Aluminum-manganese composite coagulant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sewage treatment agents, in particular to an aluminum-manganese composite coagulant and a preparation method and application thereof. The preparation method provided by the invention comprises the following steps: dissolving an aluminum salt and a manganese salt to obtain a solution containing the aluminum salt and the manganese salt; mixing the solution containing the aluminum salt and the manganese salt with an alkaline solution for the first time to obtain a first mixed solution; and secondarily mixing the first mixed solution, a sodium silicate solution and a polyacrylamide solution to obtain a second mixed solution, and standing and curing the second mixed solution to obtain the aluminum-manganese composite coagulant. The aluminum-manganese composite coagulant obtained by the preparation method disclosed by the invention has a wider pH application range, the capability of removing natural organic matters is improved, and the chromaticity problem caused by manganese residues can also be reduced. And the flocculant is extremely easy to flocculate and settle in the water treatment process, so that chemical residues can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment agents, and in particular to an aluminum-manganese composite coagulant and a preparation method and application thereof. Background Art

[0002] Humic acid (HA) is the main natural organic matter (NOM) and is widely found in soil, water and sediment. In the process of drinking water treatment, chlorine is usually used as a disinfectant. Chlorine and HA react to form disinfection by-products (DBPs), which pose a certain threat to the water quality safety of drinking water. Coagulation is an important part of the drinking water treatment process. It is widely used in water and wastewater treatment because of its low cost, simple operation and high efficiency in removing suspended particles and organic matter. The type of coagulant is the key factor in determining the coagulation effect.

[0003] Traditional aluminum-based coagulants are difficult to fully play their role in actual use due to some shortcomings (such as large dosage, large sludge discharge, low efficiency in removing small molecular organic matter, and the optimal removal pH range of 5 to 7, while the pH value of natural water bodies is usually neutral or even weakly alkaline). Compared with a single coagulant, a combination of multiple metal salts is expected to give full play to the advantages of multiple metal-based coagulants and make up for the shortcomings of a single metal-based coagulant. Chinese patent CN102897878A discloses a high-efficiency water treatment flocculant compounded with potassium permanganate, aluminum salt flocculant, and auxiliary coagulant in a specific proportion, which can maximize the coagulant ability of potassium permanganate and auxiliary coagulant, thereby improving the efficiency of composite coagulants in removing organic pollutants, algae and turbidity, eliminating the precursors of disinfection by-products in water, improving water quality and saving reagents. However, there are still some problems in this process, such as water quality safety hazards caused by aluminum and manganese residues and excessive residual manganese. At the same time, special attention should be paid to the ratio of permanganate and aluminum salt coagulants. An unbalanced ratio may cause excessive oxidation and reduce coagulation performance, or excessive coagulants and cause floc stabilization. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides an aluminum-manganese composite coagulant and a preparation method and application thereof. The aluminum-manganese composite coagulant provided by the present invention has a wider pH adaptability range, can improve the ability to remove natural organic matter, and can also reduce the chromaticity problem caused by manganese residues.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing an aluminum-manganese composite coagulant, comprising the following steps:

[0007] dissolving aluminum salt and manganese salt to obtain a solution containing aluminum salt and manganese salt;

[0008] The solution containing aluminum salt and manganese salt and the alkaline solution are first mixed to obtain a first mixed solution;

[0009] The first mixed solution, sodium silicate solution and polyacrylamide solution are mixed for a second time, and the obtained second mixed solution is left to stand and mature to obtain an aluminum-manganese composite coagulant.

[0010] Preferably, the aluminum salt is aluminum chloride and / or aluminum sulfate; and the manganese salt is manganese chloride and / or manganese sulfate.

[0011] Preferably, in the solution containing aluminum salt and manganese salt, the molar ratio of aluminum ions to manganese ions is 2 to 9:1.

[0012] Preferably, the alkaline solution is one or more of sodium hydroxide solution, sodium bicarbonate solution, potassium hydroxide solution and potassium bicarbonate solution, and the concentration of the alkaline solution is 0.25-0.50 mol / L; the alkalinity of the first mixed solution is 1.0-2.0.

[0013] Preferably, the first mixing is to stir the solution containing aluminum salt and manganese salt under water bath conditions, and at the same time, dropwise add the alkaline solution into the solution containing aluminum salt and manganese salt.

[0014] Preferably, the temperature of the water bath is 40-70° C., and the stirring speed is 350-400 rpm.

[0015] Preferably, the mass concentration of the sodium silicate solution is 10-30%; the mass concentration of the polyacrylamide solution is 2-5%.

[0016] Preferably, the static aging time is 12 to 24 hours.

[0017] The present invention also provides an aluminum-manganese composite coagulant prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides an aluminum-manganese composite coagulant prepared by the preparation method described in the above technical solution or the use of the above aluminum-manganese composite coagulant in treating organic matter in water under moderately alkaline conditions, wherein the organic matter is humic acid.

[0019] The invention provides a method for preparing an aluminum-manganese composite coagulant, comprising the following steps: dissolving an aluminum salt and a manganese salt to obtain a solution containing the aluminum salt and the manganese salt; first mixing the solution containing the aluminum salt and the manganese salt and an alkaline solution to obtain a first mixed solution; second mixing the first mixed solution, a sodium silicate solution and a polyacrylamide solution, and allowing the obtained second mixed solution to stand and mature to obtain the aluminum-manganese composite coagulant.

[0020] Compared with the prior art, the preparation method provided by the present invention has the following advantages:

[0021] (1) The preparation conditions of the present invention can be at room temperature, the operation is simple, the energy consumption is low, the process is safe and environmentally friendly, the raw materials are cheap and easy to obtain, and the obtained coagulant is economical and efficient, which is suitable for market promotion and application.

[0022] (2) The present invention utilizes the inorganic component aluminum manganese salt to dissolve, add alkali, hydrolyze and condense to form Al-O-Mn bonds to achieve compounding. The composite aluminum manganese composite coagulant combines the advantages of aluminum salt and manganese salt. The aluminum salt has a strong electrical neutralization ability. The addition of a certain amount of manganese salt makes the original single aluminum salt coagulant have a wider pH adaptability range, improves the ability to remove natural organic matter, and can also reduce the color problem caused by manganese residues.

[0023] (3) The present invention adds sodium silicate during the preparation process, and forms Si-OH-containing polysilicic acid through reaction, which has strong adsorption enhancement ability and strong adaptability to pH. It can also connect Al and Mn through condensation reaction to form a stable chemical bond, which is very easy to flocculate and settle during water treatment, thereby reducing chemical residues.

[0024] (4) In the preparation process, a certain amount of polyacrylamide is added to the present invention. The polyacrylamide is a high molecular polymer with a relatively high molecular chain and functional group. Compared with traditional inorganic coagulants, the polyacrylamide has enhanced adsorption and bridging capabilities for pollutants in water and improved removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Fourier infrared spectra of the coagulants prepared in Examples 1 to 2 of the present invention and Comparative Example 1 are shown;

[0026] Figure 2 The effect of PAC and coagulants with different aluminum-manganese ratios on humic acid removal at different pH values ​​under two alkalinities;

[0027] Figure 3 This is an analysis chart of the removal rate of humic acid at different dosages of the aluminum-manganese polymer coagulant prepared in Example 2 of the present invention and the simple compound conventional coagulant in Comparative Example 3;

[0028] Figure 4 The aluminum and manganese residual amounts of the aluminum-manganese polymer coagulant prepared in Example 2 of the present invention and the comparative example 3 after simply compounding with a conventional coagulant to treat humic acid water;

[0029] Figure 5 This is a morphological distribution diagram of the hydroxyl complex species of the aluminum-manganese hydrolysis of the aluminum-manganese polymer coagulant prepared in Examples 2 and 9-10 of the present invention. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing an aluminum-manganese composite coagulant, comprising the following steps:

[0031] dissolving aluminum salt and manganese salt to obtain a solution containing aluminum salt and manganese salt;

[0032] The solution containing aluminum salt and manganese salt and the alkaline solution are first mixed to obtain a first mixed solution;

[0033] The first mixed solution, sodium silicate solution and polyacrylamide solution are mixed for a second time, and the obtained second mixed solution is left to stand and mature to obtain an aluminum-manganese composite coagulant.

[0034] The invention dissolves aluminum salt and manganese salt to obtain a solution containing aluminum salt and manganese salt.

[0035] As an embodiment, the aluminum salt is aluminum chloride and / or aluminum sulfate. In a specific embodiment, the aluminum salt can be aluminum chloride. As an embodiment, the purity of the aluminum chloride is analytically pure.

[0036] As an embodiment, the manganese salt is manganese chloride and / or manganese sulfate. In a specific embodiment, the manganese salt can be manganese chloride. As an embodiment, the purity of the manganese chloride is analytically pure.

[0037] As an embodiment, in the solution containing aluminum salt and manganese salt, the molar ratio of aluminum ions to manganese ions is 2 to 9:1. In specific embodiments, the molar ratio of aluminum ions to manganese ions can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 and 9:1.

[0038] As an embodiment, the dissolving method is stirring, and the stirring time is ≥ 20 min.

[0039] After obtaining the solution containing aluminum salt and manganese salt, the present invention first mixes the solution containing aluminum salt and manganese salt and the alkaline solution to obtain a first mixed solution.

[0040] As an embodiment, the first mixing is to stir the solution containing aluminum salt and manganese salt under water bath conditions, and at the same time, dropwise add the alkaline solution into the solution containing aluminum salt and manganese salt.

[0041] As an embodiment, the alkaline solution is one or more of sodium hydroxide solution, sodium bicarbonate solution, potassium hydroxide solution and potassium bicarbonate solution. In a specific embodiment, the alkaline solution can be sodium hydroxide solution. As an embodiment, the concentration of the alkaline solution is 0.25-0.5 mol / L. In a specific embodiment, the concentration of the alkaline solution can be 0.3-0.45 mol / L.

[0042] As an embodiment, the temperature of the water bath is 40-70°C. In a specific embodiment, the temperature of the water bath may be 40°C.

[0043] As an implementation mode, the stirring rotation speed is 350-400 rpm.

[0044] As an embodiment, the dropping speed is 14 drops / 30s.

[0045] As an implementation manner, the alkalinity of the first mixed solution is 1.0-2.0. In a specific embodiment, the alkalinity of the first mixed solution may be 1.0 or 2.0.

[0046] After obtaining the first mixed solution, the present invention performs a second mixing of the first mixed solution, the sodium silicate solution and the polyacrylamide solution, and the obtained second mixed solution is left to stand and mature to obtain the aluminum-manganese composite coagulant.

[0047] As an embodiment, the mass concentration of the sodium silicate solution is 10-30%, and in a specific embodiment, the mass concentration of the sodium silicate solution is 20%. As an embodiment, the mass concentration of the polyacrylamide solution is 2-5%, and in a specific embodiment, the mass concentration of the polyacrylamide solution can be 3%.

[0048] As an embodiment, the second mixing method is stirring, the stirring speed is 350-400 rpm, and the time is ≥60 min.

[0049] As an implementation mode, the standing and aging time is 12 to 24 hours. In a specific embodiment, the standing and aging time can be 24 hours.

[0050] The present invention also provides an aluminum-manganese composite coagulant prepared by the above-mentioned preparation method.

[0051] The present invention also provides the aluminum-manganese composite coagulant prepared by the above-mentioned preparation method or the use of the aluminum-manganese composite coagulant in treating organic matter in water under neutral or weakly alkaline conditions.

[0052] As an embodiment, the organic matter is humic acid.

[0053] As an embodiment, during the application, the amount of the aluminum-manganese composite coagulant added is 20-30 mg per 1 L of the water to be treated. As an embodiment, the pH value of the water to be treated is 6-8.

[0054] When the aluminum-manganese composite coagulant provided by the present invention is used to treat water, it has the following advantages:

[0055] (1) The coagulant provided by the present invention combines aluminum and manganese salts, and the coagulant has strong stability and only needs to be added once to ensure a good coagulation effect. Compared with a single coagulant, the coagulant of the present invention is more convenient to use.

[0056] (2) The coagulant provided by the present invention has a stronger ability to remove humic acid under moderately alkaline conditions and has a stronger removal effect than a single aluminum-based salt coagulant.

[0057] The present invention has no special requirements for the specific method of the application, and the application can be carried out using methods well known to those skilled in the art.

[0058] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0059] Example 1

[0060] 27 mL of 1 mol / L AlCl3 solution and 3 mL of 1 mol / L MnCl2 solution were mixed in a beaker and stirred magnetically for 20 min to obtain a mixed solution;

[0061] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of a 0.5 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 2.0, to obtain an alkaline mixed solution (i.e., the first mixed solution);

[0062] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=9:1 and alkalinity 2.

[0063] Example 2

[0064] Mix 20 mL of 1 mol / L AlCl3 solution and 10 mL of 1 mol / L MnCl2 solution in a beaker, and stir magnetically for 20 min to obtain a mixed solution;

[0065] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of 0.5 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 2.0, to obtain an alkaline mixed solution;

[0066] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=2:1 and alkalinity 2.

[0067] Example 3

[0068] Mix 10 mL of 1 mol / L AlCl3 solution and 20 mL of 1 mol / L MnCl2 solution in a beaker, and stir magnetically for 20 min to obtain a mixed solution;

[0069] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of 0.5 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 2.0, to obtain an alkaline mixed solution;

[0070] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=1:2 and alkalinity 2.

[0071] Example 4

[0072] 3 mL of 1 mol / L AlCl3 solution and 27 mL of 1 mol / L MnCl2 solution were mixed in a beaker and stirred magnetically for 20 min to obtain a mixed solution;

[0073] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of 0.5 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 2.0, to obtain an alkaline mixed solution;

[0074] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=1:9 and alkalinity 2.

[0075] Example 5

[0076] 27 mL of 1 mol / L AlCl3 solution and 3 mL of 1 mol / L MnCl2 solution were mixed in a beaker and stirred magnetically for 20 min to obtain a mixed solution;

[0077] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of a 0.25 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 1.0, to obtain an alkaline mixed solution;

[0078] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=9:1 alkalinity 1.

[0079] Example 6

[0080] Mix 20 mL of 1 mol / L AlCl3 solution and 10 mL of 1 mol / L MnCl2 solution in a beaker, and stir magnetically for 20 min to obtain a mixed solution;

[0081] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of a 0.25 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 1.0, to obtain an alkaline mixed solution;

[0082] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=2:1 and alkalinity 1.

[0083] Example 7

[0084] Mix 10 mL of 1 mol / L AlCl3 solution and 20 mL of 1 mol / L MnCl2 solution in a beaker, and stir magnetically for 20 min to obtain a mixed solution;

[0085] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of a 0.25 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 1.0, to obtain an alkaline mixed solution;

[0086] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=1:2 and alkalinity 1.

[0087] Example 8

[0088] 3 mL of 1 mol / L AlCl3 solution and 27 mL of 1 mol / L MnCl2 solution were mixed in a beaker and stirred magnetically for 20 min to obtain a mixed solution;

[0089] The mixed solution was placed in a 40° C. water bath for reaction and 120 mL of a 0.25 mol / L NaOH solution was added dropwise at a rate of 14 drops per half minute until the alkalinity B reached 1.0, to obtain an alkaline mixed solution;

[0090] After obtaining the alkaline mixed solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution into the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain an aluminum-manganese composite coagulant with Al:Mn=1:9 and alkalinity 1.

[0091] Example 9

[0092] The only difference from Example 2 is that the basicity is 1.0.

[0093] Example 10

[0094] The only difference from Example 2 is that the basicity is 2.5.

[0095] Comparative Example 1

[0096] Pour 30mL of 1mol / L AlCl3 solution into a beaker and stir magnetically for 20min; put the stirred solution into a 40℃ water bath for reaction, and add 120mL of 0.5mol / LNaOH solution at a rate of 14 drops per half minute until the alkalinity B is 2.0 to obtain an alkaline solution;

[0097] After obtaining the alkaline solution, add 2 mL of 20% sodium silicate solution and 1 mL of 3% polyacrylamide solution to the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24 hours to obtain polyaluminium chloride (PAC) with alkalinity 2.

[0098] Comparative Example 2

[0099] Pour 30mL of 1mol / L AlCl3 solution into a beaker and stir magnetically for 20min; put the stirred solution into a 40℃ water bath for reaction and add 120mL of 0.25mol / LNaOH solution at a rate of 14 drops per half minute until the alkalinity B is 1.0 to obtain an alkaline solution; after obtaining the alkaline solution, add 2mL of 20% sodium silicate solution and 1mL of 3% polyacrylamide solution to the mixed solution, continue stirring and mixing for 30 minutes, put it into a wide-mouth bottle and mature it for 24h to obtain PAC with alkalinity 1.

[0100] Comparative Example 3

[0101] 20 mL of 1 mol / L AlCl3 solution and 10 mL of 1 mol / L MnCl2 solution were successively mixed into a beaker, and 120 mL of ultrapure water was added to dilute the mixture so that the aluminum-manganese concentration was consistent with the composite coagulant of Al:Mn=2:1 to obtain a simple compound mixed solution.

[0102] Figure 1 The Fourier transform infrared spectra of the coagulants prepared in Examples 1 to 2 and Comparative Example 1 are shown in FIG. Figure 1 It can be seen that: Figure 1 The main 3417cm -1 、1642cm -1 、615cm -1 、1100cm -1 These peaks correspond to Al-OH groups, HOH groups and Al-OH-Al groups, confirming the existence of aggregated states in the coagulant.

[0103] Performance characterization:

[0104] Take 20mL of humic acid mother liquor with a concentration of 1g / L into a 2000mL volumetric flask, and dilute to 2000mL to obtain a 10mg / L humic acid solution, adjust the pH to 6, 7, and 8, take 250mL of water samples into 6 stirring cups respectively, and conduct a coagulation experiment under a ZR4-6 six-joint mixer; the coagulation procedure includes: first rapid stirring, then slow stirring, and then sedimentation. The stirring speed of the rapid stirring is 200rpm, the time of rapid stirring is 2min, the stirring speed of the slow stirring is 40rpm, the stirring time is 30min, and the sedimentation time is 30min; after coagulation, take the supernatant and measure the UV254 value with an ultraviolet spectrophotometer.

[0105] Different amounts of the coagulants obtained in the examples and comparative examples were added to the humic acid solution for coagulation water treatment. The treatment results are shown in Figure 2 , Figure 2 Figures a to c are the removal effects of UV254 at different dosages of PAC with alkalinity 2 and coagulants with aluminum-manganese ratios of 9:1, 2:1, 1:2, and 1:9 at pH 6, 7, and 8; Figure 2 d~f are the removal effects of UV254 at different dosages of PAC with alkalinity 1 and aluminum-manganese ratios of 9:1, 2:1, 1:2, and 1:9 at pH = 6, 7, and 8. Figure 2(a~c) It can be seen that at pH=6, the removal rate of the coagulant with PAC and Al:Mn=9:1 of Comparative Example 1 and Example 1 quickly reaches 100% as the dosage increases; at pH=8, the removal rate of PAC of Comparative Example 1 at a dosage of 20 mg / L is 46.79%, while the removal rate of Al:Mn=2:1 coagulant of Example 2 at 20 mg / L is 79.21%. In comparison, the efficiency of manganese-containing coagulants is about 30% higher than that of coagulants without manganese. And under the three pH conditions, the humic acid removal efficiency of the coagulants with Al:Mn=1:2 of Example 3 and Al:Mn=1:9 of Example 4 is worse than that of PAC, Al:Mn=2:1 of Example 2 and Al:Mn=9:1 of Example 1, indicating that the proportion of manganese has an impact on the coagulation effect and should be maintained at a certain proportion to achieve better coagulation efficiency. In addition, Figure 2 In (d~f), it can be seen from the treatment efficiency of the coagulants in comparative example 2 and embodiments 5, 6, 7 and 8 that the humic acid removal rate is lower than that of the coagulants in comparative example 1 and embodiments 1, 2, 3 and 4 at each pH, ​​indicating that the lower the alkalinity, the worse the effect of coagulation in removing humic acid.

[0106] Figure 3 This is an analysis chart of the removal rate of humic acid by the aluminum-manganese polymer coagulant prepared in Example 2 of the present invention and the simple compound conventional coagulant in Comparative Example 3 at different dosages. Figure 3 It can be seen that under the same dosage of coagulant, the aluminum-manganese polymer coagulant prepared in Example 2 has a significantly higher removal performance for humic acid than the simple compound conventional coagulant prepared in Example 3, with the removal rate increased by 20-41%, indicating that the aluminum-manganese composite coagulant has a higher pollutant removal effect than the traditional simple compound coagulant, has richer dominant aluminum species, and is more conducive to electrical neutralization and adsorption of pollutants. More importantly, Figure 4 ( Figure 4 As shown in the figure, the aluminum and manganese residual amounts after treating humic acid water with the aluminum-manganese polymer coagulant prepared in Example 2 of the present invention and the simply compounded conventional coagulant in Example 3 can be seen that the aluminum and manganese residual amounts in the effluent after removing humic acid with the aluminum-manganese polymer coagulant prepared in Example 2 are significantly reduced compared to the aluminum and manganese residual amounts in the effluent after removing humic acid with the simply compounded conventional coagulant in Example 3, wherein the aluminum residual amount is reduced by 83% and the manganese residual amount is reduced by 65%, and both are lower than the requirements in the relevant drinking water quality standards, indicating that the aluminum-manganese composite coagulant is safer and can ensure healthy water supply.

[0107] Figure 5 The morphological distribution diagram of the hydroxyl complex species of the aluminum-manganese polymer coagulant aluminum-manganese hydrolysis prepared in Examples 2 and 9-10 of the present invention; Figure 5 It can be seen that as the amount of NaOH added increases and the alkalinity increases from 1.0 to 2.5, the dominant species in the aluminum-manganese coagulation is the aggregate (Al+Mn).b The content increased by 35%.

[0108] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an aluminum-manganese composite coagulant, comprising the following steps: dissolving aluminum salt and manganese salt to obtain a solution containing aluminum salt and manganese salt; The solution containing aluminum salt and manganese salt and the alkaline solution are first mixed to obtain a first mixed solution; The first mixed solution, sodium silicate solution and polyacrylamide solution are mixed for a second time, and the obtained second mixed solution is left to stand and mature to obtain an aluminum-manganese composite coagulant.

2. The preparation method according to claim 1, characterized in that The aluminum salt is aluminum chloride and / or aluminum sulfate; the manganese salt is manganese chloride and / or manganese sulfate.

3. The preparation method according to claim 1, characterized in that: In the solution containing aluminum salt and manganese salt, the molar ratio of aluminum ion to manganese ion is 2 to 9:

1.

4. The preparation method according to claim 1, characterized in that: The alkaline solution is one or more of sodium hydroxide solution, sodium bicarbonate solution, potassium hydroxide solution and potassium bicarbonate solution, and the concentration of the alkaline solution is 0.25-0.50 mol / L; the alkalinity of the first mixed solution is 1.0-2.

0.

5. The preparation method according to claim 1, characterized in that: The first mixing is to stir the solution containing aluminum salt and manganese salt under water bath conditions, and at the same time, drop the alkaline solution into the solution containing aluminum salt and manganese salt.

6. The preparation method according to claim 1, characterized in that: The temperature of the water bath is 40-70° C., and the rotation speed of the stirring is 350-400 rpm.

7. The preparation method according to claim 1, characterized in that: The mass concentration of the sodium silicate solution is 10-30%; the mass concentration of the polyacrylamide solution is 2-5%.

8. The preparation method according to claim 1, characterized in that: The standing and aging time is 12 to 24 hours.

9. The aluminum-manganese composite coagulant prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the aluminum-manganese composite coagulant prepared by the preparation method according to any one of claims 1 to 8 or the aluminum-manganese composite coagulant according to claim 9 in treating organic matter in water under moderate alkaline conditions, characterized in that: The organic matter is humic acid.

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