Method of obtaining water-insoluble sulphur-containing chitosan-based biomaterial

FIELD: chemistry.

SUBSTANCE: invention relates to the field of organic synthesis. A method of obtaining a water-insoluble sulphur-containing chitosan-based biopolymer includes interaction of chitosan with a thiomethylating agent, preliminarily obtained by saturation of a formaldehyde solution with gaseous H2S, with molar ratio chitosan: formaldehyde: hydrogen sulphide 1:6:4, at a temperature of 60°C for 20-25 hours.

EFFECT: invention ensures obtaining the water-insoluble sulphur-containing chitosan-based biopolymer, which possesses a complexing activity to ions of noble metals (Pd, Pt).

1 ex, 1 tbl

 

The invention relates to organic chemistry, in particular to a method for producing sulfur-containing crosslinked derivative of chitosan (1), having the structural formula:

Sulfur-containing derivatives of chitosan can be used as a highly effective sorbents of heavy metals to wastewater treatment, extractants for the separation of rare and precious metals, as well as selective complexing agents.

It is known that chitosan and its derivatives are promising polysaccharide materials to create ion-exchange membranes used in ultrafiltration and dialysis, and their complexing ability can be used for selective extraction of some metals from seawater (Evert, Lnterface // USP, 2001, CH, No. 1, p.72-87.). Chitosan and its phosphate derivatives, in particular phosphate chitosan can be used as biocompatible materials (Wang X., MA J., Wang Y., He, B. // Biomaterials, 2001, V.22, No.16, P.2247), sorbents for the extraction of uranium (Sakaguchi T., Hirokoshi T., Nakajima A. // Agric. Biol. Chem., 1981, V.45, No.10, P.2191), chiral matrices to create a metal-complex catalysts (E. Guibal // Prog. Polym. Sci., 2005, V.30, No.1, P.71).

According to literature data, the chemical modification of chitosan can be carried out for all functional groups. Thus, the known method the floor is placed N,O-carboxymethyl-N,O-sulfotransferase chitosan (Zhao Xia, LV Zhihua, XU Jiamin, YU Guangli // Journal of Ocean University of Qingdao, 2003, V.2, No.1, P.69-74)with inhibitory activity against platelet blood:

There are ways of modification of chitosan solely by the primary amino group of the polysaccharide to obtain N-alkyl derivatives of chitosan. The method is based on the interaction of chitosan with aliphatic aldehydes by introduction of alkyl substituents on the amino group of the original polymer via Schiff's base (Keisuke Kurita, Satoko Mori, Yasuhiro Nishiyama, Manabu Harata // Polymer Bulletin, 2002, 48, 159-166). It was shown that with increasing alkyl radical increases antibacterial activity of derivatives of chitosan (Chun But Kim, Jang Won Choi, Heung Jae Chun, Suk Kyu Choi // Polymer Bulletin, 1997, V.38, No.4, P.387-393).

A method of obtaining sulfur-containing biopolymer by modification of chitosan component sulfur-containing agent with obtaining N-thiocarbamoylation [Aviston, Shubraska, Abelardo, Waaramaa, Ugetsu. Thiocarbamoylation - new sorbent with high capacity and selectivity for ions of gold (III), platinum (IV) and palladium (II). WPI. An. A series of chemical, 2010, No. 7, s-1276]. As the two sulfur-containing agent, a mixture of ammonium thiocyanate and thiourea, modified chitosan is carried out at a temperature of 130°C for at least 4 hours. About the TPC is subjected to cold extraction with water until a negative reaction to the thiocyanate ion.

The disadvantage of this method is the need for process modification of chitosan at high temperature, use as a sulfur-containing reagent thiourea and ammonium thiocyanate - deficient reagents.

A method of obtaining sulfur-containing biopolymer by modification of chitosan with formaldehyde and sulfur-containing reagent to obtain N-metilsulfate grafted derived hitozuma (D.J.Macquarria, Hardy, J.J.E. // Ind. Eng. Chem. Res., 2005, Vol.44, No. 23, P. 8499-8520).

As the sulfur-containing reagent is used thiol-mercaptohexanol acid HSCH2COOH.

In this way cannot be obtained stitched sulfur-containing derivative of chitosan (1).

Closest to the proposed technical essence is a method of obtaining sulfur-containing biopolymer consisting in the reaction of chitosan with formaldehyde and H2S in the ratio of chitosan : formaldehyde : hydrogen of 1:2:1, leading to a heterocyclic derivative of chitosan, forming a stable gel with water [Dzhemilev sea level, Rakhimov E.B., minlebaev A.B., Akhmetov V.R., Kunakova RV Application No. 2010122540/04.22.09.2010].

The known method cannot be obtained water-insoluble sulfur-containing derivative of chitosan, altausee property of the sorbent of metal ions.

The purpose of the invention is to obtain water-insoluble sulfur-containing biopolymer chitosan with complexing activity to ions of noble metals (Pd, Pt).

This goal is achieved by modification of chitosan myometrium agent obtained by saturation of an aqueous solution of formaldehyde gas H2S. the Modification is carried out by interaction of hydrochloric acid solution of chitosan and timetreasure agent at a molar ratio of chitosan : formaldehyde : hydrogen of 1:6:4 at a temperature of 0-60°C for 20-25 hours.

The reaction modification of chitosan proceeds according to the scheme:

obtaining water-insoluble crosslinked sulfur-containing derivative of chitosan (1), where n=300-1800.

The method is illustrated with an example.

Example 1. In a three-neck flask equipped with a stirrer and a bubbler, thermostated at 20°C, loaded the calculated amount of 37%formalin (0,03 mole), 30 minutes was barbotirovany hydrogen (derived from the estimated number of Na2S and HCl)to form dimethylurea mixture "CH2O and H2S". Then the reaction mass was added dropwise to 0.005 mole of chitosan (0.8 g)dissolved in diluted hydrochloric acid (0,365 g HCl in 8 ml of H2O) at a given temperature (0, 20, 60°C). The mixture was stirred is at a given temperature (0, 20, 60°C) within 24 hours. The reaction mass was neutralized with diluted NaOH solution to pH=7. The modified chitosan of the reaction mass was besieged by treatment with 70%ethanol in a volume of 150 ml, was added a few drops of concentrated NaCl solution to coagulate the polymer. The precipitated biopolymer was centrifuged and washed three times with 70%alcohol. The result was 1.26 g at 0°C, 1.32 g at 20°C and 1.38 g at 60°C sulfur-containing derivative of chitosan (1).

Characteristics of sulfur-containing derivative of chitosan (1)

Elemental composition. Found (percent): C, 40.54; H, 5.86; N, 6.3; S, 23.54. Calculated (%): C, 41.95; H, 5.59; N, 4.89; S, 22.37. IR spectrum, ν, cm-1: CL 529, 588 SL and 639 CL (C-S) 750, 1050, 1170, 1650, 2166, 2900, 3400.

IR spectra were obtained on a spectrophotometer "Specord 75IR" in suspension in vaseline oil. Elemental analysis of the compound (1) (C, H, N, S, O) was determined on the analyzer company Karlo Erba model 1106.

The optimal conditions for the modification process are: maintaining the molar ratio of chitosan : formaldehyde : hydrogen sulfide is 1:6:4; temperature 60°C, duration of 20-25 hours.

Reducing the number dimethylurea mixture is less than the molar ratio of chitosan : formaldehyde : hydrogen of 1:6:4, it leads to the formation of the target product. The increase in the number dimethylurea mixture is higher than the mole is E. the ratio of chitosan : hydrogen sulfide, equal to 1:4, leads to the formation side of the cyclic sulphur compounds. Lowering the process temperature below 60°C leads to a reduction of the yield of sulfur-containing derivative of chitosan (1). Increasing the process temperature above 60°C does not significantly affect the output (1). Reducing process time less than 20 hours leads to a decrease of the degree of functionalization of the biopolymer. The increase in the length of more than 25 hours is inappropriate.

The proposed method allows to obtain a water-insoluble sulfur-containing biopolymer chitosan with complexing activity to ions of noble metals (Pd, Pt).

For compound (1) were studied sorption properties for extracting ions of Pd (II) and Pt (IV) from hydrochloric acid solutions. The table presents the dependence of the distribution coefficients (Kd) and the degree of extraction (R) ions Pd (II) and Pt (IV) sample (1) from the original acidity of a solution at a concentration of [K2PdCl4]0=0.0237 M, [H2RtCl6]0=0.0185 M and the ratio of solid : liquid=1:300, τ=24 h revealed that the most effective sorbent extracts Pt(IV) from weakly acidic solutions. With increasing acidity of the aqueous phase up to 5 M HCl capacity of the sorbent is reduced.

The dependence of coefficie the Ltd distribution and the degree of extraction of Pd (II) and Pt (IV) example (8) from the original acidity of a solution if [K 2PdCl4]0=0.0237 M, [H2PtCl6]0=0.0188 M, t:W=1:300, τ=24 h
CHClMPd (II)Pt( IV)
Kdml/dR%Kdml/dR%
pH ~433452.7
0.024155583.8
0.1267589.973571.0
0.5221888.150262.6
1.0143682.736154.6
2.015834.524144.5
3.0 3911.522142.5
4.0329.68221.5
5.0216.410626.0

A method of obtaining a water-insoluble sulfur-containing biopolymer (1) based on chitosan, which consists in the interaction of chitosan with myometrium agent, prior saturation of the solution of formaldehyde in gaseous H2S, wherein the reaction is carried out at a molar ratio of chitosan : formaldehyde : hydrogen of 1:6:4 at a temperature of 60°C for 20-25 hours.



 

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