Efficient chitosan-polyferric sulfate composite coagulant and preparation method thereof

Abstract

The invention relates to the technical field of water treatment, and provides an efficient chitosan-polyferric sulfate composite coagulant and a preparation method thereof. In order to solve the problems that a traditional inorganic coagulant is prone to secondary pollution, an organic coagulant is high in cost and complex in process control and the like, the invention provides a solution that natural chitosan serves as a raw material, the charge characteristic of the natural chitosan is enhanced through quaternary ammonium salt modification, and then the natural chitosan is compounded with the inorganic coagulant according to a specific proportion. The preparation method comprises the following steps: dissolving chitosan in a 2% acetic acid solution, adjusting the pH value to weak acidity, introducing quaternary ammonium salt, carrying out catalysis by an initiator at a constant temperature of 70 DEG C to complete a reaction, and carrying out centrifugal washing and vacuum drying to obtain modified chitosan; and then compounding with an inorganic coagulant according to a mass ratio of 1: (3-5) to form a composite system with charge neutralization and adsorption bridging functions. According to the invention, by accurately controlling the ratio of the components and process parameters, the preparation process is simple and controllable, and the obtained composite coagulant has the characteristics of high treatment efficiency, environmental friendliness and moderate cost.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and more specifically to a high-efficiency chitosan-polyferric sulfate composite coagulant and a preparation method thereof. Background Art

[0002] In the field of water treatment, coagulants, as key chemical agents, play a vital role in improving water quality, removing suspended solids, colloids and some soluble organic matter, etc. With the increasingly stringent environmental protection requirements and the increasing shortage of water resources, the development of efficient, environmentally friendly and economical coagulants has become a hot topic in current water treatment technology research.

[0003] At present, the common coagulants on the market are mainly divided into two categories: inorganic coagulants and organic coagulants. Inorganic coagulants, such as aluminum sulfate and polyaluminum chloride, have the advantages of low cost and simple preparation process, but their treatment effect is often affected by many factors such as water quality conditions, pH value, temperature, etc., and more sludge may be generated during use, increasing the difficulty and cost of subsequent treatment. Organic coagulants, such as natural polymer coagulants (chitosan, starch, etc.) and synthetic polymer coagulants (polyacrylamide, etc.), have better flocculation effect and adaptability, but they also have problems such as high cost and easy secondary pollution.

[0004] In view of the problems existing in the existing inorganic coagulants and organic coagulants, it is a feasible solution to combine the two to obtain a composite coagulant that has the advantages of both inorganic coagulants and organic coagulants. However, there are still some problems in the preparation and application of the existing composite coagulants. For example, the proportional relationship between the components, stirring time, temperature and other conditions in the preparation process have a great influence on the performance of the composite coagulant and need to be strictly controlled. In addition, the composite coagulant may be interfered by various factors such as water quality conditions, pH value, temperature, etc. during use, resulting in unstable coagulation effect and treatment efficiency. At the same time, the existing composite coagulants still need to be further optimized in terms of preparation cost, environmental performance, etc. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a high-efficiency chitosan-polyferric sulfate composite coagulant and a preparation method thereof. Aiming at the defects of traditional inorganic coagulants that are prone to secondary pollution and insufficient organic matter removal efficiency, the present invention adopts a technical scheme of compounding a modified chitosan organic coagulant and an inorganic coagulant in a specific mass ratio, and obtains a composite coagulant with stable performance, environmental friendliness and good coagulation effect by optimizing the preparation process parameters of the modified chitosan and controlling the mixing ratio, thereby improving the sewage treatment efficiency.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A high-efficiency chitosan-polyferric sulfate composite coagulant is prepared by compounding a modified chitosan organic coagulant and an inorganic coagulant in a mass ratio of 1:3-5; the inorganic coagulant comprises one or more of polyferric sulfate, polyaluminium chloride and polyaluminium ferrosilicate; the modified chitosan organic coagulant is prepared by the following steps:

[0008] Step S1, weighing chitosan powder, adding it to a 2% acetic acid solution and stirring it to dissolve the chitosan in the acetic acid solution;

[0009] Step S2, adjusting the pH value of the solution to 6.0-6.5, adding the quaternary ammonium salt to the chitosan solution, and continuing to stir;

[0010] Step S3, heating the reaction system to 70° C., adding an initiator and conducting a constant temperature reaction at 70° C., and maintaining stirring during the constant temperature reaction;

[0011] Step S4, after the reaction is completed, the reaction system is cooled to room temperature, and the precipitate is collected by centrifugation, and the precipitate is washed alternately with anhydrous ethanol and deionized water;

[0012] Step S5, placing the washed precipitate in a vacuum drying oven for drying to obtain the final modified chitosan organic coagulant.

[0013] As a further embodiment of the present invention, the quaternary ammonium salt is at least one of dodecyldimethylbenzylammonium chloride, dimethyldiallylammonium chloride and acryloyloxyethylammonium chloride.

[0014] As a further solution of the present invention, in step S1, the mass of the chitosan powder is 5 g, the volume of the acetic acid solution is 200 mL, and the mixture is stirred at a speed of 200-300 rpm for 2 hours until the chitosan powder is completely dissolved to form a uniform solution.

[0015] As a further solution of the present invention, in step S2, after adding the quaternary ammonium salt, stirring is continued at a rotation speed of 200-300 rpm for 0.5-1 hour.

[0016] As a further solution of the present invention, in step S3, the constant temperature reaction time is 4 hours, and the stirring speed is 200-300 rpm.

[0017] As a further solution of the present invention, in step S4, the alternating washing is repeated 3 times.

[0018] As a further solution of the present invention, in step S5, the temperature of the drying treatment is 60° C., and the time of the drying treatment is 12 hours.

[0019] A method for preparing a high-efficiency chitosan-polyferric sulfate composite coagulant comprises mixing a modified chitosan organic coagulant solution and an inorganic coagulant sol at a mass ratio of 1:3-5, wherein the mixing method comprises adding the modified chitosan organic coagulant solution to the inorganic coagulant sol under stirring, aging after stirring, to obtain the composite coagulant; or adding the inorganic coagulant sol to the modified chitosan organic coagulant solution under stirring, stirring evenly, to obtain the composite coagulant.

[0020] Compared with the prior art, the beneficial effects of the high-efficiency chitosan-polyferric sulfate composite coagulant and the preparation method thereof of the present invention are:

[0021] The present invention selects biodegradable natural polymer compound chitosan as the raw material of the organic coagulant, and obtains the modified chitosan organic coagulant by modifying it with quaternary ammonium salt, and its degradation product is safe and harmless. However, the organic coagulants commonly used in the prior art, such as synthetic polymer materials such as polyacrylamide, are difficult to degrade, easily cause secondary pollution, and increase the environmental burden.

[0022] The present invention strictly controls the mass ratio of modified chitosan to inorganic coagulant of 1:3-5 and accurately sets the process parameters such as stirring time and temperature to obtain a composite coagulant with stable performance. The composite coagulant preparation process in the prior art lacks effective control of the proportion of each component and process parameters, resulting in unstable product performance, and the coagulation effect is greatly affected by factors such as pH value and temperature.

[0023] The present invention combines modified chitosan organic coagulant with inorganic coagulant, which not only exerts the high-efficiency flocculation effect of organic coagulant, but also takes advantage of the low cost of inorganic coagulant, which can significantly improve the treatment efficiency and reduce the production cost. In the prior art, the treatment effect of using inorganic coagulant alone is poor, and the cost of using organic coagulant alone is too high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the chitosan structure.

[0025] Figure 2 The present invention is a flow chart of the steps of preparing a modified chitosan organic coagulant of a high-efficiency chitosan-polyferric sulfate composite coagulant and a preparation method thereof. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] The invention discloses a high-efficiency chitosan-polyferric sulfate composite coagulant, which is composited by a modified chitosan organic coagulant and an inorganic coagulant in a mass ratio of 1:3-5.

[0029] Chitosan is a natural cationic biopolymer material made from chitin by deacetylation, and its basic structural unit is D-glucosamine. Figure 1 The above is a schematic diagram of the chitosan structure. The chitosan molecule contains a large number of hydroxyl (-OH) and amino (-NH2) active groups, which not only make it have good water solubility and biocompatibility, but also can introduce new functional groups through chemical modification to further improve its performance. The present invention utilizes the active groups in the chitosan molecule, further introduces long-chain alkyl and quaternary ammonium groups through quaternary ammonium salt modification, enhances the charge density and hydrophobicity of chitosan, and thus improves its bridging and electrical neutralization capabilities.

[0030] The inorganic coagulant in the embodiment of the present invention includes one or more of polyferric sulfate, polyaluminium chloride and polyaluminium ferrosilicate.

[0031] Among them, polyferric sulfate is a highly efficient inorganic coagulant, which contains a large amount of polynuclear hydroxyl complex iron in its molecules, and has strong electrical neutralization ability and bridging effect. Polyaluminium chloride is a basic aluminium chloride, and its hydrolysis product contains a variety of positively charged aluminium ion species, which can react with colloidal particles to undergo electrical neutralization. Polyaluminium silicate ferric combines the advantages of iron salts and aluminium salts, has better flocculation performance and a wider applicable pH range, and has the characteristics of fast sedimentation rate and small amount of sludge.

[0032] The modified chitosan organic coagulant in the embodiment of the present invention is prepared by the following steps:

[0033] Step S1, weighing 5 g of chitosan powder, slowly adding it into 200 mL of 2% acetic acid solution and stirring for 2 h to fully dissolve the chitosan in the acetic acid solution, during which the stirring speed is controlled at 200-300 rpm;

[0034] Step S2, adjusting the pH value of the solution to 6.0-6.5, slowly adding the quaternary ammonium salt to the chitosan solution, and continuing to stir at a speed of 200-300 rpm for 0.5-1 h;

[0035] Step S3, heating the reaction system to 70° C. and slowly adding the initiator, and conducting a constant temperature reaction at 70° C. for 4 hours, and maintaining stirring at a speed of 200-300 rpm during the constant temperature reaction;

[0036] Step S4, after the reaction is completed, the reaction system is cooled to room temperature, and the precipitate is collected by centrifugation, and the precipitate is washed three times alternately with anhydrous ethanol and deionized water;

[0037] Step S5, placing the washed precipitate in a vacuum drying oven and drying it at 60° C. for 12 hours to obtain the final modified chitosan organic coagulant.

[0038] The quaternary ammonium salt in the embodiment of the present invention is at least one of dodecyldimethylbenzyl ammonium chloride, dimethyldiallyl ammonium chloride and acryloyloxyethyl ammonium chloride. These quaternary ammonium salt compounds all have a relatively long carbon chain and a quaternary ammonium group, among which dodecyldimethylbenzyl ammonium chloride has strong hydrophilicity and surface activity; dimethyldiallyl ammonium chloride contains an active double bond and can participate in the grafting reaction; acryloyloxyethyl ammonium chloride has both a quaternary ammonium group and an acryloyl group, which is conducive to the modification reaction.

[0039] Example 2

[0040] A method for preparing a high-efficiency chitosan-polyferric sulfate composite coagulant comprises mixing a modified chitosan organic coagulant solution and an inorganic coagulant sol at a mass ratio of 1:3-5.

[0041] The mixing method in the embodiment of the present invention includes adding the modified chitosan organic coagulant solution to the inorganic coagulant sol under stirring, aging after stirring, to obtain the composite coagulant; or adding the inorganic coagulant sol to the modified chitosan organic coagulant solution under stirring, stirring evenly, to obtain the composite coagulant.

[0042] Example 3

[0043] The preparation method of modified chitosan organic coagulant comprises the following steps:

[0044] Step 1: weigh 5 g chitosan powder and slowly add it into 200 mL 2% acetic acid solution, control the stirring speed to 200-300 rpm, and continue stirring for 2 hours until the chitosan is completely dissolved to form a uniform solution;

[0045] Step 2: adjust the pH value of the solution to 6.0-6.5, then weigh 1.5 g of dodecyl dimethyl benzyl ammonium chloride, slowly add it to the chitosan solution, maintain a stirring speed of 200-300 rpm, and continue stirring for 30 minutes;

[0046] Step 3, heat the reaction system to 70°C, slowly add 0.2 g of benzoyl peroxide, and react at 70°C for 4 hours, maintaining a stirring speed of 200-300 rpm;

[0047] Step 4: After the reaction is completed, the reaction system is cooled to room temperature, the precipitate is collected by centrifugation, and the precipitate is washed three times with anhydrous ethanol and deionized water alternately;

[0048] Step 5: placing the washed precipitate in a vacuum drying oven and drying it at 60° C. for 12 hours to obtain a modified chitosan organic coagulant.

[0049] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0050] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-efficiency chitosan-polyferric sulfate composite coagulant, characterized in that: The modified chitosan organic coagulant and the inorganic coagulant are compounded in a mass ratio of 1:3-5; the inorganic coagulant comprises one or more of polyferric sulfate, polyaluminium chloride and polyaluminium ferrosilicate; the modified chitosan organic coagulant is prepared by the following steps: Step S1, weighing chitosan powder, adding it to a 2% acetic acid solution and stirring it to dissolve the chitosan in the acetic acid solution; Step S2, adjusting the pH value of the solution to 6.0-6.5, adding the quaternary ammonium salt to the chitosan solution, and continuing to stir; Step S3, heating the reaction system to 70° C., adding an initiator and conducting a constant temperature reaction at 70° C., and maintaining stirring during the constant temperature reaction; Step S4, after the reaction is completed, the reaction system is cooled to room temperature, and the precipitate is collected by centrifugation, and the precipitate is washed alternately with anhydrous ethanol and deionized water; Step S5, placing the washed precipitate in a vacuum drying oven for drying to obtain the final modified chitosan organic coagulant.

2. A high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: The quaternary ammonium salt is at least one of dodecyldimethylbenzylammonium chloride, dimethyldiallylammonium chloride and acryloyloxyethylammonium chloride.

3. A high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: In step S1, the mass of the chitosan powder is 5 g, the volume of the acetic acid solution is 200 mL, and the mixture is stirred at a speed of 200-300 rpm for 2 hours until the chitosan powder is completely dissolved to form a uniform solution.

4. A high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: In step S2, after adding the quaternary ammonium salt, stirring is continued at a rotation speed of 200-300 rpm for 0.5-1 hour.

5. The high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: In step S3, the constant temperature reaction time is 4 hours, and the stirring speed is 200-300 rpm.

6. The high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: In step S4, the alternating washing is repeated 3 times.

7. The high-efficiency chitosan-polyferric sulfate composite coagulant according to claim 1, characterized in that: In step S5, the temperature of the drying process is 60° C., and the time of the drying process is 12 hours.

8. A method for preparing a high-efficiency chitosan-polyferric sulfate composite coagulant according to any one of claims 1 to 7, characterized in that: The method comprises mixing a modified chitosan organic coagulant solution and an inorganic coagulant sol in a mass ratio of 1:3-5; the mixing method comprises adding the modified chitosan organic coagulant solution to the inorganic coagulant sol under stirring, aging after stirring, to obtain the composite coagulant; or adding the inorganic coagulant sol to the modified chitosan organic coagulant solution under stirring, stirring evenly, to obtain the composite coagulant.

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