RU2175268C2 - Method of preparing carboxy-containing cationite - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: described is synthesis of carboxy-containing cationite by grafted copolymerization of acrylic and methacrylic acid with polymer-rubber crumb pretreated with tert- butylhydroperoxide in acid medium for 8-16 h at rubber crumb to tert- butylhydroperoxide weight ratio of 1:1-2.5, copolymerization being carried out at 60-70 C in the presence of peroxide group decomposition activator and at polymer to vinyl monomer weight ratio of 1:1-1.5. Cationite contains carboxy groups (from 9.7 to 12.4%) which make it possible to extract ions of heavy metals, particularly, copper, nickel, cobalt and mercury from aqueous solutions of salts thereof. EFFECT: more efficient preparation method. 18 ex, 4 tbl

Description

 The invention relates to a method for producing carboxyl-containing cation exchanger, which can be used in the chemical and metallurgical industries for wastewater treatment from copper, nickel, cobalt, and mercury ions.

 A known method of producing a carboxyl-containing cation exchange resin by alkylation of a grafted copolymer of cellulose with poly-2-methyl-5-vinylpyridine with monochloroacetaldehyde, followed by oxidation of the aldehyde groups to carboxyl. (Korotkova A.Ya., Kryazhev Yu.G., Rogovin Z.A. [Cellulose and its derivatives] // High-molecular compounds - 1964. - N 6).

 The disadvantages of the proposed method are a significant amount of the resulting homopolymer, a low content of carboxyl groups in the cation exchange resin, as well as insufficient static exchange capacity, which leads to a decrease in sorption properties.

 A known method of producing carboxyl-containing cation exchange resin by preliminary thermal oxidation of the polymer or by exposure to ionizing radiation, followed by thermal or catalytic destruction of the hydroperoxides formed during the oxidation (Orphan A.G. Modification of the structure and properties of polyolefins. -L .: - Chemistry, 1984. - 146 from.).

 The disadvantage of this method is the partial destruction of the polymer during thermal oxidation and ionizing irradiation, which reduces the mechanical strength, cation exchange rate and its service life.

 A known method of producing a carboxyl-containing cation exchange resin by hydrolysis of a polyacrylonitrile fiber crosslinked with hydrazihydrate. (Enthalpy and thermokinetics of sorption of 3d-metal ions by carboxyl ion-exchange fiber VION KN-1 / Kopylova V.D., Valdman A.I., Valdman D.I., Portnykh I.V., T.I. Ivanova // Journal of Applied Chemistry . - 1996. - N 2. - P. 302).

 The disadvantages of this method are the destruction of the polymer during its hydrolysis, the low content of carboxyl groups in the resulting cation exchange resin, a decrease in mechanical strength and the inability to use it in aggressive environments.

 A known method for producing fibrous ion-exchange materials by free-radical grafting of vinyl monomers to cellulose containing vinylogenic groups or groups capable of being converted to ionogenic (USSR Author's Certificate N 444773, class C 08 C 15/00, 1975).

 The disadvantage of this method is that when grafting monomers to cellulose, such as, for example, acrylic or methacrylic acid, an increase in swelling occurs, which prevents the repeated use of fibrous ion exchanger in the process of sorption and desorption.

 The closest is a method for producing carboxyl-containing cation exchange resin, which consists in pretreating viscose fiber with an aqueous solution of Mohr's salt, followed by grafting vinyl monomers to the fiber and treating it with alkali (USSR Author's Certificate N 806692, C 08 F 251/02, 1981).

 The disadvantages of this method are the multi-stage process, the formation of a large amount of homopolymer, which reduces the efficiency of grafting, high swelling of the fiber, its partial destruction, which reduces mechanical strength and does not allow its use repeatedly, as well as the inability to use it in aggressive environments.

 The objective of the proposed technical solution is the development of a new highly efficient method for producing carboxyl-containing cation exchange resin, capable of working in aggressive environments, as well as its repeated use.

 The technical result is to improve the manufacturability of the process, increase the efficiency of grafting, the ability of cation exchanger to work in aggressive environments, the ability to extract heavy metal ions from solutions, increase the life of the cation exchanger.

The technical result is achieved by the fact that the synthesis of carboxyl-containing cation exchange resin is carried out by graft copolymerization of a vinyl monomer with a polymer, moreover, rubber crumb (PK) is used as the polymer, pretreated for 8-16 hours with tert-butyl hydroperoxide (TBHP) in an acidic medium with mass the ratio of RK: TBHP = 1: 1-2.5, and the copolymerization is carried out at a temperature of 60-70 ^o C in the presence of an activator of the decay of peroxide groups and the mass ratio of polymer and vinyl monomer = 1: 1-1.5.

 The invention consists in the following.

 By the interaction of TBHP with RK in an acidic medium, peroxidized crumb rubber (PRK) is obtained with the content of peroxide groups from 1 to 5.6% (Scheme 1). Then, vinyl monomer, acrylic (AK) or methacrylic acid (MK) is added, and in the presence of an activator for the decomposition of peroxide groups of copper sulfate or iron sulfate, the synthesis of a carboxyl-containing cation exchange resin is carried out (Scheme 2).

The initiating ability of the introduced peroxide groups was studied calorimetrically, as a result of which it was found that the grafting of the vinyl monomer to PPH begins at a temperature of at least 60 ^o C in the presence of a decay activator of peroxide groups, which is used as ferrous sulfate or copper sulfate. It was also established that the PRK resulting from the decay of tert. The butoxy radical promotes the formation of a homopolymer, and the macroradical initiates the grafting of the vinyl monomer. The resulting product is a weakly acid cation exchanger.

 Such cation exchange resin contains carboxyl groups (from 9.7 to 12.4%), which allow the extraction of heavy metal ions from solutions.

 The proposed method allows to obtain a carboxyl-containing cation exchange resin with better properties.

 The formation of a sufficiently strong chemical bond between the cross-linked polymer matrix of the Republic of Kazakhstan with the vinyl monomer leads to an increase in the mechanical strength of the cation exchanger, which allows it to be used repeatedly.

 Note that in the proposed method for the synthesis of grafted copolymers, grafting is highly effective, which allows to obtain cation exchange resin with a high content of carboxyl groups, which confirms the manufacturability of the proposed method.

 The increase in sorption capacity is associated with an increase in the number of grafted polymer to the polymer matrix of chips. The crosslinked, elastic, water-resistant polymer base of the cation exchanger allows sorption of metal ions in various media over a wide range of pH of the solution.

 The method is as follows.

RK with an average size of 1-1.12 mm is treated for 8-16 hours at a temperature of 20 ^o C TBHP (mass ratio of RK: TBHP = 1: 1-2.5) in the presence of 65.8% sulfuric acid, the molar ratio of TBHP: H ₂ SO ₄ = 1: 0.13.

PPH with a peroxide content of 1 to 5.6% is reacted with a vinyl monomer (AK or MK) at a weight ratio of 1: 1-1.5, respectively, in the presence of copper sulfate or iron sulfate at a temperature of 60-70 ^o C. The concentration of copper sulfate or iron sulfate in solution is 0.005-0.01 wt.%. The mass ratio of PRK: H ₂ O = 1: 1. Obtaining PPH is illustrated by the following examples.

Example 1. To 10 g of PK with an average size of 1.12 mm add 10 g of TBHP (wt. Rel. 1: 1), 0.71 g of sulfuric acid with a concentration of 65.8%. The reaction mass is stirred at a temperature of 20 ^o C for 8 hours. After completion of the reaction, the reaction mass is extracted in a Sockett device with a mixture of chloroform and isopropyl alcohol solvents (mass ratio 1: 1) until the adsorbed hydroperoxide is completely removed, after which the product is dried in a vacuum oven at a temperature of 60-70 ^o C and the content of chemically fixed peroxide groups is determined in baby iodometric method. The content of peroxide groups in the Republic of Kazakhstan is 1.0%.

 Example 2. In contrast to example 1, the mass ratio of RK: TBHP = 1: 1.5. The content of peroxide groups in the Republic of Kazakhstan is 2.4%.

 Example 3. In contrast to example 1, the mass ratio of RK: TBHP is 1: 2, the reaction time is 16 hours. The content of peroxide groups in the crumb is 5.6%.

 Example 4. In contrast to example 1 in this example, the mass ratio of RK: TBHP = 1: 2.5. The content of peroxide groups in the crumb is 3.0%.

 Example 5. In this example, the prohibitive value of the mass ratio of RK: TBHP = 1: 0.5 was taken. The peroxide content of the RK group decreases to 0.6%.

 Example 6. In contrast to examples 3, the reaction time is 18 hours. As can be seen from the table. 1, an increase in the reaction time leads to a slight increase in the content of peroxide groups in the crumb (up to 5.8%), which is impractical.

 The increase in the mass ratio of RK: TBHP more than 1: 2.5 does not lead to a noticeable increase in the content of peroxide groups in the crumb.

 The results of the studies are presented in table. 1.

 Vaccination is carried out in aqueous solutions of AK or MK. The preparation of a carboxyl-containing cation exchanger is illustrated by the following examples.

 Example 7

10 g of AK (PRK: AK = 1: 1), 50 ml of water and 0.45 g of CuSO ₄ (0.005% in solution) are added to 10 g of PPH of a dispersion degree of 1-1.12 mm with a peroxide content of 1%. The reaction mass is stirred for 4 hours at a temperature of 60 ^o C. With stirring, a sample is taken to control changes in the concentration of AA in the solution. To determine the resulting homopolymer, the concentration of AA is determined by the bromide-bromate and alkalimetric method. After completion of the reaction, the product is washed from the homopolymer with a solution of acetone with water (mass ratio 1: 3), dried to constant weight, and the content of carboxyl groups in the crumb is determined. Under these conditions, the content of carboxyl groups is 9.7%. Vaccination efficiency 92%. Investigation of the influence of reaction time showed that an increase in reaction time up to 4 hours leads to an increase in grafted carboxyl groups, a further increase in time is impractical, since it does not lead to an increase in grafted polymer.

 Example 8 is carried out analogously to example 7. The difference is the ratio of PRK: AK = 1: 1.25. The content of carboxyl groups in the crumb is 10.8%. Vaccination efficiency 92%.

 Example 9. In contrast to example 7, the ratio of PRK: AK take 1: 1.5.

 The content of carboxyl groups in the modified product is 10.3%, and the grafting efficiency is 90%.

Example 10. In this example, to increase the content of carboxyl groups in the crumb, 10 g of PRK with a content of peroxide groups of 5.6%, 10 g of AK (PRK: AK = 1: 1), 50 ml of water and 0.67 g of CuSO ₄ (0.075% in solution) are taken ) The reaction mass is stirred at a temperature of 70 ^o C, for 4 hours. Under these conditions, the content of carboxyl groups in the crumb is 12.4%, and the vaccination efficiency is 98%.

 Example 11. In contrast to example 7 in this example, the content of peroxide groups in the RK is 2.4%, and the mass ratio of PRK: AK = 1: 1. The content of carboxyl groups in the product after the reaction is 9.8%. The vaccination efficiency is 97%.

 Example 12. In contrast to example 7, the content of copper sulfate in the solution is 0.67 g (0.075% in solution), the content of peroxide groups in the crumb - 5.6%. In the resulting product, the content of carboxyl groups is 11.4%. Vaccination efficiency 95%.

 Example 13. In the above example, in contrast to example 12, the amount of copper sulfate in the solution is 0.01% (0.90 g). The content of carboxyl groups in the product is 10.5%, and the vaccination efficiency is 97%.

Example 14 and 15. In contrast to examples 7-13, we took prohibitive ratios of PRK and AK, temperature. From the data presented table. 2 shows that when the mass ratio of PRK and AK is 1: 0.5, the content of carboxyl groups decreases to 5.8%, and an increase in temperature from 60 to 80 ^o C and the ratio of PRK and AK to 1: 1.75 reduces the vaccination efficiency, i.e., a sharp an increase in the amount of homopolymer with a slight increase in the amount of grafted polymer.

 Example 16. In contrast to examples 7-15, in this example, iron sulfate is used as an activator of the decomposition of peroxide groups.

 Example 17, 18. In contrast to examples 7-16, MK is used as a monomer in this example. In example 17, vaccination is carried out with the participation of an activator of the decomposition of peroxide groups of iron sulfate, and in example 18 - copper sulfate.

From the presented data it is seen that a change in the mass ratio of PPH: AK more or less 1: 1.5 reduces the effectiveness of vaccination. The same pattern is observed with an increase in the reaction temperature, an increase in temperature above 70 ^o C leads to a sharp increase in the homopolymer. The amount of peroxide groups and copper sulfate has a negligible effect on the content of carboxyl groups in the Republic of Kazakhstan and on the effectiveness of vaccination. The best results are obtained when using peroxide groups of copper sulfate as an activator of decomposition, and AK as a monomer.

A sufficiently high (12.4%) amount of carboxyl groups in the crumbs allowed the use of this product for the extraction of heavy metal ions. In this regard, we conducted studies on the extraction of metal ions, in particular, copper, nickel, cobalt, mercury ions from aqueous solutions of their salts {Cu (No. ₃ ) ₂ : NiSO ₄ ; CoSO ₄ ; Hg (CH ₃ COO) ₂ }.

 The static exchange capacity (SOE) is determined according to the standard method (GOST 20255.1-89 Method for determining the static exchange capacity. - Publishing house of standards, 1989. - 112 p.).

 An example of the extraction of metal ions is carried out as follows: a solution containing metal ions (5 mg / L) is placed in a conical flask and 1 g of carboxyl-containing crumb is added at a strictly defined pH. After 24 hours, determine the concentration of the solution according to the standard method (Saldadze K. M., Pashkov AB, Titov B. S. Ion-exchanged high molecular weight compounds. - M .: Goskhimizdat, 1960. - 365 p.). pH vary in the range of 3.5-7.8. RK is used with a carboxyl group content of 9.7-12.4%. The results of the studies are presented in table. 3.

 It can be seen from the presented data that under the studied conditions, samples of carboxyl-containing crumbs of AK have a higher sorption capacity in the Na form than samples in the H form. Moreover, the highest values of sorption capacity are observed for copper ions.

 As can be seen from the data presented in table. 3, the proposed cation exchange resin is able to work at a solution pH of 3.5-7.8. At a solution pH less than 3.5, a sharp decrease in sorption capacity is observed in connection with a decrease in the concentration of coordination-active (unprotonated) carboxyl groups. When the pH of the solution is greater than 7.8, the degree of swelling of cation exchanger increases, its complexity increases, which also leads to a decrease in sorption capacity.

 Of great importance is the ability of an ion exchanger to retain its properties after repeated sorption - regeneration cycles. In the table. 4 presents data on the extraction of copper ions from solutions after 6 cycles of sorption - regeneration. Regeneration is carried out 0.1 N. hydrochloric acid solution according to the standard method (Volzhinsky A.I., Konstantinov V.A. Ionite regeneration. Theory of the process and calculation of apparatuses. - L .: Chemistry, 1990. - 240 p.)

 As can be seen from the data presented in Table 4, after 6 cycles of sorption and regeneration, the SOE practically does not change, which indicates the possibility of reuse of the obtained cation exchanger.

Claims (1)

A method of producing a carboxyl-containing cation exchange resin by graft copolymerization of a vinyl monomer with a polymer, characterized in that acrylic or methacrylic acid is used as a vinyl monomer, rubber crumb is used as a polymer, pretreated for 8-16 hours with tert-butyl hydroperoxide in an acidic medium in bulk ratio of crumb rubber and tert-butyl hydroperoxide of 1: 1-2.5, wherein the copolymerization is carried out at 60 - 70 ^o C in the presence of activator and peroxygen groups decay mass Aspect Britain and polymer of vinyl monomer of 1: 1-1.5.

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