A cellulose-based flocculant for industrial wastewater treatment and a preparation method thereof

Abstract

The present application belongs to the field of wastewater treatment, and discloses a cellulose-based flocculant for industrial wastewater treatment and a preparation method thereof. The present application uses renewable cellulose as raw material, and prepares efficient flocculant through an environmentally friendly process. In the present application, functional groups and magnetic ferroferric oxide are introduced, which can simultaneously remove heavy metals, dyes and colloidal particles, and can also be recycled for use, thereby reducing costs. The cellulose-based flocculant is compounded with ferroferric oxide particles, and has high charge density and three-dimensional network structure. The cellulose in the cellulose-based flocculant has a rough and porous surface structure, which significantly improves the surface area, and this large surface area effectively enhances the adsorption capacity and bridging effect of the flocculant. The preparation method has the characteristics of green substitution and high efficiency and multifunction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment, and relates to a cellulose-based flocculant and a preparation method thereof, in particular to a cellulose-based flocculant for industrial wastewater treatment and a preparation method thereof. BACKGROUND

[0002] Coagulation-flocculation process is a commonly used method in water and wastewater treatment due to its effectiveness in removing organic matter, suspended solids, turbidity and color. The commonly used coagulation-flocculation process involves the addition of inorganic and organic synthetic flocculants, such as polyaluminum chloride and polyacrylamide, polyaluminum chloride and cationic polyacrylamide, etc. These compounds are widely used mainly due to their outstanding free radical polymerization activity, excellent water solubility and low market price. However, they have various disadvantages from the health and environmental perspectives. In-depth analysis has been made on the possible impacts of using compounds as coagulants / flocculants, including high levels of chemical residues, toxic sludge and health diseases after long-term consumption. For example, the application of polyacrylamide in water treatment has great potential environmental and health risks, and the United States and the European Union have formulated strict regulations on the use of this polymer. Acrylamide monomer is carcinogenic and neurotoxic to humans. In addition, they usually also produce secondary solid pollution, called sludge, which has low or no biodegradability and has toxic effects.

[0003] Therefore, considering all these facts, it should be considered as an urgent need to replace synthetic chemical coagulants / flocculants with effective and harmless natural products in order to minimize environmental pollution and health risks caused by the use of chemical coagulants. Since natural polymer coagulants have biodegradable and environmentally friendly properties, the use of natural polymer coagulants in water treatment is of great significance and broad application prospects from the perspectives of biological health and environmental sustainability.

[0004] Natural polymers refer to high molecular compounds existing in nature and living organisms. As a sustainable resource, natural polymers are increasingly valued due to their abundant sources, low prices and wide applications. Natural polymers used in water and wastewater treatment systems mainly include cellulose, starch, chitosan, chitin and lignin, etc. Cellulose is a viable option for water and wastewater treatment because of its wide availability, renewability, durability and surface modification capability.

[0005] However, the use of unmodified cellulose is limited because cellulose cannot be dissolved in water. But the cellulose macromolecule contains a large number of active hydroxyl groups, and the free hydroxyl groups can be endowed with excellent chemical activity of cellulose through oxidation, esterification, crosslinking, graft copolymerization and other reactions. At the same time, cellulose has the advantages of non-toxic, biodegradable, low price and strong reaction performance and reaction designability, making it very suitable as a natural organic polymer modified flocculant base material. Many studies have reported the application of modified cellulose to water and wastewater treatment.

[0006] At present, the preparation of cellulose-based flocculants is mainly divided into heterogeneous synthesis and homogeneous synthesis. Heterogeneous synthesis is to disperse cellulose in an organic solvent (such as isopropyl alcohol), and then modify the cellulose through graft copolymerization or etherification reaction to make the cellulose have a high charge density, thereby having flocculation effect. But the main disadvantage of directly modifying cellulose-based flocculants is similar to that of inorganic flocculants, that is, a large dose is needed to effectively flocculate. Moreover, due to the highly ordered intermolecular hydrogen bond network and high crystallinity of cellulose, it has almost no strong water solubility in common organic or inorganic solvents, which seriously affects the modification effect of cellulose. The homogeneous reaction system can effectively overcome these obstacles; various homogeneous solutions have been proposed in the past research. Among them, sodium hydroxide / urea solution is considered as an ideal solvent due to its non-toxicity, low cost and environmental protection. In summary, the prior art has the following technical defects:

[0007] (1) Environmental risk: non-degradability of synthetic flocculants (such as polyacrylamide) and metal ion residue problem of inorganic flocculants (polyaluminum chloride, alum, etc.).

[0008] (2) Efficiency limitation: natural cellulose flocculants have insufficient active groups and weak adsorption capacity for various pollutants (such as anionic dyes, emulsified oil), which is not enough to meet the requirements of removing wastewater pollutants.

[0009] (3) High process cost: some modification methods require catalysts or high temperature and high pressure conditions, which are difficult to industrialize and have high cost. SUMMARY

[0010] The present application overcomes the above-mentioned defects and provides a cellulose-based flocculant for industrial wastewater treatment and a preparation method thereof. The preparation method of the present application has the characteristics of green substitution and high efficiency and multifunction. Although the flocculation effect of natural cellulose is not good, the flocculation capacity can be greatly improved after modification. The present application uses renewable cellulose as raw material and prepares high-efficiency flocculants through an environmentally friendly process (reducing secondary pollution). In the present application, functional groups (such as quaternary ammonium groups to enhance cationicity) and magnetic ferroferric oxide are introduced, which can simultaneously remove heavy metals, dyes and colloidal particles, and can also have certain recycling use to reduce cost.

[0011] The present application aims to solve the following problems existing in traditional industrial wastewater treatment flocculants:

[0012] (1) Environmental secondary pollution: Traditional inorganic flocculants (such as aluminum salt, iron salt) may leave metal ions, long-term use leading to soil and water pollution; synthetic organic flocculants (such as polyacrylamide) are difficult to degrade, and there is an ecological toxicity risk.

[0013] (2) Insufficient efficiency and applicability: Natural polymer flocculants (such as starch, chitosan, cellulose) have limited adsorption and flocculation effect on complex pollutants (such as heavy metals, dyes, colloids) due to low charge density or poor structural stability.

[0014] (3) Cost and sustainability: Some bio-based flocculants rely on high-purity raw materials or complex processes, making it difficult to be applied on a large scale. The present application designs a new environmentally friendly flocculant based on cellulose, which improves the removal efficiency of pollutants while achieving biodegradability and low-cost preparation.

[0015] The technical scheme of the present application is as follows.

[0016] A preparation method of a cellulose-based flocculant for industrial wastewater treatment, comprising the following steps:

[0017] (1) adding microcrystalline cellulose into NaOH aqueous solution, continuously stirring to activate it sufficiently; then washing it with deionized water until it is neutral, drying the moisture in a drying box and grinding into powder to obtain alkali cellulose powder;

[0018] (2) adding the alkali cellulose powder obtained in step (1) into a sodium hydroxide / urea solution system, pre-cooling at-12℃ to-20℃ for 2-4h to obtain a clear and uniformly dispersed cellulose solution;

[0019] (3) carrying out water bath reaction on the cellulose solution obtained in step (2) under stirring condition;

[0020] (4) slowly adding 2,3-epoxypropyltrimethylammonium chloride solution and continuing the reaction;

[0021] (5) taking out the product after reaction, soaking and washing to obtain etherified cellulose;

[0022] (6) mixing the obtained etherified cellulose with Fe3O4 powder suspension; ultrasonic dispersing and heating the mixture at 55-75℃ for 4-6h, and then cooling to room temperature; washing with anhydrous ethanol and distilled water, and then freeze-drying to obtain the final product.

[0023] In the method, in step (1), the concentration of the NaOH aqueous solution is 7-10 wt%; the mass percentage concentration of the microcrystalline cellulose in the NaOH aqueous solution is 2.00%-3.50%.

[0024] In the method, in step (1), the stirring time is 1-4 h.

[0025] In the method, in step (2), the sodium hydroxide / urea solution system is composed of deionized water, sodium hydroxide and urea, the deionized water is 20.00-22.50 ml, the sodium hydroxide is 1.75-2.00 g, and the urea is 3.00-4.00 g.

[0026] In the method, in step (3), the constant temperature of the water bath reaction is 40-60 DEG C, and the stirring time is 10-15 min.

[0027] In the method, in step (4), the concentration of the 2,3-epoxypropyl trimethyl ammonium chloride solution is 30-50 wt%; the 2,3-epoxypropyl trimethyl ammonium chloride solution contains 2,3-epoxypropyl trimethyl ammonium chloride 4.71-9.42 g; and the reaction time is 4-6 h.

[0028] In the method, in step (5), the soaking is 100 mL of anhydrous ethanol for 8-14 h; and the washing is washing and centrifugation three times with anhydrous ethanol:deionized water = 1:1.

[0029] In the method, in step (6), the concentration of Fe3O4 in the Fe3O4 powder suspension is 0.20-0.80 g / mL.

[0030] The "pre-alkalization-etherification" strategy adopted in the application is used for synthesizing modified cellulose, and then the modified cellulose is compounded with Fe3O4 nanoparticles to synthesize a cellulose-based flocculant, and the synthesis principle is as shown in the figure. Figure 2 The cellulose-based flocculant is compounded with Fe3O4 particles, has high charge density and three-dimensional network structure, and has good removal rate effect on wastewater pollutants; the cellulose in the cellulose-based flocculant has a rough and porous surface structure, which significantly improves the surface area, and the huge surface area effectively enhances the adsorption capacity and bridging effect of the flocculant.

[0031] In the application, the realization of the green and environmentally friendly function benefits from: the cellulose which can be naturally degraded is used as the main material, and the remaining chemical reagents also do not have potential safety threats, and have excellent environmental friendliness; and the flocculant can be naturally degraded and can be used together with other flocculants, so as to reduce the environmental pollution and health risks caused by the use of chemical coagulants.

[0032] The high efficiency and multifunctionalization are achieved by: first, the method uses pre-alkalization as the first step, which aims to destroy part of the hydrogen bonds of cellulose and reduce the crystallinity, laying a foundation for the subsequent operations (such as dissolving cellulose and increasing the reaction rate). The alkalized cellulose can increase the reaction rate and the degree of substitution of the product (the number of quaternary ammonium groups replacing hydroxyl groups, which is a maximum of 3). Generally speaking, the higher the degree of substitution, the higher the charge density of the flocculant. Industrial wastewater is generally negatively charged, and the cellulose-based flocculant of the present application is a cationic flocculant with introduced quaternary ammonium groups, which achieves the effect of flocculating wastewater pollutants. Moreover, the flocculant is compounded with ferroferric oxide particles, so that the flocculant has a certain metal ion adsorption capacity.

[0033] The cost and sustainability are achieved by: the experiment uses relatively inexpensive raw materials and reagents, and the preparation process is simple and does not consume a large amount of financial and material resources. Since the flocculant has a certain magnetic property, it can be recycled after recovery.

[0034] Compared with the prior art, the advantages of the present application are:

[0035] (1) The present application can reduce environmental pollution. The raw materials, reagents and methods used in the present application are relatively environmentally friendly, and the product has the ability of natural degradation, and there is no secondary pollution problem like chemical flocculants.

[0036] (2) The present application can improve the performance of the product and reduce the cost. The present application first alkalinizes the cellulose to increase the reaction rate of the cellulose and the etherification reagent, which can increase the charge density of the cellulose-based flocculant and reduce the use of etherification reagent (about 20%). At the same time, compared with other cellulose-based flocculants, the present application is compounded with magnetic ferroferric oxide, which can improve the treatment effect of the flocculation process (such as accelerating the settling speed and adsorbing metal ions); and has the possibility of recycling, which reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the preparation method of the present application;

[0038] Figure 2 is a synthesis principle diagram of the present application;

[0039] Figure 3 is a morphology change diagram of cellulose before and after modification used in Example 1 of the present application; wherein (a) is before modification, and (b) is after modification.

[0040] Figures 4a to 4c is the influence of settling time and Fe3O4 ratio on the wastewater removal effect. DETAILED DESCRIPTION

[0041] The application will be further described in detail below with reference to specific examples, but the embodiments of the application are not limited thereto. For the process parameters not specifically mentioned, refer to the conventional techniques.

[0042] Example 1

[0043] An environment-friendly cellulose-based flocculant is prepared from the following raw materials by weight: 1.00 g of microcrystalline cellulose, 6.75 g of sodium hydroxide, 3.00 g of urea, 4.71 g of 2,3-epoxypropyl trimethyl ammonium chloride, 0.20 g of ferroferric oxide, and 167.50 g of deionized water, with the total mass of the above substances being 183.16 g.

[0044] Preparation method of the cellulose-based flocculant

[0045] 1) Add 1 part of microcrystalline cellulose to 50 mL of 10 wt% NaOH aqueous solution, continuously stir for 1-2 h to fully activate it. Then rinse it with deionized water until it is neutral, dry the moisture in a drying oven, and then grind it into powder.

[0046] 2) Mix 22.50 g of deionized water, 1.75 g of 7% wt concentration sodium hydroxide, and 3.00 g of 14% wt concentration urea, and stir until uniform to obtain a sodium hydroxide / urea system; dissolve the alkalized cellulose obtained in (1) in the sodium hydroxide / urea system and mix uniformly, and then place the mixed solution in a refrigerator for freezing. Specifically, after freezing for 2 hours, thaw, and the freezing temperature is -12℃.

[0047] 4) During the reaction, slowly add 4.71 g of 2,3-epoxypropyl trimethyl ammonium chloride and react for 6 hours;

[0048] 5) Take out the product after the reaction, pour it into anhydrous ethanol for precipitation for 8-14 hours;

[0049] 6) Wash with deionized water: anhydrous ethanol = 1:1 for 3 times to obtain etherified cellulose;

[0050] 7) Mix the obtained etherified cellulose with 100 g of deionized water (containing 0.20 g of Fe3O4 powder as required), ultrasonic dispersion, and heat for 6 hours;

[0051] 8) Rinse with anhydrous ethanol and distilled water, and then freeze-dry to obtain the final product;

[0052] Figure 3 The morphology change diagram of cellulose before and after modification in this example, Figure 3 Fig. (a) is the morphology of cellulose before modification, Figure 3The cellulose after etherification modification in the middle (b) presents a rough and porous surface structure, which significantly improves its surface area. This huge surface area effectively enhances the adsorption capacity and bridging effect of the flocculant.

[0053] The synthetic flocculant was added to the thermosensitive paper wastewater (pH = 7.21) with a suspended substance of 236 mg / L, a colority of 535 pcu, and a COD of 3951 mg / L at a dosage of 350 mg / L, stirred for 3 min (250 r / min), and after stopping stirring, precipitated for 10 min. The supernatant was taken for measurement, and the suspended substance, colority, and COD were 36 mg / L, 76 PCU, and 1845 mg / L, respectively. cr The suspended substance, colority, and COD were 36 mg / L, 76 PCU, and 1845 mg / L, respectively. cr The removal rates of the suspended substance, colority, and COD were 84.75%, 85.79%, and 53.30%, respectively. cr The suspended substance, colority, and COD were 36 mg / L, 76 PCU, and 1845 mg / L, respectively.

[0054] Example 2

[0055] An environmentally friendly cellulose-based flocculant was prepared from the following raw materials by weight: 1.00 g of microcrystalline cellulose, 6.75 g of sodium hydroxide, 3.00 g of urea, 6.59 g of 2,3-epoxypropyltrimethylammonium chloride, 0.20 g of ferroferric oxide, and 167.50 g of deionized water, with a total mass of 185.04 g.

[0056] Preparation method of the cellulose-based flocculant:

[0057] 1) Add 1 part of microcrystalline cellulose to 50 mL of 10 wt% NaOH aqueous solution, continuously stir for 1-2 h to fully activate it. Then rinse it with deionized water until it is neutral, dry the moisture in a drying box, and grind it into powder.

[0058] 2) Mix 22.50 g of deionized water, 1.75 g of 7% wt sodium hydroxide, and 3.00 g of 14% wt urea, and stir evenly; dissolve the alkali cellulose obtained in (1) in the sodium hydroxide / urea system and mix evenly, then place the mixed solution in a refrigerator for freezing. Specifically, freeze for 2 hours and thaw, with a freezing temperature of -12°C.

[0059] 3) Move the thawed cellulose solution to a single-necked flask, add a rotor in the flask, and react on a magnetic stirring water bath, stirring for 10-15 min in a constant-temperature water bath at 60°C;

[0060] 4) Slowly add 6.59 g of 2,3-epoxypropyltrimethylammonium chloride during the reaction for 6 hours;

[0061] 5) Take out the product after the reaction, pour it into anhydrous ethanol for precipitation for 8-14 hours;

[0062] 6) Wash 3 times with deionized water: anhydrous ethanol = 1 : 1, to obtain etherified cellulose;

[0063] 7) Mix the obtained etherified cellulose with 100 g of deionized water (containing the required Fe304 powder 0.20 g), ultrasonically disperse and heat for 6 hours;

[0064] 8) Rinse with anhydrous ethanol and distilled water, then freeze-dry to obtain the final product;

[0065] The synthesized flocculant is added to the heat-sensitive paper wastewater (pH = 7.21 or so) at a dosage of 350 mg / L, with a suspended matter of 236 mg / L, a colority of 535 pcu, and a COD cr of 3951 mg / L, using stirring (250 r / min) for 3 min, stopping stirring for 10 min, and taking the supernatant to measure, the suspended matter, colority and COD cr are 28 mg / L, 48 PCU and 1761 mg / L, respectively, and the removal rates of the suspended matter, colority and COD cr are 88.14%, 91.03% and 55.43%, respectively.

[0066] Example 3

[0067] An environmentally friendly cellulose-based flocculant is prepared from the following raw materials by weight: 1.00 g of microcrystalline cellulose, 6.75 g of sodium hydroxide, 3.00 g of urea, 9.42 g of 2.3-epoxypropyltrimethylammonium chloride, 0.20 g of ferric oxide, and 167.50 g of deionized water, with a total mass of 187.87 g.

[0068] Method for preparing the cellulose-based flocculant:

[0069] 1) Add 1 part of microcrystalline cellulose to 50 mL of 10 wt% NaOH aqueous solution, continuously stir for 1-2 h to fully activate it. Then rinse it with deionized water until it is neutral, dry the moisture in a drying oven, and then grind it into powder.

[0070] 2) Mix 22.50 g of deionized water, 1.75 g of 7% wt concentration sodium hydroxide, and 3.00 g of 14% wt concentration urea, and stir until uniform; dissolve the alkali cellulose obtained in (1) in the sodium hydroxide / urea system, mix uniformly, and then place the mixed solution in a refrigerator for freezing. Specifically, freeze for 2 hours, then thaw, and the freezing temperature is -12°C.

[0071] 3) Move the thawed cellulose solution to a single-necked flask, and add a rotor in the flask, react on a magnetic stirring water bath, and stir for 10-15 min in a constant temperature water bath at 60°C;

[0072] 4) During the reaction, 9.42 g of 2, 3-epoxypropyl trimethyl ammonium chloride was slowly added and the reaction was carried out for 6 hours;

[0073] 5) The product after the reaction was taken out and precipitated in anhydrous ethanol for 8-14 hours;

[0074] 6) Washing with deionized water: anhydrous ethanol = 1:1 for 3 times, and the etherified cellulose was obtained;

[0075] 7) The obtained etherified cellulose was mixed with 100 g of deionized water (containing 0.20 g of Fe304 powder required), ultrasonic dispersed and heated for 6 hours;

[0076] 8) Rinsing with anhydrous ethanol and distilled water, and freeze-drying to obtain the final product;

[0077] The synthesized flocculant was added to the heat-sensitive paper wastewater (pH = 7.21 or so) with suspended solids of 236 mg / L, color of 535 pcu, and COD cr 3951 mg / L at a dosage of 350 mg / L, stirred for 3 min (250 r / min), and after stopping stirring, precipitated for 10 min, and the supernatant was measured, the suspended solids, color and COD cr were 17 mg / L, 21 PCU and 1728 mg / L respectively, and the removal rates of suspended solids, color and COD cr were 92.80%, 96.07% and 56.26% respectively.

[0078] Example 4

[0079] An environmentally friendly cellulose-based flocculant was prepared from the following raw materials by weight: 1.00 g of microcrystalline cellulose, 6.75 g of sodium hydroxide, 3.00 g of urea, 9.42 g of 2, 3-epoxypropyl trimethyl ammonium chloride, 0.40 g of ferroferric oxide, and 167.50 g of deionized water, and the total mass of the above substances was 188.07 g.

[0080] Preparation method of cellulose-based flocculant:

[0081] 1) 1 part of microcrystalline cellulose was added to 50 mL of 10 wt% NaOH aqueous solution, and stirred constantly for 1-2 h to fully activate it. Then it was washed with deionized water until it was neutral, and dried in a drying oven to remove moisture, and then ground into powder.

[0082] 2) 22.50 g of deionized water, 1.75 g of sodium hydroxide with a concentration of 7% wt, 3.00 g of urea with a concentration of 14% wt are mixed and stirred uniformly; the alkali cellulose obtained in (1) is dissolved in the sodium hydroxide / urea system and mixed uniformly, and then the mixed solution is placed in a refrigerator for freezing. Specifically, after freezing for 2 hours, it is thawed, and the freezing temperature is -12°C.

[0083] 3) The cellulose solution after thawing is moved to a single-necked flask, and a rotor is added in the flask, and the reaction is carried out on a magnetic stirring water bath, and is placed in a constant temperature water bath at 60°C and stirred for 10-15 minutes;

[0084] 4) During the reaction, 6.59 g of 2,3-epoxypropyltrimethylammonium chloride is slowly added and reacted for 6 hours;

[0085] 5) The product after the reaction is taken out and poured into anhydrous ethanol for precipitation for 8-14 hours;

[0086] 6) Washing 3 times with deionized water: anhydrous ethanol = 1:1, to obtain etherified cellulose;

[0087] 7) The etherified cellulose obtained is mixed with 100 parts of deionized water (containing 0.40 g of Fe3O4 powder required), ultrasonic dispersion and heating for 4-6 hours;

[0088] 8) Rinsing with anhydrous ethanol and distilled water, and then freeze-drying to obtain the final product;

[0089] The synthesized flocculant is added to the heat-sensitive paper wastewater (pH = about 7.21) with a suspended substance of 236 mg / L, a colority of 535 pcu, and a COD cr of 3951 mg / L at a dosage of 350 mg / L, stirring for 3 min (250 r / min), stopping stirring and precipitating for 10 min, and then measuring the supernatant, the suspended substance, the colority and the COD cr are 12 mg / L, 5 PCU and 1705 mg / L respectively, and the removal rates of the suspended substance, the colority and the COD cr are 94.91%, 99.06% and 56.85% respectively.

[0090] Example 5

[0091] 1. The weight fraction of cellulose (microcrystalline cellulose MCC), 2. 3-epoxypropyltrimethylammonium chloride EPTMAC, and Fe3O4 on the flocculant.

[0092] Table 1 The effect of the weight fraction of cellulose, EPTMAC, and Fe3O4 on the flocculant

[0093]

[0094] By comparison, the interaction between microcrystalline cellulose MCC and 2.3-epoxypropyltrimethylammonium chloride EPTMAC has a significant impact on the flocculation reaction, and the more EPTMAC, the more suspended solids, color and COD cr The better the removal effect is, which is determined by the flocculation mechanism. When the flocculant is added to the water, it carries a positive charge and has an electric neutralization reaction with the surface of the negatively charged colloidal particles. This interaction leads to the aggregation of particles, forming flocs.

[0095] By comparison, the cellulose flocculant compounded with Fe3O4 nanoparticles can enhance the adsorption capacity of pollutants, especially for negatively charged pollutants with stronger electrostatic bonding effect, greatly improving the purification capacity of wastewater.

[0096] In addition, it is also known that the temperature has little effect on the removal effect of wastewater. This may be due to the pre-alkalization treatment, which can better perform etherification reaction to connect quaternary ammonium groups to the cellulose chain without high temperature, thereby promoting flocculation synthesis.

[0097] 2. The effect of settling time on the removal effect of wastewater

[0098] As Figures 4a to 4c shown, under the condition of 350 mg / L dosage, compared with the flocculant without Fe3O4 compounding, the flocculant with Fe3O4 compounding can complete the settlement in a shorter time and has obvious improvement in removal effect. When the settling time is 10 min, the removal effect of the flocculant with Fe3O4 compounding reaches stability, and the removal rates of suspended solids, color and COD cr of wastewater are 88.10%, 94.02% and 54.37% respectively. While the flocculant without Fe3O4 compounding needs to settle for 20 min to reach stability, which takes twice the time.

[0099] This phenomenon can be attributed to the presence of Fe3O4. First, the flocculant with Fe3O4 compounding has a higher density than the one without compounding, which can settle to the bottom faster during flocculation and settlement; second, the flocculant with Fe3O4 compounding has better effect, which is due to the large specific surface area of Fe3O4 itself, providing abundant active sites for physical adsorption of pollutants.

[0100] It can be seen that the flocculants prepared by the pre-alkalization and homogeneous synthesis method in the application are combined with the ferroferric oxide particles; the product has high charge density and three-dimensional network structure, and has good removal rate effect on wastewater pollutants. The above-described embodiments only express several embodiments of the application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method for preparing a cellulose-based flocculant for industrial wastewater treatment, characterized in that, Includes the following steps: (1) Add microcrystalline cellulose to NaOH aqueous solution and stir continuously to fully activate it; then rinse with deionized water until it is neutral, dry the moisture and grind it into powder to obtain alkalized cellulose powder. (2) Add the alkalized cellulose powder obtained in step (1) to the sodium hydroxide / urea solution system and pre-cool it at -12℃ to -20℃ for 2 to 4 hours to obtain a clear and uniformly dispersed cellulose solution. (3) The cellulose solution obtained in step (2) is subjected to a water bath reaction under stirring conditions; (4) Add 2,3-epoxypropyltrimethylammonium chloride solution and continue the reaction; (5) The product after the reaction is taken out, soaked and washed to obtain etherified cellulose; (6) The obtained etherified cellulose is mixed with Fe3O4 powder suspension; the mixture is ultrasonically dispersed and heated at 55-75℃ for 4-6 hours, and then cooled to room temperature; it is washed with anhydrous ethanol and distilled water, and then freeze-dried to obtain the final product.

2. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (1), the concentration of the NaOH aqueous solution is 7-10 wt%; the mass percentage concentration of the microcrystalline cellulose in the NaOH aqueous solution is 2.00%-3.50%.

3. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (1), the stirring time is 1 to 4 hours.

4. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (2), the sodium hydroxide / urea solution system is composed of deionized water, sodium hydroxide and urea, wherein the deionized water is 20.00-22.50 ml, the sodium hydroxide is 1.75-2.00 g and the urea is 3.00-4.00 g.

5. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (3), the constant temperature of the water bath reaction is 40-60℃, and the mixture is stirred for 10-15 minutes.

6. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (4), the concentration of the 2,3-epoxypropyltrimethylammonium chloride solution is 30-50 wt%; the 2,3-epoxypropyltrimethylammonium chloride solution contains 4.71-9.42 g of 2,3-epoxypropyltrimethylammonium chloride; and the reaction time is 4-6 h.

7. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (5), the soaking is soaking in 100 mL of anhydrous ethanol for 8 to 14 hours; the washing is washing and centrifuging 3 times with anhydrous ethanol:deionized water = 1:

1.

8. The method for preparing a cellulose-based flocculant for industrial wastewater treatment according to claim 1, characterized in that, In step (6), the concentration of Fe3O4 in the Fe3O4 powder suspension is 0.20 to 0.80 g / mL.

9. A cellulose-based flocculant is prepared by the preparation method according to any one of claims 1 to 8.

10. The cellulose-based flocculant according to claim 9, characterized in that, The cellulose-based flocculant incorporates iron oxide particles, possessing both high charge density and a three-dimensional network structure. The cellulose in the cellulose-based flocculant exhibits a rough and porous surface structure, significantly increasing its surface area. This large surface area effectively enhances the flocculant's adsorption capacity and bridging effect.

Images