A method for treating phosphorus-containing wastewater and recovering phosphorus and a cellulose composite material used therein

Abstract

The invention discloses a phosphorus-containing sewage treatment and phosphorus recovery method and a cellulose composite material used therein. The invention makes full use of the unique three-dimensional network structure and easy modification of bacterial cellulose, covalently fixes amino acid chains on cellulose by chemical methods, realizes controllable dispersion of amino acid chains, and then utilizes the interaction between amino acid chains and phosphorus to absorb phosphorus in sewage, and the hydroxyl groups on cellulose and amino acid chains form hydrogen bonds to interact with each other to stabilize phosphorus; through simple pH adjustment, the amino acid chains collapse and release the enriched phosphorus, so as to achieve the purpose of enriching and recovering phosphorus resources from sewage; the invention does not need to add chemical reagents when treating phosphorus-containing sewage, does not generate any chemical sludge in the process, the phosphorus resource recovery operation is simple, and the cellulose composite material used can be recycled, fundamentally solving the problems existing in the existing chemical and biological methods of recovering phosphorus, and achieving the purpose of efficiently realizing the resource utilization of phosphorus in phosphorus-containing sewage.

Description

Technical Field

[0001] The invention belongs to the technical field of rural sewage treatment, and specifically relates to a phosphorus-containing sewage treatment and phosphorus recovery method and a cellulose composite material used therein. Background Art

[0002] As human society's demand for various material resources continues to increase, some non-renewable but essential resources are facing exhaustion. On the other hand, these essential resources are discharged into the environment in the form of wastewater and other wastes, causing environmental pollution. Phosphorus is a typical example: according to statistics, at the current consumption rate, the phosphorus resources on the earth will be exhausted within a hundred years; however, as an indispensable but non-renewable resource in life activities, a large amount of phosphorus is directly discharged in the form of industrial and agricultural wastewater, which not only brings about environmental pollution problems, but also leads to the waste of precious phosphorus resources.

[0003] In order to solve the above problems, scientists have tried to use phosphorus-containing wastewater as a source of phosphorus resources, extract and recover phosphorus resources from it through different technical means, and then reuse them in areas where they are urgently needed, so as to achieve the goal of obtaining high value-added products while dealing with environmental pollution problems.

[0004] At present, the commonly used methods for obtaining phosphorus resources from phosphorus-containing wastewater are chemical methods and biological methods. The chemical method adds chemical reagents to the sewage, uses chemical reactions to convert the phosphorus in the sewage into a certain substance, and then purifies the substance through certain technical means. This type of method has a clear mechanism of action and a stable treatment effect, but it has the disadvantages of high reagent consumption, easy generation of chemical sludge, difficulty in extracting phosphorus resources, and possible secondary pollution. Biological methods often use the specific interaction of microorganisms with phosphorus treatment capabilities with phosphorus to recover phosphorus resources, including prokaryotic processes that enhance biological phosphorus removal, eukaryotic technologies such as floating algae cultivation, and artificial wetland recovery systems. However, when implementing the recovery of phosphorus resources, these technologies often require more complex operating conditions; at the same time, given the inherent limitations of the microorganisms themselves, their process optimization is quite difficult, which also limits their practical application to a certain extent.

[0005] As we all know, phosphate groups are widely present in the phospholipid molecules of cell membranes and are also an important component of nucleic acids. The specific binding between phosphate groups and the amino acid chains of proteins is the basis for the realization of many functions and pathways within cells. The study of the interaction between amino acid chains and phosphate groups is one of the hot topics in the field of biology. Summary of the invention

[0006] The purpose of the present invention is to provide a method for efficiently recovering phosphorus from phosphorus-containing wastewater and a cellulose composite material grafted with amino acid chains used therein, in view of the reality that phosphorus-containing industrial and agricultural wastewater causes serious environmental pollution and the precious phosphorus resources are wasted, and the existing chemical phosphorus recovery technology has the defects of high cost, easy generation of chemical sludge, difficulty in extracting phosphorus resources and possible secondary pollution, and the biological phosphorus recovery method has the problems of complex operating conditions, difficult process optimization, and difficulty in practical promotion and application. The present invention makes full use of the unique three-dimensional network structure of bacterial cellulose and its easy modification, and covalently fixes the amino acid chains on cellulose by chemical method, thereby achieving the goal of amino acid chain recovery. The invention discloses a method for controlling the dispersion of phosphorus in sewage by controlling the interaction between amino acid chains and phosphorus, and absorbing phosphorus in sewage by using the interaction between amino acid chains and phosphorus, and the hydroxyl groups on cellulose and amino acid chains form hydrogen bonds to interact with each other to stabilize phosphorus; through simple pH adjustment, the amino acid chains collapse and release the enriched phosphorus, so as to achieve the purpose of enriching and recovering phosphorus resources from sewage; the invention does not need to add chemical reagents when treating phosphorus-containing sewage, does not generate any chemical sludge during the process, and the phosphorus resource recovery operation is simple and convenient; the cellulose composite material grafted with amino acid chains can be recycled, and the problems existing in the existing chemical and biological methods for recovering phosphorus are fundamentally solved, so as to achieve the purpose of efficiently realizing the resource utilization of phosphorus in phosphorus-containing sewage.

[0007] In a first aspect, the present invention provides a method for treating phosphorus-containing wastewater and recovering phosphorus; the method comprises the following steps:

[0008] a. Phosphorus capture stage. Add the cellulose composite material grafted with amino acid chains into phosphorus-containing wastewater, and adjust the pH value to 5-8, so that the cellulose composite material grafted with amino acid chains can capture phosphorus in the phosphorus-containing wastewater. The preparation process of the cellulose composite material grafted with amino acid chains is as follows: first, oxidize the hydroxyl groups on the bacterial cellulose membrane into aldehyde groups using an oxidant; then, modify the oxidized bacterial cellulose membrane using decanediamine, glutaraldehyde, and amino acid chains in sequence to obtain the cellulose composite material grafted with amino acid chains.

[0009] b. Recovery stage: The cellulose composite material grafted with amino acid chains is taken out from the phosphorus-containing wastewater and placed in an alkaline system with a pH value greater than or equal to 9, so that the phosphorus captured by the cellulose composite material grafted with amino acid chains is released; finally, the phosphorus in the alkaline system is recovered.

[0010] Preferably, the pH value in step a is adjusted to 6. In step b, the pH value is adjusted to 12.

[0011] Preferably, the initial phosphate phosphorus (PO4 3- -P) value is 20 mg / L-400 mg / L. Phosphate phosphorus value indicates the concentration of all inorganic phosphorus in phosphate.

[0012] Preferably, in step a, the amount of amino acid chains in the cellulose composite material grafted with amino acid chains to phosphorus in the phosphorus-containing wastewater is (1.45-1.92): 1. The amount of the cellulose composite material grafted with amino acid chains is calculated based on the mass ratio of amino acid chains to cellulose, the concentration of phosphorus in the phosphorus-containing wastewater, and the volume of the phosphorus-containing wastewater; generally, the amount of the cellulose composite material grafted with amino acid chains relative to the phosphorus-containing wastewater is controlled at 0.25 g / L to 5 g / L.

[0013] Preferably, in steps a and b, the sewage is adjusted to the desired pH value by using 1 mol / L hydrochloric acid solution and 1 mol / L sodium hydroxide solution.

[0014] Preferably, the reaction conditions in step a are: reaction temperature 10 ° C-60 ° C, reaction time 5 min-60 min. The reaction conditions in step b are: reaction temperature 10 ° C-60 ° C, reaction time 5 min-60 min.

[0015] In a second aspect, the present invention provides a method for preparing a cellulose composite material grafted with amino acid chains, comprising the following steps:

[0016] Step 1: Immerse the bacterial cellulose membrane in a sodium periodate solution, add hydroxyapatite, and react.

[0017] Step 2: Immerse the product obtained in step 1 in a decanediamine solution, drop a hydrochloric acid solution, and then add a zeolite molecular sieve to react.

[0018] Step 3: Immerse the product obtained in step 2 in glutaraldehyde solution, add sodium sulfite, and react.

[0019] Step 4: Immerse the product obtained in step 3 in a solution containing amino acid chains, add sodium sulfite, and continue the reaction to obtain a cellulose composite material grafted with amino acid chains.

[0020] Preferably, in step 1, the concentration of the sodium periodate solution is 0.02 mol / L-0.2 mol / L; the hydroxyapatite is used as a catalyst, and its addition amount relative to the sodium periodate solution is 0.1 g / L-1 g / L; the reaction conditions are: reaction temperature 20 °C-60 °C, reaction time 2 h-12 h.

[0021] Preferably, in step 2, the CAS number of the decanediamine is 646-25-3, purchased from Shanghai Myrel Biochemical Technology Co., Ltd.; the decanediamine solution is a solution obtained by dissolving decanediamine in anhydrous ethanol, and its concentration is 5 g / L-50 g / L; the concentration of the hydrochloric acid solution is 6 mol / L, so that the pH value of the system becomes acidic; the zeolite molecular sieve is a Y-type molecular sieve, and its amount relative to the decanediamine solution is 0.02 g / L~0.20 g / L; the reaction conditions are: reaction temperature 20 °C-80 °C, reaction time 2 h-8 h.

[0022] Preferably, in step three, the glutaraldehyde solution is a glutaraldehyde aqueous solution with a mass concentration of 25%; the amount of sodium sulfite added relative to the glutaraldehyde solution is 2 g / L-10 g / L; and the reaction conditions are: reaction temperature 0 °C-50 °C, reaction time 0.5 h-5 h.

[0023] Preferably, in step 4, the solution containing amino acid chains is an aqueous solution containing hexapeptide-10, and its concentration is 1 g / L-20 g / L; the CAS number of the hexapeptide-10 is 146439-94-3, and the molecular formula is C 28 H 53 N7O8 was purchased from Sinopharm Chemical Reagent Co., Ltd.; the reaction conditions were: reaction temperature 0 °C-50 °C, reaction time 1 h-4 h.

[0024] Preferably, the product obtained in step 1 is washed with deionized water and then dried. The product obtained in step 2 is washed with 75% ethanol and deionized water in turn and then dried. The product obtained in step 3 is washed with deionized water and then dried. The product obtained in step 4 is washed with 75% ethanol and deionized water in turn and then dried.

[0025] In a third aspect, the present invention provides a cellulose composite material grafted with amino acid chains, which is prepared by the aforementioned preparation method, wherein the mass ratio of the amino acid chains to the cellulose is 0.22 to 3.52.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention utilizes bacterial cellulose loaded with amino acid chains to treat phosphorus-containing wastewater, and enriches phosphorus resources in wastewater through the interaction between amino acid chains and phosphorus. The hydrophobic interaction between alkyl chains can aggregate the molecular chains, and the hydrogen bond interaction between the hydroxyl groups on the bacterial cellulose and the amino acid chains can stabilize the phosphorus. The conformation of the amino acid chains grafted on the cellulose composite material is restricted to a certain extent due to the covalent fixation and the hydrophobic interaction between the alkyl chains; at the same time, at a pH value of 5 to 8, the electrostatic repulsion effect between the protonated amino groups on the amino acid chains makes the distance between the amino acid chains farther, and the molecular chains curl into a conformation that is conducive to phosphorus absorption, thereby improving the ability to capture phosphorus.

[0028] 2. The present invention utilizes the disappearance of the repulsive effect between active end molecules at high pH values, causing the amino acid chain to collapse and release the enriched phosphorus. Compared with conventional amino acid chains or protein molecules, the present invention utilizes bacterial cellulose to make the amino acid chain in a controllable dispersed state, and its conformation is partially restricted. The purpose of enriching and recovering phosphorus resources from sewage can be achieved by simple pH adjustment.

[0029] 3. The present invention makes full use of the unique three-dimensional network structure of bacterial cellulose and its easy modification. The hydrophobic alkyl chain is first bonded to the bacterial cellulose, and then the amino acid chain is covalently fixed through coupling, thereby achieving controllable dispersion of the amino acid chain, and preparing a cellulose composite material grafted with amino acid chains, which is both scientific and creative in functional material design.

[0030] 4. In the cellulose composite material grafted with amino acid chains, the adsorption of phosphorus by the amino acid chains is not a single chain action, but a multi-chain collaborative innovative action mode. In addition to being a carrier of the amino acid chains, the bacterial cellulose in the present invention also plays a role in limiting the free movement of the amino acid chains and making multiple amino acid chains in a collaborative phosphorus capture state, thereby significantly enhancing the phosphorus capture effect of the composite material.

[0031] 5. The present invention does not require the addition of chemical reagents when treating phosphorus-containing wastewater, does not produce any chemical sludge during the process, and is easy to operate for phosphorus resource recovery. The cellulose composite material grafted with amino acid chains used can be recycled, which fundamentally solves the problems existing in the existing chemical and biological methods for recovering phosphorus. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a typical reaction schematic diagram during the preparation process of a cellulose composite material grafted with amino acid chains.

[0033] Figure 2 Typical field emission scanning electron microscopy comparison diagrams of bacterial cellulose membrane and the composite material provided in Example 1; (a) is the bacterial cellulose membrane, and (b) is the composite material provided in Example 1.

[0034] Figure 3 The X-ray photoelectron spectrum comparison diagram of the bacterial cellulose membrane and the composite material provided in Example 1; (a) is the bacterial cellulose membrane, and (b) is the composite material provided in Example 1.

[0035] Figure 4 The composite material provided in Example 1 is effective for phosphorus phosphate (PO4 3- -P) removal rate changes with the pH value of sewage.

[0036] Figure 5 This is a curve diagram showing the change in the recovery rate of phosphorus resources of the composite material provided in Example 1 as a function of pH value.

[0037] Figure 6 It is a comparison chart of the phosphate removal rates corresponding to Example 1 of the present invention and Comparative Examples 1-3.

[0038] Figure 7 Schematic diagram of the hydrophobic interaction between hydrophobic chains and the electrostatic repulsion between amino acid chains in the composite material provided in Example 1.

[0039] Figure 8 This is a comparison chart of the phosphorus absorption effects of composite materials with different amino acid chain contents used in Examples 1 to 5.

[0040] Fig. 9 This is a graph of the cyclic phosphorus absorption-release recovery performance of the composite material provided in Example 1, in which the hollow squares and solid circles represent the phosphorus phosphate fixation rates of the cellulose composite material grafted with amino acid chains at pH=6 and pH=12, respectively. DETAILED DESCRIPTION

[0041] The technical solutions in the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] A method for treating phosphorus-containing wastewater and recovering phosphorus, wherein a cellulose composite material grafted with amino acid chains is added to the phosphorus-containing wastewater and the pH value is adjusted to 5-8, so that the cellulose composite material grafted with amino acid chains captures phosphorus phosphate (PO4 3- -P); then the cellulose composite material grafted with amino acid chains after phosphorus capture is placed in an alkaline system with a pH value of more than 10, so that the captured phosphorus phosphate (PO4 3- -P) is released again, thus realizing phosphorus resource recovery.

[0044] A cellulose composite material grafted with amino acid chains, the preparation method of which comprises the following steps:

[0045] (1) Take 50 mg of bacterial cellulose membrane, immerse it in 100 mL of 0.10 mol / L sodium periodate solution, add 1 g / L hydroxyapatite as a catalyst, and react at 50 °C for 4 h. After the reaction, take out the bacterial cellulose membrane modified with sodium periodate, wash it with deionized water, and dry it at 25 °C.

[0046] (2) The product obtained in step (1) was immersed in 20 mL of 10 g / L decanediamine solution (solvent is anhydrous ethanol), 0.5 mL of 6 mol / L hydrochloric acid solution was added dropwise, and then 0.10 g / L of Y-type zeolite molecular sieve was added, and the reaction was carried out at 40 °C for 6 h. After the reaction was completed, the bacterial cellulose membrane modified with decanediamine was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C.

[0047] (3) The product obtained in step (2) was immersed in 20 mL of 25% glutaraldehyde aqueous solution, 6 g / L of sodium sulfite was added, and the reaction was carried out at 25 °C for 3 h. After the reaction was completed, the bacterial cellulose membrane modified with glutaraldehyde was taken out, washed with deionized water, and dried at 25 °C.

[0048] (4) The product obtained in step (3) was immersed in 20 mL of 5 g / L hexapeptide-10 solution, and 6 g / L sodium sulfite was added, and the reaction was continued at 25 °C for 2 h. After the reaction was completed, the solid was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C to obtain a cellulose composite material grafted with amino acid chains.

[0049] In the obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose measured by micro-Kjeldahl nitrogen determination method was 1.92:1.

[0050] Typical reactions in the above preparation process are as follows Figure 1 The structure of the bacterial cellulose membrane used in step (1) of this embodiment is as shown in Figure 2 As shown in part (a), the thickness of the fibers in the membrane is relatively uniform, with a diameter of about tens of nanometers, and the fibers are piled up to form a three-dimensional network structure. After multiple steps of chemical modification, there is a certain degree of adhesion between the fibers (see Figure 2 (b)), which may be caused by partial cross-linking during the modification process, but the overall framework of the membrane did not change significantly, indicating that the bacterial cellulose membrane has good chemical stability.

[0051] Figure 3Part (a) and part (b) in the figure correspond to the X-ray photoelectron energy spectra of the unmodified bacterial cellulose membrane and the cellulose composite material grafted with amino acid chains obtained in this example, respectively. Compared with the unmodified bacterial cellulose membrane, the characteristic signal peak of the cellulose composite material grafted with amino acid chains at a binding energy of about 400 eV is significantly enhanced, and this peak belongs to the characteristic signal of N 1s, indicating that the nitrogen content on the membrane has increased sharply. The increase in the nitrogen content on the cellulose composite material grafted with amino acid chains can be attributed to the many nitrogen atoms on the amino acid chain molecules, thereby confirming that the amino acid chains have been successfully grafted on the bacterial cellulose membrane.

[0052] In order to illustrate the effect of the prepared cellulose composite material grafted with amino acid chains on phosphorus-containing wastewater treatment and phosphorus resource recovery, the following experiments were conducted:

[0053] 10 mL of phosphorus-containing wastewater from the supernatant of a primary sedimentation tank of a farm was taken. The initial phosphate phosphorus (PO4 3- -P) value was 102.38 mg / L. Multiple experimental groups were set up, and the pH value of the sewage in each experimental group was adjusted to different values ​​between 2-12 with 1 mol / L hydrochloric acid solution and 1 mol / L sodium hydroxide solution. Then 5 mg of the cellulose composite material grafted with amino acid chains prepared in this embodiment was added, and the reaction was carried out at 25 °C for 10 min, and the cellulose composite material grafted with amino acid chains was taken out. The treated sewage phosphate (PO4 3- -P) value changes with the pH value of sewage Figure 4 shown.

[0054] Depend on Figure 4 It can be seen that at pH = 6, the cellulose composite material grafted with amino acid chains can make the phosphate phosphorus (PO4 3- -P) value decreased by 99.78%, and the remaining phosphate phosphorus (PO4 3- -P) value was 0.23 mg / L, and total phosphorus (TP) value was 0.24 mg / L, which was significantly lower than the total phosphorus discharge standard (<0.50 mg / L) of Class A effluent specified in the Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB18918-2002). The results show that the cellulose composite material grafted with amino acid chains has an excellent treatment effect on phosphorus-containing wastewater; and under the conditions of pH values ​​of 5, 7, and 8, the cellulose composite material grafted with amino acid chains can achieve 95.18%, 98.50%, and 94.2% phosphate phosphorus removal rates, respectively, all reaching a phosphate phosphorus removal rate significantly exceeding 90%.

[0055] In order to further test the recovery performance of the amino acid chain grafted cellulose composite material for phosphorus resources, the amino acid chain grafted cellulose composite material enriched with phosphorus at pH = 6 was placed in 10 mL of deionized water, and the pH value was adjusted to 7-12 with 1 mol / L sodium hydroxide solution. The reaction was carried out at 25 °C for 10 min, and the amino acid chain grafted cellulose composite material was taken out. After treatment, phosphorus phosphate (PO4 3- -P) value changes with pH value as shown in Figure 5 As shown. Figure 5 It can be seen that when pH=12, phosphate phosphorus (PO4 3- -P) value was 97.31 mg / L, which means that about 95.26% of the phosphorus resources in the cellulose composite material grafted with amino acid chains were effectively recovered. The experimental results show that the cellulose composite material grafted with amino acid chains has excellent phosphorus resource recovery ability. In addition, at pH values ​​of 10 and 11, the phosphate phosphorus recovery rates reached 88.79% and 93.93%, respectively.

[0056] Comparative Example 1

[0057] A method for treating phosphorus-containing wastewater; the difference between this comparative example and Example 1 is that the phosphorus-containing wastewater is directly treated with an unmodified bacterial cellulose membrane (the same bacterial cellulose membrane used in Example 1), and other experimental conditions remain the same as in Example 1. When pH = 6, the unmodified bacterial cellulose membrane can make the phosphorus phosphate (PO4 3- -P) value decreased by 10.45% (see Figure 6 ), indicating that the bacterial cellulose membrane can directly participate in the adsorption of phosphate, but the role it can play is significantly lower than that of Example 1.

[0058] Comparative Example 2

[0059] A method for treating phosphorus-containing wastewater; the difference between this comparative example and Example 1 is that the preparation method of the cellulose composite material used in this comparative example does not perform step (2) and step (3) of Example 1, and the other steps remain the same as Example 1. Finally, a cellulose composite material of grafted amino acid chains without hydrophobic alkyl chains is obtained, wherein the mass ratio of amino acid chains to cellulose is 2.24:1, which is slightly higher than the relative content of amino acid chains in the composite material obtained in Example 1.

[0060] The obtained cellulose composite material with grafted amino acid chains without hydrophobic alkyl chains was used to treat phosphorus-containing wastewater, and other experimental conditions were kept the same as those in Example 1. At pH = 6, the bacterial cellulose membrane with grafted amino acid chains without hydrophobic alkyl chains can reduce the phosphorus phosphate (PO4 3- -P) value decreased by 29.88% (see Figure 6 ), which is significantly lower than Example 1.

[0061] Comparative Example 3

[0062] A method for treating phosphorus-containing wastewater; the difference between this comparative example and Example 1 is that an amino acid chain (i.e., hexapeptide-10) is directly added to the phosphorus-containing wastewater, and its amount is the same as the amino acid chain content of the cellulose composite material grafted with amino acid chains in Example 1, and other experimental conditions are the same as those in Example 1. When pH=6, hexapeptide-10 can reduce the phosphorus phosphate (PO4 3- -P) value decreased by 11.09%, and at pH = 12, hexapeptide-10 can reduce the phosphate phosphorus (PO4 3- -P) value decreased by 78.64%, indicating that under strong alkaline environment, the free molecular state of hexapeptide-10 has a good binding ability for phosphorus in sewage (see Figure 6 ). It is worth noting that high-speed centrifugation is required to separate hexapeptide-10 from wastewater after treatment.

[0063] Comparing the results of Example 1 with those of Comparative Examples 2-3, it can be seen that the mechanism of action between the amino acid chains in the free molecular state and the covalently fixed state and the phosphoric acid molecules is completely different. For the cellulose composite material grafted with amino acid chains, the conformation of the amino acid chains is subject to certain restrictions due to the covalent fixation and the hydrophobic interaction between the alkyl chains. At pH = 6, due to the electrostatic repulsion effect between the protonated amino groups on the amino acid chains, the distance between the amino acid chains is relatively far, and the molecular chains can curl into a conformation that is conducive to phosphorus absorption (see Figure 7 ); On the contrary, in a high pH environment, this electrostatic repulsion will disappear, and the amino acid chains will be tightly packed, which will significantly restrict their conformational changes, leading to a sharp decrease in their ability to bind to phosphorus.

[0064] Example 2

[0065] A method for treating phosphorus-containing wastewater and recovering phosphorus, the difference between this embodiment and embodiment 1 is that the concentration of hexapeptide-10 in step (4) is different when preparing the cellulose composite material. In this embodiment, the concentration of hexapeptide-10 is 2 g / L, and the other steps are the same as those in embodiment 1. In the final obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose is 0.83:1.

[0066] Example 3

[0067] A method for treating phosphorus-containing wastewater and recovering phosphorus, the difference between this embodiment and embodiment 1 is that the concentration of hexapeptide-10 in step (4) when preparing the cellulose composite material is different. In this embodiment, the concentration of hexapeptide-10 is 3.5 g / L, and the other steps are the same as those in embodiment 1. In the final obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose is 1.41:1.

[0068] Example 4

[0069] A method for treating phosphorus-containing wastewater and recovering phosphorus, the difference between this embodiment and embodiment 1 is that the concentration of hexapeptide-10 in step (4) is different when preparing the cellulose composite material. In this embodiment, the concentration of hexapeptide-10 is 6.5 g / L, and the other steps are the same as those in embodiment 1. In the final obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose is 2.38:1.

[0070] Example 5

[0071] A method for treating phosphorus-containing wastewater and recovering phosphorus, the difference between this embodiment and embodiment 1 is that the concentration of hexapeptide-10 in step (4) when preparing the cellulose composite material is different. In this embodiment, the concentration of hexapeptide-10 is 8 g / L, and the other steps are the same as those in embodiment 1. In the final obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose is 2.54:1.

[0072] The comparative experiments on phosphorus-containing wastewater treatment based on Examples 1-5 are as follows:

[0073] 10 mL of phosphorus-containing wastewater from the supernatant of a primary sedimentation tank of a farm was taken. The initial phosphate phosphorus (PO4 3- -P) value was 102.38 mg / L. Multiple experimental groups were set up, and the pH value of the sewage in each experimental group was adjusted to different values ​​between 6 with 1 mol / L hydrochloric acid solution and 1 mol / L sodium hydroxide solution, and then 5 mg of the cellulose composite material grafted with amino acid chains prepared in this embodiment was added, and the reaction was carried out at 25 °C for 10 min, and the cellulose composite material grafted with amino acid chains was taken out.

[0074] Since the mass ratios of amino acid chains to cellulose in the cellulose composite materials used in Examples 1 to 5 are different, the molar ratios of amino acid chains to phosphorus in the system are also different, namely 1.45, 0.63, 1.06, 1.80, and 1.92, respectively; the final phosphorus removal rates of the composite materials are 99.78%, 34.29%, 67.55%, 99.92%, and 99.96%, respectively (see Figure 8 ). The above results show that in the cellulose composite material grafted with amino acid chains, the molar ratio of amino acid chains to adsorbed phosphorus is not close to 1:1, indicating that the adsorption of phosphorus by amino acid chains is not a single-chain effect, but a multi-chain collaborative innovation mode. In addition to being a carrier of amino acid chains, bacterial cellulose also plays a role in limiting the free movement of amino acid chains and placing multiple amino acid chains in a collaborative phosphorus capture state, thereby significantly enhancing the phosphorus capture effect of the composite material. At the same time, it is shown that when the molar ratio between amino acid chains and adsorbed phosphorus reaches (1.45-1.92):1, sufficient phosphorus resource recovery can be achieved.

[0075] In order to investigate the phosphorus absorption stability of the obtained cellulose composite material grafted with amino acid chains and compare it with free amino acid chains, the cellulose composite material grafted with amino acid chains that have captured phosphorus in Example 1 (pH=6) and the free amino acid chains that have captured phosphorus in Comparative Example 3 (pH=12) were placed in 10 mL of deionized water, respectively, and the pH values ​​were adjusted to 6 and 12, and the phosphate phosphorus content in the water was measured to be 1.75 mg / L and 13.16 mg / L, respectively, indicating that the cellulose composite material grafted with amino acid chains has significantly higher phosphorus absorption stability than free amino acid chains. In addition to the covalent fixation and hydrophobic interactions between alkyl chains that make the amino acid molecular chain easy to curl into a conformation that is conducive to phosphorus absorption, the hydrogen bond interaction between the hydroxyl groups on the bacterial cellulose and the amino acid chains also plays a role in stabilizing phosphorus absorption to a certain extent.

[0076] Example 6

[0077] A method for treating phosphorus-containing wastewater and recovering phosphorus; the difference between this embodiment and embodiment 1 is that the concentration of the partial solution used in the preparation method of the cellulose composite material grafted with amino acid chains is different;

[0078] The method for preparing the cellulose composite material grafted with amino acid chains used in this embodiment comprises the following steps:

[0079] (1) Take 50 mg of bacterial cellulose membrane, immerse it in 100 mL of 0.20 mol / L sodium periodate solution, then add 1 g / L hydroxyapatite, and react at 50 °C for 4 h. After the reaction is completed, take out the bacterial cellulose membrane modified with sodium periodate, wash it with deionized water, and dry it at 25 °C;

[0080] (2) The product obtained in step (1) was immersed in 20 mL of 20 g / L decanediamine solution (solvent is anhydrous ethanol), 0.5 mL of 6 mol / L hydrochloric acid solution was added dropwise, and then 0.10 g / L Y-type zeolite molecular sieve was added, and the reaction was carried out at 40 °C for 6 h. After the reaction was completed, the bacterial cellulose membrane modified with decanediamine was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C;

[0081] (3) The product obtained in step (2) was immersed in 40 mL of 25% glutaraldehyde aqueous solution, 6 g / L sodium sulfite was added, and the reaction was carried out at 25 °C for 3 h. After the reaction was completed, the bacterial cellulose membrane modified with glutaraldehyde was taken out, washed with deionized water, and dried at 25 °C;

[0082] (4) The product obtained in step (3) was immersed in 20 mL of 10 g / L hexapeptide-10 solution, and 6 g / L sodium sulfite was added, and the reaction was continued at 25 °C for 2 h. After the reaction was completed, the solid was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C to obtain a cellulose composite material grafted with amino acid chains.

[0083] In the obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose measured by micro-Kjeldahl nitrogen determination method was 3.05:1.

[0084] The prepared cellulose composite material grafted with amino acid chains was used for phosphorus-containing wastewater treatment and phosphorus resource recovery, and the experimental conditions were the same as those in Example 1. When pH = 6, the cellulose composite material grafted with amino acid chains can reduce the phosphorus phosphate (PO4 3- -P) value decreased by 99.92%. At pH=12, about 95.77% of the phosphorus resources in the cellulose composite material grafted with amino acid chains were effectively recovered. The results show that the obtained cellulose composite material grafted with amino acid chains has excellent phosphorus treatment effect and phosphorus resource recovery ability.

[0085] In order to investigate the recycling absorption and recovery performance of the amino acid chain grafted cellulose composite material used in this embodiment on phosphorus resources in sewage, the amino acid chain grafted cellulose composite material prepared in this embodiment was added to the treated phosphorus-containing sewage, the pH was adjusted to 6, and the amino acid chain grafted cellulose composite material was taken out after 10 minutes of reaction, and placed in deionized water, the pH was adjusted to 12, and the amino acid chain grafted cellulose composite material was taken out after another 10 minutes of reaction, and placed in new phosphorus-containing sewage to be treated, and the treatment conditions remained unchanged. Fig. 9 As shown, after 5 cycles of phosphorus absorption-release recycling, the phosphorus absorption rate of a cellulose composite material grafted with amino acid chains for phosphorus-containing wastewater is still above 95%, and the phosphorus recovery rate is also above 90%, indicating that the obtained cellulose composite material grafted with amino acid chains has excellent cyclic phosphorus resource recovery capacity.

[0086] Example 7

[0087] A method for treating phosphorus-containing wastewater and recovering phosphorus; the difference between this embodiment and embodiment 1 is that the concentration of the partial solution used in the preparation method of the cellulose composite material grafted with amino acid chains is different;

[0088] The preparation method of a cellulose composite material grafted with amino acid chains used in this embodiment comprises the following steps:

[0089] (1) Take 50 mg of bacterial cellulose membrane, immerse it in 100 mL of 0.10 mol / L sodium periodate solution, then add 2 g / L hydroxyapatite, and react at 50 °C for 4 h. After the reaction, take out the bacterial cellulose membrane modified by sodium periodate, wash it with deionized water, and dry it at 25 °C;

[0090] (2) The product obtained in step (1) was immersed in 20 mL of 10 g / L decanediamine solution (solvent is anhydrous ethanol), 0.5 mL of 6 mol / L hydrochloric acid solution was added dropwise, and then 0.20 g / L Y-type zeolite molecular sieve was added, and the reaction was carried out at 40 °C for 6 h. After the reaction was completed, the bacterial cellulose membrane modified with decanediamine was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C;

[0091] (3) The product obtained in step (2) was immersed in 20 mL of 25% glutaraldehyde aqueous solution, 8 g / L of sodium sulfite was added, and the reaction was carried out at 25 °C for 3 h. After the reaction was completed, the bacterial cellulose membrane modified with glutaraldehyde was taken out, washed with deionized water, and dried at 25 °C;

[0092] (4) The product obtained in step (3) was immersed in 20 mL of 5 g / L hexapeptide-10 solution, and 8 g / L sodium sulfite was added, and the reaction was continued at 25 °C for 2 h. After the reaction was completed, the solid was taken out, washed with 75% ethanol and deionized water in turn, and dried at 25 °C to obtain a cellulose composite material grafted with amino acid chains.

[0093] In the obtained cellulose composite material grafted with amino acid chains, the mass ratio of amino acid chains to cellulose measured by micro-Kjeldahl nitrogen determination method was 2.02:1.

[0094] In order to illustrate the effect of the prepared cellulose composite material grafted with amino acid chains on phosphorus-containing wastewater treatment and phosphorus resource recovery, the following experiments were conducted:

[0095] 10 mL of phosphorus-containing wastewater from an industry was taken, and its initial phosphate phosphorus (PO4 3- -P) value was 386.16 mg / L. The pH of the sewage was adjusted to 6, and 15 mg of the cellulose composite material grafted with amino acid chains prepared above was added, and the reaction was carried out at 25 °C for 10 min, and the cellulose composite material grafted with amino acid chains was taken out. The phosphate phosphorus (PO4 3--P) value decreased by 99.89%, indicating that the obtained amino acid chain grafted cellulose composite material has excellent treatment effect on phosphorus-containing wastewater. The above-mentioned phosphorus-enriched amino acid chain grafted cellulose composite material was placed in 10 mL of deionized water and the pH was adjusted to 12. About 95.49% of the phosphorus resources in the amino acid chain grafted cellulose composite material can be effectively recovered, indicating that the obtained amino acid chain grafted cellulose composite material has excellent phosphorus resource recovery ability.

[0096] The above descriptions are merely preferred embodiments of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. In other words, equivalent changes and modifications made within the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for treating phosphorus-containing wastewater and recovering phosphorus, characterized in that: It includes the following steps: a. Phosphorus capture stage: adding the cellulose composite material grafted with amino acid chains into phosphorus-containing wastewater, and adjusting the pH value to 5-8, so that the cellulose composite material grafted with amino acid chains captures phosphorus in the phosphorus-containing wastewater; the preparation process of the cellulose composite material grafted with amino acid chains is: firstly oxidizing the hydroxyl groups on the bacterial cellulose membrane into aldehyde groups by using an oxidant; then modifying the oxidized bacterial cellulose membrane with decanediamine, glutaraldehyde, and amino acid chains in sequence to obtain the cellulose composite material grafted with amino acid chains; b. Recovery stage: The cellulose composite material grafted with amino acid chains is taken out from the phosphorus-containing wastewater and placed in an alkaline system with a pH value greater than or equal to 9, so that the phosphorus captured by the cellulose composite material grafted with amino acid chains is released.

2. A method for treating phosphorus-containing wastewater and recovering phosphorus according to claim 1, characterized in that: The pH value in step a is adjusted to 6; in step b, the pH value is adjusted to 11.

3. The method for treating phosphorus-containing wastewater and recovering phosphorus according to claim 1, characterized in that: The initial phosphate phosphorus value of the treated phosphorus-containing wastewater is 20 mg / L-400 mg / L.

4. The method for treating phosphorus-containing wastewater and recovering phosphorus according to claim 1, characterized in that: In step a, the molar ratio of the amino acid chains in the cellulose composite material grafted with amino acid chains to the phosphorus in the phosphorus-containing wastewater is (1.45-1.92):

1.

5. A method for preparing a cellulose composite material grafted with amino acid chains, characterized in that: The following steps are involved: Step 1: immerse the bacterial cellulose membrane in a sodium periodate solution, add hydroxyapatite, and react; Step 2, immersing the product obtained in step 1 in a decanediamine solution, adding a hydrochloric acid solution dropwise, and then adding a zeolite molecular sieve to react; Step 3, immersing the product obtained in step 2 in a glutaraldehyde solution, adding sodium sulfite, and reacting; Step 4: Immerse the product obtained in step 3 in a solution containing amino acid chains, add sodium sulfite, and continue the reaction to obtain a cellulose composite material grafted with amino acid chains.

6. The method for preparing a cellulose composite material grafted with amino acid chains according to claim 5, characterized in that: In step 1, the concentration of the sodium periodate solution is 0.02 mol / L-0.2 mol / L; the hydroxyapatite is used as a catalyst, and its addition amount relative to the sodium periodate solution is 0.1 g / L-1 g / L; the reaction conditions are: reaction temperature 20°C-60°C, reaction time 2 h-12 h.

7. The method for preparing a cellulose composite material grafted with amino acid chains according to claim 5, characterized in that: In step 2, the concentration of the decanediamine solution is 5 g / L-50 g / L; the zeolite molecular sieve is a Y-type molecular sieve, and its amount relative to the decanediamine solution is 0.02 g / L-0.20 g / L; the reaction conditions are: reaction temperature 20 ° C-80 ° C, reaction time 2 h-8 h; In step three, the glutaraldehyde solution is a glutaraldehyde aqueous solution with a mass concentration of 25%; the amount of sodium sulfite added relative to the glutaraldehyde solution is 2 g / L-10 g / L; and the reaction conditions are: reaction temperature 0 °C-50 °C, reaction time 0.5 h-5 h.

8. The method for preparing a cellulose composite material grafted with amino acid chains according to claim 5, characterized in that: In step 4, the solution containing the amino acid chain is an aqueous solution containing hexapeptide-10, and its concentration is 1 g / L-20 g / L; the reaction conditions are: reaction temperature 0 °C-50 °C, reaction time 1 h-4 h.

9. The method for preparing a cellulose composite material grafted with amino acid chains according to claim 5, characterized in that: The product obtained in step 1 is washed with deionized water and then dried; the product obtained in step 2 is washed with 75% ethanol and deionized water in turn and then dried; the product obtained in step 3 is washed with deionized water and then dried; the product obtained in step 4 is washed with 75% ethanol and deionized water in turn and then dried.

10. A cellulose composite material grafted with amino acid chains, characterized in that: It is prepared by the preparation method as described in any one of claims 5 to 9; the mass ratio of amino acid chain to cellulose is 0.22 to 3.52.

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