RU2596256C1 - Method of producing sorbent for dichromate ions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to sorption technologies. Disclosed is a method of producing sorbent of dichromate ions, consisting of inert support and active sorbent polymer layer of polyaniline. Sorbent layer is produced by oxidative polymerisation of aniline on a support in presence of hydrochloric acid. Support used is rubber crumbs with particle size of 0.125-1.0 mm. Oxidative polymerisation is carried out with molar ratio of aniline to ammonium persulphate and to hydrochloric acid equal to 1:1.25:(0.12-0.47). Weight ratio of aniline to rubber crumbs is (3.32-0.23):1.

EFFECT: simplified process with increase of its sorption capacity with respect to dichromate ions.

1 cl, 2 tbl, 6 ex

Description

The invention relates to the field of chemical technology, and in particular to a method for producing sorption materials that can be used to extract chromium contained in aqueous solutions in the form of a dichromate ion.

A known method of purification of wastewater from chromium compounds [Patent RU 2458010, IPC C02F 1/28, B01J 20/24, C02F 101/22, 08/10/2012], which is carried out by reducing the dichromate ion and sorption of chromium (III) cations by a sorbent matrix . As a sorbent, hair and sulfonated coal are successively used. Chromium regeneration is carried out by burning spent sorbents.

, будет восстанавливаться до хрома (III) и удаляться в процессе очистки сточных вод, кроме того предлагаемые сорбенты (волосы и сульфоуголь) малопригодны для очистки стоков больших объемов ввиду малого тоннажа этого вида сорбентов.The disadvantage of this method is the need to carry out the sorption process at pH <7, since only in this case, chromium VI contained in $$C{r}_2{O}_7^{-2}$$

, will be reduced to chromium (III) and disposed of in the wastewater treatment process, in addition, the proposed sorbents (hair and sulfonated coal) are unsuitable for treating large volumes of wastewater due to the small tonnage of this type of sorbent.

It is known to use as a sorbent for removing dichromate ion from aqueous solutions of industrial and domestic wastewater at pH <7 agricultural products: alfalfa seed and / or clover [Patent RU 2110481, IPC C02F 1/28, C02F 1/62, C02F 1 / 76, 05/10/1998].

The disadvantages of these sorbents are: their low efficiency, as well as the specific nature of the sorbents (alfalfa and clover), which are agricultural crops, which determines a limited number of regions of growth and additional costs for their transportation.

A known method of producing a sorbent for the extraction of metal ions from solutions [Patent RU 2221752, IPC C02F 1/42, B01J 39/04, 01/20/2004], which consists in the modification of rubber crumb by the interaction of sulfated rubber crumb with sulfur content of 11-67% with water sodium hydroxide solution in a mass ratio of 1: 0.28-1.7, and sorption is carried out at pH 7-10.5 in a 10% aqueous solution of sodium hydroxide at 80 ° C.

The disadvantage of this method is the technological complexity of the process of producing kateonite, where in the first stage sulfidized rubber crumb is obtained in a sulfur melt at 140 ° C for 5 hours; in addition, there is a decrease in the sorption capacity of the modified rubber crumb in acidic environments.

A known method of producing a modified sorbent of platinum metals [Patent RU 2491990, IPC B01J 20/30, B01J 20/26, 09/10/2013]. Modified sorbent receive on an inert carrier, which contains 2.5-15% of the mass. active polymer sorbent layer, which is a polyaniline. Polyaniline is produced by the oxidative polymerization of aniline on a support. To convert polyaniline to the form of emeraldine base it is treated with 0.1-0.5 M ammonia solution. As an inert carrier, the sorbent contains a carbon mineral base obtained by carbonization of sapropel, or silica gel.

The closest solution to the claimed technical essence is a method for producing a heterogeneous complexing sorbent [Patent RU 2141377, IPC B01J 20/26, B01J 20/30, 20.11.1999]. A heterogeneous sorbent is obtained as a result of oxidative polymerization of aniline in the amount of 0.4-15% of the mass. on a carrier that is taken in an amount of 85-99.6% of the mass. The polymerization of aniline is carried out in a slightly acidic aqueous medium at 0-5 ° C, the molar ratio of monomer (aniline): oxidizing agent (ammonium persulfate) = 1: 1. It is proposed to use silica gel, alumina, polysorb-1 as a carrier.

A common drawback of the considered methods for producing sorbents is the presence of an additional technological stage — the treatment of polyaniline with ammonia — as a result of which the polymer acquires the structure of an emeraldine base, which determines the impossibility of using the obtained sorbents for the treatment of industrial wastewater contaminated with anions containing heavy metals (for example, bichromate ions).

The objective of the invention is to develop a technologically advanced method for producing a sorbent for the extraction of chromium contained in aqueous solutions in the form of a dichromate ion.

The technical result of the invention is to simplify the method of obtaining the sorbent of the bichromat ion, increasing the sorption capacity of the sorbent relative to the bichromat ions.

The technical result is achieved in a method for producing a sorbent of a dichromate ion, consisting of an inert carrier and an active sorbent polymer layer, which is a polyaniline obtained by oxidative polymerization of aniline on a carrier in the presence of hydrochloric acid, while rubber crumb with a particle size of 0.125- is used as an inert carrier 1.0 mm, and oxidative polymerization is carried out with a molar ratio of aniline: ammonium persulfate: hydrochloric acid, equal to 1: 1.25: (0.12-0.47), and the mass ratio of aniline: rubber I'm a baby equal to (3.32-0.23): 1.

Aniline polymerization is a two-stage process [Kobryansky V.M., Arnautov S.A., Motyakin M.V. Studying the mechanism of aniline condensation reaction by the example of obtaining a water-soluble polymer // Naval Forces. Series A. - 1995. - T. 37, No. 1. - S. 35-38.]. At the first stage, aniline is oxidized with the formation of polyaniline oligomers and their further oxidation to the structure of pernigraniline, which has a dark blue precipitate. At the second stage, the structural reorganization of the chain occurs from the structure with alternating leuko-emeraldine and per-framed fragments to the structure of the emeraldine salt. Protonated emeraldine is the most stable form of polyaniline and is a dark green precipitate. Moreover, polyaniline in the synthesis process is formed in the form of a fine powder, which complicates its individual use as a sorbent in the wastewater treatment process.

In the proposed technical solution, polyaniline was obtained as part of a stable system of polyaniline-rubber crumb, which was studied as a sorbent for the extraction of chromium contained in aqueous solutions in the form of a dichromate ion. The sorbent obtained by the oxidative polymerization of aniline on crumb rubber with a particle size of 0.125-1.0 mm in the presence of hydrochloric acid with a molar ratio of aniline: ammonium persulfate: hydrochloric acid, equal to 1: 1.25: (0.12-0.47), and a mass ratio of aniline: crumb rubber equal to (3.32-0.23): 1, contains polyaniline in the form of an emeraldine salt and exhibits high sorption activity with respect to the dichromate ion.

In the oxidative polymerization of aniline in the presence of an additionally introduced substrate - rubber crumb - initially, up to the exhaustion of 70% aniline, the polymerization proceeds on the surface of the substrate in the complete absence of polyaniline formed in the volume of the reaction solution, and only then an adsorption polyaniline layer is formed. Thus, the polymerization of aniline on the surface of rubber crumb is a priority process, which allows a method for producing a sorbent and increase its efficiency.

As an inert carrier, the tread rubber crumb of the Volzhsky Tire Plant, crushed in accordance with TU-38-108015-87, the composition and main characteristics of which are presented in table 1, was used.

The rubber crumb was fractionated. As an inert carrier for applying polyaniline, a fraction of rubber crumb with a particle size of 0.125-1.0 mm was used, as the most representative.

A feature of rubber crumb is high elasticity, as well as a developed inner surface, which allows the polymerization of aniline both on its outer and inner surfaces, and the subsequent process of sorption of anions on a larger area of the sorbent.

The oxidative polymerization of aniline on a support was carried out in aqueous solutions in the presence of hydrochloric acid with a molar ratio of aniline: ammonium persulfate: hydrochloric acid 1: 1.25: (0.12-0.47) and aniline: rubber crumb mass ratio (3.32- 0.23): 1. Corresponding concentrations of aqueous solutions of aniline 0.42-2.5 mol / L and ammonium persulfate 0.158-0.625 mol / L. Hydrochloric acid was taken in excess in the form of a 36% solution with a volume of 3.7-14.4 ml. The oxidation process was carried out at a temperature of 0-5 ° C, pH = 0-0.5. The precipitate formed was filtered off, washed with distilled water, acetone, and dried to constant weight. The content of the active polymer sorbent layer (polyaniline) in the sorbent is from 14.5 to 77.3 mass. %

To show the effectiveness of the sorbent, which is a rubber crumb with a surface polyaniline layer, we studied the process of extracting from the solution - wastewater of the galvanic production of JSC VZTDiN - anion, which contains chromium in the form of a dichromate ion. Purified aqueous solution in a volume of 200 ml containing potassium dichromate concentration of 1.0 mmol / DM, was placed in a conical flask. At pH = 7, 1.0 g of sorbent was added. The resulting mixture was kept for a day, then the suspension was filtered off, and the content of dichromate ions was determined in the filtrate. Evaluation of the sorption properties of polyaniline and sorbents based on rubber crumb was carried out using the method of measuring the mass concentration of dichromate ion in wastewater by the photometric method [Quantitative chemical analysis of water. The methodology for measuring the mass concentration of dichromate ion in natural and waste water by the photometric method with diphenylcarbazide. PND F 14.1: 2.52-96, M: Ministry of Natural Resources of the Russian Federation. - 14 s.]. The results of the experiments are presented in table 2.

An analysis of the results shows that polyaniline, both an individual polymer (PANi), and applied in the form of a film on the surface of an inert carrier (sorbents 1-6), is capable of efficiently absorbing chromium from the dichromate ion from solutions. In sorbents 1-6 when recalculating the sorption capacity to the sorbing polymer, the sorption capacity of samples 1-6 is, mmol / g: 0.185, 0.205, 0.262, 0.326, 0.381, 0.498, respectively.

The invention is illustrated by the following examples.

Example 1

In a four-necked reactor equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 9.3 g (0.1 mol) of distilled aniline, 40 ml of distilled water and 2.8 g of crumb rubber with a particle size of 0.125-1.0 mm are charged. The resulting dispersion is stirred for 30 minutes. Then, 14.5 ml (0.47 mol) of 36% hydrochloric acid are slowly added in portions to the reactor. After that, the reaction mixture is cooled to 0 ° C, purged with an inert gas (argon) for 10 minutes. The pH of the resulting reaction mixture was 0.5. A solution containing 28.5 g (0.125 mol) of ammonium persulfate in 200 ml of distilled water is slowly added dropwise to the resulting solution. The temperature of the reaction mass is maintained from -5 to 0 ° C throughout the process. After the introduction of the oxidizing agent, the reaction mass is maintained at a temperature of 20-22 ° C and with constant stirring for another 1.5 hours. During the synthesis, a precipitate precipitates, which initially has a dark blue color, and then changes color to dark green. The precipitate is filtered off, washed with 150 ml of distilled water, 20 ml of acetone, dried in vacuum at 50 ° C. Next, the precipitate is purified from unreacted starting reagents and secondary oxidation products by extraction with acetone in a Soxhlett apparatus, dried in vacuum at 50 ° C / 20 mm Hg The yield of sorbent is 12.3 g (88.6%). The content of polyaniline in the sorbent is 77.3 mass. %

Found,%: N 9.65; Cl 8.17.

IR data, ν, cm ^-1 : 1580 (C = C); 1500 (C-C); 1313 and 1164 (C-N); 1260 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 833 (C-H).

Example 2

Prepare the sorbent of example 1, load 40 ml of distilled water and 5 g of rubber crumb with a particle size of 0.125-1.0 mm The output of the sorbent is 14.1 g (84.9%)., The content of polyaniline in the sorbent is 64.5 mass. %

Found,%: N 8.18; C1 7.06.

IR data, ν, cm ^-1 : 1584 (C = C); 1500 (C-C); 1316 and 1156 (CN); 1268 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 836 (C-H).

Example 3

Prepare the sorbent of example 1, load 60 ml of distilled water and 10 g of rubber crumb with a particle size of 0.125-1.0 mm The yield of sorbent is 18.7 g (81.1%). The content of polyaniline in the sorbent is 46.5 mass. %

Found,%: N 6.35; Cl 5.37.

IR data, ν, cm ^-1 : 1591 (C = C); 1510 (C-C); 1314 and 1173 (CN); 1264 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 830 (C-H).

Example 4

Prepare the sorbent according to example 1, load 80 ml of distilled water and 15 g of rubber crumb with a particle size of 0.125-1.0 mm The sorbent yield is 23.1 g (75.5%). The content of polyaniline in the sorbent is 35.0 mass. %

Found,%: N 5.13; Cl 4.35.

IR data, ν, cm ^-1 : 1572 (C = C); 1508 (C-C); 1312 and 1144 (CN); 1280 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 834 (CH).

Example 5

The sorbent is prepared according to Example 1, 4.65 g (0.05 mol) of distilled aniline, 60 ml of distilled water and 10 g of rubber crumb with a particle size of 0.125-1.0 mm are loaded. The resulting dispersion is stirred for 30 minutes. Then 7.3 ml (0.24 mol) of 36% hydrochloric acid are slowly added in portions to the reactor. After that, the reaction mixture is cooled to 0 ° C, purged with an inert gas (argon) for 10 minutes. The pH of the resulting reaction mixture was 0.5. A solution containing 14.25 g (0.063 mol) of ammonium persulfate in 200 ml of distilled water is slowly added dropwise to the resulting solution.

The sorbent yield is 13.6 g (67.4%). The content of polyaniline in the sorbent is 26.5 mass. %

Found,%: N 4.43; Cl 3.75.

IR data, ν, cm ^-1 : 1578 (C = C); 1492 (C-C); 1300 and 1168 (CN); 1282 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 853 (CH).

Example 6

Prepare the sorbent according to example 1, load 2.3 g (0.025 mol) of distilled aniline, 60 ml of distilled water and 10 g of rubber crumb with a particle size of 0.125-1.0 mm. The resulting dispersion is stirred for 30 minutes. Then, 3.7 ml (0.12 mol) of 36% hydrochloric acid are slowly added in portions to the reactor. After that, the reaction mixture is cooled to 0 ° C, purged with an inert gas (argon) for 10 minutes. The pH of the resulting reaction mixture was 0.5. A solution containing 7.1 g (0.031 mol) of ammonium persulfate in 200 ml of distilled water is slowly added dropwise to the resulting solution.

The output of the sorbent is 11.7 g (63.3%). The content of polyaniline in the sorbent is 14.5 mass. %

Found,%: N 2.49; Cl 2.11.

IR data, ν, cm ^-1 : 1518 (C = C); 1522 (C-C); 1310 and 1142 (CN); 1269 (-C ₆ H ₄ -NH-C ₆ H ₄ -); 838 (CH).

Thus, the proposed method for producing a sorbent consisting of an active sorbing polymer layer of polyaniline on crumb rubber with a particle size of 0.125-1.0 mm, in which oxidative polymerization is carried out at a molar ratio of aniline: ammonium persulfate: hydrochloric acid, equal to 1: 1.25 : (0.12-0.47), and the mass ratio of aniline: rubber crumb, equal to (3.32-0.23): 1, allows a technologically advanced method to obtain a sorbent of a dichromate ion with a high sorption capacity relative to the dichromate ion.

Claims (1)

A method of producing a dichromate ion sorbent consisting of an inert carrier and an active sorbent polymer layer, which is polyaniline, obtained by oxidative polymerization of aniline on a carrier in the presence of hydrochloric acid, characterized in that rubber crumb with a particle size of 0.125-1 is used as an inert carrier 0 mm, and oxidative polymerization is carried out with a molar ratio of aniline: ammonium persulfate: hydrochloric acid, equal to 1: 1.25: (0.12-0.47), and a mass ratio of aniline: rubber crumb, equal to (3.32-0 , 23): 1 .