Composite phosphorus removal agent as well as preparation method and application thereof

Abstract

The invention relates to a composite phosphorus removal agent as well as a preparation method and application thereof. The composite phosphorus removal agent comprises 45wt%-75wt% of a modified inorganic high-molecular coagulant, 2wt%-15wt% of a modified natural high-molecular polymer, 5wt%-40wt% of inorganic salt, 0.5 wt%-5wt% of a coagulant aid and 0.1 wt%-0.5 wt% of a solvent, wherein the modified inorganic polymer coagulant comprises modified polyaluminum chloride and / or modified polyaluminum ferric chloride; the basicity of the modified inorganic polymer coagulant is 40-85 wt%; the modified natural high-molecular polymer is prepared from one or more of a dimethyl diallyl ammonium chloride-acrylamide-modified starch copolymer and a methacryloyloxyethyl trimethyl ammonium chloride-acrylamide-modified starch copolymer; the relative molecular mass of the modified natural high-molecular polymer is 50-450 million. The composite water purifying agent disclosed by the invention is low in cost and simple in production and preparation method, does not introduce excessive metal salts, does not cause secondary pollution and does not cause excessive metal in a water body, and has a better effect of removing phosphorus and turbidity under the condition of low water temperature.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular, to a composite phosphorus removal agent and a preparation method and application thereof. Background Art

[0002] With the growth of industrial and agricultural production, the rapid increase in urban scale, and the extensive use of phosphorus-containing fertilizers, pesticides, and detergents, the phosphorus salt content in urban sewage receiving pipes is generally high. Although nitrogen and phosphorus are both important nutrients for aquatic organisms, aquatic organisms such as algae are more sensitive to phosphorus. Moreover, when the nitrogen concentration in the water body is low, the blue algae and green algae in the water body can supplement the insufficient nitrogen concentration through nitrogen fixation. It can be seen that phosphorus is the most important controlling factor for eutrophication of water bodies. Therefore, effectively reducing the phosphorus content in discharged wastewater has become one of the important ways to prevent and control eutrophication of water bodies. In order to control the eutrophication of water bodies, it is necessary to increase the discharge requirements for urban sewage treatment plants.

[0003] In terms of phosphorus removal, actual operating experience at home and abroad shows that almost all sewage treatment plants need to adopt biological and chemical phosphorus removal processes to meet the requirements of effluent phosphorus content lower than the control emission requirements. At present, most sewage treatment plants use post-sedimentation process for chemical phosphorus removal. The treatment process is stable and mature, and there are strict requirements for total phosphorus discharged from the outlet. However, considering the unstable raw water volume, the long production and operation period in the low temperature environment in the north, the short hydraulic retention time in the deep treatment section, the frequent abnormal impact of the influent, and the higher requirements for total phosphorus in the downstream river sections of some water plant discharge outlets, this will increase the consumption of sewage treatment plants. There are many methods for phosphorus removal from sewage, including chemical, microbial, aquatic, physical adsorption, membrane technology treatment and soil treatment. The mainstream methods of phosphorus removal in sewage treatment plants are: chemical phosphorus removal and biological phosphorus removal. Chemical phosphorus removal includes chemical precipitation, ion exchange, reverse osmosis and other methods. Among them, chemical precipitation is the most cost-effective and widely used method. Its mechanism is to add metal salts during sewage treatment to react with phosphorus in the water to form granular, insoluble substances such as phosphates and polyphosphates. After sedimentation separation and filtration treatment, the phosphorus in the sewage is removed.

[0004] The chemical phosphorus removal agents commonly used at present can be mainly divided into metal salt phosphorus removal agents such as aluminum salts, iron salts, and calcium salts. However, the phosphorus removal effect of metal salt phosphorus removal agents is relatively poor and they are prone to cause new pollution. For example, polyaluminum chloride is a metal salt inorganic polymer phosphorus removal agent. Although the chemical reaction is fast and the precipitation is fast in the process of sewage phosphorus removal, the probability of the precipitate forming compact flocs after treatment is low, and the solid-liquid separation is poor, resulting in large overall dosage and low cost performance, which can no longer meet actual needs.

[0005] There are also related disclosures about the technology of phosphorus removal agents in the prior art. For example, CN113896307A discloses a composite phosphorus removal agent for sewage treatment and a preparation method thereof, wherein the composite phosphorus removal agent is composed of a mixture of a phosphorus removal agent A and a phosphorus removal agent B. The phosphorus removal agent A includes glucose, white sugar, soda ash, magnesium salts and calcium salts, and the phosphorus removal agent B includes ferric chloride, copper sulfate, polydimethyldiallylammonium chloride, coagulant, polyferric sulfate, ferrous sulfate, aluminum sulfate, polyaluminum chloride, sodium aluminate, lime, caustic soda, stabilizer, etc. The flocculation degree of the treated sewage is determined by regulating the content of the phosphorus removal agent A and the phosphorus removal agent B, which not only plays a role in flocculation and phosphorus removal during sewage treatment, but also plays a role in controlling the dosage to a certain extent.

[0006] Although the above existing technologies can have a phosphorus removal effect within a certain range, their components are complex and they often cause secondary pollution after being used for phosphorus removal, especially when too many metal salts are introduced, which can easily cause excessive heavy metal content in water bodies; when sugars and rare earths are used as the main raw materials, it is inconvenient to obtain the raw materials and the production cost is high; this type of phosphorus removal agent even needs to be added at 80~500ppm, and its dosage consumption is too high, and the actual phosphorus removal rate is not high; when two or more agents are used in coordination, the hydraulic retention time interval is long and the sedimentation time is too long, which cannot be fully applicable to the actual needs of deep water treatment sections such as high-efficiency sedimentation tanks in sewage treatment plants; better treatment effects can only be achieved at an appropriate temperature (such as room temperature), and there are no cases of rapid phosphorus and turbidity removal under low temperature conditions (such as 12°C and below), and there are no application cases of sewage treatment when the influent is impacted at low temperatures. Summary of the invention

[0007] The purpose of the present invention is to provide a composite phosphorus removal agent and a preparation method and application thereof. After the composite phosphorus removal agent reacts in sewage, flocs are formed compactly, precipitate quickly, have high phosphorus and turbidity removal efficiency, and produce low sludge.

[0008] In order to achieve the above-mentioned object, the first aspect of the present disclosure provides a composite phosphorus removal agent, which comprises 45 wt% to 75 wt% of a modified inorganic polymer coagulant, 2 wt% to 15 wt% of a modified natural polymer, 5 wt% to 40 wt% of an inorganic salt, 0.5 wt% to 5 wt% of a coagulant aid and 0.1 wt% to 0.5 wt% of a solvent; Among them, the modified inorganic polymer coagulant includes modified polyaluminum chloride and / or modified polyaluminum ferric chloride; the basicity of the modified inorganic polymer coagulant is 40~85wt%; the modified natural polymer includes one or more of dimethyldiallylammonium chloride-acrylamide-modified starch copolymer and methacryloyloxyethyltrimethylammonium chloride-acrylamide-modified starch copolymer; the relative molecular mass of the modified natural polymer is 500,000~4.5 million.

[0009] Optionally, the composite phosphorus removal agent comprises 50wt% to 70wt% of a modified inorganic polymer coagulant, 3wt% to 10wt% of a modified natural polymer, 8wt% to 33wt% of an inorganic salt, 1wt% to 4.5wt% of a coagulant aid and 0.2wt% to 0.45wt% of a solvent; The basicity of the modified inorganic polymer coagulant is 50-75wt%; the relative molecular mass of the modified natural polymer is 1-3 million.

[0010] Optionally, the inorganic salt includes one or more of aluminum chloride, aluminum sulfate, calcium chloride, ferric chloride and ferric sulfate; The coagulant aid includes one or more of polyethyleneimine, polyvinyl pyrrolidone and polyethylene oxide; The solvent includes water and an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, ethylene glycol and acetic acid.

[0011] Optionally, the preparation method of the modified polyaluminium chloride comprises the following steps: Contacting hydrochloric acid, sulfuric acid, aluminum hydroxide and first bauxite to perform a first reaction to obtain a first reactant; contacting the first reactant, high-calcium fly ash, first calcium aluminate powder and water to perform a second reaction, and subjecting the second reactant to a first filter press treatment; The conditions of the first reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the second reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the first filter press treatment include: at 85-95°C, the plate frame mesh number used in the filter press treatment is 80-120 mesh; The raw materials for preparing the modified polyaluminium chloride include: 2.5 wt% to 8.5 wt% of high calcium fly ash, 2.5 wt% to 25 wt% of first bauxite, 5 wt% to 30 wt% of first calcium aluminate powder, 0 wt% to 30 wt% of aluminium hydroxide, 45 wt% to 60 wt% of hydrochloric acid and 2 wt% to 5 wt% of sulfuric acid; Among them, the concentration of the hydrochloric acid is 20%~31%; the concentration of the sulfuric acid is 90%~98%; the mass fraction of aluminum oxide in the aluminum hydroxide is 60%~68%, and the particle size is 130~160 mesh; the mass fraction of aluminum oxide in the first bauxite is 25%~35%, and the particle size is 180~220 mesh; the mass fraction of aluminum oxide in the high-calcium fly ash is more than 25%, the mass fraction of silicon dioxide is less than 45%, the mass fraction of active calcium oxide is more than 10%, the water absorption is more than 120%, and the particle size is 280~320 mesh; the mass fraction of aluminum oxide in the first calcium aluminate powder is 40%~50%, and the particle size is 180~220 mesh.

[0012] Optionally, the preparation method of the modified polyaluminium ferric chloride comprises the following steps: The hydrochloric acid, sulfuric acid, aluminum hydroxide and the second bauxite are contacted to perform a third reaction to obtain a third reactant; the third reactant, high calcium fly ash, the second calcium aluminate powder and water are contacted to perform a fourth reaction, and the fourth reactant is subjected to a second filter press treatment; The conditions of the third reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the fourth reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the second filter press treatment include: at 85-95°C, the plate frame mesh number used in the second filter press treatment is 80-120 mesh; The raw materials for preparing the modified polyaluminium ferric chloride include: 2.5wt% to 5wt% of high-calcium fly ash, 10wt% to 30wt% of a second bauxite, 5wt% to 30wt% of a second calcium aluminate powder, 0wt% to 15wt% of aluminium hydroxide, 40wt% to 60wt% of hydrochloric acid and 2.5wt% to 5wt% of sulfuric acid; Among them, the mass fraction of aluminum oxide in the second bauxite is 25%~35%, the mass fraction of iron oxide is 3%~5%, and the particle size is 180~220 mesh; the mass fraction of aluminum oxide in the second calcium aluminate powder is 40%~50%, the mass fraction of iron oxide is 3%~8%, and the particle size is 180~220 mesh.

[0013] Optionally, the preparation method of the dimethyldiallylammonium chloride-acrylamide-modified starch copolymer comprises: Mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and dimethyldiallylammonium chloride; The mass ratio of the dimethyldiallylammonium chloride, the acrylamide and the modified starch is (0.2-2.5): (1-3.5): 1, preferably (0.8-2.0): (1.5-3.3): 1; the reaction temperature is 40-60°C, and the reaction time is 2-3h; the initiator includes urea and / or ammonium persulfate; The modified starch is cationic etherified modified starch and / or phosphate modified corn starch, and the particle size is 150-200 meshes.

[0014] Optionally, the preparation method of the methacryloyloxyethyl trimethylammonium chloride-acrylamide-modified starch copolymer comprises: Mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and methacryloyloxyethyl trimethylammonium chloride; The mass ratio of the methacryloyloxyethyl trimethylammonium chloride, the acrylamide and the modified starch is (0.3-2.4):(1-3.5):1, preferably (0.8-2.0):(1.5-3.3):1; the reaction temperature is 45-70°C, and the reaction time is 2-3h; the initiator includes sodium thiosulfate and / or sodium persulfate.

[0015] The second aspect of the present disclosure provides a method for preparing the composite phosphorus removal agent according to the first aspect of the present disclosure, the method comprising: The modified inorganic polymer coagulant and the inorganic salt are mixed for the first time to obtain a first mixed solution; the coagulant aid, the solvent and the modified natural polymer are mixed for the second time to obtain a second mixed solution; and the second mixed solution and the first mixed solution are mixed for the third time.

[0016] Optionally, the first mixing condition includes: carrying out under stirring condition, the stirring rate is 60-120 rpm, and the stirring time is 15-30 min; The second mixing conditions include: carrying out under stirring conditions, the stirring rate is 30-60 rpm, and the stirring time is 20-30 min; The third mixing condition includes: carrying out under stirring condition, the stirring rate is 45-65 rpm, and the stirring time is 30-50 min.

[0017] The third aspect of the present disclosure provides an application of the composite water purifier described in the second aspect of the present disclosure in sewage and wastewater treatment, wherein the content of phosphorus in the sewage and wastewater is 1-8 mg / L, and the mass ratio of the composite water purifier to the phosphorus is 30-150:1.

[0018] Through the above technical scheme, the composite phosphorus removal agent disclosed in the present invention includes a modified inorganic polymer coagulant of a specific mass, a modified natural polymer, an inorganic salt, a coagulant aid and a solvent; wherein the modified inorganic polymer coagulant is modified polyaluminum chloride and / or modified polyaluminum chloride iron, which has a certain basicity, is a stable suspended liquid with high electrical neutralization, high molecular weight and strong adsorption, and has a strong neutralization, sweeping and adsorption and coagulation ability for sediments in sewage; the modified natural polymer includes dimethyldiallylammonium chloride-acrylamide- One or more of modified starch copolymer, methacryloyloxyethyl trimethylammonium chloride-acrylamide-modified starch copolymer has a relatively low molecular weight, contains a variety of polar groups, hydrogen bonds and covalent bonds, and has a certain adsorption capacity, so that colloids and fine suspended solids in sewage are effectively removed; the present invention uses a modified inorganic polymer coagulant with a high degree of polymerization and a modified natural polymer with a low molecular weight, so that the two can work together, and after reacting in sewage, the flocs are formed compactly, precipitate quickly, and have high phosphorus and turbidity removal efficiency and low sludge production. The composite water purifier disclosed in the present invention has low cost, convenient raw material acquisition, simple production and preparation method, and does not require high temperature and high pressure equipment; it will not introduce too many metal salts, will not cause secondary pollution and excessive metals in the water body, and has better effect in phosphorus and turbidity removal under low water temperature conditions of 12°C or below.

[0019] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0021] The first aspect of the present disclosure provides a composite phosphorus removal agent, the composite phosphorus removal agent comprising 45 wt% to 75 wt% of a modified inorganic polymer coagulant, 2 wt% to 15 wt% of a modified natural polymer, 5 wt% to 40 wt% of an inorganic salt, 0.5 wt% to 5 wt% of a coagulant aid, and 0.1 wt% to 0.5 wt% of a solvent; Among them, the modified inorganic polymer coagulant includes modified polyaluminum chloride and / or modified polyaluminum ferric chloride; the basicity of the modified inorganic polymer coagulant is 40~85wt%; the modified natural polymer includes one or more of dimethyldiallylammonium chloride-acrylamide-modified starch copolymer and methacryloyloxyethyltrimethylammonium chloride-acrylamide-modified starch copolymer; the relative molecular mass of the modified natural polymer is 500,000~4.5 million.

[0022] The composite phosphorus removal agent disclosed in the present invention comprises a modified inorganic polymer coagulant of a specific mass, a modified natural polymer, an inorganic salt, a coagulant aid and a solvent; wherein the modified inorganic polymer coagulant is modified polyaluminum chloride and / or modified polyaluminum ferric chloride, which is a stable suspended liquid with high electrical neutralization, high molecular weight and strong adsorption capacity, and has a strong neutralization, sweeping and adsorption and coagulation capacity for sediments in sewage; the modified natural polymer comprises one or more of dimethyldiallylammonium chloride-acrylamide-modified starch copolymer and methacryloyloxyethyltrimethylammonium chloride-acrylamide-modified starch copolymer, which has a lower molecular weight, contains a variety of polar groups, hydrogen bonds and covalent bonds, has a certain adsorption capacity, and effectively removes colloids and fine suspended matter in sewage; the present invention uses a modified inorganic polymer coagulant with a high degree of polymerization and a modified natural polymer with a low molecular weight, so that the two work synergistically, and after reacting in sewage, the flocs are formed compactly, precipitate quickly, have high phosphorus removal and turbidity removal efficiency, and have low sludge production. The composite water purifier disclosed in the present invention has low cost, convenient raw material acquisition, simple production and preparation method, and does not require high-temperature and high-pressure equipment; it does not introduce excessive metal salts, does not cause secondary pollution and excessive metals in the water body, and has better effects in removing phosphorus and turbidity at low water temperatures of 12°C or below.

[0023] In this disclosure, basicity refers to the OH content in the modified inorganic polymer coagulant. - Ions and metal ions (such as Al 3+ ) by mass percentage.

[0024] According to an embodiment of the present disclosure, the composite phosphorus removal agent includes 50wt% to 70wt% of a modified inorganic polymer coagulant, 3wt% to 10wt% of a modified natural polymer, 8wt% to 33wt% of an inorganic salt, 1wt% to 4.5wt% of a coagulant aid, and 0.2wt% to 0.45wt% of a solvent. The above embodiment is conducive to obtaining a better composite water purifier, so that the composite water purifier has a more compact flocculent formation after reacting in sewage, precipitates quickly, has a higher phosphorus and turbidity removal efficiency, and produces less mud.

[0025] According to one embodiment of the present disclosure, the basicity of the modified inorganic polymer coagulant is 50-75wt%; the relative molecular mass of the modified natural polymer is 1-3 million, preferably 1-2.5 million. The above embodiment is conducive to better synergistic effect of the modified inorganic polymer coagulant and the modified natural polymer, and obtains a better composite water purifier, so that the composite water purifier has more compact flocs after reaction in sewage, rapid precipitation, higher phosphorus and turbidity removal efficiency, and low sludge production.

[0026] According to an embodiment of the present disclosure, the inorganic salt includes one or more of aluminum chloride, aluminum sulfate, calcium chloride, ferric chloride and ferric sulfate; the coagulant includes one or more of polyethyleneimine, polyvinyl pyrrolidone and polyethylene oxide; the solvent includes water and an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, ethylene glycol and acetic acid. The above embodiment is conducive to obtaining a better composite water purifier, so that the composite water purifier can form more compact flocs after reacting in sewage, precipitate quickly, remove phosphorus and turbidity more efficiently, and produce less mud.

[0027] According to one embodiment of the present disclosure, the preparation method of the modified polyaluminium chloride comprises the following steps: The first reaction is carried out by contacting hydrochloric acid, sulfuric acid, aluminum hydroxide and first bauxite to obtain a first reactant; the first reactant, high-calcium fly ash, first calcium aluminate powder and water are contacted to carry out a second reaction, and the second reactant is subjected to filter pressing treatment.

[0028] According to an embodiment of the present disclosure, the conditions of the first reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the second reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the filter press treatment include: at 85-95°C, the plate frame mesh number used in the filter press treatment is 80-120 mesh. The above embodiment is conducive to obtaining a modified inorganic polymer coagulant with high electrical neutralization, high molecular weight and strong adsorption, and has stronger neutralization, sweeping and adsorption coagulation capabilities for sediments in sewage.

[0029] According to an embodiment of the present disclosure, 2.5 wt% to 8.5 wt% of high-calcium fly ash, 2.5 wt% to 25 wt% of first bauxite, 5 wt% to 30 wt% of first calcium aluminate powder, 0 wt% to 30 wt% of aluminum hydroxide, 45 wt% to 60 wt% of hydrochloric acid, and 2 wt% to 5 wt% of sulfuric acid. The above embodiment is conducive to obtaining a modified inorganic polymer coagulant with high electrical neutralization, high molecular weight, and strong adsorption, and has stronger neutralization, sweeping, adsorption and coagulation capabilities for sediments in sewage.

[0030] According to one embodiment of the present disclosure, the concentration of the hydrochloric acid is 20%~31%; the concentration of the sulfuric acid is 90%~98%; the mass fraction of aluminum oxide in the aluminum hydroxide is 60%~68%, and the particle size is 130~160 mesh; the mass fraction of aluminum oxide in the first bauxite is 25%~35%, and the particle size is 180~220 mesh; the mass fraction of aluminum oxide in the high-calcium fly ash is more than 25%, the mass fraction of silicon dioxide is less than 45%, the mass fraction of active calcium oxide is more than 10%, the water absorption is more than 120%, and the particle size is 280~320 mesh; the mass fraction of aluminum oxide in the first calcium aluminate powder is 40%~50%, and the particle size is 180~220 mesh.

[0031] According to one embodiment of the present disclosure, the preparation method of the modified polyaluminium ferric chloride comprises the following steps: The third reaction is carried out by contacting hydrochloric acid, sulfuric acid, aluminum hydroxide and the second bauxite to obtain a third reactant; the third reactant, high calcium fly ash, the second calcium aluminate powder and water are contacted to carry out a fourth reaction, and the fourth reactant is subjected to filter pressing treatment.

[0032] According to an embodiment of the present disclosure, the conditions of the third reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the fourth reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the filter press treatment include: at 85-95°C, the plate frame mesh number used in the filter press treatment is 80-120 mesh. The above embodiment is conducive to obtaining a modified inorganic polymer coagulant with high electrical neutralization, high molecular weight and strong adsorption, and has stronger neutralization, sweeping and adsorption coagulation capabilities for sediments in sewage.

[0033] According to one embodiment of the present disclosure, the raw materials for preparing the modified polyaluminium ferric chloride include: 2.5wt%~5wt% of high-calcium fly ash, 10wt%~30wt% of second bauxite, 5wt%~30wt% of second calcium aluminate powder, 0wt%~15wt% of aluminium hydroxide, 40wt%~60wt% of hydrochloric acid and 2.5wt%~5wt% of sulfuric acid. The above embodiment is conducive to obtaining a modified inorganic polymer coagulant with high electrical neutralization, high molecular weight and strong adsorption, and has stronger neutralization, sweeping and adsorption coagulation capabilities for sediments in sewage.

[0034] According to one embodiment of the present disclosure, the concentration of the hydrochloric acid is 20% to 31%; the concentration of the sulfuric acid is 90% to 98%; the mass fraction of aluminum oxide in the aluminum hydroxide is 60% to 68%, and the particle size is 130 to 160 meshes; the mass fraction of aluminum oxide in the second bauxite is 25% to 35%, the mass fraction of iron oxide is 3% to 5%, and the particle size is 180 to 220 meshes; the mass fraction of aluminum oxide in the second calcium aluminate powder is 40% to 50%, the mass fraction of iron oxide is 3% to 8%, and the particle size is 180 to 220 meshes. The above embodiment is conducive to obtaining a modified inorganic polymer coagulant with high electrical neutralization, high molecular weight, and strong adsorption, and has stronger neutralization, sweeping, adsorption and coagulation capabilities for sediments in sewage.

[0035] According to one embodiment of the present disclosure, the preparation method of the dimethyldiallylammonium chloride-acrylamide-modified starch copolymer (PDMD-AM-St) includes: mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and dimethyldiallylammonium chloride; in a further embodiment, the dimethyldiallylammonium chloride, the acrylamide and the modified starch are (0.2~2.5):(1~3.5):1, preferably (0.8~2.0):(1.5~3.3):1; the reaction temperature is 40~60°C, and the reaction time is 2~3h; the initiator includes urea and / or ammonium persulfate. The above embodiment is conducive to obtaining a low molecular weight modified natural high molecular polymer, and is conducive to effectively removing colloids and fine suspended matter in sewage.

[0036] According to one embodiment of the present disclosure, the preparation method of the dimethyldiallylammonium chloride-acrylamide-modified starch copolymer (PDMD-AM-St) includes continuously introducing nitrogen into the reaction system for 20 to 40 minutes to exclude oxygen and form the inert atmosphere before adding the initiator.

[0037] According to one embodiment of the present disclosure, the preparation method of the methacryloyloxyethyl trimethyl ammonium chloride-acrylamide-modified starch copolymer (PDMC-AM-St) includes: mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and methacryloyloxyethyl trimethyl ammonium chloride; in a further embodiment, the mass ratio of the methacryloyloxyethyl trimethyl ammonium chloride, the acrylamide and the modified starch is (0.3~2.4): (1~3.5): 1, preferably (0.8~2.0): (1.5~3.3): 1; the reaction temperature is 45~70°C, and the reaction time is 2~3h; the initiator includes sodium thiosulfate and / or sodium persulfate. The above embodiment is conducive to obtaining a low molecular weight modified natural high molecular polymer and is conducive to effectively removing colloids and fine suspended matter in sewage.

[0038] According to one embodiment of the present disclosure, the preparation method of the methacryloyloxyethyltrimethylammonium chloride-acrylamide-modified starch copolymer (PDMC-AM-St) includes continuously introducing nitrogen into the reaction system for 20 to 40 minutes to exclude oxygen and form the inert atmosphere before adding the initiator.

[0039] According to an embodiment of the present disclosure, the modified starch is a cationic etherified modified starch and / or a phosphate modified corn starch, and the particle size is 150-200 mesh; the concentration of the dimethyldiallylammonium chloride is 60% or more; the purity of the acrylamide is 98% or more; the concentration of the methacryloyloxyethyltrimethylammonium chloride is 78% or more. The above embodiment is conducive to obtaining a low molecular weight modified natural high molecular polymer, and is conducive to effectively removing colloids and fine suspended matter in sewage.

[0040] The second aspect of the present disclosure provides a method for preparing the composite phosphorus removal agent according to the first aspect of the present disclosure, the method comprising: The modified inorganic polymer coagulant and the inorganic salt are mixed for the first time to obtain a first mixed solution; the coagulant aid, the solvent and the modified natural polymer are mixed for the second time to obtain a second mixed solution; and the second mixed solution and the first mixed solution are mixed for the third time.

[0041] According to an embodiment of the present disclosure, the first mixing condition includes: under stirring conditions, the stirring rate is 60-120 rpm, and the stirring time is 15-30 minutes; the second mixing condition includes: under stirring conditions, the stirring rate is 30-60 rpm, and the stirring time is 20-30 minutes; the third mixing condition includes: under stirring conditions, the stirring rate is 45-65 rpm, and the stirring time is 30-50 minutes. The above embodiment is conducive to obtaining a better composite water purifier, so that the composite water purifier can form more compact flocs after reacting in sewage, precipitate quickly, remove phosphorus and turbidity more efficiently, and produce less mud.

[0042] The third aspect of the present disclosure provides the application of the composite water purifier described in the second aspect of the present disclosure in the treatment of sewage and wastewater, wherein the content of phosphorus in the sewage and wastewater is 1~8mg / L, and the mass ratio of the composite water purifier to the phosphorus is 30~150:1. The mass ratio of the commercially available water purifier to the phosphorus in sewage and wastewater is generally 50~300:1. In practical applications, the composite water purifier is used in the form of a solution, and the effective content of aluminum oxide in the configured solution can be 1~12wt%. When using it, technicians in this field can configure a solution with a specific aluminum oxide content according to the sewage water quality, which is a conventional technical means in this field. Compared with commercially available water purifiers, the present disclosure can save the dosage of water purifiers and reduce treatment costs. When the composite water purifier of the present disclosure treats sewage and wastewater, it will not introduce too many metal salts, will not cause secondary pollution, and will not cause excessive metals in the water body.

[0043] According to an embodiment of the present disclosure, the water temperature of the wastewater is below 12° C. The composite water purifier disclosed in the present disclosure has a better effect of removing phosphorus and turbidity under low water temperature conditions.

[0044] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0045] Unless otherwise specified, the other chemical reagents used in the examples are commercially available products. The basicity is tested by titration with sodium hydroxide standard solution.

[0046] Example 1 According to the percentage by mass, the composite water purifier S-1 of Example 1 includes 70wt% modified inorganic polymer coagulant, 8wt% modified natural polymer (PDMD-AM-St), 20wt% inorganic salt, 1.5wt% coagulant and 0.5wt% solvent; the inorganic salt is a mixture of aluminum chloride trihydrate and anhydrous ferric sulfate, with a mass ratio of 1:1; the coagulant is polyethyleneimine; the solvent is ethylene glycol; the modified inorganic polymer coagulant is modified polyaluminum chloride, with a basicity of 70wt%; the relative molecular mass of the modified natural polymer (PDMD-AM-St) is 2.6 million; The preparation method of composite water purifier S-1 comprises: (1) First, the modified polyaluminium chloride is pumped into the 1# enameled reactor and stirred at a speed of 120 rpm; (2) The inorganic salt mixture is pumped into the 1# reactor and stirred for 20 min to obtain a mixed solution A; (3) The coagulant and solvent are pumped into the 2# reactor and stirred at a slow speed of 55 rpm for 20 min, and the modified natural high molecular polymer PDMD-AM-St is slowly added into the reactor. After continuous stirring for 30 min, a mixed solution B is obtained; (4) The mixed solution B from the 2# reactor is pumped into the 1# enameled reactor and stirred with the mixed solution A at a speed of 45 rpm for 40 min to obtain a composite water purifier; The preparation method of modified polyaluminium chloride comprises: adding hydrochloric acid and sulfuric acid solution into a reactor, adding aluminium hydroxide and bauxite in sequence under stirring, reacting at 115°C for 3 hours under normal pressure to obtain an acidic system solution, wherein the main component of the system is aluminium chloride and contains a small amount of oligomeric polyaluminium chloride; cooling to 75°C, adding high-calcium fly ash, calcium aluminate powder and pure water in sequence under stirring, reacting at 110°C for 2 hours, and after the reaction is completed, filtering at 95°C through a 120-mesh plate and frame filter to obtain a suspended modified polyaluminium chloride solution; The raw materials for preparing the modified polyaluminium chloride include: 7.5 wt% of high calcium fly ash, 15 wt% of bauxite, 5 wt% of aluminium hydroxide, 8.5 wt% of calcium aluminate powder, 60 wt% of hydrochloric acid, and 4 wt% of sulfuric acid; The concentration of hydrochloric acid used is 25%; the concentration of sulfuric acid is 95%; the mass content of aluminum oxide in aluminum hydroxide is 60%, and the particle size is 150 mesh; the mass content of aluminum oxide in bauxite is 30%, and the particle size is 200 mesh; the mass content of aluminum oxide in high-calcium fly ash is 20%, the mass content of silicon dioxide is 40%, the mass content of active calcium oxide is 12%, the water absorption is more than 120%, and the particle size is 300 mesh; the mass content of aluminum oxide in calcium aluminate powder is 50%, and the particle size is 200 mesh; The method for preparing the modified natural high molecular polymer PDMD-AM-St comprises: Put modified starch St and pure water into a reactor, start stirring, and form a St emulsion suspension; after stirring for 10 minutes, introduce nitrogen for 30 minutes to fully remove oxygen, heat the reactor jacket, and ensure that the suspension is heated to 45°C; add urea and oxidant ammonium persulfate solution to the reactor one by one, and after 10 minutes, add the prepared acrylamide AM solution and dimethyldiallyl ammonium chloride DMD solution to the reactor at a certain drop rate at the same time. After 40 minutes, the dropwise addition is completed, stop stirring, and continue to react at 45°C for 2 hours to obtain a viscous and translucent modified natural polymer PDMD-AM-St copolymer; the raw materials for preparing the modified natural polymer PDMD-AM-St include: 12wt% St, 16wt% DMD, 25wt% AM, and 47wt% pure water; wherein the mass ratio of DMD, AM, and St is 1.33:2.08:1; St starch is phosphate-modified starch, industrial grade, with a particle size of 200 mesh; DMD is a colorless, transparent or slightly yellow liquid with a concentration of 60% and a salt content of ≤1.5%; AM is a colorless, transparent crystalline granule with a purity of ≥98%; urea is granular, reagent grade, with a content of ≥46%; ammonium persulfate is a crystalline granule, reagent grade, with a content of ≥98%.

[0047] Example 2 According to the percentage by mass, the composite water purifier S-2 of Example 2 includes 55 wt% modified inorganic polymer coagulant, 10 wt% modified natural polymer (PDMC-AM-St), 33 wt% inorganic salt, 1.5 wt% coagulant and 0.5 wt% solvent; the inorganic salt is a mixture of aluminum chloride trihydrate and calcium chloride, with a mass ratio of 7:3; the coagulant is polyethylene oxide; the solvent is ethanol; the modified inorganic polymer coagulant is modified polyaluminum chloride, and the basicity is 60wt%; the relative molecular mass of the modified natural polymer (PDMC-AM-St) is 2.9 million; The preparation method of composite water purifier S-2 comprises: (1) First, the modified polyaluminium chloride is pumped into the 1# enameled reactor and stirred at a speed of 60 rpm; (2) The inorganic salt mixture is pumped into the 1# reactor and stirred for 20 min to obtain a mixed solution A; (3) The coagulant and solvent are pumped into the 2# reactor and stirred at a slow speed of 30 rpm for 20 min, and the modified natural polymer PDMC-AM-St is slowly added into the reactor. After continuous stirring for 25 min, a mixed solution B is obtained; (4) The mixed solution B from the 2# reactor is pumped into the 1# enameled reactor and stirred with the mixed solution A at a speed of 45 rpm for 40 min to obtain a composite water purifier; The preparation method of modified polyaluminium chloride comprises: adding hydrochloric acid and sulfuric acid solution into a reactor, adding aluminium hydroxide and bauxite in sequence under stirring, reacting at 110°C for 2.5 hours under normal pressure to obtain an acidic system solution, wherein the main component of the system is aluminium chloride and contains a small amount of oligomeric polyaluminium chloride; cooling to 70°C, adding high-calcium fly ash, calcium aluminate powder and pure water in sequence under stirring, reacting at 100°C for 2.5 hours, and after the reaction is completed, filtering at 90°C through a 100-mesh plate-frame filter to obtain a suspended modified polyaluminium chloride solution; The raw materials for preparing the modified polyaluminium chloride include: 7wt% high calcium fly ash, 20wt% bauxite, 3wt% aluminium hydroxide, 8wt% calcium aluminate powder, 60wt% hydrochloric acid and 2wt% sulfuric acid; The concentration of hydrochloric acid used is 25%; the concentration of sulfuric acid is 95%; the mass content of aluminum oxide in aluminum hydroxide is 64%, and the particle size is 150 mesh; the mass content of aluminum oxide in bauxite is 30%, and the particle size is 200 mesh; the mass content of aluminum oxide in high-calcium fly ash is 26.5%, the mass content of silicon dioxide is 40.1%, the mass content of active calcium oxide is 11.3%, the water absorption is 125%, and the particle size is 300 mesh; the mass content of aluminum oxide in calcium aluminate powder is 50%, and the particle size is 200 mesh; The method for preparing the modified natural macromolecular polymer PDMC-AM-St comprises: Put modified starch St and pure water into a reactor, start stirring, and form a St emulsion suspension; after stirring for 10 minutes, introduce nitrogen for 30 minutes to fully remove oxygen, heat the reactor jacket, and ensure that the suspension is heated to 50°C; add sodium thiosulfate and sodium persulfate solutions to the reactor one by one, and after 10 minutes, add the prepared acrylamide AM solution and methacryloyloxyethyl trimethyl ammonium chloride DMC solution to the reactor at a certain drop rate at the same time, and the dropwise addition is completed after 40 minutes, stop stirring, and continue to react at 50°C for 2.5 hours to obtain a liquid modified natural polymer PDMC-AM-St copolymer; the raw materials for preparing the modified natural polymer PDMC-AM-St include: 10wt% St starch, 14wt% DMC, 26wt% AM, and 50wt% pure water; wherein the mass ratio of methacryloyloxyethyl trimethyl ammonium chloride, acrylamide and modified starch is 1.4:2.6:1; St starch is phosphate modified starch, industrial grade, with a particle size of 200 mesh; DMC is a colorless, transparent or slightly yellow liquid with a salt content of 78.8% and a salt content of ≤1.5%; AM is a colorless, transparent crystalline granule with a content of ≥98%; sodium thiosulfate is granular, industrial grade, with a content of ≥46%; sodium persulfate is a crystalline granule, reagent grade, with a content of ≥98%.

[0048] Example 3 According to the percentage by mass, the composite water purifier S-3 of Example 1 includes 64 wt% modified inorganic polymer coagulant, 6 wt% modified natural polymer (PDMD-AM-St), 28 wt% inorganic salt, 1.5 wt% coagulant and 0.5 wt% solvent; the inorganic salt is a mixture of aluminum sulfate and ferric chloride, with a mass ratio of 4:6; the coagulant is polyvinyl pyrrolidone and polyethylene oxide, with a mass ratio of 3:7; the solvent is acetic acid; the modified inorganic polymer coagulant is modified polyaluminum ferric chloride, with a basicity of 55wt%; the relative molecular mass of the polymer (PDMD-AM-St) is 2.55 million; The preparation method of composite water purifier S-3 comprises: (1) First, the modified polyaluminium ferric chloride is pumped into the 1# enameled reactor and stirred at a speed of 120 rpm; (2) The inorganic salt mixture is pumped into the 1# reactor and stirred for 20 min to obtain a mixed solution A; (3) The coagulant and solvent are pumped into the 2# reactor and stirred at a slow speed of 55 rpm for 20 min, and the modified natural high molecular polymer PDMD-AM-St is slowly added into the reactor. After continuous stirring for 30 min, a mixed solution B is obtained; (4) The mixed solution B from the 2# reactor is pumped into the 1# enameled reactor and stirred with the mixed solution A at a speed of 45 rpm for 40 min to obtain a composite water purifier; The preparation method of modified polyaluminium ferric chloride comprises: adding hydrochloric acid and sulfuric acid solution into a reactor, adding aluminium hydroxide and bauxite in sequence under stirring, reacting at 100°C for 3 hours under normal pressure to obtain an acidic system solution, wherein the main component of the system is aluminium chloride and contains a small amount of oligomeric polyaluminium chloride; cooling to 75°C, adding high-calcium fly ash, calcium aluminate powder and pure water in sequence under stirring, reacting at 110°C for 2.5 hours, and after the reaction is completed, filtering at 90°C through a 100-mesh plate and frame filter to obtain a suspended modified polyaluminium ferric chloride solution; The raw materials for preparing the modified polyaluminium ferric chloride include: 3.5wt% high-calcium fly ash, 25wt% bauxite, 2wt% aluminium hydroxide, 8.5wt% calcium aluminate powder, 58wt% hydrochloric acid, and 3wt% sulfuric acid; The concentration of hydrochloric acid used is 25%; the concentration of sulfuric acid is 95%; the mass content of aluminum oxide in aluminum hydroxide is 64%, and the particle size is 150 mesh; the mass content of aluminum oxide in bauxite is 30%, of which the iron oxide content is 3.5wt%, and the particle size is 200 mesh; the mass content of aluminum oxide in high-calcium fly ash is 25%, the mass content of silicon dioxide is 40%, the mass content of active calcium oxide is 10%, the water absorption is 120%, and the particle size is 300 mesh; the mass content of aluminum oxide in calcium aluminate powder is 50%, the iron oxide content is 4%, and the particle size is 200 mesh; The method for preparing the modified natural high molecular polymer PDMD-AM-St comprises: St and pure water were put into the reactor, stirring was started to form a St emulsion suspension; after stirring for 10 minutes, nitrogen was introduced for 30 minutes to fully remove oxygen, and the reactor jacket was heated to ensure that the suspension was heated to 45°C; urea and ammonium persulfate solution were added to the reactor one by one, and after 10 minutes, the prepared AM solution and DMD solution were added to the reactor at a certain drop rate at the same time, and the dropwise addition was completed after 40 minutes, stirring was stopped, and the reaction was continued at 45°C for 2 hours to obtain a viscous and translucent modified natural polymer PDMD-AM-St copolymer; the raw materials for preparing the modified natural polymer PDMD-AM-St include: 9wt% St, 14wt% DMD, 22wt% AM, and 55wt% pure water; wherein the mass ratio of DMD, AM, and St is 1.56:2.44:1; St starch is phosphate-modified starch, industrial grade, with a particle size of 200 mesh; DMD is a colorless, transparent or slightly yellow liquid with a salt content of 60% and a salt content of ≤1.5%; AM is a colorless, transparent crystalline granule with a salt content of ≥98%; urea is granular, reagent grade, with a salt content of ≥46%; ammonium persulfate is a crystalline granule, reagent grade, with a salt content of ≥98%.

[0049] Example 4 The method of this embodiment is the same as that of Example 1, except that the mass fraction of the modified inorganic polymer coagulant of the composite dephosphorization agent S-4 of this embodiment is 75wt%, the mass fraction of the modified natural polymer is 10wt%, the mass fraction of the inorganic salt is 14wt%, the mass fraction of the coagulant aid is 0.5wt%, and the mass fraction of the solvent is 0.5wt%.

[0050] Example 5 The method of this embodiment is the same as that of Embodiment 1, except that in the composite phosphorus removal agent S-5 of this embodiment, the basicity of the modified inorganic polymer coagulant is 40 wt %, and the relative molecular mass of the modified natural polymer is 4.5 million.

[0051] Example 6 The method of this embodiment is the same as that of Embodiment 1, except that in the preparation method of the composite dephosphorization agent S-6 of this embodiment, the stirring rate of step (3) is 130 rpm, and the stirring rate of step (4) is 125 rpm.

[0052] Example 7 The method of this embodiment is the same as that of Example 1, except that when preparing the modified natural high molecular polymer in the composite phosphorus removal agent S-7 of this embodiment, the mass ratio of dimethyldiallylammonium chloride, acrylamide and modified starch is 0.1:5.0:1.

[0053] Comparative Example 1 This comparative example uses commercially available polyaluminium chloride as a water purifier, with the product number being Y0528ZSBB-2.

[0054] Comparative Example 2 The method of this comparative example is the same as that of Example 1, except that the composite water purifier D-2 of this comparative example does not include a modified natural high molecular polymer; it is composed of 78% modified inorganic high molecular coagulant, 20% inorganic salt, 1.5% coagulant aid and 0.5% solvent.

[0055] Comparative Example 3 The method of this comparative example is the same as that of Example 1, except that the composite water purifier D-3 of this comparative example does not include a modified inorganic polymer coagulant; it is composed of 78% modified natural polymer, 20% inorganic salt, 1.5% coagulant aid and 0.5% solvent.

[0056] Comparative Example 4 The method of this comparative example is the same as that of Example 1, except that the composite water purifier D-4 of this comparative example uses a modified inorganic polymer coagulant polyaluminum chloride with a basicity of 40wt%, and the modified natural polymer uses a DMD-AM copolymer polymer with a relative molecular mass of 6 million.

[0057] Test Case The composite water purifiers of Examples 1, 4 to 7 and Comparative Examples 1 to 4 were tested. The composite water purifiers were tested in Zaohua Sewage Treatment Plant. After a certain amount of the composite water purifier was added and the hydraulic retention time was 15 minutes, the supernatant was taken for detection. The results are shown in Table 1. When 0 ml (initial) was added, the remaining total phosphorus was 1.12 mg / L and the remaining turbidity (NTU) was 17.22. The composite water purifiers of Example 2 and Comparative Example 1 were tested. The composite water purifiers were tested in a western sewage treatment plant. After a certain amount of the composite water purifier was added and the hydraulic retention time was 15 minutes, the supernatant was taken for testing. The results are shown in Table 2. The composite water purifiers of Example 3 and Comparative Example 1 were tested. The composite water purifiers were tested in the Xiannv River Sewage Treatment Plant. After adding a certain amount of the composite water purifier, the supernatant was taken for detection. The results are shown in Table 3. In water treatment, the effective content of alumina in liquid polyaluminium chloride is generally 10wt%. For accurate comparison of test results, the effective content of alumina in the examples and comparative examples was diluted 10 times to a value of 1wt% during the test of this application. Blank parallel samples were set for each test, and errors were allowed between the blank parallel samples. In the test examples of this application, the initial residual phosphorus content (TP) and the residual turbidity (NTU) of the sewage were within a reasonable error range and did not affect the removal rate.

[0058] The total phosphorus content was detected by a visible light spectrophotometer; the total phosphorus removal rate was calculated as follows: (total phosphorus content when x mL was added - initial residual total phosphorus content) / initial residual total phosphorus content * 100%; The turbidity is tested by a turbidity meter, and the turbidity removal rate is calculated as follows: (turbidity when x mL is added - initial residual turbidity) / initial residual turbidity * 100%; Dosage of reagent: (dosage when the total phosphorus removal rate and turbidity removal rate of the comparison example are optimal - the minimum dosage when the total phosphorus removal rate and turbidity removal rate of the embodiment are better than the comparison example) / dosage when the total phosphorus removal rate and turbidity removal rate of the comparison example are optimal * 100%.

[0059] Table 1

[0060] According to the data in Table 1, the total phosphorus removal rate and turbidity removal rate of the composite water purifier disclosed in the present invention are higher than those of the comparative example, and the effect of the composite water purifier is better than that of the comparative example. According to the results in Table 1, when the dosage of the water purifier of comparative example 1 is 1.4 ml, the phosphorus removal rate and turbidity removal rate are both at the best values, which are 77.68% and 68.52% respectively. The minimum dosage of the composite water purifier S-1 for the phosphorus removal rate to reach more than 77.68% is 0.8 ml. At this time, the phosphorus removal rate and turbidity removal rate are 78.57% and 84.26% respectively, which are better than the removal rate when the dosage of D-1 is 1.4 ml. It can be theoretically calculated that the composite water purifier S-1 can save about 42.86% of the dosage of the agent compared with D-1.

[0061] By comparing Example 1 and Example 4, it can be seen that the mass fraction of each component of the composite water purifier of Example 1 is within the preferred range of the present disclosure, the purification effect of the composite water purifier is better, and the total phosphorus removal rate and turbidity removal rate are higher. By comparing Example 1 and Example 5, it can be seen that the basicity of the modified inorganic polymer coagulant and the relative molecular mass of the modified natural polymer of the composite water purifier of Example 1 are within the preferred range of the present disclosure, the purification effect of the composite water purifier is better, and the total phosphorus removal rate and turbidity removal rate are higher. By comparing Example 1 and Example 6, it can be seen that the conditions during the preparation of the composite water purifier of Example 1 are within the preferred range of the present disclosure, the purification effect of the composite water purifier is better, and the total phosphorus removal rate and turbidity removal rate are higher. By comparing Example 1 and Example 7, it can be seen that the proportion of the preparation raw materials of the modified natural polymer in the composite water purifier of Example 1 is within the preferred range of the present disclosure, the purification effect of the composite water purifier is better, and the total phosphorus removal rate and turbidity removal rate are higher.

[0062] Table 2

[0063] According to the data in Table 2, when the dosage of D-1 is 1.6 ml, the phosphorus removal rate and turbidity removal rate are at the best values, which are 84.62% and 62.23% respectively; the total phosphorus removal rate of the composite water purifier S-2 in Example 2 reaches more than 84.62%, and the minimum dosage when the remaining total phosphorus is less than 0.20 mg / L is 1.2 ml. At this time, the total phosphorus removal rate and turbidity removal rate are 89.23% and 86.96% respectively, which are better than the removal rate when the dosage of D-1 is 1.6 ml. It is calculated that the composite water purifier S-2 in Example 2 can save about 25% of the dosage of the agent compared with D-1.

[0064] Table 3

[0065] According to the data in Table 3, the purification effect of composite water purifier S-3 under low temperature, low turbidity and high total phosphorus conditions is better than that of D-1; when the dosage of D-1 is 1.4 ml, its phosphorus removal rate reaches the best level, which is 80.94%. The total phosphorus removal rate of composite water purifier S-3 reaches above 80.94%, and the minimum dosage for the remaining total phosphorus to be less than 0.77 mg / L is 1.0 ml. It can be calculated that composite water purifier S-3 can save 28.57% of the dosage of the agent compared with D-1.

[0066] According to the data in Tables 1 to 3, the composite water purifier disclosed in the present invention has good phosphorus and turbidity removal effects under various working conditions, has a strong broad spectrum, and has a strong ability to resist the impact of abnormal water inflow.

[0067] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0069] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A composite phosphorus removal agent, characterized in that: The composite phosphorus removal agent comprises 45 wt% to 75 wt% of a modified inorganic polymer coagulant, 2 wt% to 15 wt% of a modified natural polymer, 5 wt% to 40 wt% of an inorganic salt, 0.5 wt% to 5 wt% of a coagulant aid and 0.1 wt% to 0.5 wt% of a solvent; Among them, the modified inorganic polymer coagulant includes modified polyaluminum chloride and / or modified polyaluminum ferric chloride; the basicity of the modified inorganic polymer coagulant is 40~85wt%; the modified natural polymer includes one or more of dimethyldiallylammonium chloride-acrylamide-modified starch copolymer and methacryloyloxyethyltrimethylammonium chloride-acrylamide-modified starch copolymer; the relative molecular mass of the modified natural polymer is 500,000~4.5 million.

2. The composite phosphorus removal agent according to claim 1, wherein The composite phosphorus removal agent comprises 50wt% to 70wt% of a modified inorganic polymer coagulant, 3wt% to 10wt% of a modified natural polymer, 8wt% to 33wt% of an inorganic salt, 1wt% to 4.5wt% of a coagulant aid and 0.2wt% to 0.45wt% of a solvent; The basicity of the modified inorganic polymer coagulant is 50-75wt%; the relative molecular mass of the modified natural polymer is 1-3 million.

3. The composite phosphorus removal agent according to claim 1, wherein The inorganic salt includes one or more of aluminum chloride, aluminum sulfate, calcium chloride, ferric chloride and ferric sulfate; The coagulant aid includes one or more of polyethyleneimine, polyvinyl pyrrolidone and polyethylene oxide; The solvent includes water and an organic solvent, and the organic solvent is selected from one or more of methanol, ethanol, ethylene glycol and acetic acid.

4. The composite phosphorus removal agent according to claim 1, wherein The preparation method of the modified polyaluminium chloride comprises the following steps: Contacting hydrochloric acid, sulfuric acid, aluminum hydroxide and first bauxite to perform a first reaction to obtain a first reactant; contacting the first reactant, high-calcium fly ash, first calcium aluminate powder and water to perform a second reaction, and subjecting the second reactant to a first filter press treatment; The conditions of the first reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the second reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the first filter press treatment include: at 85-95°C, the plate frame mesh number used in the filter press treatment is 80-120 mesh; The raw materials for preparing the modified polyaluminium chloride include: 2.5 wt% to 8.5 wt% of high calcium fly ash, 2.5 wt% to 25 wt% of first bauxite, 5 wt% to 30 wt% of first calcium aluminate powder, 0 wt% to 30 wt% of aluminium hydroxide, 45 wt% to 60 wt% of hydrochloric acid and 2 wt% to 5 wt% of sulfuric acid; Among them, the concentration of the hydrochloric acid is 20%~31%; the concentration of the sulfuric acid is 90%~98%; the mass fraction of aluminum oxide in the aluminum hydroxide is 60%~68%, and the particle size is 130~160 mesh; the mass fraction of aluminum oxide in the first bauxite is 25%~35%, and the particle size is 180~220 mesh; the mass fraction of aluminum oxide in the high-calcium fly ash is more than 25%, the mass fraction of silicon dioxide is less than 45%, the mass fraction of active calcium oxide is more than 10%, the water absorption is more than 120%, and the particle size is 280~320 mesh; the mass fraction of aluminum oxide in the first calcium aluminate powder is 40%~50%, and the particle size is 180~220 mesh.

5. The composite phosphorus removal agent according to claim 1, wherein The preparation method of the modified polyaluminium ferric chloride comprises the following steps: The hydrochloric acid, sulfuric acid, aluminum hydroxide and the second bauxite are contacted to perform a third reaction to obtain a third reactant; the third reactant, high calcium fly ash, the second calcium aluminate powder and water are contacted to perform a fourth reaction, and the fourth reactant is subjected to a second filter press treatment; The conditions of the third reaction include: temperature of 75-115°C, time of 2-3h; the conditions of the fourth reaction include: temperature of 55-75°C, time of 2-3h; the conditions of the second filter press treatment include: at 85-95°C, the plate frame mesh number used in the second filter press treatment is 80-120 mesh; The raw materials for preparing the modified polyaluminium ferric chloride include: 2.5wt% to 5wt% of high-calcium fly ash, 10wt% to 30wt% of a second bauxite, 5wt% to 30wt% of a second calcium aluminate powder, 0wt% to 15wt% of aluminium hydroxide, 40wt% to 60wt% of hydrochloric acid and 2.5wt% to 5wt% of sulfuric acid; Among them, the mass fraction of aluminum oxide in the second bauxite is 25%~35%, the mass fraction of iron oxide is 3%~5%, and the particle size is 180~220 mesh; the mass fraction of aluminum oxide in the second calcium aluminate powder is 40%~50%, the mass fraction of iron oxide is 3%~8%, and the particle size is 180~220 mesh.

6. The composite phosphorus removal agent according to claim 1, wherein The preparation method of the dimethyldiallylammonium chloride-acrylamide-modified starch copolymer comprises: Mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and dimethyldiallylammonium chloride; The mass ratio of the dimethyldiallylammonium chloride, the acrylamide and the modified starch is (0.2-2.5): (1-3.5): 1, preferably (0.8-2.0): (1.5-3.3): 1; the reaction temperature is 40-60°C, and the reaction time is 2-3h; the initiator includes urea and / or ammonium persulfate; The modified starch is cationic etherified modified starch and / or phosphate modified corn starch, and the particle size is 150-200 meshes.

7. The composite phosphorus removal agent according to claim 1, wherein: The preparation method of the methacryloyloxyethyl trimethylammonium chloride-acrylamide-modified starch copolymer comprises: Mixing modified starch and water to form a modified starch suspension, placing the modified starch suspension under an inert atmosphere, adding an initiator, and reacting the modified starch suspension, acrylamide and methacryloyloxyethyl trimethylammonium chloride; The mass ratio of the methacryloyloxyethyl trimethylammonium chloride, the acrylamide and the modified starch is (0.3-2.4):(1-3.5):1, preferably (0.8-2.0):(1.5-3.3):1; the reaction temperature is 45-70°C, and the reaction time is 2-3h; the initiator includes sodium thiosulfate and / or sodium persulfate.

8. A method for preparing the composite phosphorus removal agent according to any one of claims 1 to 7, characterized in that: The method comprises: The modified inorganic polymer coagulant and the inorganic salt are mixed for the first time to obtain a first mixed solution; the coagulant aid, the solvent and the modified natural polymer are mixed for the second time to obtain a second mixed solution; and the second mixed solution and the first mixed solution are mixed for the third time.

9. The method according to claim 8, wherein: The first mixing conditions include: carrying out under stirring conditions, the stirring rate is 60-120 rpm, and the stirring time is 15-30 min; The second mixing conditions include: being carried out under stirring conditions, the stirring rate is 30-60 rpm, and the stirring time is 20-30 min; The third mixing condition includes: carrying out under stirring condition, the stirring rate is 45-65 rpm, and the stirring time is 30-50 min.

10. Use of the composite water purifier according to any one of claims 1 to 7 in sewage and wastewater treatment, characterized in that: The content of phosphorus in the wastewater is 1-8 mg / L, and the mass ratio of the composite water purifier to the phosphorus is 30-150:1.

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