Biological composite flocculant and preparation method thereof

Abstract

The invention provides a biological composite flocculant and a preparation method thereof, and belongs to the field of wastewater treatment.The method comprises the following steps that 1, konjac glucomannan is dissolved in deionized water, an initiator is added into the deionized water, a dimethyl diallyl ammonium chloride solution is added into the deionized water under the heating condition, and a mixed solution is obtained; a modified polymer is obtained after the reaction is completed; 2, adding oleic acid into polyether, uniformly mixing, adding an initiator under a heating condition, and reacting to obtain a cross-linking agent; and step 3, adding the cross-linking agent into deionized water, uniformly mixing to obtain a cross-linking agent solution, dropwise adding the cross-linking agent solution into the modified polymer, and uniformly mixing to obtain the modified polymer. According to the biological composite flocculant disclosed by the invention, the modified konjac glucomannan polymer and the synthesized green cross-linking agent are cross-linked, and the obtained flocculant is high in settling speed on impurities in wastewater, good in flocculation effect, relatively good in biodegradability and beneficial to environmental protection.

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 organic synthetic polymer flocculants and natural polymer flocculants. Most of them on the market are organic synthetic polymer flocculants, among which the most are polyacrylamide series. They are mainly used in the treatment of industrial sewage, special sewage and sludge. However, due to the toxicity of its residual monomers and its difficult biodegradability, the application of polyacrylamide in water treatment, food processing industry and fermentation industry has been greatly hindered. Natural polymer flocculants are obtained by specific chemical modification of certain natural organic polymer substances in agricultural and sideline products. They have many active groups, wide sources, low prices, no toxicity, and easy biodegradation, which makes this type of flocculant gradually attract attention.

[0003] Therefore, the research on bioflocculants has attracted great attention from academia and business circles, especially after the 1990s, when there has been a worldwide upsurge in the research and development of bioflocculants.

[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, the polyacrylamide cationic flocculants commonly used in the market may contain toxic monomers (such as acrylamide), and long-term exposure may pose risks to aquatic organisms and human health (such as neurotoxicity and carcinogenicity). In addition, 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: A method for preparing a biocomposite flocculant comprises the following steps: Step 1 is to dissolve konjac glucoside in deionized water, add an initiator thereto, add a dimethyldiallylammonium chloride solution thereto under heating conditions, and obtain a modified polymer after the reaction is completed; 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; 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 reaches 5000-8000 r / min, thereby obtaining the biocomposite flocculant.

[0008] 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.

[0009] Furthermore, the initiator is acidified cerium ammonium nitrate; and the mass concentration of the methyl diallyl ammonium chloride solution is 30-60%.

[0010] 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.

[0011] Furthermore, the mass ratio of oleic acid, polyether and initiator in step 2 is 5:60:0.5.

[0012] 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 time of the reaction step in step 2 is 2-3 hours.

[0013] Furthermore, the initiator in step 2 is dibenzoyl peroxide and / or dicumyl peroxide.

[0014] Furthermore, the solid-liquid ratio of the cross-linking agent to deionized water in step 3 is 0.5-5 g:50 mL.

[0015] A biological composite flocculant prepared by using the preparation method.

[0016] The reaction process of step 1 is shown in formula (I): Formula (I) Konjac glucoside (KGM) is a neutral polysaccharide that can be extracted from konjac tubers, with good biocompatibility and biodegradability. Compared with most polysaccharides, the number of hydrophilic groups -OH contained in the skeleton of KGM is richer. Compared with many other biopolymer flocculants, KGM has better water solubility, and KGM molecules can be aggregated into huge giant molecules through hydrogen bonds, molecular dipoles, induced dipoles, instantaneous dipoles and other forces. After being combined with cationic monomers to prepare cationic flocculants, colloidal particles are adsorbed to form bridge connections through van der Waals forces, hydrogen bonds, coordination bonds, charge adsorption, etc., and agglomerated into large aggregates to destabilize and precipitate.

[0018] Conventional KGM crosslinking agents 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 crosslinking agents to produce precipitation and thus fail.

[0019] The advantage of cross-linking the cationic modified polymer prepared by KGM with the prepared green cross-linker is that the shielding effect of the long side chain of the cross-linker 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.

[0020] Compared with the prior art, the present invention has the following advantages: The biocomposite flocculant of the invention cross-links the modified konjac glucoside polymer with a synthetic green cross-linking agent. The obtained flocculant has a fast sedimentation speed for impurities in wastewater, a good flocculation effect, is biodegradable, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the effect of the biocomposite flocculant described in Example 1 of the present invention; Figure 2 This is a diagram showing the effect of the flocculant described in Comparative Example 1 of the present invention; Figure 3 This is a physical picture of the biocomposite flocculant described in Example 1 of the present invention; Figure 4 This is a physical picture of the flocculant described in Comparative Example 2 of the present invention; Figure 5 This is a physical picture of the biocomposite flocculant in water according to Example 1 of the present invention; Figure 6 This is a physical picture of the flocculant described in Comparative Example 3 of the present invention in water. DETAILED DESCRIPTION

[0022] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0023] The present invention will be described in detail below with reference to the embodiments.

[0024] Example 1 A method for preparing a biocomposite flocculant comprises the following steps: 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 thereto, add 25 ml of dimethyldiallylammonium chloride solution (concentration of 40%) thereto under heating conditions at 70° C., and react for 2 hours to obtain a modified polymer; Step 2 is to add 5 g of oleic acid to 60 g of polyether (molecular weight 1000) and mix them evenly, add 0.5 g of dibenzoyl peroxide initiator thereto under heating condition of 80° C., and react for 3 hours to obtain a crosslinking agent; Step 3 is to add the 0.5 g cross-linking agent into 50 ml deionized water and mix evenly to obtain a cross-linking agent solution, and then dropwise add the cross-linking agent solution into the modified polymer and mix until the solution viscosity reaches 7000 r / min to obtain the biocomposite flocculant.

[0025] Comparative Example 1 A method for preparing a flocculant comprises the following steps: Step 1 is to dissolve 1g of konjac glucoside in 1000g of deionized water, add 0.03g of acidified cerium ammonium nitrate initiator, add 25ml of dimethyldiallylammonium chloride solution (concentration of 40%) under heating conditions at 70°C, and react for 2 hours to obtain the product.

[0026] Comparative Example 2 A method for preparing a biocomposite flocculant comprises the following steps: 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 thereto, add 25 ml of dimethyldiallylammonium chloride solution (concentration of 40%) thereto under heating conditions at 70° C., and react for 2 hours to obtain a modified polymer; 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.

[0027] Comparative Example 3 A method for preparing a flocculant comprises the following steps: Prepare a 1% solution of commercially available cationic polyacrylamide, take 50 ml of the solution, add 0.5 g of sodium tripolyphosphate into it, and mix well.

[0028] The flocculants obtained in Example 1 and Comparative Examples 1-3 were tested, and the data are shown in Table 1.

[0029] Table 1 Test results

[0030] Note: Sewage pH = 8, treatment temperature 30℃.

[0031] As shown in Table 1, under the same dosage, the COD removal rate of Example 1 is 95%, and the turbidity removal rate is 92%, which is an excellent effect.

[0032] The 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 adsorbed by the charge of the colloidal particles themselves, which not only promotes the agglomeration of colloidal particles, but also the three-dimensional network polymer will capture and sweep the colloidal particles and suspended turbidity particles in the water like a large sieve to achieve rapid sedimentation, with better flocculation effect. Figure 1 As shown in the actual picture Figure 3 shown.

[0033] Comparative Example 1, in the case of no cross-linking, has only the effect of neutralization adsorption and agglomeration, and does not have the effect of net capture and sweeping, so the effect is slightly worse. Figure 2 shown.

[0034] Comparative Example 2 uses common konjac crosslinking agent 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.

[0035] Comparative Example 3 is a conventional cationic polyacrylamide on the market, and it is 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 is 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.

[0036] 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 charge neutralization ability.

[0037] 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 spacing between cross-linking points, retaining the flexibility and extensibility of the cyclic units to form a porous mesh framework. The network pores can capture tiny particles, while the cyclic units expand the adsorption area through rolling contact, achieving "dynamic sweeping" and improving flocculation efficiency.

[0038] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a biocomposite flocculant, characterized in that: The steps include: Step 1 is to dissolve konjac glucoside in deionized water, add an initiator thereto, add a dimethyldiallylammonium chloride solution thereto under heating conditions, and obtain a modified polymer after the reaction is completed; 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; 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 reaches 5000-8000 r / min, thereby obtaining the biocomposite flocculant.

2. The method for preparing the biocomposite flocculant according to claim 1, characterized in that: The solid-to-liquid ratio of the konjac polysaccharide solution, initiator, dimethyldiallylammonium 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, characterized in that: The initiator is acidified cerium ammonium nitrate; 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, characterized in that: 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, characterized in that: The mass ratio of oleic acid, polyether and initiator in step 2 is 5:60:0.

5.

6. The method for preparing the biocomposite flocculant according to claim 1, characterized in that: 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.

7. The method for preparing the biocomposite flocculant according to claim 1, characterized in that: The initiator in step 2 is dibenzoyl peroxide and / or dicumyl peroxide.

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

9. A biocomposite flocculant prepared by the preparation method according to any one of claims 1 to 8.

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