A manganese-doped functionalized polyaluminium chloride flocculant and its preparation method and application

Abstract

The present invention provides a manganese-doped functionalized polyaluminium chloride flocculant, a preparation method, and an application thereof. The method comprises the following steps: respectively weighing manganese dichloride and aluminum chloride, mixing, and stirring uniformly to obtain a manganese-aluminium mixture; mixing water with the manganese-aluminium mixture to obtain a manganese-aluminium mixed solution; mixing a silane reagent with the manganese-aluminium mixed solution, and stirring uniformly to obtain a silane-doped manganese-aluminium mixed slurry; subjecting the silane-doped manganese-aluminium mixed slurry to low-temperature plasma irradiation to obtain a mixed-valence manganese polyaluminium chloride initial liquid; drying and grinding the mixed-valence manganese polyaluminium chloride initial liquid to obtain a manganese-doped functionalized polyaluminium chloride flocculant. The preparation process of the present invention is simple, and the required raw materials are few and easily available. Compared with traditional polyaluminium chloride flocculant materials, the manganese-doped functionalized polyaluminium chloride flocculant prepared by the present invention has a higher COD removal capacity and an oxidation function, and can quickly and efficiently purify high-chroma and high-COD wastewater.

Description

Technical Field

[0001] The present invention belongs to the field of research and development of new environmental protection reagents, and in particular relates to a manganese-doped functionalized polyaluminium chloride flocculant, a preparation method and an application thereof. Background Art

[0002] Polyaluminum chloride (PAC) is currently widely used in the treatment of domestic and industrial wastewater. PAC is an inorganic flocculant that can be used to treat wastewaters of varying water qualities. It offers significant water purification effectiveness, low equipment corrosion, and a wide pH range. It is particularly effective in purifying wastewaters containing high levels of suspended solids. However, when using PAC flocculants to treat wastewaters with high COD and color content, achieving optimal treatment results or high COD removal rates often requires increasing the PAC dosage and combining it with other inorganic or organic flocculants. For some water quality issues, optimal results require pre-adjusting the initial pH of the wastewater and combining it with a coagulant. Therefore, PAC's use is limited in the treatment of wastewaters with high COD and color content, resulting in poor purification performance.

[0003] Currently, polyaluminium chloride (PAC) production methods are relatively simple (acid dissolution or acid leaching and neutralization), and the development of new functionalised PAC flocculants is slow. Existing PAC products on the market are no longer able to meet the increasingly diverse wastewater treatment needs of modern industries. Therefore, addressing existing challenges and industry needs, further developing new technologies and producing new functionalised PAC flocculants is crucial. Summary of the Invention

[0004] In response to the above technical problems, one of the purposes of one embodiment of the present invention is to provide a method for preparing a manganese-doped functionalized polyaluminum chloride flocculant. The preparation process of the present invention is simple, the required raw materials are few and easy to obtain, and the high-chroma and high-COD wastewater can be quickly and efficiently purified.

[0005] One of the purposes of one embodiment of the present invention is to provide a manganese-doped functionalized polyaluminium chloride flocculant, which is prepared by the above-mentioned preparation method of the manganese-doped functionalized polyaluminium chloride flocculant.

[0006] One of the purposes of one embodiment of the present invention is to provide an application of a manganese-doped functionalized polyaluminium chloride flocculant, and the application of the manganese-doped functionalized polyaluminium chloride flocculant in the field of sewage treatment.

[0007] Note that the inclusion of these objectives does not preclude the existence of other objectives. One embodiment of the present invention does not necessarily achieve all of the above objectives. Objectives other than the above objectives may be extracted from the description, drawings, and claims.

[0008] The present invention achieves the above technical objectives through the following technical means.

[0009] A method for preparing a manganese-doped functionalized polyaluminium chloride flocculant comprises the following steps:

[0010] Prepare a manganese-aluminum mixture: weigh manganese dichloride and aluminum chloride respectively, mix and stir evenly to obtain a manganese-aluminum mixture;

[0011] Preparation of silane-doped manganese-aluminum mixed slurry: water and the manganese-aluminum mixture are stirred to obtain a manganese-aluminum mixed solution, and the silane reagent and the manganese-aluminum mixed solution are mixed and stirred to obtain a silane-doped manganese-aluminum mixed slurry;

[0012] The manganese-doped functionalized polyaluminium chloride flocculant is prepared by subjecting the silane-doped manganese-aluminium mixed slurry to low-temperature plasma irradiation to obtain a mixed-valence manganese polyaluminium chloride initial liquid, drying and grinding the mixed-valence manganese polyaluminium chloride initial liquid to obtain the manganese-doped functionalized polyaluminium chloride flocculant.

[0013] In the above scheme, the steps of preparing the manganese-aluminum mixture are specifically as follows:

[0014] Manganese dichloride and aluminum chloride are weighed respectively according to the mass ratio of manganese dichloride to aluminum chloride (0.5-5.5):100, mixed, and stirred evenly to obtain a manganese-aluminum mixture.

[0015] In the above scheme, the steps for preparing the silane-doped manganese-aluminum mixed slurry are specifically as follows:

[0016] Mix water and manganese-aluminum mixture at a water-to-solid ratio of (1-3) mL:1 mg and stir for 10-30 minutes to obtain a manganese-aluminum mixed solution. Mix the silane reagent and the manganese-aluminum mixed solution at a volume ratio of (0.5-4.5) : 100, stir evenly, and obtain a silane-doped manganese-aluminum mixed slurry.

[0017] In the above scheme, the silane reagent is one of tetradecyltrichlorosilane, butyltrichlorosilane, trichlorohexylsilane, and chloro(dodecyl)dimethylsilane.

[0018] In the above scheme, the steps for preparing the manganese-doped functionalized polyaluminium chloride flocculant are specifically as follows: subjecting the silane-doped manganese-aluminium mixed slurry to low-temperature plasma irradiation for 1 to 5 hours to obtain a mixed-valence manganese polyaluminium chloride initial liquid, drying the mixed-valence manganese polyaluminium chloride initial liquid, and grinding it to obtain the manganese-doped functionalized polyaluminium chloride flocculant.

[0019] In the above scheme, the low-temperature plasma irradiation voltage is 5~75kV, and the low-temperature plasma atmosphere is oxygen.

[0020] A manganese-doped functionalized polyaluminium chloride flocculant is prepared according to the preparation method of the manganese-doped functionalized polyaluminium chloride flocculant.

[0021] An application of the manganese-doped functionalized polyaluminium chloride flocculant is disclosed, and the application of the manganese-doped functionalized polyaluminium chloride flocculant in the field of sewage treatment.

[0022] Preferably, in the present invention, manganese dichloride and aluminum chloride are weighed at a mass ratio of 0.5-5.5:100, mixed, and stirred to obtain a manganese-aluminum mixture. Water and the manganese-aluminum mixture are stirred for 10-30 minutes at a water-to-solid ratio of 1-3 mL:1 mg to obtain a manganese-aluminum mixed solution. A silane reagent is mixed with the manganese-aluminum mixed solution at a volume ratio of 0.5-4.5:100 and stirred to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagent is tetradecyltrichlorosilane, butyltrichlorosilane, trichlorohexylsilane, or chloro(dodecyl)dimethylsilane. The silane-doped manganese-aluminum mixed slurry is subjected to low-temperature plasma irradiation for 1-5 hours to obtain a mixed-valent manganese polyaluminum chloride initial solution, wherein the low-temperature plasma irradiation voltage is 5-75 kV and the low-temperature plasma atmosphere is oxygen. The mixed-valent manganese polyaluminum chloride initial solution is dried and ground to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0023] During low-temperature plasma irradiation, oxygen and water vapor ionize and dissociate in the discharge channel, generating oxygen and hydroxide radicals. These radicals oxidize the divalent manganese ions in the silane-doped manganese-aluminum slurry into a multivalent manganese mixture containing trivalent, tetravalent, pentavalent, hexavalent, and heptavalent manganese. The multivalent manganese mixture reacts with aluminum ions and hydroxide to form a binary multivalent manganese-aluminum hydroxide. Aluminum chloride reacts with the oxygen and hydroxide radicals to form polyaluminum chloride via a hydrolysis-polymerization mechanism. The chlorine in the silane reagent reacts with the oxygen and hydroxide radicals, converting them into free chlorine radicals. The original chlorine-attached positions in the silane reagent are replaced by hydroxyl groups, forming dechlorohydroxysilane. Simultaneously, some alkyl groups in the silane reagent are oxidized to carboxyl and carbonyl groups, directly severing some carbon-carbon chains. The silicon-oxygen bond in the dechlorinated hydroxyl silane reacts with binary multivalent manganese-aluminum hydroxide, aluminum chloride, and chlorine free radicals to undergo hydrolysis and polycondensation to generate a manganese-doped functionalized polyaluminum chloride flocculant with silicon-aluminum-manganese bonding, carbon chain support, and chloride ion equilibrium potential.

[0024] When manganese-doped functionalized polyaluminium chloride flocculant is added to high-chroma and high-COD wastewater, the manganese-doped functionalized polyaluminium chloride flocculant not only has the traditional polyaluminium chloride net capture, sweeping and hydroxyl bridge effects, but also the multivalent manganese in the manganese-doped functionalized polyaluminium chloride flocculant can quickly destroy and degrade the molecular structure of pigment molecules and other organic pollutants. The manganese-doped functionalized polyaluminium chloride flocculant is also a manganese-doped functionalized three-dimensional polyaluminium chloride flocculant, and its three-dimensional structure can also increase the capacity for adsorbing organic and inorganic pollutants, thereby achieving efficient purification of high-chroma and high-COD wastewater.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The preparation process is simple, requiring a limited number of readily available raw materials. Compared to conventional polyaluminum chloride flocculant materials, the manganese-doped functionalized polyaluminum chloride flocculant prepared in the present invention has a higher COD removal capacity and an oxidation function, enabling rapid and efficient purification of high-color and high-COD wastewater. The manganese-doped functionalized polyaluminum chloride flocculant prepared in the present invention has a maximum COD removal capacity of 7034 mg / g, and the color of the wastewater after treatment is reduced by less than 10 times.

[0027] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of the above effects. Effects other than the above can be clearly seen and extracted from the description of the specification, drawings, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the processing method of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with specific embodiments, but the scope of protection of the present invention is not limited thereto. The raw materials, reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources or can be prepared by conventional methods in the art.

[0030] Example 1 Effect of the mass ratio of manganese dichloride to aluminum chloride on the performance of the prepared manganese-doped functionalized polyaluminum chloride flocculant

[0031] According to the mass ratio of manganese dichloride to aluminum chloride of 0.5:100, 1.5:100, 2.5:100, 3.5:100, 4.5:100 and 5.5:100, manganese dichloride and aluminum chloride are weighed respectively, mixed and stirred evenly to obtain a manganese aluminum mixture. Water and the manganese aluminum mixture are stirred for 10 minutes according to a water-solid ratio of 1mL:1mg to obtain a manganese aluminum mixed solution. The silane reagent and the manganese aluminum mixed solution are mixed according to a volume ratio of silane reagent to the manganese aluminum mixed solution of 0.5:100, stirred evenly to obtain a silane-doped manganese aluminum mixed slurry, wherein the silane reagent is tetradecyltrichlorosilane. The silane-doped manganese aluminum mixed slurry is subjected to low-temperature plasma irradiation for 1 hour to obtain a mixed-valence manganese polyaluminum chloride initial solution, wherein the low-temperature plasma irradiation voltage is 5kV and the low-temperature plasma action atmosphere is oxygen. The mixed-valence manganese polyaluminum chloride initial solution is dried and ground to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0032] Dyeing wastewater sampling and basic properties: The dyeing wastewater concentrate used in the experiment was collected from a dyeing factory in Shaoxing. The suspended solids concentration of this batch of landfill leachate was 12783 mg / L COD and 1325 times the chroma.

[0033] Purification test: add 1g of manganese-doped functionalized polyaluminium chloride flocculant to 1L of printing and dyeing waste liquid concentrate, mix, stir for 5 minutes, centrifuge at 5000rpm for 5 minutes to complete the purification test.

[0034] COD concentration detection and COD removal capacity calculation: The solution chemical oxygen demand (COD) concentration was determined according to the national standard "Water quality determination of chemical oxygen demand - dichromate method" (GB 11914-1989). The COD removal capacity was calculated according to formula (1), where is the COD removal capacity (mg / g), and are the COD concentrations of landfill leachate before and after treatment (mg / L), m is the mass of the added high-efficiency softening hard water functionalized polyaluminum chloride flocculant (1 g), and V is the volume of the wastewater used in the experiment (1 L).

[0035] (1)

[0036] Determination of chromaticity: The chromaticity of the purified wastewater is determined in accordance with the "Dilution Multiple Method for Determination of Chromaticity of Water Quality" (HJ 1182-2021).

[0037] The COD removal capacity and color results are shown in Table 1.

[0038] Table 1 Effect of the mass ratio of manganese dichloride and aluminum chloride on the performance of the prepared manganese-doped functionalized polyaluminum chloride flocculant

[0039] Mass ratio of manganese dichloride to aluminum chloride COD removal capacity (mg / g) Chroma (times) 0.5:100 5972 124 1.5:100 5837 88 2.5:100 6024 75 3.5:100 6185 69 4.5:100 6250 84 5.5:100 5948 62

[0040] As shown in Table 1, manganese dichloride and aluminum chloride were weighed and mixed at a mass ratio of 0.5 to 5.5:100 to prepare a manganese-aluminum mixture. During low-temperature plasma irradiation, oxygen and water vapor ionize and dissociate in the discharge channel, generating oxygen and hydroxyl radicals. These oxygen and hydroxyl radicals oxidize the divalent manganese ions in the silane-doped manganese-aluminum mixture into a multivalent manganese mixture containing trivalent, tetravalent, pentavalent, hexavalent, and heptavalent manganese. The multivalent manganese mixture and aluminum ions react with hydroxyl radicals to form a binary multivalent manganese-aluminum hydroxide. Aluminum chloride reacts with the oxygen and hydroxyl radicals to form polyaluminum chloride (PAC) via a hydrolysis-polymerization mechanism. The prepared manganese-doped functionalized PAC flocculants exhibited COD removal capacities exceeding 5948 mg / g, and the color of the wastewater after treatment was 62 times greater than or equal to that of the treated wastewater.

[0041] Example 2 Effect of the Volume Ratio of Silane Reagent and Manganese-Aluminum Mixed Solution on the Performance of the Prepared Manganese-Doped Functionalized Polyaluminium Chloride Flocculant

[0042] Manganese dichloride and aluminum chloride were weighed at a mass ratio of 5.5:100, mixed, and stirred to obtain a manganese-aluminum mixture. Water was added to the manganese-aluminum mixture at a water-to-solid ratio of 2 mL:1 mg and stirred for 20 minutes to obtain a manganese-aluminum mixed solution. Silane reagent was mixed with the manganese-aluminum mixed solution at volume ratios of 0.5:100, 1.5:100, 2.5:100, 3.5:100, and 4.5:100, respectively, and stirred to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagent was tetradecyltrichlorosilane. The silane-doped manganese-aluminum mixed slurry was subjected to low-temperature plasma irradiation for 3 hours to obtain a mixed-valent manganese polyaluminum chloride initial solution. The low-temperature plasma irradiation voltage was 40 kV and the low-temperature plasma atmosphere was oxygen. The mixed-valent manganese polyaluminum chloride initial solution was dried and ground to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0043] The sampling and basic property description of printing and dyeing wastewater, purification test, COD concentration detection and COD removal capacity calculation, and chromaticity determination were the same as in Example 1. The COD removal capacity and chromaticity results are shown in Table 2.

[0044] Table 2 Effect of the volume ratio of silane reagent and manganese-aluminum mixed solution on the performance of the prepared manganese-doped functionalized polyaluminum chloride flocculant

[0045] Volume ratio of silane reagent and manganese aluminum mixed solution COD removal capacity (mg / g) Chroma (times) 0.5:100 6452 54 1.5:100 6577 46 2.5:100 6629 42 3.5:100 6614 31 4.5:100 6538 47

[0046] As shown in Table 2, the silane reagent and manganese-aluminum mixed solution were mixed at a volume ratio of 0.5 to 4.5:100 and stirred evenly to obtain a silane-doped manganese-aluminum mixed slurry. During low-temperature plasma irradiation, the chlorine in the silane reagent reacted with oxygen and hydroxyl radicals, converting them into free chlorine radicals. The chlorine-linked positions in the silane reagent were replaced by hydroxyl groups, forming dechlorohydroxysilane. Simultaneously, some alkyl groups in the silane reagent were oxidized to carboxyl and carbonyl groups, and some carbon-carbon chains were directly broken. The silicon-oxygen bonds in the dechlorohydroxysilane reacted with binary multivalent manganese-aluminum hydroxide, aluminum chloride, and chlorine radicals, undergoing hydrolysis and polycondensation to form a manganese-doped functionalized polyaluminum chloride flocculant with silicon-aluminum-manganese bonding, carbon chain support, and a chloride ion equilibrium potential. The prepared manganese-doped functionalized polyaluminum chloride flocculant achieved a COD removal capacity of ≥6452 mg / g, and the color of the wastewater after treatment was ≤54 times higher.

[0047] Example 3 Effect of low temperature plasma irradiation time on the performance of prepared manganese-doped functionalized polyaluminium chloride flocculant

[0048] Manganese dichloride and aluminum chloride were weighed in a mass ratio of 5.5:100, mixed, and stirred to obtain a manganese-aluminum mixture. Water and the manganese-aluminum mixture were stirred for 30 minutes at a water-to-solid ratio of 3 mL:1 mg to obtain a manganese-aluminum mixed solution. Silane reagent and the manganese-aluminum mixed solution were mixed in a volume ratio of 4.5:100 and stirred to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagent was tetradecyltrichlorosilane. The silane-doped manganese-aluminum mixed slurry was subjected to low-temperature plasma irradiation for 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours, respectively, to obtain a mixed-valence manganese polyaluminum chloride initial solution. The low-temperature plasma irradiation voltage was 75 kV, and the low-temperature plasma atmosphere was oxygen. The mixed-valence manganese polyaluminum chloride initial solution was dried and ground to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0049] The sampling and basic property description of printing and dyeing wastewater, purification test, COD concentration detection and COD removal capacity calculation, and color determination were the same as in Example 1. The COD removal capacity and color results are shown in Table 3.

[0050] Table 3 Effect of low temperature plasma irradiation time on the performance of prepared manganese-doped functionalized polyaluminium chloride flocculant

[0051] Low temperature plasma irradiation time (hours) COD removal capacity (mg / g) Chroma (times) 1 6854 21 2 6785 26 3 7011 13 4 6942 17 5 7034 8

[0052] Table 3 shows that when the low-temperature plasma irradiation time is 1–5 hours, oxygen and water vapor undergo ionization and dissociation in the discharge channel during the low-temperature plasma irradiation process, generating oxygen and hydroxide radicals. These oxygen and hydroxide radicals oxidize the divalent manganese ions in the silane-doped manganese-aluminum slurry into a multivalent manganese mixture containing trivalent, tetravalent, pentavalent, hexavalent, and heptavalent manganese. The multivalent manganese mixture and aluminum ions react with hydroxide to form a binary multivalent manganese-aluminum hydroxide. Aluminum chloride reacts with the oxygen and hydroxide radicals to form polyaluminum chloride via a hydrolysis-polymerization mechanism. The chlorine in the silane reagent reacts with the oxygen and hydroxide radicals, converting them into free chlorine radicals. The original chlorine-attached positions in the silane reagent are replaced by hydroxyl groups, forming dechlorohydroxysilane. Simultaneously, some alkyl groups in the silane reagent are oxidized to carboxyl and carbonyl groups, directly scissoring some carbon-carbon chains. The silicon-oxygen bonds in the dechlorinated hydroxyl-substituted silane react with binary multivalent manganese-aluminum hydroxide, aluminum chloride, and chlorine radicals, undergoing hydrolysis and polycondensation to form a manganese-doped functionalized polyaluminum chloride flocculant with a silicon-aluminum-manganese bond, carbon chain support, and a chloride ion equilibrium potential. Ultimately, the prepared manganese-doped functionalized polyaluminum chloride flocculant exhibited a COD removal capacity greater than or equal to 6785 mg / g, and the color of the wastewater after treatment was less than or equal to 26 times.

[0053] Example 4 Effect of Silane Reagent Type on the Performance of Manganese-doped Functionalized Polyaluminium Chloride Flocculant

[0054] Manganese dichloride and aluminum chloride were weighed in a mass ratio of 5.5:100, mixed, and stirred to obtain a manganese-aluminum mixture. Water and the manganese-aluminum mixture were stirred for 30 minutes at a water-to-solid ratio of 3 mL:1 mg to obtain a manganese-aluminum mixed solution. Silane reagents were mixed with the manganese-aluminum mixed solution in a volume ratio of 4.5:100, and stirred to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagents were tetradecyltrichlorosilane, butyltrichlorosilane, trichlorohexylsilane, and chloro(dodecyl)dimethylsilane. The silane-doped manganese-aluminum mixed slurry was subjected to low-temperature plasma irradiation for 5 hours to obtain a mixed-valence manganese polyaluminum chloride initial solution. The low-temperature plasma irradiation voltage was 75 kV, and the low-temperature plasma atmosphere was oxygen. The mixed-valence manganese polyaluminum chloride initial solution was dried and ground into powder to obtain a manganese-doped functionalized polyaluminum chloride flocculant. The sampling and basic property description of printing and dyeing wastewater, purification test, COD concentration detection and COD removal capacity calculation, and chromaticity determination were the same as in Example 1. The COD removal capacity and chromaticity results are shown in Table 4.

[0055] Table 4 Effect of silane reagent type on the performance of prepared manganese-doped functionalized polyaluminium chloride flocculant

[0056] Silane reagent types COD removal capacity (mg / g) Chroma (times) Tetradecyltrichlorosilane 7034 8 Butyltrichlorosilane 7021 9 Trichlorohexylsilane 6908 7 Chloro(dodecyl)dimethylsilane 6957 8

[0057] As shown in Table 4, when the silane reagents are tetradecyltrichlorosilane, butyltrichlorosilane, trichlorohexylsilane, and chloro(dodecyl)dimethylsilane, respectively, during the low-temperature plasma irradiation process, the chlorine in the silane reagent reacts with oxygen free radicals and hydroxyl free radicals to convert into free chlorine free radicals, and the position originally connected to the chlorine in the silane reagent is replaced by a hydroxyl group to form a dechlorohydroxy silane. At the same time, some alkyl groups in the silane reagent are oxidized to carboxyl and carbonyl groups, and some carbon-carbon chains are directly broken. The silicon-oxygen bonds in the dechlorohydroxy silane react with binary multivalent manganese aluminum hydroxide, aluminum chloride, and chlorine free radicals, undergoing hydrolysis and polycondensation reactions to generate a manganese-doped functionalized polyaluminum chloride flocculant with silicon-aluminum-manganese bonding, carbon chain support, and chloride ion equilibrium potential. Ultimately, the prepared manganese-doped functionalized polyaluminum chloride flocculant has a COD removal capacity greater than or equal to 6908 mg / g, and the color of the waste liquid after treatment is less than or equal to 9 times.

[0058] Comparative Example: Effects of different processes on the performance of prepared flocculants

[0059] The process of the present invention comprises the following steps: weighing manganese dichloride and aluminum chloride in a mass ratio of 5.5:100, mixing and stirring to obtain a manganese-aluminum mixture. Adding water to the manganese-aluminum mixture in a water-solid ratio of 3 mL:1 mg, stirring for 30 minutes, and obtaining a manganese-aluminum mixed solution. Mixing the silane reagent and the manganese-aluminum mixed solution in a volume ratio of 4.5:100, stirring to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagent is tetradecyltrichlorosilane. The silane-doped manganese-aluminum mixed slurry is subjected to low-temperature plasma irradiation for 5 hours to obtain a mixed-valence manganese polyaluminum chloride initial liquid, wherein the low-temperature plasma irradiation voltage is 75 kV, and the low-temperature plasma action atmosphere is oxygen. The mixed-valence manganese polyaluminum chloride initial liquid is dried and ground into powder to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0060] Comparative Process 1: Weigh manganese dichloride and aluminum chloride at a mass ratio of 5.5:100, mix, and stir evenly to obtain a manganese-aluminum mixture. Stir water and the manganese-aluminum mixture for 30 minutes at a water-to-solid ratio of 3 mL:1 mg to obtain a manganese-aluminum mixed solution. Irradiate the manganese-aluminum mixed solution with low-temperature plasma for 5 hours to obtain a mixed-valent manganese polyaluminum chloride initial solution, wherein the low-temperature plasma irradiation voltage is 75 kV and the low-temperature plasma action atmosphere is oxygen. Dry the mixed-valent manganese polyaluminum chloride initial solution and grind it into powder to obtain a manganese-doped functionalized polyaluminum chloride flocculant.

[0061] Comparative process 2: Weigh manganese dichloride and aluminum chloride according to a mass ratio of manganese dichloride to aluminum chloride of 5.5:100, mix and stir evenly to obtain a manganese-aluminum mixture. Stir water and manganese-aluminum mixture according to a water-solid ratio of 3 mL:1 mg for 30 minutes to obtain a manganese-aluminum mixed solution. Mix the silane reagent and the manganese-aluminum mixed solution according to a volume ratio of silane reagent to manganese-aluminum mixed solution of 4.5:100, stir evenly to obtain a silane-doped manganese-aluminum mixed slurry, wherein the silane reagent is tetradecyltrichlorosilane. Dry the silane-doped manganese-aluminum mixed slurry and grind it into powder to obtain a manganese-doped polyaluminum chloride flocculant.

[0062] The sampling and basic property description of printing and dyeing wastewater, purification test, COD concentration detection and COD removal capacity calculation, and chromaticity determination were the same as in Example 1. The COD removal capacity and chromaticity results are shown in Table 5.

[0063] Table 5 Effects of different processes on the properties of prepared flocculants

[0064] Process Type COD removal capacity (mg / g) Chroma (times) Process of the present invention 7034 8 Comparison process 1 3578 436 Comparison process 2 3394 364

[0065] As shown in Table 5, the performance of the manganese-doped functionalized polyaluminium chloride flocculant prepared by the process of the present invention is significantly better than that of the manganese-doped functionalized polyaluminium chloride flocculant and the manganese-doped polyaluminium chloride flocculant prepared by comparative process 1 and comparative process 2.

[0066] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a manganese-doped functionalized polyaluminium chloride flocculant, characterized in that: The following steps are involved: Prepare a manganese-aluminum mixture: weigh manganese dichloride and aluminum chloride respectively, mix and stir evenly to obtain a manganese-aluminum mixture; Preparation of silane-doped manganese-aluminum mixed slurry: water and the manganese-aluminum mixture are stirred to obtain a manganese-aluminum mixed solution, and the silane reagent and the manganese-aluminum mixed solution are mixed and stirred to obtain a silane-doped manganese-aluminum mixed slurry; The manganese-doped functionalized polyaluminium chloride flocculant is prepared by subjecting the silane-doped manganese-aluminium mixed slurry to low-temperature plasma irradiation to obtain a mixed-valence manganese polyaluminium chloride initial liquid, drying and grinding the mixed-valence manganese polyaluminium chloride initial liquid to obtain the manganese-doped functionalized polyaluminium chloride flocculant.

2. The method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claim 1, characterized in that: The steps of preparing the manganese aluminum mixture are specifically as follows: Manganese dichloride and aluminum chloride are weighed respectively according to the mass ratio of manganese dichloride to aluminum chloride (0.5-5.5):100, mixed, and stirred evenly to obtain a manganese-aluminum mixture.

3. The method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claim 1, characterized in that: The specific steps for preparing silane-doped manganese-aluminum mixed slurry are: Water and the manganese-aluminum mixture are stirred for 10-30 minutes at a water-solid ratio of (1-3) mL:1 mg to obtain a manganese-aluminum mixed solution; the silane reagent and the manganese-aluminum mixed solution are mixed at a volume ratio of (0.5-4.5) to 100, and stirred evenly to obtain a silane-doped manganese-aluminum mixed slurry.

4. The method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claim 1, characterized in that: The silane reagent is one of tetradecyltrichlorosilane, butyltrichlorosilane, trichlorohexylsilane and chloro(dodecyl)dimethylsilane.

5. The method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claim 1, characterized in that: The steps for preparing the manganese-doped functionalized polyaluminium chloride flocculant are as follows: subjecting a silane-doped manganese-aluminium mixed slurry to low-temperature plasma irradiation for 1 to 5 hours to obtain a mixed-valence manganese polyaluminium chloride initial liquid; drying and grinding the mixed-valence manganese polyaluminium chloride initial liquid to obtain the manganese-doped functionalized polyaluminium chloride flocculant.

6. The method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claim 1, characterized in that: The low-temperature plasma irradiation voltage is 5~75kV, and the low-temperature plasma atmosphere is oxygen.

7. A manganese-doped functionalized polyaluminium chloride flocculant, characterized in that: The flocculant is prepared according to the method for preparing the manganese-doped functionalized polyaluminium chloride flocculant according to claims 1-6.

8. An application of the manganese-doped functionalized polyaluminium chloride flocculant according to claim 7, characterized in that: Application of the manganese-doped functionalized polyaluminium chloride flocculant in the field of sewage treatment.

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