Phosphorus removal reagent for treating sweet potato starch processing wastewater as well as preparation method and treatment process of phosphorus removal reagent

Abstract

The invention relates to the technical field of sweet potato starch processing wastewater treatment, in particular to a phosphorus removal reagent for treating sweet potato starch processing wastewater as well as a preparation method and a treatment process of the phosphorus removal reagent. The phosphorus removal reagent is prepared from the following raw materials: soluble lanthanum salt, soluble bivalent manganese salt, strong alkali, magnetic iron oxide and activated bentonite. The molar ratio of lanthanum ions in the soluble lanthanum salt to divalent manganese ions in the soluble divalent manganese salt is (1: 0.8)-(1: 1.2). The lanthanum ions are synergistically enhanced through the divalent manganese ions, so that the capturing capability of the phosphorus removal reagent on phosphate in the sweet potato starch processing wastewater is remarkably enhanced. The phosphorus removal reagent is loaded on the activated bentonite. The activated bentonite has larger specific surface area and stronger adsorption capacity, can provide more reaction sites, and further enhances the effect of removing phosphorus and other pollutants. The magnetic iron oxide also has the advantage of being convenient to recycle through a magnetic separation technology.

Description

Technical Field

[0001] The invention relates to the technical field of sweet potato starch processing wastewater treatment, and in particular to a dephosphorization reagent for treating sweet potato starch processing wastewater, a preparation method thereof and a treatment process thereof. Background Art

[0002] Sweet potatoes have high nutritional and economic value and are widely used in food, starch, feed and medicine industries, especially in the starch industry. In sweet potato producing areas, the sweet potato starch processing industry occupies an important economic position. The cleaning process of sweet potato raw materials, the separation and cleaning process of sweet potato starch and cell juice will produce sweet potato starch processing wastewater. With the expansion of the scale of sweet potato starch processing, the high-concentration organic wastewater generated has become one of the key issues restricting the sustainable development of the industry.

[0003] Sweet potato starch processing wastewater contains a large amount of organic matter, suspended solids and nutrients. Its chemical oxygen demand (COD) is usually as high as tens of thousands of mg / L, which mainly comes from starch, sugars and other soluble organic matter. It is an important indicator to measure the degree of organic pollution in wastewater. The wastewater also includes suspended solids (SS) such as undissolved starch particles and cellulose. These suspended substances not only affect the transparency of the water body, but also pose challenges to subsequent treatment processes. In addition, the wastewater also contains phosphates from raw materials, resulting in a high content of total phosphorus (TP), which can easily cause eutrophication of water bodies. At the same time, ammonia nitrogen (NH3-N) and total nitrogen (TN) produced by protein decomposition are also present in the wastewater. Excessive nitrogen can cause ecological imbalance in the water body.

[0004] At present, the treatment methods for sweet potato starch processing wastewater mainly include chemical methods, biological methods and advanced oxidation methods. The chemical method promotes the precipitation of phosphates by adding coagulants such as polyaluminium chloride, polyacrylamide or iron salts, aluminium salts, etc. This method can remove phosphorus to a certain extent, but the removal efficiency of phosphorus is usually low. Biological methods, such as activated sludge method and biofilm method, use microbial metabolism to degrade organic matter and have good removal effects on COD and ammonia nitrogen. However, the removal of phosphorus by biological methods mainly depends on the assimilation of microorganisms. This natural process is relatively slow and unstable, especially under high phosphorus loads. The phosphorus removal capacity of biological systems is obviously insufficient. Advanced oxidation methods mainly decompose organic pollutants by producing strongly oxidizing free radicals, while phosphorus exists in wastewater in an inorganic form and is not easily oxidized and degraded, so the role of advanced oxidation methods in phosphorus removal is limited.

[0005] Therefore, the currently used treatment methods for sweet potato starch processing wastewater have poor phosphorus removal capabilities, resulting in the total phosphorus index in the drainage being difficult to meet the discharge standards. Therefore, it is necessary to improve the total phosphorus treatment capacity for sweet potato starch processing wastewater so that the drainage meets the standards. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In order to solve the problem that the treatment method of sweet potato starch processing wastewater in the prior art has poor phosphorus removal ability, the present invention provides a phosphorus removal reagent for treating sweet potato starch processing wastewater, a preparation method and a treatment process thereof.

[0008] (II) Technical solution

[0009] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0010] In a first aspect, the present invention provides a dephosphorization agent for treating sweet potato starch processing wastewater, wherein the raw materials for preparing the dephosphorization agent include a soluble lanthanum salt, a soluble divalent manganese salt, a strong base, magnetic iron oxide, and bentonite that has been activated;

[0011] The molar ratio of the lanthanum ions in the soluble lanthanum salt to the divalent manganese ions in the soluble divalent manganese salt is 1:0.8-1:1.2.

[0012] In a second aspect, the present invention provides a method for preparing the above-mentioned dephosphorization reagent for treating sweet potato starch processing wastewater, comprising the following steps:

[0013] S1: activating bentonite with an acid to obtain activated bentonite;

[0014] S2: adding a strong base solution to the soluble lanthanum salt solution under stirring to obtain a lanthanum hydroxide solution with a pH of 10-11;

[0015] S3: adding a soluble divalent manganese salt solution to the lanthanum hydroxide solution to obtain a doping mixed solution;

[0016] S4: mixing the activated bentonite with the doping mixed solution, then subjecting the mixture to ultrasonic treatment, and drying to obtain lanthanum-manganese co-doped bentonite;

[0017] S5: The lanthanum-manganese co-doped bentonite and magnetic iron oxide are mixed in a solution, then ultrasonically treated and dried to obtain a phosphorus removal agent.

[0018] The method for preparing the phosphorus removal agent for treating sweet potato starch processing wastewater as described above, preferably, in step S1, the bentonite is activated by an acid solution with a concentration of 0.5-2 mol / L for 2-4 hours;

[0019] The acid solution is hydrochloric acid, sulfuric acid or nitric acid, the solid-liquid ratio of bentonite to the acid solution is 1g:(8-10)mL, and the particle size of the bentonite is ≤0.1mm.

[0020] The method for preparing the dephosphorization agent for treating sweet potato starch processing wastewater as described above, preferably, in step S2, after the reaction between the lanthanum salt and the strong base is completed, ultrasonic treatment is performed for 10-20 minutes to obtain a lanthanum hydroxide solution;

[0021] The soluble lanthanum salt is any one of lanthanum chloride, lanthanum nitrate and crystalline hydrates thereof, and the strong base is potassium hydroxide or sodium hydroxide;

[0022] The concentration of lanthanum ions in the soluble lanthanum salt solution is 0.1-0.15 mol / L, and the concentration of the strong base solution is 0.8-1.2 mol / L.

[0023] The method for preparing the dephosphorization agent for treating sweet potato starch processing wastewater as described above, preferably, in step S3, a soluble divalent manganese salt solution is added to the lanthanum hydroxide solution, and the solution is ultrasonically treated for 20-30 minutes after stirring to obtain a doped mixed solution;

[0024] The soluble manganese salt is any one of manganese sulfate, manganese nitrate, manganese chloride and their crystalline hydrates; the concentration of manganese ions in the soluble divalent manganese salt solution is 0.1-0.15 mol / L;

[0025] The molar ratio of the manganese element in the soluble divalent manganese salt solution to the lanthanum element in the lanthanum hydroxide solution is 1:0.8-1:1.2.

[0026] In the method for preparing the dephosphorization agent for treating sweet potato starch processing wastewater as described above, preferably, in step S4, the solid-liquid ratio of the activated bentonite to the doping mixed solution is 1 g:(10-20) mL, and the ultrasonic treatment time is 2-3 h.

[0027] In the method for preparing the dephosphorization agent for treating sweet potato starch processing wastewater as described above, preferably, in step S5, the mass ratio of lanthanum-manganese co-doped bentonite to magnetic iron oxide is 2:1-4:1, and the ultrasonic treatment time is 10-15 min.

[0028] In a third aspect, the present invention further provides a method for treating sweet potato starch processing wastewater, comprising the following steps:

[0029] A1: Filter and treat the sweet potato starch processing wastewater to obtain filtered water;

[0030] A2: Add the phosphorus removal reagent prepared by the preparation method according to claim 1 or any one of claims 2 to 7 to the filtered water, and let it stand for 24 to 72 hours to obtain phosphorus-removed water;

[0031] A3: The phosphorus removal water body is subjected to hydrolysis acidification treatment, anoxic treatment, aerobic treatment and deep treatment in sequence to obtain water that meets the discharge standards.

[0032] In the method for treating sweet potato starch processing wastewater as described above, preferably, in step A1, the COD concentration in the sweet potato starch processing wastewater is 24000-26000 mg / L, the ammonia nitrogen concentration is 1200-1350 mg / L, the total phosphorus concentration is 200-300 mg / L, and the total nitrogen concentration is 1400-1500 mg / L.

[0033] In the method for treating sweet potato starch processing wastewater as described above, preferably, in step A2, the amount of phosphorus removal agent added to the filtered water body is 5-10 g / L.

[0034] (III) Beneficial effects

[0035] The present invention synergistically strengthens lanthanum ions by divalent manganese ions, significantly enhancing the ability of the phosphorus removal agent to capture phosphate in sweet potato starch processing wastewater. This synergistic effect not only improves the phosphorus removal efficiency, but also promotes a more stable and faster precipitation reaction, ensuring that the total phosphorus content in the treated wastewater can meet the discharge standard.

[0036] The phosphorus removal agent of the present invention is loaded on bentonite that has been activated. The activated bentonite has a larger specific surface area and stronger adsorption capacity, and can be used as a carrier to fix the phosphorus removal agent to prevent its loss, and provide more reaction sites, thereby improving the utilization rate and stability of the active agent, and further enhancing the effect of removing phosphorus and other pollutants.

[0037] The raw materials for preparing the phosphorus removal agent also include magnetic iron oxide, which makes the formed precipitate magnetic, making it easy to recover through magnetic separation technology, thereby realizing the recycling of resources.

[0038] The phosphorus removal reagent of the present invention is used to treat the sweet potato starch processing wastewater, and the total phosphorus concentration can be reduced to the Class A standard specified in GB18918-2002 "Pollutant Discharge Standard for Urban Sewage Treatment Plants". In addition, the phosphorus removal reagent of the present invention also reduces other pollutant indicators such as chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen in the wastewater to varying degrees, and comprehensively improves the overall performance of wastewater treatment. DETAILED DESCRIPTION

[0039] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with specific implementation methods.

[0040] The invention provides a dephosphorization agent for treating sweet potato starch processing wastewater, wherein the raw materials for preparing the dephosphorization agent include a soluble lanthanum salt, a soluble divalent manganese salt, a strong base, magnetic iron oxide and activated bentonite, wherein the molar ratio of lanthanum ions in the soluble lanthanum salt to divalent manganese ions in the soluble divalent manganese salt is 1:0.8-1:1.2.

[0041] The present invention synergistically strengthens lanthanum ions by divalent manganese ions, significantly enhancing the ability of the phosphorus removal agent to capture phosphate in sweet potato starch processing wastewater. This synergistic effect not only improves the phosphorus removal efficiency, but also promotes a more stable and faster precipitation reaction, ensuring that the total phosphorus content in the treated wastewater can meet the discharge standard.

[0042] The activated bentonite has a larger specific surface area and stronger adsorption capacity. It can act as a carrier to fix the phosphorus removal agent, prevent its loss, and provide more reaction sites, thereby improving the utilization and stability of the active agent, and further enhancing the effect on total phosphorus and other pollutants.

[0043] The raw materials for preparing the phosphorus removal agent also include magnetic iron oxide. The magnetic iron oxide makes the formed precipitate magnetic, which is convenient for recovery through magnetic separation technology, thus realizing the recycling of resources.

[0044] The phosphorus removal reagent of the present invention is used to treat the sweet potato starch processing wastewater, and the total phosphorus concentration can be reduced to the Class A standard specified in GB18918-2002 "Pollutant Discharge Standard for Urban Sewage Treatment Plants". In addition, the phosphorus removal reagent of the present invention also reduces other pollutant indicators such as chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen in the wastewater to varying degrees, and comprehensively improves the overall performance of wastewater treatment.

[0045] The present invention also provides a method for preparing the above-mentioned dephosphorization reagent for treating sweet potato starch processing wastewater, comprising the following steps:

[0046] S1: Activating bentonite with an acid to obtain activated bentonite.

[0047] S2: adding a strong base solution to the soluble lanthanum salt solution under stirring to obtain a lanthanum hydroxide solution with a pH of 10-11.

[0048] S3: adding a soluble divalent manganese salt solution to the lanthanum hydroxide solution to obtain a doping mixed solution.

[0049] S4: Mixing the activated bentonite with the doping mixed solution, then subjecting the mixture to ultrasonic treatment, and drying to obtain lanthanum-manganese co-doped bentonite.

[0050] S5: The lanthanum-manganese co-doped bentonite and magnetic iron oxide are mixed in a solution, then ultrasonically treated and dried to obtain a phosphorus removal agent.

[0051] Preferably, in the above step S1, the bentonite is activated by an acid solution with a concentration of 0.5-2 mol / L for 2-4 hours.

[0052] The acid solution used in step S1 is preferably hydrochloric acid, sulfuric acid or nitric acid, the solid-liquid ratio of bentonite to the acid solution is 1 g:(8-10) mL, and the particle size of the bentonite is ≤0.1 mm.

[0053] Specifically, bentonite powder with a particle size of less than 0.1 mm can be added to an acid solution, soaked for 2-4 hours under stirring conditions, and then repeatedly washed with deionized water until neutral to ensure that the remaining acid is completely removed. The washed activated bentonite is then placed in an oven at 60°C and dried overnight until constant weight is reached.

[0054] Acid leaching can effectively remove impurity minerals in bentonite, increase its purity, and destroy the cations in the bentonite crystal structure, thereby expanding the interlayer spacing, providing more adsorption sites, and exposing more active groups, which is beneficial to subsequent ion exchange and fixation.

[0055] Preferably, in the above step S2, after the reaction of the lanthanum salt and the strong base is completed, ultrasonic treatment is performed for 10-20 minutes to obtain a lanthanum hydroxide solution. 3+ The ions form insoluble lanthanum hydroxide, which improves the stability of the material, and ultrasonic treatment helps prevent particle agglomeration and ensures uniform dispersion.

[0056] The soluble lanthanum salt can be any one of lanthanum chloride, lanthanum nitrate and their crystalline hydrates, and the strong base can be potassium hydroxide or sodium hydroxide. The concentration of lanthanum ions in the soluble lanthanum salt solution is 0.1-0.15 mol / L, and the concentration of the strong base solution is 0.8-1.2 mol / L.

[0057] Preferably, in the above step S3, a soluble divalent manganese salt solution is added to the lanthanum hydroxide solution, and the solution is ultrasonically treated for 20-30 minutes after stirring to obtain a doped mixed solution.

[0058] Mn 2+ It can participate in the advanced oxidation process and accelerate the degradation of organic matter. 3+ and Mn 2+ The combined effect can improve the adsorption and fixation efficiency of phosphate.

[0059] Soluble manganese salt can be any one of manganese sulfate, manganese nitrate, manganese chloride and its crystal hydrate, the concentration of manganese ion in soluble divalent manganese salt solution is 0.1-0.15mol / L, and the molar ratio of manganese element in soluble divalent manganese salt solution to lanthanum element in lanthanum hydroxide solution is 1:0.8-1:1.2. Divalent manganese ion can enhance the adsorption and precipitation ability of lanthanum ion to phosphate, and improve phosphorus removal efficiency. Specifically, the molar ratio of lanthanum ion to divalent manganese ion is 1:0.8-1:1.2, and within this ratio range, the best synergistic effect can be formed between lanthanum ion and divalent manganese ion. If it exceeds this ratio range, it may not be possible to maximize this synergistic effect, thereby affecting the treatment effect of phosphorus removal reagent on total phosphorus.

[0060] Preferably, in above-mentioned step S4, the solid-to-liquid ratio of the bentonite and doping mixed solution after activation treatment is 1g:(10-20)mL, and the time of ultrasonic treatment is 2-3h. Ultrasonic treatment helps lanthanum and manganese to be uniformly attached to the surface of activated bentonite, avoids the agglomeration phenomenon caused by local excess. After the ultrasonic treatment of step S4 ends, the product can also be washed to ensure that all unreacted substances are completely removed, the solid product after washing is sieved to ensure that the particle size is consistent, and the powder after sieving is dried to constant weight.

[0061] Preferably, in the above step S5, the mass ratio of lanthanum-manganese co-doped bentonite to magnetic iron oxide (Fe3O4) is 2:1-4:1, and the ultrasonic treatment time is 10-15 minutes. Fe3O4 can give the material good magnetic responsiveness, which is convenient for rapid separation and recycling in subsequent processing.

[0062] The present invention also provides a method for treating sweet potato starch processing wastewater, comprising the following steps:

[0063] A1: Filter the sweet potato starch processing wastewater to remove large suspended particles and obtain filtered water.

[0064] A2: Add the above-mentioned phosphorus removal reagent to the filtered water and let it stand for 24-72 hours to obtain phosphorus-removed water.

[0065] A3: The phosphorus removal water body is subjected to hydrolysis acidification treatment, anoxic treatment, aerobic treatment and deep treatment in sequence to obtain water that meets the discharge standards.

[0066] In step A1, the COD concentration in the sweet potato starch processing wastewater is 24000-26000 mg / L, the ammonia nitrogen concentration is 1200-1350 mg / L, the total phosphorus concentration is 200-300 mg / L, and the total nitrogen concentration is 1400-1500 mg / L.

[0067] Preferably, in the above step A2, the amount of phosphorus removal agent added to the filtered water is 5-10 g / L.

[0068] After the above step A2, the total phosphorus concentration in the water body can be reduced to the Class A standard specified in GB18918-2002 "Pollutant Discharge Standard for Urban Wastewater Treatment Plants", which is lower than 0.5 mg / L. The removal rate of COD and ammonia nitrogen in the water body can reach about 30%, and the removal rate of total nitrogen can reach about 25-29%.

[0069] After the phosphorus removal treatment, the water body is further subjected to hydrolysis acidification treatment, anoxic treatment, aerobic treatment and deep treatment in step A3 to obtain water that meets the discharge standards.

[0070] Compared with the prior art of treating pollutants in sweet potato starch processing wastewater through hydrolysis acidification treatment, AAO process and deep treatment process, the present invention can omit the anaerobic treatment of the water body and has a more thorough phosphorus removal effect.

[0071] Specifically, the hydrolysis stage of hydrolysis acidification treatment mainly decomposes insoluble macromolecular organic matter in sewage, such as proteins and polysaccharides, into soluble small molecular organic matter through the action of microbial extracellular enzymes. In the acidification stage, the hydrolyzed small molecular organic matter can be further converted into simple organic matter. Hydrolysis acidification treatment mainly removes some organic pollutants, improves the biodegradability of sewage, and creates favorable conditions for subsequent biological treatment processes.

[0072] Anoxic treatment mainly involves denitrification to remove nitrogen pollutants from wastewater. In the aerobic treatment stage, aerobic microorganisms thoroughly oxidize and decompose organic matter, converting it into harmless substances such as carbon dioxide and water, thereby removing organic pollutants from wastewater. Aerobic microorganisms also carry out nitrification, converting ammonia nitrogen into nitrates and nitrites.

[0073] Deep treatment can effectively remove suspended matter in the water, including fine particulate matter, and can also remove difficult-to-degrade organic matter in the water, further reducing the COD in the water.

[0074] In order to further clarify the scheme of the present invention and its technical advancement, the following is a description in conjunction with specific embodiments and technical effects.

[0075] Example 1

[0076] This embodiment provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, comprising the following steps:

[0077] S1: Soak bentonite with a particle size of 0.05 mm in a hydrochloric acid solution with a concentration of 1 mol / L, with a solid-liquid ratio of 1 g:9 mL, stir for 3 h, wash with deionized water until neutral, and dry to obtain activated bentonite.

[0078] S2: adding a sodium hydroxide solution with a concentration of 1 mol / L to a lanthanum chloride solution with a concentration of 0.12 mol / L under stirring, and ultrasonically treating for 15 min to obtain a lanthanum hydroxide solution with a pH of 10.

[0079] S3: adding manganese sulfate solution to the lanthanum hydroxide solution, stirring and then ultrasonically treating for 25 minutes to obtain a doping mixed solution. The concentration of manganese ions in the manganese sulfate solution is 0.12 mol / L, and the molar ratio of manganese element to lanthanum element is 1:1.

[0080] S4: The activated bentonite was mixed with the doping mixed solution at a solid-liquid ratio of 1 g:15 mL, and then ultrasonically treated for 2.5 h. After drying, lanthanum-manganese co-doped bentonite was obtained.

[0081] S5: The lanthanum-manganese co-doped bentonite and the magnetic iron oxide are mixed in a solution, wherein the mass ratio of the lanthanum-manganese co-doped bentonite to the magnetic iron oxide is 3:1, and then ultrasonically treated for 12 minutes, and dried to obtain a phosphorus removal agent.

[0082] Example 2

[0083] This embodiment provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, comprising the following steps:

[0084] S1: Soak bentonite with a particle size of 0.07 mm in a 2 mol / L sulfuric acid solution with a solid-liquid ratio of 1 g:8 mL, stir for 2 h, wash with deionized water until neutral, and dry to obtain activated bentonite.

[0085] S2: adding a 0.8 mol / L sodium hydroxide solution to a 0.1 mol / L lanthanum nitrate solution under stirring, and ultrasonically treating for 10 min to obtain a lanthanum hydroxide solution with a pH of 10.5.

[0086] S3: adding manganese chloride solution to the lanthanum hydroxide solution, stirring and then ultrasonically treating for 20 minutes to obtain a doping mixed solution. The concentration of manganese ions in the manganese chloride solution is 0.1 mol / L, and the molar ratio of manganese element to lanthanum element is 1:0.8.

[0087] S4: The activated bentonite was mixed with the doping mixed solution at a solid-liquid ratio of 1 g:10 mL, and then ultrasonically treated for 2 h. After drying, lanthanum-manganese co-doped bentonite was obtained.

[0088] S5: The lanthanum-manganese co-doped bentonite and the magnetic iron oxide are mixed in a solution, wherein the mass ratio of the lanthanum-manganese co-doped bentonite to the magnetic iron oxide is 2:1, and then ultrasonically treated for 10 minutes, and dried to obtain a dephosphorization reagent.

[0089] Example 3

[0090] This embodiment provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, comprising the following steps:

[0091] S1: Soak bentonite with a particle size of 0.04 mm in a hydrochloric acid solution with a concentration of 0.5 mol / L, with a solid-liquid ratio of 1 g:10 mL, stir for 4 h, wash with deionized water until neutral, and dry to obtain activated bentonite.

[0092] S2: adding a sodium hydroxide solution with a concentration of 1.2 mol / L to a lanthanum chloride solution with a concentration of 0.15 mol / L under stirring, and ultrasonically treating for 20 min to obtain a lanthanum hydroxide solution with a pH of 11.

[0093] S3: adding manganese sulfate solution to the lanthanum hydroxide solution, stirring and then ultrasonically treating for 30 minutes to obtain a doping mixed solution. The concentration of manganese ions in the manganese sulfate solution is 0.15 mol / L, and the molar ratio of manganese element to lanthanum element is 1:1.2.

[0094] S4: The activated bentonite was mixed with the doping mixed solution at a solid-liquid ratio of 1 g:20 mL, and then ultrasonically treated for 3 h. After drying, lanthanum-manganese co-doped bentonite was obtained.

[0095] S5: Lanthanum-manganese co-doped bentonite and magnetic iron oxide are mixed in a solution, the mass ratio of lanthanum-manganese co-doped bentonite to magnetic iron oxide is 4:1, and then ultrasonically treated for 15 minutes, and dried to obtain a dephosphorization reagent.

[0096] Example 4

[0097] This embodiment provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, comprising the following steps:

[0098] S1: Soak bentonite with a particle size of 0.06 mm in a hydrochloric acid solution with a concentration of 0.8 mol / L, with a solid-liquid ratio of 1 g:9.5 mL, stir for 3.5 h, wash with deionized water until neutral, and dry to obtain activated bentonite.

[0099] S2: adding a sodium hydroxide solution with a concentration of 1.1 mol / L to a lanthanum nitrate solution with a concentration of 0.13 mol / L under stirring, and ultrasonically treating for 14 min to obtain a lanthanum hydroxide solution with a pH of 10.4.

[0100] S3: adding manganese chloride solution to the lanthanum hydroxide solution, stirring and then ultrasonically treating for 26 minutes to obtain a doped mixed solution. The concentration of manganese ions in the manganese chloride solution is 0.11 mol / L, and the molar ratio of manganese element to lanthanum element is 1:0.9.

[0101] S4: The activated bentonite was mixed with the doping mixed solution at a solid-liquid ratio of 1 g:12 mL, and then ultrasonically treated for 2.2 h. After drying, lanthanum-manganese co-doped bentonite was obtained.

[0102] S5: The lanthanum-manganese co-doped bentonite and the magnetic iron oxide are mixed in a solution, wherein the mass ratio of the lanthanum-manganese co-doped bentonite to the magnetic iron oxide is 2.5:1, and then ultrasonically treated for 13 minutes, and dried to obtain a dephosphorization reagent.

[0103] Example 5

[0104] This embodiment provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, comprising the following steps:

[0105] S1: Soak bentonite with a particle size of 0.08 mm in a hydrochloric acid solution with a concentration of 1.5 mol / L, with a solid-liquid ratio of 1 g:8 mL, stir for 2 h, wash with deionized water until neutral, and dry to obtain activated bentonite.

[0106] S2: adding a sodium hydroxide solution with a concentration of 1.1 mol / L to a lanthanum chloride solution with a concentration of 0.15 mol / L under stirring, and ultrasonically treating for 18 min to obtain a lanthanum hydroxide solution with a pH of 11.

[0107] S3: adding manganese sulfate solution to the lanthanum hydroxide solution, stirring and then ultrasonically treating for 25 minutes to obtain a doped mixed solution. The concentration of manganese ions in the manganese sulfate solution is 0.14 mol / L, and the molar ratio of manganese element to lanthanum element is 1:1.1.

[0108] S4: The activated bentonite was mixed with the doping mixed solution at a solid-liquid ratio of 1 g:17 mL, and then ultrasonically treated for 2.6 h. After drying, lanthanum-manganese co-doped bentonite was obtained.

[0109] S5: The lanthanum-manganese co-doped bentonite and the magnetic iron oxide are mixed in a solution, wherein the mass ratio of the lanthanum-manganese co-doped bentonite to the magnetic iron oxide is 3.2:1, and then ultrasonically treated for 14 minutes, and dried to obtain a phosphorus removal agent.

[0110] Comparative Example 1

[0111] This comparative example provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, which is different from Example 1 in that the bentonite in step S1 is not treated with acid activation.

[0112] Comparative Example 2

[0113] This comparative example provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, which is different from Example 1 in that the molar ratio of manganese element to lanthanum element in step S3 is 1:2.

[0114] Comparative Example 3

[0115] This comparative example provides a method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater, which is different from Example 1 in that the molar ratio of manganese element to lanthanum element in step S3 is 1:0.3.

[0116] The phosphorus removal reagents prepared in the above Examples 1-5 and Comparative Examples 1-3 were used to treat sweet potato starch processing wastewater, and the specific treatment steps were as follows:

[0117] A1: Filter the sweet potato starch processing wastewater to obtain filtered water.

[0118] A2: Add the dephosphorization reagents prepared in Examples 1-5 and Comparative Examples 1-3 to the filtered water, respectively, and let stand for 72 hours to obtain dephosphorized water.

[0119] A3: The phosphorus removal water body is subjected to hydrolysis acidification treatment, anoxic treatment, aerobic treatment and deep treatment in sequence to obtain treated water body.

[0120] In step A1, the COD concentration in the sweet potato starch processing wastewater is 25664 mg / L, the ammonia nitrogen concentration is 1334 mg / L, the total phosphorus concentration is 232 mg / L, and the total nitrogen concentration is 1436 mg / L.

[0121] In step A2, the amount of phosphorus removal agent added to the filtered water is 8 g / L.

[0122] The concentrations of various pollutants in the dephosphorization water and the treated water were tested respectively, and the results are shown in Tables 1 and 2.

[0123] Table 1 Statistical table of pollutant treatment effects in phosphorus removal water bodies of Examples 1-5 and Comparative Examples 1-3

[0124]

[0125]

[0126] It can be seen from Table 1 that the total phosphorus concentration in the phosphorus removal water body treated with the phosphorus removal reagents of Examples 1-5 is less than 0.5 mg / L, all of which meet the Class A standard specified in GB18918-2002 "Pollutant Discharge Standard for Urban Sewage Treatment Plants", and the removal rates of COD and ammonia nitrogen in the water body are basically around 30%, and the removal rate of total nitrogen is about 26%. Since the phosphorus removal reagent of Comparative Example 1 did not activate the bentonite, the total phosphorus concentration in the water body was higher than 0.5 mg / L. In Comparative Examples 2 and 3, since the molar ratio of manganese to lanthanum exceeded the limited range of 1:0.8-1:1.2, the synergistic effect of manganese ions and lanthanum ions was affected, thereby affecting the treatment effect of the phosphorus removal reagent on total phosphorus.

[0127] Table 2 Statistical table of pollutant treatment effects in water treated by Examples 1-5 and Comparative Examples 1-3

[0128] COD concentration Ammonia nitrogen concentration Total nitrogen concentration Total phosphorus concentration Example 1 37.4mg / L 4.0mg / L 11.4mg / L 0.30mg / L Example 2 41.8mg / L 4.2mg / L 12.7mg / L 0.41mg / L Example 3 43.3mg / L 4.2mg / L 12.1mg / L 0.36mg / L Example 4 40.1mg / L 4.1mg / L 13.6mg / L 0.35mg / L Example 5 39.2mg / L 4.3mg / L 14.1mg / L 0.40mg / L Comparative Example 1 38.7mg / L 3.8mg / L 12.9mg / L 3.09mg / L Comparative Example 2 40.4mg / L 4.2mg / L 10.7mg / L 5.14mg / L Comparative Example 3 39.6mg / L 4.7mg / L 11.8mg / L 4.26mg / L

[0129] It can be seen from Table 2 that in the treated water bodies treated with the phosphorus removal reagents of Examples 1-5, the COD concentrations were all less than 50 mg / L, the ammonia nitrogen concentrations were all less than 5 mg / L, the total nitrogen concentrations were all less than 15 mg / L, and the total phosphorus concentrations were all less than 0.5 mg / L, all reaching the Class A standard specified in GB18918-2002 "Pollutant Discharge Standards for Urban Sewage Treatment Plants". In the treated water bodies treated with the phosphorus removal reagents of Comparative Examples 1-3, except for the total phosphorus concentration, the COD concentrations, ammonia nitrogen concentrations, and total nitrogen concentrations all reached the Class A standard specified in GB18918-2002 "Pollutant Discharge Standards for Urban Sewage Treatment Plants".

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dephosphorization agent for treating sweet potato starch processing wastewater, characterized in that: The raw materials for preparing the phosphorus removal agent include soluble lanthanum salt, soluble divalent manganese salt, strong alkali, magnetic iron oxide and bentonite after activation treatment; The molar ratio of the lanthanum ions in the soluble lanthanum salt to the divalent manganese ions in the soluble divalent manganese salt is 1:0.8-1:1.

2.

2. A method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater according to claim 1, characterized in that: The steps include: S1: activating bentonite with an acid to obtain activated bentonite; S2: adding a strong base solution to the soluble lanthanum salt solution under stirring to obtain a lanthanum hydroxide solution with a pH of 10-11; S3: adding a soluble divalent manganese salt solution to the lanthanum hydroxide solution to obtain a doping mixed solution; S4: mixing the activated bentonite with the doping mixed solution, then subjecting the mixture to ultrasonic treatment, and drying to obtain lanthanum-manganese co-doped bentonite; S5: The lanthanum-manganese co-doped bentonite and magnetic iron oxide are mixed in a solution, then ultrasonically treated and dried to obtain a phosphorus removal agent.

3. The preparation method of the dephosphorization reagent for treating sweet potato starch processing wastewater according to claim 2, characterized in that, In step S1, the bentonite is activated by an acid solution with a concentration of 0.5-2 mol / L for 2-4 hours; The acid solution is hydrochloric acid, sulfuric acid or nitric acid, the solid-liquid ratio of bentonite to the acid solution is 1g:(8-10)mL, and the particle size of the bentonite is ≤0.1mm.

4. The method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater according to claim 2, wherein: In step S2, after the reaction between the lanthanum salt and the strong base is completed, ultrasonic treatment is performed for 10-20 minutes to obtain a lanthanum hydroxide solution; The soluble lanthanum salt is any one of lanthanum chloride, lanthanum nitrate and crystalline hydrates thereof, and the strong base is potassium hydroxide or sodium hydroxide; The concentration of lanthanum ions in the soluble lanthanum salt solution is 0.1-0.15 mol / L, and the concentration of the strong base solution is 0.8-1.2 mol / L.

5. The preparation method of the dephosphorization reagent for treating sweet potato starch processing wastewater according to claim 2, characterized in that, In step S3, a soluble divalent manganese salt solution is added to the lanthanum hydroxide solution, and the mixture is ultrasonically treated for 20-30 minutes after stirring to obtain a doped mixed solution; The soluble manganese salt is any one of manganese sulfate, manganese nitrate, manganese chloride and their crystalline hydrates; the concentration of manganese ions in the soluble divalent manganese salt solution is 0.1-0.15 mol / L; The molar ratio of the manganese element in the soluble divalent manganese salt solution to the lanthanum element in the lanthanum hydroxide solution is 1:0.8-1:1.

2.

6. The method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater according to claim 2, characterized in that: In step S4, the solid-liquid ratio of the activated bentonite to the doping mixed solution is 1 g: (10-20) mL, and the ultrasonic treatment time is 2-3 h.

7. The method for preparing a dephosphorization agent for treating sweet potato starch processing wastewater according to claim 2, characterized in that: In step S5, the mass ratio of lanthanum-manganese co-doped bentonite to magnetic iron oxide is 2:1-4:1, and the ultrasonic treatment time is 10-15 minutes.

8. A method for treating sweet potato starch processing wastewater, characterized in that: The steps include: A1: Filter and treat the sweet potato starch processing wastewater to obtain filtered water; A2: Add the phosphorus removal reagent prepared by the preparation method according to claim 1 or any one of claims 2 to 7 to the filtered water, and let it stand for 24 to 72 hours to obtain phosphorus-removed water; A3: The phosphorus removal water body is subjected to hydrolysis acidification treatment, anoxic treatment, aerobic treatment and deep treatment in sequence to obtain water that meets the discharge standards.

9. The method for treating sweet potato starch processing wastewater according to claim 1, wherein: In step A1, the COD concentration in the sweet potato starch processing wastewater is 24000-26000 mg / L, the ammonia nitrogen concentration is 1200-1350 mg / L, the total phosphorus concentration is 200-300 mg / L, and the total nitrogen concentration is 1400-1500 mg / L.

10. The method for treating sweet potato starch processing wastewater according to claim 1, characterized in that: In step A2, the amount of phosphorus removal agent added to the filtered water is 5-10 g / L.

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