A biological composite flocculant and its preparation method

Abstract

The present invention provides a biocomposite flocculant and a preparation method thereof, belonging to the field of wastewater treatment. The method comprises the following steps: Step 1 is to dissolve konjac glucoside in deionized water, add an initiator thereto, add a dimethyldiallyl ammonium chloride solution thereto under heating conditions, and obtain a modified polymer after the reaction is completed; Step 2 is to add oleic acid to polyether and mix them uniformly, add an initiator thereto under heating conditions, and obtain a crosslinker after the reaction is completed; Step 3 is to add the crosslinker to deionized water and mix them uniformly to obtain a crosslinker solution, and dropwise add the crosslinker solution to the modified polymer and mix them uniformly. The biocomposite flocculant of the present invention crosslinks the modified konjac glucoside polymer with a synthetic green crosslinker. The obtained flocculant has a fast sedimentation rate for impurities in wastewater, a good flocculation effect, is easily biodegradable, and is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and in particular relates to a biological composite flocculant and a preparation method thereof. Background Art

[0002] Organic polymer flocculants can generally be divided into synthetic organic polymer flocculants and natural polymer flocculants. The majority of these flocculants are synthetic organic polymers, with the most common being polyacrylamide, which holds an 80% market share in Japan and the United States, with an annual production of tens of thousands of tons in my country. These flocculants are primarily used in the treatment of industrial wastewater, special wastewater, and sludge. However, due to the toxicity of its residual monomers and its resistance to biodegradation, polyacrylamide's application in water treatment, food processing, and fermentation has been significantly hindered. Natural polymer flocculants are derived from certain naturally occurring organic polymers found in agricultural and sideline products through specific chemical modifications. These flocculants, characterized by their numerous active groups, wide availability, low cost, non-toxicity, and biodegradability, have steadily attracted attention.

[0003] Therefore, the research on bioflocculants has attracted great attention from academia and business circles. Especially after the 1990s, there has been a boom in the research and development of bioflocculants around the world.

[0004] Cationic flocculants are widely used because they can effectively neutralize negatively charged colloidal particles and pollutants, promote flocculation and sedimentation, are suitable for various types of wastewater, and can effectively enhance sludge dewatering performance.

[0005] However, commonly used polyacrylamide cationic flocculants may contain residual toxic monomers (such as acrylamide), which can pose risks to aquatic life and human health (such as neurotoxicity and carcinogenicity) through long-term exposure. Furthermore, they are poorly biodegradable and easily accumulate in the environment. Summary of the Invention

[0006] In view of this, the present invention aims to overcome the defects in the prior art and proposes a biocomposite flocculant and a preparation method thereof.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A method for preparing a biocomposite flocculant comprises the following steps:

[0009] Step 1 is to dissolve konjac glucoside in deionized water, add an initiator thereto, add dimethyldiallyl ammonium chloride solution thereto under heating conditions, and obtain a modified polymer after the reaction is completed;

[0010] Step 2 is to add oleic acid to the polyether and mix them evenly, add an initiator thereto under heating conditions, and obtain a crosslinking agent after the reaction is completed;

[0011] Step 3 is to add the crosslinking agent into deionized water and mix evenly to obtain a crosslinking agent solution, and then dropwise add the crosslinking agent solution into the modified polymer and mix until the solution viscosity is 5000-8000 mpa•s to obtain the biocomposite flocculant.

[0012] Furthermore, the solid-to-liquid ratio of the konjac polysaccharide solution, initiator, dimethyldiallylammonium chloride solution and deionized water in step 1 is 1 g: 0.02-0.05 g: 25-45 mL: 800-1000 g.

[0013] Furthermore, the initiator is acidified ceric ammonium nitrate; and the mass concentration of the methyl diallyl ammonium chloride solution is 30-60%.

[0014] Furthermore, the temperature of the heating step in step 1 is 60-80° C.; the time of the reaction step in step 1 is 1-3 hours.

[0015] Furthermore, the mass ratio of oleic acid, polyether and initiator in step 2 is 5:60:0.5.

[0016] Furthermore, the molecular weight of the polyether in step 2 is 1000-2400; the temperature of the heating step in step 2 is 60-80° C.; and the reaction time in step 2 is 2-3 hours.

[0017] Furthermore, the initiator in step 2 is dibenzoyl peroxide and / or dicumyl peroxide.

[0018] Furthermore, the solid-liquid ratio of the cross-linking agent to deionized water in step 3 is 0.5-5 g:50 mL.

[0019] A biological composite flocculant prepared using the preparation method.

[0020] The reaction process of step 1 is shown in formula (I):

[0021]

[0022] Formula (I)

[0023] Konjac glucoside (KGM) is a neutral polysaccharide extracted from konjac tubers, exhibiting excellent biocompatibility and biodegradability. Compared to most polysaccharides, KGM's backbone contains a greater number of hydrophilic -OH groups. Compared to many other biopolymer flocculants, KGM has better water solubility. Furthermore, KGM molecules aggregate into large, giant molecules through hydrogen bonds, molecular dipoles, induced dipoles, and transient dipoles. When combined with cationic monomers to form a cationic flocculant, KGM adsorbs colloidal particles through van der Waals forces, hydrogen bonds, coordination bonds, and charge adsorption, forming bridges and connections, leading to agglomeration into large aggregates and destabilization.

[0024] Conventional KGM crosslinkers are generally small molecule substances such as citric acid, borax, sodium tripolyphosphate, etc. However, after KGM is modified into a cationic polymer, the cationic polymer is very easy to combine with the anions of these small molecule crosslinkers to produce precipitation and thus fail.

[0025] The advantage of cross-linking the cationic modified polymer prepared by KGM with the green cross-linking agent is that the shielding effect of the long side chain of the cross-linking agent and the huge structure of KGM make it difficult for the COO - Directly with N + Therefore, no white precipitate of anion and cation combination appeared in the experiment. However, since KGM occupies a large proportion in the structure, COO - It is easy to undergo esterification with the hydroxyl groups on its structure to produce cross-linking, thereby preparing a polymer with a macromolecular three-dimensional network structure, which can capture and sweep down colloidal particles and suspended particles in the water like a sieve.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The biocomposite flocculant of the present invention is prepared by cross-linking a modified konjac glucoside polymer with a synthetic green cross-linking agent. The obtained flocculant has a fast sedimentation rate for impurities in wastewater, a good flocculation effect, is easily biodegradable, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a diagram showing the effect of the biocomposite flocculant described in Example 1 of the present invention;

[0029] Figure 2 This is a diagram showing the effect of the flocculant described in Comparative Example 1 of the present invention;

[0030] Figure 3 This is a physical picture of the biocomposite flocculant described in Example 1 of the present invention;

[0031] Figure 4This is a physical picture of the flocculant described in Comparative Example 2 of the present invention;

[0032] Figure 5 This is a physical picture of the biocomposite flocculant described in Example 1 of the present invention in water;

[0033] Figure 6 This is a physical picture of the flocculant described in Comparative Example 3 of the present invention in water. DETAILED DESCRIPTION

[0034] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0035] The present invention will be described in detail below with reference to the embodiments.

[0036] Example 1

[0037] A method for preparing a biocomposite flocculant comprises the following steps:

[0038] Step 1 is to dissolve 1 g of konjac glucoside in 1000 g of deionized water, add 0.03 g of acidified cerium ammonium nitrate initiator, add 25 ml of dimethyldiallylammonium chloride solution (concentration of 40%) under heating conditions at 70° C., and react for 2 hours to obtain a modified polymer;

[0039] Step 2 is to add 5 g of oleic acid to 60 g of polyether (molecular weight of 1000) and mix them evenly, add 0.5 g of dibenzoyl peroxide initiator thereto under heating conditions of 80°C, and react for 3 hours to obtain a crosslinking agent;

[0040] Step 3 is to add the 0.5g crosslinker to 50ml deionized water and mix evenly to obtain a crosslinker solution, and then dropwise add the crosslinker solution to the modified polymer and mix until the solution viscosity reaches 7000 mpa•s to obtain the biocomposite flocculant.

[0041] Comparative Example 1

[0042] A method for preparing a flocculant comprises the following steps:

[0043] Step 1 is to dissolve 1 g of konjac glucoside in 1000 g of deionized water, add 0.03 g of acidified cerium ammonium nitrate initiator, add 25 ml of dimethyldiallyl ammonium chloride solution (concentration of 40%) under heating conditions at 70° C., and react for 2 hours to obtain the product.

[0044] Comparative Example 2

[0045] A method for preparing a biocomposite flocculant comprises the following steps:

[0046] Step 1 is to dissolve 1 g of konjac glucoside in 1000 g of deionized water, add 0.03 g of acidified cerium ammonium nitrate initiator, add 25 ml of dimethyldiallylammonium chloride solution (concentration of 40%) under heating conditions at 70° C., and react for 2 hours to obtain a modified polymer;

[0047] Step 2 is to add the 0.5 g of sodium tripolyphosphate into 50 ml of deionized water and mix them evenly to obtain a crosslinker solution, and then dropwise add the crosslinker solution into the modified polymer and mix them to obtain a flocculant.

[0048] Comparative Example 3

[0049] A method for preparing a flocculant comprises the following steps:

[0050] Prepare a 1% solution of commercially available cationic polyacrylamide, take 50 ml of the solution, add 0.5 g of sodium tripolyphosphate, and mix well.

[0051] The flocculants obtained in Example 1 and Comparative Examples 1-3 were tested, and the data are shown in Table 1.

[0052] Table 1 Test results

[0053]

[0054] Note: Sewage pH = 8, treatment temperature 30℃.

[0055] As shown in Table 1, under the same dosage, the COD removal rate of Example 1 was 95%, and the turbidity removal rate was 92%, which was an excellent effect.

[0056] Its main principle is to cross-link cationic polymers to form a large network structure, thereby preparing a polymer with a three-dimensional network structure containing a large number of positively charged macromolecules. When interacting with colloidal particles in sewage, the charge is neutralized and the charge of the adsorbed colloidal particles themselves is adsorbed, which not only promotes the agglomeration of colloidal particles, but also the three-dimensional network polymer will capture the colloidal particles and suspended turbidity particles in the water like a large sieve to achieve rapid sedimentation, and the flocculation effect is better. Figure 1 As shown in the actual picture Figure 3 shown.

[0057] Comparative Example 1, when not cross-linked, has only the effect of neutralizing adsorption and agglomeration, and does not have the effect of net capture and sweeping, so the effect is slightly worse. Figure 2 shown.

[0058] Comparative Example 2 uses a common konjac sugar crosslinker sodium tripolyphosphate, and flocculent precipitation occurs, and the viscosity drops sharply. It may be that the cationic structure combines with the phosphate ions exposed to the outside to produce precipitation and cause failure. The actual picture is as follows Figure 4 shown.

[0059] Comparative Example 3 is a conventional cationic polyacrylamide on the market, which has been cross-linked. At the same addition amount, the effect is significantly lower than that of Comparative Example 1. This is because conventional cationic polyacrylamide is a long-chain polymer, which becomes a three-dimensional network polymer after cross-linking. The network cross-linking limits the free extension of the polymer chain, resulting in insufficient exposure of the adsorption sites and reduced bridging efficiency.

[0060] At the same time, the grid formed by the cross-linking points may wrap some cationic groups, reduce the effective charge density, and weaken the electrical neutralization ability.

[0061] like Figure 5-6 As shown, konjac glucomannan itself is a cyclic polymer. Moderate cross-linking allows the KGM cyclic units to form a loose three-dimensional network with a large distance between cross-linking points, retaining the flexibility and extensibility of the cyclic units to form a porous network framework; the network pores can capture tiny particles, and at the same time, the cyclic units expand the adsorption area through rolling contact, achieving "dynamic sweeping" and improving flocculation efficiency.

[0062] 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 scope of protection of the present invention.

Claims

1. A method for preparing a biocomposite flocculant, characterized by: The steps include: Step 1 is to dissolve konjac glucoside in deionized water, add an initiator thereto, and add dimethyldiallyl ammonium chloride solution thereto under heating conditions, and after the reaction is completed, a modified polymer is obtained; the initiator is acidified ceric ammonium nitrate; Step 2 is to add oleic acid to polyether and mix them evenly, add an initiator thereto under heating conditions, and obtain a crosslinking agent after the reaction is completed; the initiator in step 2 is dibenzoyl peroxide and / or dicumyl peroxide; the molecular weight of the polyether in step 2 is 1000-2400; the mass ratio of oleic acid, polyether and initiator in step 2 is 5:60:0.5; Step 3 is to add the crosslinking agent into deionized water and mix evenly to obtain a crosslinking agent solution, and then dropwise add the crosslinking agent solution into the modified polymer and mix until the solution viscosity is 5000-8000 mpa•s to obtain the biocomposite flocculant.

2. The method for preparing the biocomposite flocculant according to claim 1, wherein: The solid-to-liquid ratio of the konjac polysaccharide solution, initiator, dimethyldiallyl ammonium chloride solution and deionized water in step 1 is 1g:0.02-0.05g:25-45mL:800-1000g.

3. The method for preparing the biocomposite flocculant according to claim 1, wherein: The mass concentration of the methyl diallyl ammonium chloride solution is 30-60%.

4. The method for preparing the biocomposite flocculant according to claim 1, wherein: The temperature of the heating step in step 1 is 60-80° C.; the time of the reaction step in step 1 is 1-3 hours.

5. The method for preparing the biocomposite flocculant according to claim 1, wherein: The temperature of the heating step in step 2 is 60-80° C.; the reaction time in step 2 is 2-3 hours.

6. The method for preparing the biocomposite flocculant according to claim 1, wherein: The solid-liquid ratio of the cross-linking agent to deionized water in step 3 is 0.5-5 g:50 mL.

7. A biocomposite flocculant prepared using the preparation method according to any one of claims 1 to 6.

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