EA042842B1 - METHOD FOR PRODUCING FLOCCULANT FOR WATER PURIFICATION BASED ON CHITOSAN, FLOCCULANT PRODUCED BY THIS METHOD, ITS APPLICATION AND METHOD FOR WATER PURIFICATION USING THIS FLOCCULANT - Google Patents

Description

The invention relates to the field of obtaining means for water purification and to the field of ecology, namely, to a method for obtaining a new effective flocculant for water purification based on chitosan, its application and to a method for purifying water from natural and man-made pollution in various fields of human economic activity.

Purification of low-quality water with low sanitary and hygienic indicators from natural and man-made pollution in various areas of human economic activity is one of those urgent environmental problems that requires an effective solution.

Currently, there are the following problems in the field of water treatment:

impossibility at relatively small capital and operating costs to obtain the appropriate quality of water purification;

limited water treatment technologies that can immediately affect a wide range of contaminants;

significant power consumption of water treatment plants associated with a long technological process;

low productivity of water treatment plants and narrow selectivity of the membrane to the types of contaminants when using the hyperfiltration method;

the need to manufacture an anode from insoluble alloys or coatings, the danger of obtaining toxic and explosive products of water electrolysis, high capital and operating costs caused by the significant cost of manufacturing and operating electrode systems and power supply installations when using an electrochemical cleaning method based on the electrolysis of water and solutions, accompanied by two processes: anodic oxidation and cathodic reduction;

high sensitivity to the composition of the source water and, as a result, a limited scope.

Known polyacrylamide flocculant modified with chitosan, and a method for its production (CN 106008822, 10/12/2016), including the preparation of a solution of chitosan of a certain concentration, a solution of acrylamide of a certain concentration, a solution of an initiator of a certain concentration, a solution of an amine of a certain concentration and a solution of formaldehyde of a certain concentration; heating at normal pressure a solution of chitosan and a solution of acrylamide to 45-50°C, with a continuous supply of nitrogen for 20-40 min; adding an initiator solution, an amine solution and a formaldehyde solution at a system temperature of 45-50°C for 8-12 hours; adding after the end of the reaction of deionized water to obtain a flocculant.

The preparation method is mild in reaction conditions, simple in process and convenient in operation; the molecular weight of the prepared modified flocculant is high, the chemical oxygen demand and the removal rate of suspended solids from wastewater are high, and the flocculant has a high flocculation effect and good performance.

The disadvantages of this invention are the presence of a mandatory temperature exposure and a continuous supply of nitrogen to carry out the reaction, which complicates the process, as well as the presence of formaldehyde in the composition, which has a wide range of applications, but has carcinogenic properties.

A known method for the preparation and use of a synthesized agent for removing turbidity initiated by plasma (CN 105622848, priority dated March 21, 2016), including the addition of a natural macromonomer to an acid solution, until complete dissolution, followed by the addition of acrylamide monomer and a functional monomer until complete dissolution to obtain a mixture of monomers ; introducing the monomer mixture into the plasma initiator at room temperature, pre-purging with nitrogen gas for deoxygenation, and performing a discharge reaction after deoxygenation, and continuously purging with nitrogen during the discharge reaction; a post-polymerization reaction in a mixed solution under constant nitrogen purge during post-polymerization, and further for 10 to 60 minutes after completion of the reaction to obtain a haze remover and a calcium fluoride colloidal solution.

The disadvantages of this invention are the plasma initiation of the polymerization process and the constant nitrogen purge during the post-polymerization reaction and, as a result, the complexity and cost of the manufacturing process.

In the article by P.V. Tatarinov, A.E. Mochalova, I.V. Belysheva, L.A. Smirnova, I.V. Bodrikov Induced degradation of chitosan coupled with block copolymerization with acrylamide (Journal of Applied Chemistry, 2010, v. 83, issue 7), a method is described that includes the preparation of a block copolymer of chitosan acrylamide by induced initiation of chitosan degradation in the presence of acrylamide at low temperature ( 21-23°C). Block copolymerization of acrylamide and chitosan was carried out in 1–2% aqueous acetic acid solutions (pH 3.4–3.8) with a polysaccharide content of 1 wt %. Calculated amounts of ascorbic acid acrylamide and hydrogen peroxide were successively added to the polysaccharide solution with stirring. The molar ratios AA/glucosamine unit and glucosamine/H2O2 unit in the reaction mixture varied from 10 to 45.36 and from 20 to 100, respectively. The obtained chitosan-acrylamide block copolymers were ambifunctional systems in which coagulating and flocculating fragments are combined in the same macromolecules of block copolymers, which ensures efficient wastewater treatment. However, despite the wide range of concentrations under the indicated synthesis conditions, chitosan chains were significantly degraded to a molecular weight of ~8000 and polysaccharide chains with a molecular weight not exceeding ~800000 were grafted, which is insufficient for efficient flocculation of contaminants during wastewater treatment. In addition, the content of the obtained copolymer up to 45 parts of acrylamide units per one part of chitosan significantly reduces the environmental safety of this product, due to the high content of acrylamide. Also, this article shows the possibility of using a flocculant to treat only one type of polluted water, namely, to treat wastewater from the production of latex, which indicates the limited use of the resulting flocculant.

In the article by D.S. Skotnikova, A.E. Mochalova, L.A. Smirnova Sorption of metal ions by copolymers of chitosan with vinyl monomers (Journal of Applied Chemistry, 2019, vol. 92, issue 5), the synthesis of chitosan copolymers with 4-N-vinylpyridine, acrylamide, acrylic acid and the study of their sorption capacity for Cr (III) ions are described , IV). To synthesize graft copolymers, a 3% solution of chitosan in 1.2% acetic acid (or 0.75% hydrochloric acid) was placed in a reactor; the calculated amount of 4-N-vinylpyridine, acrylamide, or acrylic acid ([chitosan]/[vinyl monomer] ratio from 1/1 to 1/3 base mol/mol), stirred for 10 min at T = 50°C. Then, 1.4-10'3 mol- _l ' ¹ ammonium persulfate was added and the _synthesis was carried out _for 3 hours. ) And

H ₂ O ₂ ([chitosan]/[H ₂ O ₂ ]=50 base mol/mol).

During the process, samples were taken every 15-30 minutes to determine the conversion of vinyl monomers. A block copolymer of chitosan with acrylamide and acrylic acid was obtained in the molar ratio of chitosan:acrylamide:acrylic acid = 1:3:1 base-mol:mol:mol at room temperature. The sorption properties of chitosan and the resulting copolymers were tested in the treatment of wastewater from one of the electroplating plants in Nizhny Novgorod. The sorption capacity of copolymers of chitosan with vinyl monomers for chromium ions increases in the series chitosan-acrylamide < chitosan-4-N-vinylpyridine << chitosan-acrylamide-acrylic acid at the same sorbent concentration of 1.3 wt %. The degree of purification from chromium ions is 18.1<39.4<81.5%, respectively. The introduction of monomer units of acrylic acid into the structure of the chitosan-acrylamide copolymer increases the efficiency of the sorbent by a factor of 4.

The disadvantages of this study include the lack of data on the molecular weight of the copolymers obtained and the limited scope of their application, namely, for the purification of wastewater from galvanic production from chromium ions: Cr(total) Cr(III), Cr(VI). It is noteworthy that the authors studied in detail and compared with each other mainly the properties of double copolymers of different compositions. Only one example is given for a 1:3:1 XTS-AA-AK ternary copolymer without a detailed description of its synthesis and any characteristics of the product.

It is known that synthetic polymers based on polyacrylamide and acrylic acid, traditionally used for solving water purification problems, have a number of disadvantages: resistance to biological degradation, toxicity and carcinogenicity due to the presence of a residual amount of unpolymerized acrylamide. This significantly limits the use of synthetic flocculants for water treatment in a number of industries. In this regard, biodegradable and non-toxic natural polymers can become an economically viable alternative to synthetic flocculants.

The problem solved by the present invention was the development of a method for obtaining a new flocculant based on natural chitosan polysaccharide with an optimal molecular weight ratio and the content of acid groups, which has increased efficiency, allowing it to be used for treating water with a wide range of contaminants at existing treatment facilities.

The technical result from the use of the invention is to increase the environmental safety and efficiency of the flocculant, expand the scope of its application, simplify the technological process of its production and use.

The task is achieved by the fact that a method for producing a flocculant for water purification based on chitosan, in which a water-acetic acid solution of chitosan with an acetic acid content of 1.2-3 wt.% or a hydrochloric acid solution of chitosan with a hydrochloric acid content of 0.5-1 wt. .% at pH values of 4-6, a water-acetic acid solution of chitosan or a hydrochloric acid solution of chitosan containing hydrochloric acid and acrylamide monomer and/or its derivatives are copolymerized at a ratio, base-mol/mol: chitosan - 1, acrylamide - 3, then blowing is carried out reaction mixture of a solution of chitosan and acrylamide with argon, the copolymerization is carried out in the presence of a redox system, including ascorbic acid dissolved in water in a ratio of C ₆ H ₈ O ₆ :H ₂ O ₂ - 1:1 mol, and hydrogen peroxide at a ratio of basic

- 2 042842 mol/mol: chitosan - 10-75, H2O2 - 1, after which acrylic acid is introduced, previously neutralized with sodium hydroxide NaOH, in the following ratio of components, base-mol/mol: chitosan - 1, acrylic acid - 3-10 , the synthesis is carried out at a temperature of 15-30°C for 3.5-6 hours; use chitosan with a molecular weight of 150,000-250,000 and a degree of deacetylation of 78-85%; instead of acrylamide, its derivatives are used, such as methacrylamide, N-alkylacrylamide; the ratio of ascorbic acid and hydrogen peroxide is 1:1 mol; using a 30% aqueous solution of hydrogen peroxide; the ratio of acrylic acid and sodium hydroxide is 1:1 mol.

This task is also achieved by the fact that the flocculant for water purification based on chitosan, obtained by the proposed method, is a copolymer of chitosan/acrylamide/acrylic acid with a molecular weight of at least 1270000 in the following ratio of components, base mol/mol: chitosan - 1, acrylamide - 3 , acrylic acid - 3-10, in which the content of chitosan is not less than 15 wt.%, the content of acid groups is not less than 8.7 wt.%, the content of the basic substance is not less than 3-5%; is a concentrated solution - gel with a viscosity of at least 250 cSt.

This task is also achieved by using a flocculant for water purification based on chitosan, obtained by the proposed method, from contaminants selected from suspended particles, chlorine, metal ions, oil products.

This task is also achieved by the fact that the method of water purification includes water treatment with a flocculant for water purification based on chitosan, obtained by the proposed method, precipitation and filtration; additionally add Aqua aurat 30.

The proposed method of obtaining a flocculant for water treatment is as follows.

First, a water-acetic acid solution of chitosan is prepared with an acetic acid content of 1.2-3 wt.% or a hydrochloric acid solution of chitosan with a hydrochloric acid content of 0.5-1 wt.% at pH values of 4-6.

Then, a water-acetic acid solution of chitosan or a hydrochloric acid solution of chitosan containing hydrochloric acid and acrylamide monomer and/or its derivatives are copolymerized at a ratio, base-mol/mol:

chitosan - 1, acrylamide - 3.

In a preferred embodiment of the invention, the reaction mixture of chitosan and monomer is purged with an inert gas, preferably argon, prior to the addition of the redox system.

The copolymerization is carried out in the presence of a redox system, including ascorbic acid dissolved in water in the ratio C ₆ H ₈ O ₆ :H ₂ O ₂ - 1:1 mol, and hydrogen peroxide in the ratio, base-mol/mol: chitosan -10 -75, H2O2-1.

After that, acrylic acid is introduced, previously neutralized with sodium hydroxide NaOH (acrylic acid: NaOH = 1:1 in mol), at a ratio, base-mol/mol:

chitosan - 1, acrylic acid - 3-10.

The synthesis is carried out at a temperature of 15-30°C for 3.5-6 hours.

Chitosan (CTS), preferably used in the method of the present invention, is a food grade (acid soluble) light cream powder (or flakes), odorless, with a molecular weight of 150,000-250,000 and a degree of deacetylation of 78-85%.

The used chitosan also has the following characteristics: mass fraction of moisture - 6.09%, mass fraction of minerals - 0.6%, pH of a 1% solution of ChTS in 2 wt.% acetic acid - 3.28, mass fraction of insoluble substances - 0, 08%, sorption activity for copper ions - 58.7 mg/g.

Chitosan is preferably used in the form of 2-4 wt.%, most preferably 3 wt.% hydroacetate or hydrochloric acid solution.

Most preferably, a 3 wt.% solution of chitosan in 1.2 wt.% aqueous acetic solution or a 3 wt.% solution of chitosan in 0.75 wt.% hydrochloric acid solution is used.

As a solvent in the method according to the present invention, hydroacetic acid solutions with an acetic acid content of 1.2 to 3 wt.%, preferably 1.2 wt.%, or hydrochloric acid solutions with a hydrochloric acid content of 0.5 to 1 wt.%, preferably 1.2 wt.% acetic acid or 0.75 wt.% hydrochloric acid.

Preferably, the method of the present invention uses acrylamide (AA), chemical grade, without further purification. Acrylamide is a colorless crystals with T. pl. 84.5°C, b.p. 25 ° C, with solubility (1 g per 100 g of solvent): in water - 211.5, methanol - 155.0, ethanol - 86.2, acetone - 63.1, ethyl acetate - 12.6, chloroform - 2, 66, benzene - 0.346, heptane - 0.0068.

Purging with an inert gas, preferably argon, is carried out for 15-30 minutes.

As a redox system in the method of the present invention, an aqueous solution of ascorbic acid and an aqueous solution of hydrogen peroxide are used at the ratio

- 3 042842 nii 1:1.

The ascorbic acid used in the present invention is a white crystalline powder with a sour taste, easily soluble in water and alcohol. The melting point of L-ascorbic acid is 190-192°C (with decomposition).

In a preferred embodiment of the invention, a 30% aqueous hydrogen peroxide solution is used. It is a colorless liquid, infinitely soluble in water, alcohol and ether. Concentrated aqueous solutions are explosive. Hydrogen peroxide is a good solvent. It is released from water in the form of an unstable crystalline hydrate H ₂ O ₂ * 2H ₂ O.

Acrylic acid (AA) used in the method of the present invention is preferably acrylic acid purified by vacuum distillation in a Claisen flask in the presence of 5% (by weight of distilled product) hydroquinone as a stabilizer (fraction taken at T=48.5 °С, Р=15 mm Hg). Acrylic acid is highly soluble in alcohol, ether and miscible with water in all proportions. It is used to obtain water-soluble polymers, as well as copolymers with other monomers.

In a preferred embodiment of the process of the present invention, acrylic acid is pre-treated with sodium hydroxide at a ratio of 1:1 mol/mol.

In a preferred embodiment, the addition of acrylic acid pretreated with sodium hydroxide to the reaction mixture is carried out after reaching a degree of acrylamide conversion of at least 75%. The control is carried out by the method of bromide-bromate titration.

In a preferred embodiment of the invention, the ratio of chitosan/acrylamide/acrylic acid is 1:3:5 base mol/mol/mol.

Instead of acrylamide, derivatives such as methacrylamide and N-alkylacrylamide can be used.

In a preferred embodiment of the invention, the copolymerization is carried out at a temperature of from 15 to 30°C, preferably at room temperature, most preferably at a temperature of from 15 to 20°C or from 24 to 30°C.

In a preferred embodiment of the invention, additional sodium hydroxide is added to the reaction system until the desired pH is obtained and the copolymerization is preferably carried out at pH values from 4 to 6.

The synthesis is carried out at room temperature for 3.5-6 hours, preferably 5 hours.

The flocculant for water purification, obtained by this method, is a chitosan/acrylamide/acrylic acid copolymer in the form of a concentrated solution (gel) with a viscosity of at least 250 cSt, with a molecular weight of at least 1,270,000, with the following ratio of components, base mol/mol/mol:

chitosan - 1, acrylamide - 3, acrylic acid - 3-10, in which the content of chitosan is not 15 wt.%, the content of acid groups is not less than 8.7 wt.%; and the content of the main substance is not less than 3-5%.

In a preferred embodiment of the invention, the content of chitosan in the copolymer is at least 22 wt.%.

The flocculant obtained by the proposed method is used to purify water, including surface and ground water, sea water (to remove suspended solids), water for household and drinking needs, wastewater from galvanic, oil refining, paint and varnish, leather, food industries, wastewater from enterprises for production of building materials, paper.

In a preferred embodiment of the invention, the flocculant of the present invention is used to purify water from contaminants, including suspended particles, metal ions, chlorine, oil products.

In a preferred embodiment of the invention, the flocculant of the invention can be used in combination with coagulants such as Aqua Aurate 30.

Sewage treatment method includes precipitation and its filtration. The amount of flocculant varies depending on the degree of contamination of natural water or effluents in specific applications and is determined empirically. The use of the resulting flocculant for wastewater treatment and in water treatment processes leads to the formation of large flakes that are easily removed without the use of special equipment, which significantly reduces the cost of the treatment process and the technological scheme, since microfiltration is not required to remove hard-to-remove contaminants, which is necessary at existing treatment facilities.

The method for obtaining flocculants according to the present invention allows organizing the industrial production of flocculants on existing equipment, including food and cosmetic enterprises.

In this invention, the optimal ratios between the values of molecular

- 4 042842 weight and the content of acid groups in the copolymer based on natural biodegradable polysaccharide - chitosan, which improves the environmental safety and efficiency of the flocculant, expands the scope of its application, simplifies the technological process of its production and use. With an increase in the molecular weight, the flocculating ability of the copolymer increases, and the presence of acidic groups in its composition imparts additional properties - the sorption of contaminants of various nature by the mechanism of electrostatic interaction.

The resulting flocculant can replace synthetic flocculants without a significant change in the technological schemes of water purification and equipment composition, which significantly expands its scope, simplifies water purification technologies and increases the environmental friendliness of the purification process by improving the quality characteristics of flocculants that are used to purify water with different acidity values. , salinity, concentration of a wide range of pollutants.

Further, the present invention is illustrated by means of examples, which do not limit the scope of claims defined by the claims.

Example 1. Synthesis of block copolymer XTS-AA-AK.

Block copolymer XTZ-AA-AK was obtained in hydrochloric acid solution of polysaccharide 3 wt.% with hydrochloric acid concentration of 0.75 wt.% at 15-200C. Block copolymerization was carried out in 2 stages: at the first stage, AA was introduced into the CTS solution - 1.98 g of AA was added with stirring to 50 ml of the chitosan solution, the reaction mixture was purged with argon for 15 min, then 0.0132 g (1.5x10 -3 mol / l) ascorbic acid dissolved in water and 0.0186 ml of 30 wt.% aqueous solution of H ₂ O ₂ at a ratio of chitosan: H ₂ O ₂ 12:1 base-mol / mol, and a ratio of C ₆ H ₈ O ₆ -H ₂ O ₂ 1:1 (in mol). In 15 min, up to 95% AA polymerized, after which AA neutralized with NaOH was introduced (the ratio of CTS/AA/AA was 1:3:3, 1:3:5, 1:3:7, 1:3:10 base mol /mol/mol). The synthesis was carried out for 5 h.

In table. 1 presents the copolymers obtained by this method at various ratios of chitosan/monomer. From Table. Table 1 shows that the synthesis of copolymers with a high content of AA in the loading mixture ([ChTS]-[AA]-[AA]=1:3:7, 1:3:10 base mol/mol/mol) is inappropriate, since the content acid groups in them does not exceed 9% (the higher the content of acid groups in the copolymer, the higher its purification efficiency from positively charged pollutants, for example, metal ions).

Also, in order to determine the molecular weight and acid groups, a copolymer of the composition XTZ-AA-AK 1:3:1, known from the article by D.S. Skotnikova, A.E. Mochalova, L.A. Smirnova Sorption of metal ions by copolymers of chitosan with vinyl monomers (Journal of applied chemistry, 2019, vol. 92, issue 5), to compare the above parameters.

In table. 1 shows the composition of the reaction mixture for the synthesis of KhTS-AA-AK copolymers per 1 liter of 3% aqueous acetic acid or hydrochloric acid solution of chitosan (T=15-20°C, 24-30°C, m(H2O2)=2.1 -0.28 g([ChTS]/[H2O2]=10:1-75:1 base mol/mol), m(ask acid)=10.87-1.4 g([H2O2]/[ Ask acid]=1:1 mol/mol)). The rest of the mass up to 1 kg - H ₂ O.

Table 1. Composition of the reaction mixture for the synthesis of KhTS-AA-AK copolymers

Acetic acid CH3COOO H 1.2-3 wt.%, g Hydrochloric acid HC1 0.5 - 1 wt.%, g HTZ, g AA, g [ChTS]/[A A]/[AA], base mol/mol/mol Acrylic acid AA, g NaOH, g ChTS content in flocculants, wt.% Duration of synthesis at t=1520°C, min. Duration of synthesis at t=2430°C, min. Molecular weight of the final copolymer The content of acid groups, wt.% 11.7-29.2 thirty 39.6 *1:3:1 13.4 7.4 36 300 210 940 000 15.9 1:3:3 40.2 22.3 27 300 210 1,270,000 21.2 1:3:5 67.0 37.2 22 300 210 1 850 000 28.8 1:3:7 93.7 52.1 18 300 210 9 1:3:10 133.9 74.4 15 300 210 8.7 13.2-26.4 thirty 39.6 *1:3:1 13.4 7.4 36 300 210 940 000 15.9 1:3:3 40.2 22.3 27 300 210 1,270,000 21.2 1:3:5 67.0 37.2 22 300 210 1 850 000 28.8 1:3:7 93.7 52.1 18 300 210 9 1:3:10 133.9 74.4 15 300 210 8.7

*For a copolymer of this composition (taken from the article by D.S. Skotnikov, A.E. Mochalov, L.A. Smirnov Sorption of metal ions by copolymers of chitosan with vinyl monomers, (Journal of Applied Chemistry, 2019, vol. 92, issue 5) ) for comparison purposes, the molecular weight and the number of acid groups were determined.

Due to the fact that the content of acid groups according to the synthesis options with the composition of the reaction mixture KhTS-AA-AA 1:3:7 and 1:3:10 is insignificant, the calculation of the molecular weight for these synthesis options was not performed.

Example 2. Results of purification of waste water from galvanic production from manganese ions.

In 100 ml of wastewater containing manganese ions, at room temperature, 1.8 ml of a 0.1% solution of the copolymer of chitosan-acrylamide-acrylic acid XTZ-AA-AA (1.8 * 10 ^-3 %) was added, semi- 5 042842 prepared according to example 1, in a ratio of 1:3:3 base mol/mol/mol and stirred for 10 minutes.

The cleaning results are presented in table.2.

Table 2. Results of purification of wastewater from electroplating from manganese ions with chitosan-acrylamide-acrylic acid copolymers according to example 1

Reagent The content of manganese ions, mg / dm ³ Source waste water 0.3 Copolymer XTZ-AA-AK 1.8*10' ³ % 0.08

The test results showed the high efficiency of flocculants in the treatment of wastewater from galvanic production from manganese ions: treatment according to the KhTZ-AA-AK scheme (1.8 * 10-3%) reduces the content of manganese ions from 0.3 to 0.08 mg / dm ³ . Given that manganese ions are complex contaminants, it can be considered that other metal ions can also be effectively sorbed using the flocculants of the present invention.

Example 3. Results of wastewater treatment of an oil refinery.

In 100 ml of waste water at room temperature, a certain amount (in accordance with Table 3) was added of the chitosan-acrylamide-acrylic acid copolymer obtained in example 1 in a ratio of 1:3:5 base-mol/mol/mol and stirred for 5 min, then the amount of Aqua aurate was added (according to Table 3). Effluent was analyzed in accordance with the Russian Federal Environmental Regulations (PND F), included in the Register of methods for quantitative chemical analysis and assessment of the state of environmental objects, which are approved for state environmental control and monitoring. The results are presented in table. 3.

Table 3. Results of wastewater treatment of an oil refinery with chitosan-acrylamide-acrylic acid copolymers according to example 1

Reagent Chemical oxygen demand (COD), mgO/dm ³ Mass concentration of oil products, mg / DM ³ Suspended substances, mg / dm ³ Initial waste water 1856 23 78 XTZ-AA-AK copolymer 1.6 * 10' ³ % Aqua aurate 1 * 10' ² % 1476 12 <3 RD for test methods PNDF 14.1:2:4.190-2003 PND F 14.1:2:4.128- 98 PNDF 14.1:2:3. 110-97

The test results showed the high efficiency of flocculants in the treatment of oily wastewater: treatment according to the KhTZ-AA-AK scheme (1.6 * 10-3%) + aqua aurate (1 * 10'2%) reduces the Chemical Oxygen Demand (COD) index from 1856 to 1476 mgO/dm ³ , oil content from 23 to 12 mg/dm ³ with simultaneous complete removal of suspended particles from wastewater.

Thus, the proposed invention improves the result of the technological process of water purification, simultaneously with an environmental orientation, according to the following criteria:

1) the ability to purify water from suspended solids, oil products, metal ions;

2) the possibility of gradual replacement of synthetic flocculants by the proposed flocculant without a significant change in the technological schemes of purification and composition of equipment, which significantly expands the scope and increases the pace of implementation of the proposed invention;

3) the flocculant is based on the environmentally friendly biodegradable natural polymer chitosan, which makes it possible to effectively use it in water treatment for household and drinking needs.

Compared with the proposed flocculant, the [XTZ]-[AA]-[AK] 1:3:1 copolymer known from the article by D.S. Skotnikova, A.E. Mochalova, L.A. Smirnova Sorption of metal ions by copolymers of chitosan with vinyl monomers (Journal of Applied Chemistry, 2019, v. 92, issue 5), containing a sufficient amount of acid groups (15.9 wt.%), but with a relatively low molecular weight (940,000), has limited scope - effective extraction of metal ions with low flocculating ability to other types of pollution.

As part of the proposed method for obtaining flocculants, the industrial production of these flocculants can be organized on the existing equipment of enterprises, including food and cosmetics.

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Claims (11)

CLAIM 1. A method for producing a flocculant for water purification based on chitosan, in which a water-acetic acid solution of chitosan is prepared with an acetic acid content of 1.2-3 wt.% or a hydrochloric acid solution of chitosan with a hydrochloric acid content of 0.5-1 wt.% at values pH 4-6, a copolymerization of a water-acetic acid solution of chitosan or a hydrochloric acid solution of chitosan and acrylamide monomer and/or its derivatives, which are methacrylamide or N-alkylacrylamide, is carried out at a ratio, base-mol/mol: chitosan - 1, acrylamide - 3, after which the reaction mixture of a solution of chitosan and acrylamide is purged with argon, while the copolymerization is carried out in the presence of a redox system, including ascorbic acid dissolved in water and hydrogen peroxide in the ratio CbH ₈ Ob:H ₂ O ₂ - 1:1 mol at a ratio, base-mol / mol: chitosan - 10-75, H ₂ O ₂ - 1, then acrylic acid is introduced, previously neutralized with sodium hydroxide NaOH, in the following ratio of components, base-mol / mol: chitosan - 1, acrylic acid - 3-10, synthesis is carried out at a temperature of 15-30°C for 3.5-6 hours. 2. The method according to claim 1, characterized in that chitosan with a molecular weight of 150000250000 and a degree of deacetylation of 78-85% is used. 3. The method according to claim 1, characterized in that acrylamide derivatives are used, which are methacrylamide, or N-alkylacrylamide. 4. The method according to claim 1, characterized in that the ratio of ascorbic acid and hydrogen peroxide is 1:1 mol. 5. Method according to claim 1, characterized in that a 30% aqueous solution of hydrogen peroxide is used. 6. The method according to claim 1, characterized in that the ratio of acrylic acid and sodium hydroxide is 1:1 mol. 7. A flocculant for water treatment, obtained by the method according to claim 1, which is a chitosan/acrylamide/acrylic acid copolymer with a molecular weight of at least 1,270,000, in the following ratio of components, base-mol/mol: chitosan - 1, acrylamide - 3, acrylic acid - 3-10, in which the content of chitosan is not less than 15 wt.%, the content of acid groups is not less than 8.7 wt.% and the content of the main substance is not less than 3-5%. 8. The flocculant according to claim 7, characterized in that it is a concentrated solution - gel with a viscosity of at least 250 cSt. 9. The use of a flocculant according to claim 7 for water purification from contaminants selected from suspended particles, chlorine, metal ions, oil products. 10. A method of water purification, including treatment of water with a flocculant according to claim 7, precipitation and its filtration. 11. The method according to claim 10, characterized in that it additionally includes the addition of Aqua aurate 30. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2