Polysiloxane modified novel polyferric flocculant as well as preparation method and application thereof

Abstract

The invention discloses a polysiloxane modified novel polyferric flocculant and a preparation method and application thereof, and belongs to the technical field of wastewater treatment agent preparation.Polysiloxane serves as a chain-shaped main body material, imidazolyl is introduced to be combined with ferric ions, a stable imidazole-iron coordination compound is formed, and the polyferric flocculant is prepared. The compound and functionalized polysiloxane are combined through hydrogen bonds to form a high-molecular-weight composite material with a net structure; the polysiloxane chain structure not only provides higher molecular weight, but also enhances the stability and mechanical strength of the flocculant, and when the flocculant is used for treating high-concentration wastewater, pollutants can be effectively adsorbed and gathered through coordinate bonds and hydrogen bonds to form large and strong flocs. Compared with the traditional flocculant, the flocculant provided by the invention has the advantages of higher floc formation speed, higher sedimentation rate and better turbidity removal effect, and is especially suitable for papermaking wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment agent preparation, and particularly relates to a novel polysiloxane-modified polyferric flocculant and a preparation method and application thereof. Background Art

[0002] With the continuous expansion of the papermaking industry, the discharge of large quantities of papermaking wastewater has become a major environmental challenge. Papermaking wastewater typically exhibits high color, high chemical oxygen demand (COD), high levels of suspended solids, and a complex composition of organic pollutants, particularly recalcitrant lignin derivatives and chlorinated organic compounds. These characteristics make it poorly biodegradable and toxic, making it challenging to treat.

[0003] Currently, the main treatment methods for papermaking wastewater include physical, chemical, and biological methods. Physical methods (such as screening, sedimentation, and membrane filtration) primarily target large suspended solids but have limited effectiveness in removing dissolved organic matter and color. Chemical methods (such as oxidation, adsorption, and coagulation / precipitation) can effectively degrade some organic matter and remove color, but are often accompanied by high energy consumption, the formation of reaction byproducts, and the risk of secondary pollution. Biological methods (such as activated sludge and sequencing batch reactors), while environmentally friendly and low-cost, are affected by refractory substances in the wastewater, have long reaction cycles, and exhibit poor stability.

[0004] Among numerous treatment methods, flocculation is widely used in papermaking wastewater treatment due to its ease of operation and cost-effectiveness. Its principle is to neutralize the negative surface charge of suspended particles by adding flocculants, enabling adsorption and bridging, causing tiny particles to aggregate into large flocs, facilitating solid-liquid separation. Commonly used flocculants include polyferric sulfate, polyaluminum chloride, polyacrylamide (PAM), and organic-inorganic composite flocculants. These materials achieve flocculation through coordination bonds, hydrogen bonds, and dipole interactions. However, these traditional flocculants have numerous shortcomings: they are sensitive to water pH and ionic strength, and their flocculation efficiency is easily affected by fluctuations in environmental conditions. Some flocculants may leave toxic metal ions or polymer residues after treatment, complicating subsequent treatment. Furthermore, traditional polymer flocculants have a simple structure and lack the synergistic effects of multifunctional groups. This limits their adsorption and bridging capabilities when dealing with complex organic pollutants in papermaking wastewater, resulting in a need for improvement in both overall treatment effectiveness and economic efficiency. Summary of the Invention

[0005] The present invention provides a novel polysiloxane-modified polyferric flocculant, a preparation method thereof, and an application thereof. The prepared flocculant contains coordination bonds, hydrogen bonds, and slight condensed covalent bonds. The synergistic effect of multiple chemical bonds results in a high-density distribution of active sites, thereby having excellent adsorption and bridging capabilities, rapid flocculation and sedimentation characteristics, and can efficiently remove organic pollutants and suspended matter in papermaking wastewater.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions: A novel polysiloxane-modified polyferric flocculant, using polysiloxane as the main chain material, introduces trivalent iron ions to combine with imidazole groups to form a stable iron-imidazole coordination complex. Simultaneously, through the cross-linking reaction between the functionalized polysiloxane and the complex, a highly stable three-dimensional network structure is constructed. The specific structure is as follows: .

[0007] The preparation method of the novel polysiloxane-modified polyferric flocculant comprises the following steps: preparing an iron ion solution; adding imidazole to the iron ion solution and stirring at 400 rpm for 1 to 2 hours at 25 to 30° C. to generate a stable imidazole-iron complex; Tetraethoxysilane (TEOS) was dissolved in a solvent, and ethylene glycol was added as a catalyst. The mixture was stirred at 300 rpm for 4 hours at 35-40°C to prepare a functionalized polysiloxane solution. The imidazole-iron complex is mixed with the functionalized polysiloxane solution, and stirred at 300 rpm for 2 to 4 hours at 30 to 40° C. to allow the two to undergo a chemical reaction, thereby constructing a polyiron flocculant with a highly stable three-dimensional network structure.

[0008] In the above steps, the molar ratio of imidazole to iron ion is (30-60):(10-15), preferably 45:12; When dissolving tetraethoxysilane, a mixed solvent of water and ethanol in a volume ratio of 1:1 is used; the volume ratio of the imidazole-iron complex to the functionalized polysiloxane solution is (1-2):(1-2), preferably 1:1, and the molar ratio of ethylene glycol to tetraethoxysilane is 1:100.

[0009] The novel polysiloxane-modified polyferric flocculant prepared above can be used to treat papermaking wastewater. The unique three-dimensional network structure and multiple chemical bonds (including coordination bonds, hydrogen bonds and slightly condensed covalent bonds) of the flocculant work synergistically to achieve efficient adsorption, rapid flocculation and sedimentation in wastewater treatment, effectively improving the removal efficiency of suspended matter and organic pollutants.

[0010] Beneficial effects: The present invention provides a novel polysiloxane-modified polyferric flocculant and its preparation method and application, which has the following advantages over the prior art: 1. Efficient bridging effect of three-dimensional network structure The present invention forms a stable coordination complex between imidazole groups and trivalent iron ions, and then cross-links them with functionalized polysiloxane to construct a dense three-dimensional network structure. This structure has a large number of dispersed active sites and can bridge multiple suspended particles at the same time. It not only enhances the physical adsorption and cross-linking effects between particles, but also forms large and dense flocs, making the solid-liquid separation faster and the floc strength higher.

[0011] 2. Multiple chemical bonds synergistically enhance adsorption and cross-linking capabilities The flocculant produced by this invention possesses coordination bonds (Fe-N bonds), hydrogen bonds (between hydroxyl groups and imidazole groups), and covalent condensation bonds. These different types of chemical bonds coexist, forming a multi-point, multi-layered binding network. The coordination bonds provide a strong and stable metal-organic framework, while the hydrogen bonds provide flexible regulation. The synergistic effect of these multiple bonds significantly enhances the capture and fixation of organic matter, colloids, and metal ions, thereby achieving efficient flocculation through multiple mechanisms of action.

[0012] 3. Environmental adaptability and durability of functionalized polysiloxane skeleton The polysiloxane chain not only imparts a high molecular weight and excellent heat, acid, and alkali resistance, but also, through the introduction of hydrophilic functional groups such as hydroxyl groups, allows the entire material to maintain a stable structure under varying pH and ionic strengths. The synergistic effect of these multiple functional groups enhances the binding with the imidazole-iron complex, while also ensuring the flocculant's excellent long-term stability and reusability even in complex water conditions.

[0013] 4. Multiple action mechanisms achieve high-density active site distribution The present invention simultaneously introduces imidazole, iron center and siloxane chain into one molecule. This design enables each polymer unit to carry multiple active functions. The metal center improves the surface charge of suspended particles through electrical neutralization, the imidazole group provides coordination and hydrogen bonding, and the siloxane skeleton constitutes a wide range of physical networks. This multiple action mechanism makes the active sites highly uniform and densely distributed at the molecular level, thereby having excellent adsorption bridging ability, rapid flocculation and sedimentation characteristics, greatly improving the flocculation efficiency, and being able to efficiently remove organic pollutants and suspended matter in papermaking wastewater. Through the dual optimization of structure and function, the present invention significantly improves the treatment efficiency of flocculants in papermaking wastewater treatment applications, reduces the risk of secondary pollution, and effectively saves operating costs, thereby achieving efficient, environmentally friendly and sustainable wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The figure is a reaction mechanism diagram of the preparation method of the present invention; Figure 2 This is a practical diagram of Example 1 of the present invention; Figure 3This is a practical diagram of Example 2 of the present invention; Figure 4 This is a practical diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: Example 1

[0016] A method for preparing a novel polysiloxane-modified polyferric flocculant comprises the following steps: In terms of molar fractions, 12 parts of ferric chloride hexahydrate are dissolved in deionized water, and an appropriate amount of hydrochloric acid is added to adjust the pH to about 4.5 to obtain an iron ion solution; 45 parts of imidazole are added to the above iron ion solution, and stirred at 400 rpm at 25-30°C for 1-2 hours to generate a stable imidazole-iron complex; 20 parts of tetraethoxysilane (TEOS) are dissolved in a mixed solvent of deionized water and ethanol (1:1 volume ratio), the pH is adjusted to about 4.5, and then 0.2 parts of ethylene glycol is added as a catalyst, and stirred at 35-40°C at 300 rpm for 4 hours to form a functionalized polysiloxane solution; the imidazole-iron complex obtained in step (2) is mixed with the polysiloxane solution in step (3) in a volume ratio of 1:1, and stirred at 300 rpm at 30-40°C for 2-4 hours to carry out a cross-linking reaction, and finally a highly cross-linked polyferric flocculant is obtained; finally, the reaction solution is cooled and filtered to obtain a new polyferric flocculant. Example 2

[0017] A method for preparing a novel polysiloxane-modified polyferric flocculant comprises the following steps: In terms of molar fractions, 15 parts of ferric chloride hexahydrate are dissolved in deionized water, and the pH is adjusted to about 4.5 with dilute hydrochloric acid to obtain an iron ion solution; 30 parts of imidazole are added to the above solution, and the mixture is stirred at 400 rpm at 25-30°C for 1-2 hours to generate an imidazole-iron complex; 15 parts of tetraethoxysilane (TEOS) are dissolved in a mixed solvent of deionized water and ethanol (1:1), the pH is adjusted to about 4.5, and then 0.15 parts of ethylene glycol are added as a catalyst, and the mixture is stirred at 300 rpm at 35-40°C for 4 hours to form a functionalized polysiloxane solution; the imidazole-iron complex prepared in step (2) is mixed with the polysiloxane solution in step (3) in a volume ratio of 1:1, and the mixture is stirred at 300 rpm at 30-40°C for 2-4 hours to carry out a cross-linking reaction, thereby finally obtaining a polyiron flocculant; after the reaction is completed, the system is cooled and filtered to obtain a new polyiron flocculant. Example 3

[0018] A method for preparing a novel polysiloxane-modified polyferric flocculant comprises the following steps: In terms of molar fractions, 10 parts of ferric chloride hexahydrate are dissolved in deionized water and the pH is adjusted to about 4.5 to obtain an iron ion solution; 60 parts of imidazole are added to the above solution and stirred at 400 rpm at 25-30°C for 1-2 hours to generate an imidazole-iron complex; 25 parts of tetraethoxysilane (TEOS) are dissolved in a mixed solvent of deionized water and ethanol (1:1), the pH is adjusted to about 4.5, and then 0.25 parts of ethylene glycol are added as a catalyst, and the mixture is stirred at 300 rpm at 35-40°C for 4 hours to form a functionalized polysiloxane solution; the imidazole-iron complex obtained in step (2) is mixed with the polysiloxane solution in step (3) in a volume ratio of 1:1, and the mixture is stirred at 300 rpm at 30-40°C for 2-4 hours to carry out a cross-linking reaction, thereby finally obtaining a polyiron flocculant; finally, the reaction system is cooled and filtered to obtain a new polyiron flocculant.

[0019] The flocculant prepared in the above example and traditional PAC were used to treat papermaking wastewater, with the mass ratio of the used flocculant solution to the original slurry being 50,000 ppm. The initial COD of the papermaking wastewater was 7,642 mg / L, and the initial SS was 6,943 mg / L.

[0020] Taking Example 1 as an example, under the optimal reaction conditions, the effluent COD and SS were 2941 and 351 mg / L, respectively. At this time, the flocculation time was 45 minutes, the dosage was 400 mg / L, and the pH was 7.6. Therefore, under the optimal operating conditions, Examples 1, 2, 3 and 4 were compared. The comparison results are shown in Table 1 (unit: mg / L): Table 1 Effluent COD and effluent SS of wastewater treated with different flocculants Sample name Outlet COD Outlet SS Example 1 2941 351 Example 2 3419 445 Example 3 3108 401 PAC 4142 946 It can be found from Table 1 that the removal rates of various indicators of the prepared novel modified polyferric flocculants Examples 1, 2, and 3 and traditional PAC are as shown in Table 2: Table 2 COD and SS removal rates of wastewater treated with different flocculants Sample name COD removal rate SS removal rate Example 1 61.52% 94.94% Example 2 55.26% 93.59% Example 3 59.33% 94.22% PAC 45.80% 86.37% Comparative experimental results show that the novel polyferric flocculants prepared in Examples 1, 2, and 3 all significantly outperformed traditional PACs in treating papermaking wastewater, with Example 1 performing the best. Example 1 employed a molar ratio of imidazole to ferric chloride hexahydrate of 45:12 and a TEOS content of 20. This ensured sufficient formation of the iron-imidazole complex and uniform mixing of the functionalized polysiloxane solution with the complex. The resulting three-dimensional network structure was neither sparse nor overcrowded, resulting in a highly uniform and dense distribution of active sites at the molecular level, thus achieving optimal adsorption, bridging, and sedimentation. In comparison, the lower molar ratio (30:10) in Example 2 resulted in fewer active sites, which in turn reduced flocculation effectiveness. While the higher molar ratio (60:15) in Example 3 generated more active sites, the overcrowded system may have deactivated some functional groups, reducing overall performance. In summary, the preparation method of Example 1 is optimal, providing an efficient, stable, economical, and environmentally friendly solution for papermaking wastewater treatment.

[0021] The above are only preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those skilled in the art, various modifications and improvements made without departing from the concept of the present invention are protected by the present invention.

Claims

1. A novel polysiloxane-modified polyferric flocculant, characterized in that: With polysiloxane as the chain body, trivalent iron ions are introduced to combine with imidazole groups to form a stable iron-imidazole coordination complex, which is combined with functionalized polysiloxane through hydrogen bonds to form a three-dimensional network structure.

2. The novel polysiloxane-modified polyferric flocculant according to claim 1, characterized in that: The structure of the flocculant is: 。 3. A method for preparing a novel polysiloxane-modified polyferric flocculant, characterized in that: The following steps are involved: preparing an iron ion solution; adding imidazole to the iron ion solution and stirring the mixture to react to form an imidazole-iron complex; Dissolving tetraethoxysilane in a solvent, adding a catalyst, and continuously stirring to prepare a functionalized polysiloxane solution; The imidazole-iron complex is mixed with a functionalized polysiloxane solution to react and form a polyiron flocculant with a three-dimensional network structure.

4. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3, characterized in that: The iron ion solution is formed by dissolving ferric chloride hexahydrate in deionized water.

5. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3, characterized in that: The molar ratio of the imidazole to the iron ion is (30-60):(10-15).

6. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3 or 5, characterized in that: The reaction temperature for generating the imidazole-iron complex is 25-30° C., the reaction time is 1-2 hours, and the stirring speed is 400 rpm.

7. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3, characterized in that: The functionalized polysiloxane solution was prepared at a reaction temperature of 35-40° C., a reaction time of 4 hours, and a stirring speed of 300 rpm. The molar ratio of the catalyst to tetraethoxysilane was 1:

100.

8. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3, characterized in that: The imidazole-iron complex and the functionalized polysiloxane solution are mixed in a volume ratio of (1-2):(1-2).

9. The method for preparing the novel polysiloxane-modified polyferric flocculant according to claim 3 or 8, characterized in that: After the imidazole-iron complex is mixed with the functionalized polysiloxane solution, the reaction temperature is 30-40° C., the reaction time is 2-4 hours, and the stirring speed is 300 rpm.

10. Use of the novel polysiloxane-modified polyferric flocculant according to any one of claims 1 to 2, characterized in that: The polyferric flocculant is used for treating papermaking wastewater.

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