deionized water, and prepare a pyrrole solution. The obtained pyrrole solution was added to the mixed solution containing the bacterial cellulose membrane obtained in step (1), and the culture was continued at 30 °C for 5 d to allow the bacterial cellulose membrane to continue growing and introduce pyrrole into the bacterial cellulose membrane.

[0102] (3) Take out the product obtained in step (2), immerse it in a potassium persulfate solution with a concentration of 8 g / L, and react at 0 °C for 6 h.

[0103] (4) Take out the product obtained in step (3), and wash it successively with 0.02 mol / L hydrochloric acid solution, 0.02 mol / L sodium hydroxide solution, 75% ethanol aqueous solution by mass concentration and deionized water, and then immerse it in a 0.15 mol / L ferrous chloride solution and perform ultrasonic treatment for 2 h.

[0104] (5) Immerse the product obtained in step (4) in a 0.20 mol / L sodium borohydride solution and react at 60 °C for 4 h. After the reaction is completed, take out the solid and wash it with deionized water to obtain a conductive bacterial cellulose composite material loaded with iron atoms. The conductivity of the obtained conductive bacterial cellulose composite material loaded with iron atoms is 860 S / m, and the mass fraction of iron atoms in the composite material is 2.46 wt%.

[0105] The conductive bacterial cellulose composite material loaded with iron atoms obtained in this example is used for the resource utilization of phosphorus-containing sewage; in order to prove the effect of the composite material prepared in this example in treating phosphorus-containing sewage, the following experiment is carried out:

[0106] Experimental group: Take 1000 mL of industrial sewage from a certain chemical plant, and its phosphoric acid phosphorus (PO4 3- -P) value is 525 mg / L, and use this sewage as the phosphorus-containing sewage to be treated. Other experimental conditions are the same as those in the experimental group of Example 1. After 6 h of reaction, the phosphoric acid phosphorus (PO4 3- -P) value of the sewage decreased by 96.21%, and at the same time, 2.0136 g of FePO4×2H2O was collected at the anode, showing excellent phosphorus-containing sewage removal and resource utilization effects.

[0107] The above is only a preferred embodiment of the present invention, so the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. A phosphorus-containing sewage treatment method based on locally controllable release of iron ions, characterized in that: Use a conductive bacterial cellulose composite material loaded with iron atoms as the anode; add the anode and cathode to the phosphorus-containing sewage and apply an electric current, so that the anode releases iron ions and a locally supersaturated state of iron ions is formed around the anode; the phosphate ions in the phosphorus-containing sewage react with the iron ions on the anode surface to form a precipitate that is enriched and in-situ deposited on the anode. The conductive bacterial cellulose composite material loaded with iron atoms is obtained by preparing a bacterial cellulose culture medium, inoculating a film-forming bacterium for culture, adding a pyrrole solution to the culture medium after the bacterial cellulose is produced, and continuing the culture, and then successively immersing the obtained product in a potassium persulfate solution, a ferrous chloride solution, and a sodium borohydride solution for reaction. The conductivity of the conductive bacterial cellulose composite material loaded with iron atoms is 20 S / m to 1600 S / m, and the mass fraction of iron atoms in the composite material is 0.40 wt% to 3.50 wt%. After the treatment of the phosphorus-containing sewage is completed, take out the conductive bacterial cellulose composite material loaded with iron atoms as the anode, and recover the iron phosphate precipitate on the anode.

2. The phosphorus-containing sewage treatment method based on locally controllable release of iron ions according to claim 1, characterized in that: The voltage applied to the anode and cathode is 0.1 V to 0.8 V.

3. A phosphorus-containing sewage treatment method based on locally controllable release of iron ions according to claim 1, characterized in that: The initial phosphate phosphorus value of the phosphorus-containing sewage is 50 mg / L to 1000 mg / L.

4. A phosphorus-containing sewage treatment method based on locally controllable release of iron ions according to claim 1, characterized in that: The iron phosphate recovered on the anode is used as a precursor for preparing lithium iron phosphate, the cathode material of a lithium-ion battery.

5. A phosphorus-containing sewage treatment method based on locally controllable release of iron ions according to claim 1, characterized in that: The preparation process of the conductive bacterial cellulose composite material loaded with iron atoms includes the following steps: Step 1: Prepare a bacterial cellulose culture medium and inoculate a film-forming bacterium for culture. Step 2: Add the pyrrole solution to the bacterial cellulose culture medium and continue the culture. Step 3: Take out the product obtained in Step 2, immerse it in the potassium persulfate solution, and react. Step 4: Take out the product obtained in Step 3, wash it, and then immerse it in the ferrous chloride solution and carry out ultrasonic treatment for 0.5 h to 5 h. Step 5: Immerse the product obtained in Step 4 in the sodium borohydride solution and react; after the reaction is completed, take out the solid product and wash it to obtain a conductive bacterial cellulose composite material loaded with iron atoms.

6. The method for treating phosphorus-containing sewage based on locally controllable release of iron ions according to claim 5, wherein: In Step 2 of the preparation process, the pyrrole solution is a solution obtained by dissolving pyrrole and nonylphenol polyoxyethylene ether in deionized water; in the pyrrole solution, the mass fraction of pyrrole is 0.2 wt% to 2 wt%, and the mass ratio of pyrrole to nonylphenol polyoxyethylene ether is 5:1 to 1:1.2; the culture conditions are: culture temperature 25 °C to 35 °C, culture time 4 d to 8 d.

7. A phosphorus-containing sewage treatment method based on locally controllable release of iron ions according to claim 5, characterized in that: In Step 3 of the preparation process, the concentration of the potassium persulfate solution is 2 g / L to 20 g / L, and the reaction conditions are: reaction temperature 0 °C to 4 °C, reaction time 4 h to 16 h; in Step 5, the concentration of the sodium borohydride solution is 0.10 mol / L to 0.50 mol / L, and the reaction conditions are: reaction temperature 20 °C to 80 °C, reaction time 2 h to 12 h.

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